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Understanding Climatic Change: A Program for Action (1975)

Chapter: NATIONAL CLIMATIC RESEARCH PROGRAM

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Suggested Citation:"NATIONAL CLIMATIC RESEARCH PROGRAM." National Research Council. 1975. Understanding Climatic Change: A Program for Action. Washington, DC: The National Academies Press. doi: 10.17226/27501.
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Suggested Citation:"NATIONAL CLIMATIC RESEARCH PROGRAM." National Research Council. 1975. Understanding Climatic Change: A Program for Action. Washington, DC: The National Academies Press. doi: 10.17226/27501.
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Suggested Citation:"NATIONAL CLIMATIC RESEARCH PROGRAM." National Research Council. 1975. Understanding Climatic Change: A Program for Action. Washington, DC: The National Academies Press. doi: 10.17226/27501.
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Suggested Citation:"NATIONAL CLIMATIC RESEARCH PROGRAM." National Research Council. 1975. Understanding Climatic Change: A Program for Action. Washington, DC: The National Academies Press. doi: 10.17226/27501.
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Suggested Citation:"NATIONAL CLIMATIC RESEARCH PROGRAM." National Research Council. 1975. Understanding Climatic Change: A Program for Action. Washington, DC: The National Academies Press. doi: 10.17226/27501.
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Suggested Citation:"NATIONAL CLIMATIC RESEARCH PROGRAM." National Research Council. 1975. Understanding Climatic Change: A Program for Action. Washington, DC: The National Academies Press. doi: 10.17226/27501.
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Suggested Citation:"NATIONAL CLIMATIC RESEARCH PROGRAM." National Research Council. 1975. Understanding Climatic Change: A Program for Action. Washington, DC: The National Academies Press. doi: 10.17226/27501.
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Suggested Citation:"NATIONAL CLIMATIC RESEARCH PROGRAM." National Research Council. 1975. Understanding Climatic Change: A Program for Action. Washington, DC: The National Academies Press. doi: 10.17226/27501.
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Suggested Citation:"NATIONAL CLIMATIC RESEARCH PROGRAM." National Research Council. 1975. Understanding Climatic Change: A Program for Action. Washington, DC: The National Academies Press. doi: 10.17226/27501.
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Suggested Citation:"NATIONAL CLIMATIC RESEARCH PROGRAM." National Research Council. 1975. Understanding Climatic Change: A Program for Action. Washington, DC: The National Academies Press. doi: 10.17226/27501.
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Suggested Citation:"NATIONAL CLIMATIC RESEARCH PROGRAM." National Research Council. 1975. Understanding Climatic Change: A Program for Action. Washington, DC: The National Academies Press. doi: 10.17226/27501.
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Suggested Citation:"NATIONAL CLIMATIC RESEARCH PROGRAM." National Research Council. 1975. Understanding Climatic Change: A Program for Action. Washington, DC: The National Academies Press. doi: 10.17226/27501.
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Suggested Citation:"NATIONAL CLIMATIC RESEARCH PROGRAM." National Research Council. 1975. Understanding Climatic Change: A Program for Action. Washington, DC: The National Academies Press. doi: 10.17226/27501.
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Suggested Citation:"NATIONAL CLIMATIC RESEARCH PROGRAM." National Research Council. 1975. Understanding Climatic Change: A Program for Action. Washington, DC: The National Academies Press. doi: 10.17226/27501.
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Suggested Citation:"NATIONAL CLIMATIC RESEARCH PROGRAM." National Research Council. 1975. Understanding Climatic Change: A Program for Action. Washington, DC: The National Academies Press. doi: 10.17226/27501.
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Suggested Citation:"NATIONAL CLIMATIC RESEARCH PROGRAM." National Research Council. 1975. Understanding Climatic Change: A Program for Action. Washington, DC: The National Academies Press. doi: 10.17226/27501.
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Suggested Citation:"NATIONAL CLIMATIC RESEARCH PROGRAM." National Research Council. 1975. Understanding Climatic Change: A Program for Action. Washington, DC: The National Academies Press. doi: 10.17226/27501.
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Suggested Citation:"NATIONAL CLIMATIC RESEARCH PROGRAM." National Research Council. 1975. Understanding Climatic Change: A Program for Action. Washington, DC: The National Academies Press. doi: 10.17226/27501.
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Suggested Citation:"NATIONAL CLIMATIC RESEARCH PROGRAM." National Research Council. 1975. Understanding Climatic Change: A Program for Action. Washington, DC: The National Academies Press. doi: 10.17226/27501.
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Suggested Citation:"NATIONAL CLIMATIC RESEARCH PROGRAM." National Research Council. 1975. Understanding Climatic Change: A Program for Action. Washington, DC: The National Academies Press. doi: 10.17226/27501.
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6 A NATIONAL CLIMATIC RESEARCH PROGRAM While there is ample evidence that past climatic changes have had profound effects on man’s activities, future changes of climate promise to have even greater impacts. The present level of use of land for agriculture, the use of water supplies for irrigation and drinking, and the use of both airsheds and watersheds for waste disposal is approach- ing the limit. A change of climate, even if sustained only for a few years’ time, could seriously disrupt this use pattern and have far-reach- ing consequences to the national economy and well-being. To this vul- nerability to natural climatic changes we must add the increasing possibility that man’s own activities may have significant climatic reper- cussions. If we are to react rationally to the inevitable climatic changes of the future, and if we are ever to predict their future course, whether they are natural or man-induced, a far greater understanding of these changes is required than we now possess. It is, moreover, important that this knowledge be acquired as soon as possible. Although much has been accomplished, and further research is under way on many prob- lems (as summarized in Chapter 5), the mechanics of the climatic system is so complex, and our observations of its behavior so incom- plete, that at present we do not know what causes any particular climatic change to occur. Our response to this state of affairs is the recommendation of an integrated research program to contain the observational, analytical, and research components necessary to acquire this understanding. 62

A NATIONAL CLIMATIC RESEARCH PROGRAM 63 Heretofore the many pieces of the climatic puzzle have been considered in relative isolation from each other, a subdivision that is natural to the traditional scientific method. We believe, however, that the time has now come to initiate a broad and coordinated attack on the problem of climate and climatic change. Such a program should not stifle the de- velopment of new and independent lines of attack nor seek to assemble all efforts under a single authority. On the contrary, its purpose should be to provide a coordinating framework for the necessary research on all aspects of this important problem, including the strengthening of those efforts already under way as well as the initiation of new efforts. Only in this manner can our limited resources be used to maximum benefit and a balanced and coherent approach maintained. THE APPROACH From the summary of recent and current research on climate and climatic variation presented in Chapter 5, it is clear that considerable effort has been devoted to this problem. It is also clear that much remains to be done. As an approach to the research program itself, we here attempt to summarize what is now known and to identify those elements that now make a greatly expanded effort both feasible and desirable. What Climatic Events and Processes Can We Now Identify? From the analysis of accumulated instrumental climatic data, we can identify some of the major characteristics of the climatic changes of the past few decades. These include the presence of seasonal and annual circulation anomalies over large regions of the earth, together with some longer-term trends. More recent satellite observations have documented changes in worldwide cloudiness, snow cover, and the global radiation balance and have served to emphasize the climatic role of the oceans. Although the necessary oceanic measurements have not yet been made, satellite observations (together with atmospheric data) indicate that the oceans accomplish between one third and one half of the total annual meridional heat transport. From the analysis of selected paleoclimatic data, it appears that ancient climates have been somewhat similar in behavior to the present- day climate, although the resolution is poorer. These data also suggest the presence of seemingly quasi-periodic climatic fluctuations on time scales of order 100,000 years, associated with the earth’s major glaciations.

64 UNDERSTANDING CLIMATIC CHANGE From the solutions of numerical general circulation models, we can identify a number of important physical elements in the mainte- nance of global climate. Primary among these is the role played by convective motions in the vertical heat flux and by the transfers of heat at the ocean surface. Climate models also show that the climate is sensitive to the extent of cloudiness and to the surface albedo. Recent solutions of global atmospheric models have shown that the accuracy of the simulations of cloudiness and precipitation is more difficult to establish than the average seasonal distribution of the large-scale patterns of pressure, temperature, and wind, which are simulated with reasonable accuracy (see Appendix B). This may be due to the pre- scription of the sea-surface temperature in the atmospheric models, serving to mask errors in the models’ heat balance. Less experience has been gained with oceanic general circulation models, although they are capable of portraying the large-scale thermal structure of the oceans and the distribution of the major current sys- tems when subject to realistic (atmospheric) surface boundary condi- tions. These and other models are just beginning to identify the energetic mesoscale eddy, which in some ways appears to be the oceanic counter- part of the transient cyclones and anticyclones in the atmosphere. From the analysis of a variety of climate models, as well as from the analysis of climatic data, we can identify a number of links or processes in the phenomenon of climatic change. On at least the shorter climatic time scales, the climatic system is regulated by a number of feedback mechanisms, especially those involving cloudiness, surface temperature, and surface albedo. Underlying these effects is the increas- ing evidence that large-scale thermal interactions between the ocean and atmosphere are the primary factor in climatic variations on time scales from months to millenia. These interactions must be examined in coupled ocean—atmosphere models, whose development has just begun. The role of the oceans in the climatic system raises the pos- sibility of some degree of useful predictability on, say, seasonal or annual time scales and is an obviously important matter for further research. From the analysis of the limited data available, we can identify a number of areas in which man’s actions may be capable of altering the course of climatic change. Chief among these is interference with the atmospheric heat balance by increasing the aerosol and particulate loading and increasing the CO, content of the atmosphere by industrial and commercial activity. While present evidence indicates that these are not now dominant factors, they may become so in the future. To these we must also add the possibility of man’s direct thermal inter-

A NATIONAL CLIMATIC RESEARCH PROGRAM 65 ference with climate by the disposal of large amounts of waste heat into the atmosphere and ocean. Although important large-scale thermal pollution effects of this sort do not appear likely before the middle of the next century, they may eventually be the factor that limits the climatically acceptable level of energy production. Why Is a Program Necessary? Although the conclusions identified above represent important research achievements, they are nevertheless concerned with separate pieces of the problem. What we cannot identify at the present time is how the complete climatic system operates, which are its most critical and sensi- tive parts, which processes are responsible for its changes, and what are the most likely future climates. In short, while we know something about climate itself, we know very little about climatic change. From among the present activities we can identify important prob- lems requiring further research. In general, these concern new observa- tions and the further analysis of older ones, the design of improved climatic models of the atmosphere and ocean, and the simulation of climatic variations under a variety of conditions for the past, present, and future. As we attempt this research on a global scale, it becomes increasingly important that we ensure the smooth flow of data and ideas, as well as of resources, among all parts of the problem. The attention devoted in each country (and internationally through GARP) to the improvement of weather forecasting (a problem whose physical basis is reasonably well understood) must be matched by a program devoted to climate and climatic variation, a problem whose global aspects are even more prominent and whose physical basis is not at all well understood. The need for a broad, sustained, and coordinated attack is therefore a fundamental reason for a climatic research program. Other circumstances also indicate that a major research program on climatic change is both timely and necessary. First, for the past few years we have had available to us the unprecedented observational capability of meteorological satellites. This capability has steadily in- creased from the initial observations of the cloudiness, radiation budget, and albedo to include the vertical distribution of temperature and moisture, the extent of snow and ice, the sea-surface temperature, the presence of particulates, and the character of the land surface. The regular global coverage provided by such satellites clearly constitutes an observational breakthrough of great importance for climatic studies. Second, the steady increase in the speed and capacity of computers, which has been taking place since their introduction in the 1950’s, has

66 UNDERSTANDING CLIMATIC CHANGE reached the point where numerical integration of global circulation models over many months or even years is now practical. Such calcula- tions, along with the associated data processing, will form the quantita- tive backbone of climatic research for many years to come, and their feasibility clearly constitutes a computational breakthrough. This com- puting capability, as represented, for example, by machines of the TI-ASC or ILLIAC-4 class, will permit extensive experimentation for the first time with the coupled global climatic system. Finally, the recent development of unified physical models of the coupled ocean—atmosphere may itself be viewed as a modeling break- through of great importance. Up to now either the atmosphere or the ocean has been considered as a separate entity in global modeling, and their solutions have consequently described a sort of quasi-equilibrium climate. The simulation of climatic variation with these models, on the other hand, is just now beginning. A future modeling breakthrough of equally great importance will be the successful parameterization of the eddy transports of baroclinic disturbances in the atmosphere and in the ocean. Aside from the practical importance (or even urgency) of the climatic problem, the breakthroughs noted above indicate that a time is at hand during which progress will be in proportion to our efforts. By co- ordinating these efforts into a coherent research program, we may therefore expect to achieve significantly greater understanding of climatic variation. THE RESEARCH PROGRAM (NCRP) We have here assembled our specific recommendations for the data, the research, and the applications that we believe constitute the needed elements of a comprehensive national research program on climatic change. We recognize that some of the elements of this program re- quire considerable further development and coordination. We also recognize that some of the recommended efforts are already under way or are planned by various groups, but we believe that their identification as parts of a coherent program is both valuable and necessary. Our recommendations for the planning and execution of this program are given later in this chapter, including those items on which we urge im- mediate action. Data Needed for Climatic Research The availability of suitable climatic data is essential to the success of climatic analysis and research, and such data are an integral part of

A NATIONAL CLIMATIC RESEARCH PROGRAM 67 the overall program. The needed data are discussed below in terms of a subprogram for climatic data assembly and analysis and a subprogram for climatic index monitoring. These are the efforts that we believe to be necessary to make the store of climatic data more useful to the climatic research community and to ensure the systematic collection of the needed climatic data in the future. Climatic Data Analysis Instrumental Data Instrumental observations of the atmosphere ade- quate to depict even a decadal climatic variation are available only for about the last half century for selected regions of the northern hemisphere, and the observational coverage of the oceans is even poorer in both space and time (see Appendix A). In order to assess more ac- curately the present data base of conventional observations and the needed extensions of such data, a number of efforts should be under- taken: A worldwide inventory of climatic data should be taken to determine the amount, nature, and location of past and present instrumental observations of the following variables: surface pressure, temperature, humidity, wind, rainfall, snowfall, and cloudiness; upper-air tempera- ture, pressure—altitude, wind, and humidity; ocean temperature, salinity, and current; the location and depth of land ice, sea ice, and snow; the surface insolation, ground temperature, ground moisture, and runoff. This inventory should identify the length of the observational record, the data quality, and the state of its availability. In addition to the usual data sources, efforts should be made to locate data from private sources, older records, and unpublished climatological summaries. Al- though some of these data have been summarized, no overall inventory of this type exists. Selected portions of these data should be systematically transferred to suitable computer storage, in a format permitting easy access and screening by variable, time period, and location. These data should then be used to compute in a systematic fashion a basic set of climatic statistics for as many time periods and for as many regions of the world as possible. These should include the means, the variances, and the ex- tremes for monthly, seasonal, annual, and decadal periods, for both individual stations and for various ensembles of stations up to and in- cluding the entire globe. Research should also be devoted to the effects of instrumental errors, observational coverage, and analysis procedures on climatic statistics. Recognizing that these data have large differences in quality, cover-

68 UNDERSTANDING CLIMATIC CHANGE age, and length-of-record and were often collected as by-products of other studies, new four-dimensional climatological data-analysis schemes should be developed, based on suitable analysis methods or models, to synthesize as much of the missing information as possible while making maximum use of the available data. Efforts should also be devoted to the design of suitable computerized graphical display and output. Once such syntheses are available, we recommend that suitable climatological diagnostic. studies be made using dynamical climate models to generate systematically the various auxiliary and unobserved climatic variables, such as evaporation, sensible heat flux, surface wind stress, and the balances of surface heat, moisture, and momentum. Such data, of course, would be artificial but may nevertheless be of diagnostic use. Insofar as possible, the pertinent statistics of the atmospheric and oceanic general circulations and their energy, mo- mentum, and heat balances should be determined. The results of such analyses should be made available in the form of new climatological atlases, supplementing and extending those now available for scattered portions of the record and for selected regions of the world. The widely used climatological summaries of Sverdrup (1942), Moller (1951), and Budyko (1963), for example, are largely based on the subjective analyses of older data of uncertain quality. Other analyses are more authoritative (Oort and Rasmusson, 1971; Newell et al., 1972) but are in need of extension. We wish to emphasize the great importance of the potentially un- matched coverage of observations from satellites. Those that are of climatic value should be systematically cataloged and summarized and made available on as timely a basis as possible. These should include observations of cloud cover, snow, and ice extent; planetary albedo; and the net radiation balance. As remote techniques for measuring the at- mosphere’s composition, motion, and temperature structure (and the surface temperature of land and ocean) are developed, these data should be systematically added to the climatological inventory. They should also be used in the analysis and model-based diagnostic efforts described above and in the climatic index monitoring program out- lined below. The presently available summaries of such data (e.g., Vonder Haar and Suomi, 1971) have yielded important new results and should be continued on an expanded basis. Historical Data As noted in Appendix A, a wealth of information has been recorded on past variations of weather and climate in historical sources such as books, manuscripts, logs, and journals during the past

A NATIONAL CLIMATIC RESEARCH PROGRAM 69 several centuries. While much of these data are fragmentary and not of a quality comparable with that of instrumental observations, it is nevertheless of value. We therefore recommend that An organized effort be made to locate, classify, and summarize historical climatic information and to identify and exploit new sources. From the studies of this sort that have already been made (e.g., Bryson and Julian, 1963; LeRoy Ladurie, 1971; Lamb, 1968, 1972), it is clear that these efforts should involve historians, archeologists, and geog- raphers on an international scale. Efforts be made to relate this material to data from other proxy sources whenever possible, and efforts made to interpret and focus the material in a climatologically meaningful way. Proxy Data We recognize the unique value of proxy data for studies of climatic change. Such data are obtained from the analysis of tree-ring growth patterns, glacier movements, lake and deep-sea sediments, ice cores, and studies of soil and periglacial stratigraphy. Data from tree rings, annually layered lake sediments, and some ice cores are capable of providing information for individual years, while those from other sources provide more generalized climatic information on time scales of decades, centuries, and millenia. Such data constitute the only source of records for the study of the structure and characteristics fluctuations of ancient climates. As discussed in Appendix A of this report, some of these past climates were quite different from the present regime and provide our only documentation of the extreme states of which the earth’s climatic system is capable. Because all proxy climatic data may contain both bias and random error components, it is essential that a variety of independent proxy records be studied. It is important that coverage be as nearly global as possible, since most of the information on climatic variations is contained in the spatial patterns of the data fields. While noting that some such activity is already in progress, we urge that the assembly and analysis of paleoclimatic data be initially focused on four time spans (see below). This represents a strategic decision in order to make the best use of the available resources. In each area it is im- portant that steps be taken to increase greatly the degree of coordina- tion and cooperation within the paleoclimatological community, and that the cross-checking of overlapping data sets, the development of complementary and independent proxy data sources, and the calibration against instrumentally observed data be undertaken whenever possible. The last 10,000 years. This is the interval within which we may hope

70 UNDERSTANDING CLIMATIC CHANGE to gain insight into the current interglacial period by the systematic assembly of a wide variety of proxy climatic data. This is also the interval of greatest practical importance for the immediate future. For this period particular attention should be given to six techniques: Studies of the structural, isotopic, and chemical properties of tree rings should be intensified and extended to a global coverage. Since forests cover large areas of the globe, it is possible in principle to de- velop climatic records over extensive continental areas and to recon- struct the spatial patterns of past climate for the past several centuries or millenia. The amount of effort depends on the availability of suitable trees and on the resolution required in the climatic reconstruction. Data on variations of the density of wood from x-ray techniques and on the concentrations of trace elements and of stable isotopes of carbon, hy- drogen, and oxygen in well-dated rings should also be developed. Special efforts should be made to calibrate the few millenia-long tree- ring records with information from other suitable proxy data sources, such as pollen, varves, and ice cores. Studies of pollen records in lakes and bogs should be extended. Most pollen analyses to date have concerned bogs created by the retreat of the last continental ice sheet. In order to permit synoptic reconstruc- tion of the global vegetational record for the past 10,000 years or so, pollen analyses with extensive ™*C dating should be extended to the nonglaciated areas of the world, particularly to low-latitude regions and to the southern hemisphere. Studies of the polar ice caps should be expanded. This should include additional short ice cores in widely distributed locations, in both Greenland and Antarctica, and more detailed isotopic analyses. Studies of the major mountain glaciers should be expanded, to ob- tain additional information on the various glaciers’ advances and re- treats, using chronological control where possible. Studies of ocean sediments in the few basins of known high deposi- tion rates should be greatly expanded. Particularly near the continental margins, the synoptic reconstruction of even the decadal variations of sea-surface temperatures (and possibly of currents as well) would be of great paleoclimatic interest. This effort will involve lithologic, faunal, and isotopic analyses of long cores collected specifically for this purpose. The records from varved sediments in closed basin lakes or land- locked seas should be extended. Such data are particularly sensitive to the climatic fluctuations in arid regions and would further our knowledge of the long-term behavior of deserts and drought. The last 30,000 years. This interval is dominated by the waxing and

A NATIONAL CLIMATIC RESEARCH PROGRAM 71 waning of continental ice sheets. In this interval the radiocarbon dating method provides a good chronology, and the possibilities for studying the relative phases of different proxy climatic records on a global basis are a maximum. In this period particular efforts should be made in the following areas: Pollen records for the interval 10,000 to 30,000 years ago should be obtained in a wide variety of sites in both hemispheres. Ice-margin data should continue to be collected for northern hem- isphere glaciers and should be extended into southern hemisphere mountain areas. Additional deep-sea cores should be obtained, especially in the Pacific and Southern Oceans, in order to reveal further the geographic pattern of marine paleoclimates. These data would be particularly useful from high-deposition-rate basins. Additional data should be obtained on the fluctuations in the extent and volume of the polar ice sheets during this time interval. Particular attention should be given to the smaller ice sheets, such as the West Antarctic and Greenland ice sheets, which react more rapidly to climatic variations. More extensive analyses of sea-level records should be made, empha- sizing the removal of tectonic and isostatic effects. Present studies on raised coral reefs should be extended, and estuarine borings should be carefully dated and given thorough lithologic analysis. The last 150,000 years. Here we should seek to increase our knowl- edge of the last 100,000-year glacial—interglacial cycle. This interval includes the last period in the climatic history of the earth that was evi- dently most like that of today. The data of this period also provide the best example of how the last interglacial period ended. Efforts should be made to further develop a number of proxy data sources, including: Extensive collection and analyses of marine sediment cores to pro- vide adequate global coverage of the world ocean. Further studies of the fluctuations of the Antarctic and Greenland ice caps, with emphasis on records extending beyond the beginning of the last interglacial. This should include a geographic network of ice cores of sufficient length to penetrate this time range, of which those at Camp Century, Byrd, and Vostok are now the only examples. Further systematic study of the loess-soil sequences in suitable regions around the world, including Argentina, Australia, China, and the Great Plains of North America. Systematic studies of desert regions and arid intermountain basin

72 UNDERSTANDING CLIMATIC CHANGE areas in order to examine the patterns of long-term changes in aridity. Present records are limited to about the last 40,000 years, and their extension will require long borings in selected lakes and playas. Extended studies of sea-level variations from coral reef and island shorelines features. Further studies of long pollen records covering previous interglacial periods. This should include data from previously unsampled regions of the world, particularly in the southern hemisphere. The last 1,000,000 years and beyond. Fluctuations in this time range should not be ignored simply because of their antiquity. Here we have the opportunity to compare the circulation patterns that have char- acterized the last several full-glacial and interglacial periods, and thereby to contribute evidence on the question of the degree of de- terminism of the earth’s climatic system. Efforts should therefore be made to extend suitable proxy records into this time range, including: Additional marine sediment cores of sufficient length (say, up to 100 m long) to cover several glacial cycles should be obtained. This will require new innovations in drilling technology, as piston cores do not penetrate deeply enough for this purpose, and rotary drills presently in use greatly disturb the sedimentary record. The record of the Antarctic ice sheet (and the associated sea-level variations) should be extended as far back as possible and in as much detail as possible. This ice mass is a living climatic fossil and may contain information about the global climate for the past several million years. Climatic Index Identification and Monitoring In addition to the data provided by conventional surface and upper-air observations, climatic studies require other contemporary data that are not now readily available. The one hope for obtaining truly global coverage of many current climatic variables rests with satellite observations. We expect that climatic studies in the foreseeable future will have to rely on a combination of conventional observations, satellite observations, and special observations designed to monitor selected climatic variables as discussed below. We should therefore make full use of the temporary expansion of the observational network planned for the FGGE in 1978 in order to design a longer-lived climatic observing program. In addition, efforts should be made to process the monitored data from both satel- lites and other systems into forms that are useful for climatic studies. Support should be given to the development of new satellite-based ob-

A NATIONAL CLIMATIC RESEARCH PROGRAM 73 servational techniques, including those designed to monitor the oceans and the earth’s surface. There remain, however, a number of processes that are important to climate that are now beyond the reach of satellite observations. Primary among these is the pattern of the planetary thermal forcing, which drives the atmospheric and oceanic circulation, and the related balance of energy at the earth’s surface. Even a measurement of the average pole-to-equator temperature difference tells us something about the circulation; and, in a similar way, the discharge of a river gives us some information on the hydrologic balance in the river’s basin. Such measurements, which represent time and space integrals of climatically important procesess, we term “climatic indices.” While efforts to monitor indices of this sort are already under way, we recom- mend that further efforts be made to identify and monitor a variety of such indices in a coordinated and sustained fashion, as part of a compre- hensive global Climatic Index Monitoring Program (CIMP) whose elements are outlined below. Atmospheric Indices The heat balance of the atmosphere is basic to the character of the general circulation and hence is a principal de- terminant of climate. It is therefore important that the primary ele- ments of this balance be monitored with as much accuracy and with as nearly global coverage as possible. In particular, we recommend that further efforts be made to Monitor the solar constant and the spectral distribution of solar radiation with appropriate satelliteborne instrumentation. Monitor the net outgoing shortwave and long-wave radiation by satellite-based measurements, from which determinations of the ab- sorbed radiation and planetary albedo may be made. Monitor the latent heat released in large-scale tropical convection, possibly with the aid of satellite cloud observations. Develop methods to monitor remotely the surface latent heat flux into the atmosphere, possibly with the aid of satellite measurements of the vertical distribution and total amount of water vapor. These methods (and those for the sensible heat flux discussed below) will require calibration against field appropriate measurements, especially over the oceans. Develop methods to monitor remotely the surface sensible heat flux into the atmosphere, especially that from the oceans, such as occurs in winter off the east coasts of the continents and in the higher latitudes. Efforts should also be made to monitor remotely the vertical sensible

74 UNDERSTANDING CLIMATIC CHANGE heat flux that occurs as a result of convective motions both over the oceans and over land. Expand the satellite monitoring of global cloud cover to include information on the clouds’ height, thickness, and liquid water content, so that their role in the heat balance may be determined. Monitor the distribution of surface wind over the oceans, possibly by radar measurements of the scattering by surface waves or from the microwave emissivity changes created by foam. Oceanic Indices In view of the fundamental role the oceans play in the processes of climatic change, special efforts should be made to monitor those oceanic variables associated with large-scale thermal interaction with the atmosphere. In addition to the low-level air tem- perature, moisture, cloudiness, surface wind, and surface radiation, the surface heat exchange depends critically on the sea-surface temperature and heat storage in the oceanic surface layer itself. We therefore recom- mend that further efforts be made to Monitor the worldwide distribution of sea-surface temperature by a combination of all available ship, buoy, coastal, and satellite-based measurements. Sea-surface temperature analyses, such as now per- formed operationally by the Navy’s Fleet Numerical Weather Central in Monterey, should be extended and supplemented for climatic pur- poses on a global basis by improved satellite observations capable of penetrating cloud layers. The drifting buoy observations of sea-surface temperature planned for the FGGE should be expanded and maintained on a routine basis. Monitor the heat storage in the surface layer of the ocean by a program of observations from satellite-interrogated expandable drifting buoys and by expendable bathythermograph (xBT) observations from ships-of-opportunity in those areas of the world ocean traveled by commercial ships. It is estimated that there are several hundred such transits each year across most major oceans of the world. An expan- sion of XBT observations from merchant ships-of-opportunity is being undertaken by the North Pacific project (NORPAX), in cooperation with the Navy’s Fleet Numerical Weather Central and NoAa’s National Marine Fisheries Service. Similar programs should be undertaken in the other oceans, and especially in the oceans of the southern hemisphere, with special efforts made to place instruments aboard ships on uncon- ventional routes and on selected government vessels. This XBT program should be supplemented by buoy measurements in selected locations

A NATIONAL CLIMATIC RESEARCH PROGRAM 75 and by xBT’s launched from aircraft on meridional flight paths in the more inaccessible ocean areas. Expand the present data buoy programs now under way by NOAA and others, so that the volume and heat transport of the major ocean cur- rents can be monitored. Suitably deployed bottom-mounted sensors, moored buoys, or both should be used to monitor the transport of the Gulf Stream, Kuroshio, and Antarctic circumpolar currents in selected locations, such as is planned for the Drake Passage as part of the Inter- national Southern Ocean Studies (1sos). The water mass balance of individual basins such as the Arctic should also be monitored. Monitor the complete temperature structure in selected regions of the ocean, such as meridional cross sections through the major gyral circulations. The several long-term local observational series (such as the Panulirus, Plymouth, and Murmansk sections) should be main- tained and new efforts started in regions of special interest. Monitor the vertical salinity structure of the oceans in those high- latitude regions where salinity plays an important role in determining the density field of the upper ocean layers. Near-surface salinity is also important in regions where ocean bottom water is formed, such as in the Weddell Sea. This might best be done by a combination of moored buoys and ship observations. Monitor the large-scale distribution of sea level by the use of an expanded network of tide gauges. Such a measurement program at island sites in the equatorial Pacific is being undertaken in connection with NORPAX, and other measurements are planned in the Indian Ocean as part of the Indian Ocean Experiment (INDEX). Radar altimeters such as those proposed for the SEASAT-A satellite should also be useful for this purpose. Monitor the oceanic chemical composition at selected sites and in selected sections, including the concentrations of dissolved gases and trace substances. Such measurements now being performed as part of the GEOSECS program should be expanded and continued. Cryospheric Indices In view of the great influence of snow and ice cover on the surface energy balance, further efforts should be made to Monitor the distribution of sea ice in the polar oceans and the ice in major lakes and estuaries. Efforts should also be made to measure as many as possible of the ice’s physical properties by remote sensing. Devote further study to the current mass budgets of the Antarctic and Greenland ice caps, from both glaciological field observations and

76 UNDERSTANDING CLIMATIC CHANGE from airborne and satellite measurements. Such observations should include changes in ice-edge locations, in the numbers and sizes of ice- bergs, and in the ice caps’ firnline height. Methods for the remote aerial sensing of surface temperature and possibly ice accumulation rate should also be further developed. Extend the monitoring of the movement and mass budget of se- lected mountain glaciers. Monitor the extent, depth, and characteristics of worldwide snow cover. Surface and Hydrologic Indices In association with the monitoring of the elements of the surface heat balance, and of the various oceanic and cryospheric climatic indices, initially lower priority but neverthe- less important efforts should be made to Monitor the natural changes of surface vegetative cover, possibly by observations from earth resources satellites. Monitor the variations of soil moisture and groundwater, possibly by satellite-based techniques. Monitor the flow and discharge of the major river systems of the world. Monitor the level and water balance of the major lakes of the world. Monitor the total precipitation (especially rainfall over the oceans), possibly by satelliteborne radar observations and surface gauges. Composition and Turbidity Indices In view of the role that at- mospheric constituents and aerosols play in the heat balance of the atmosphere, further efforts should be made to Monitor the chemical composition of the atmosphere at a number of sites throughout the world, with particular reference to the content of CO,. Measurements such as those at Mauna Loa should be con- tinued and extended to additional selected sites. The composition of the higher atmosphere should also be periodically determined, especially the water vapor in the stratosphere and the ozone concentration in the stratosphere and mesosphere. Monitor the total aerosol and dust loading of the atmosphere, to- gether with determinations of the vertical and horizontal aerosol distri- bution, by an extension of such programs as NCAR’s Global Atmospheric Aerosol Study (GAARS). In addition to turbidity measurements, the aerosol particle-size distribution and optical properties should be de- termined when possible. Efforts should also be made to monitor the

A NATIONAL CLIMATIC RESEARCH PROGRAM 77 occurrence of large-scale forest fires and volcanic eruptions, together with estimates of their particulate loading of the atmosphere. Anthropogenic Indices In view of man’s increasing interference with the environment, further efforts should be made to Monitor the addition of waste heat into the atmosphere and ocean. Although the present levels of thermal pollution are relatively small on a global basis, steadily increasing levels of energy generation pose a threat to the stability of at least the local climate and possibly the larger-scale climate as well. Therefore both the local thermal discharges of power generating and industrial facilities should be monitored, along with the thermal pollution from urbanized areas. Monitor the climate-sensitive chemical pollution of the atmosphere and ocean. Measurement programs such as those of the Environmental Protection Agency and the Atomic Energy Commission should be ex- panded on a global basis and extended to the oceans. Monitor the changes of large-scale land use, including forest clear- ing, irrigation, and urbanization, possibly by the use of earth resources satellites. Summary of Climatic Index Monitoring A summary of the elements of the recommended program is given in Table 6.1. Here we have not made an assessment of the required accuracy of the various monitored indices, nor has the capability of presently available instrumentation been thoroughly reviewed. Further analysis is also needed to determine the characteristic variability of each climatic index. In general, the surface heat and hydrologic balances should be monitored with an accuracy of a few percent, so that space- and time-averaged climatic statistics will have at least a 5 percent accuracy. It is important that this monitoring activity be undertaken on a continuing and long-term basis for at least two decades in order to assemble a meaningful body of data for climatic analyses. As noted below, these efforts should be coordinated on an international scale and be a part of an international climatic program. Research Needed on Climatic Variation We here outline the research that we believe needs to be performed, in terms of model development, theoretical research, and empirical and diagnostic studies. While research in some of these areas is already under way as part of GARP activities in anticipation of the FGGE, these

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80 UNDERSTANDING CLIMATIC CHANGE efforts are the necessary ingredients of the much broader climatic research program that we recommend be carried out in the years ahead. Theoretical Studies of Climatic Change Mechanisms We recognize the importance of theoretical studies in a problem as complex as climatic variation and the essential interaction that must take place between theory and the complementary observational and numerical modeling studies. Our present knowledge of the mechanisms of climatic variation is SO meager, however, and progress in this area so difficult to anticipate, that any recommendations are subject to modification as new avenues of attack open up or as old ones prove fruitless. There are, however, certain fundamental problems to which further study must be directed: The question of the degree of predictability of (natural) climatic change must be given further theoretical attention. While the local details of weather do not appear to be predictable beyond a few weeks’ time, the consequences of this fact for climatic variations are not clear. In such studies a clear definition of the internal climatic system needs to be made, and particular attention must be given to the roles of the ocean and ice. This question has an obvious and important bearing on our eventual capability to predict climatic variation. The related question of the possible intransitivity of climatic states needs further study, again with particular attention to the oceans and ice. The whole question of climatic variation may be viewed as a stability problem for a system containing elements with very different time constants, and support should be given to such theoretical ap- proaches. Theoretical research should be directed to the nature and stability of the various climatic feedback mechanisms identified earlier, par- ticularly those involving the sea-surface temperature, cloudiness, albedo, and land-surface character. Further theoretical research should be directed to the general prob- lem of the development of statistical-hydrodynamical representations of climate and to the parameterization of transient phenomena on a variety of time and space scales. Additional theoretical studies should also be made of specific climatic phenomena, such as drought and the growth of arid regions, ice ages and the stability of polar ice cover, and the effects of global pollution from natural and artificial sources. Atmospheric General Circulation Models The global dynamical models of the atmospheric general circulation (or GCM’s) that have been

A NATIONAL CLIMATIC RESEARCH PROGRAM 81 developed in recent years represent the most sophisticated mathe- matical tools ever available for the study of this system and are the testing grounds for many of our theoretical ideas. The latest versions of these models (see Appendix B) embody much of the physics that governs the larger scales of atmospheric behavior, along with physical parameterizations of smaller-scale processes. In addition to the simula- tion of the free-air temperature, pressure, wind, and humidity distribu- tions over the globe with a resolution of several hundred kilometers, such atmospheric models provide solutions for the various components of the heat and moisture balances, such as the fluxes of shortwave and long-wave radiation, sensible heat flux, evaporation, precipitation, sur- face runoff, and ground temperature. The surface boundary conditions usually assumed are the distributions of sea-surface temperature and sea ice, and the assumption of a heat balance over land surfaces. After a spin-up period of a month or so during which the temperature comes into statistical equilibrium (with the sun’s heating and the ocean surface temperature), the average global climate simulated by such models shows a reasonable resemblance to observation; several examples of such simulations are shown in Appendix B. In order to improve the fidelity of such global atmospheric models for the simulation of the various processes of climatic change, and to ensure their increased availability for the conduct of climatic experi- ments, efforts should be made to Improve the models’ treatment of clouds, especially those of the nonprecipitating high-altitude cirrus and the low-level stratus type. Account should be taken of the liquid-water content of clouds and the full interaction of clouds with atmospheric radiative transfer. Attention should also be given to the modeling of cloud evaporation and advection. Improve the parameterization of turbulent, convective, and mesoscale processes by comparing the performance of alternative schemes against appropriate observations of the fluxes of heat, moisture, and momentum. Particular attention should be given to improved parameterizations of the fluxes within the surface boundary layer, to the parameterization of cumulus convection, and to the treatment of energy flux by gravity waves. Improve the treatment of ground cover and land usage in the calcula- tion of the surface heat and moisture balances. Particular attention should be given to the improvement of the prognostic schemes for snow cover, as this may prove of importance in seasonal climatic variations. Parameterize the role of aerosols in such models, so that the effects

82 UNDERSTANDING CLIMATIC CHANGE of both natural and anthropogenic particulates on the heating rate of the atmosphere may be determined. Improve the numerical resolution of the solutions by the use of finer grids (or the use of graded meshes in regions of special interest) and increase the computational efficiency by the development of more accurate numerical algorithms and improved solution methods. Simulate the annual cycle of atmospheric circulation with models using observed forcing functions to obtain the surface fluxes of heat, momentum, and water vapor. Such numerical integrations are necessary in order to ensure adequate model calibration and to simulate climatic statistics for the atmosphere. Determine the noise level or sensitivity of the model-simulated climate to changes in the initial conditions (including random errors) and to changes in the parameterizations of the model. Such studies are neces- sary in order to determine the physical significance of numerical climate- change experiments made with atmospheric models. Oceanic General Circulation Models The oceanic general circulation models (or GCM’s) are generally at a less advanced stage of develop- ment than their atmospheric counterparts and have only recently been extended to the global ocean (see Appendix B). With the surface bound- ary conditions of specified thermal forcing and wind stress (plus the kinematic and insulated wall boundary conditions at the bottom and lateral sides of the ocean basin), such models simulate with fair ac- curacy the large-scale distributions of ocean temperature and current with a resolution of several hundred kilometers. If the density structure is specified from observations, a model will spin up from rest in a few months’ time and show a reasonable correspondence with observed drift current patterns at the surface. The simulated transport of the major western boundary currents in the models is generally less than that indicated by available observations but nevertheless quantitatively more accurate than the predictions of previous theories. Areas of coastal and equatorial upwelling show the same strong relationship to the surface wind-stress pattern in the model as is observed in the real ocean. The more relevant calculation with respect to climate modeling is one in which the density field as well as the velocity field is predicted from boundary conditions that determine the vertical flux of momentum, heat, and water at the ocean surface. However, this problem involves much longer time scales—the spin-up time of a prestratified ocean is of the order of two or three decades; but if changes in the abyssal thermal structure are to be predicted, then the “turnover” time of the

A NATIONAL CLIMATIC RESEARCH PROGRAM 83 ocean is the order of several centuries. Preliminary results (see, for ex- ample, Bryan and Cox, 1968) show that such models can successfully simulate the gross features of the density structure of the world ocean, although more detailed calculations must be made to provide a critical test. In order to improve the accuracy of ocean models and to lay the foundation for their successful coupling with atmospheric models, efforts should be made to Improve our knowledge of the structure, behavior, and role of mesoscale eddies in the ocean. In the atmosphere there is a peak in the kinetic energy spectrum observed at wavelengths of a few thousand kilometers, whereas in the ocean the peak kinetic energy is in eddies that have a radius (or quarter-wavelength) of the order of 10? km. Thus an ocean circulation model requires about an order of magnitude greater horizontal resolution to resolve its most energetic eddies than does an atmospheric GcM. Further field studies such as those conducted under the Mid-ocean Dynamics Experiment (MODE), the North Pacific Experiment (NORPAX), and those planned under the joint Soviet— American (POLYMODE) experiment, are needed to determine the transfer of heat and momentum by such eddies. Such observational experiments should provide the basis for the interpretation of high-resolution nu- merical experiments, which are necessary to resolve the details of the eddy motions and to establish their role in the oceanic general circulation. Intensify research on the parameterization of turbulent and meso- scale motions both in the surface mixed layer and the deeper ocean layers, including thermohaline convection, so that the results of field measurements may be usefully incorporated into global ocean circulation models. Improve the prediction of sea-surface temperature and heat transport by the inclusion of the depth and structure of the surface mixed layer as a predicted variable in oceanic general circulation models. This should include experiments on the numerical forecasting of the oceanic surface layer, as driven by observed surface conditions, and the forma- tion and behavior of pools of anomalously warm or cold water. Simulate the annual cycle of sea-surface temperature and currents with models using observed forcing functions to obtain the surface fluxes of momentum, heat, and water (precipitation minus evaporation). Such numerical integrations must be carried out over several annual cycles, in order to ensure adequate model calibration and to simulate climatic statistics for the ocean.

84 UNDERSTANDING CLIMATIC CHANGE Subject the ocean models to the same kind of diagnostic testing and sensitivity analysis as performed for atmospheric models, in order to determine the roles of possible oceanic feedback processes and the levels of predictability associated with various oceanic variables. Apply high-resolution versions of global oceanic circulation models (or regional versions thereof) to the study of the behavior of local in- tense currents, such as the eddying motion of western boundary cur- rents and the structure of equatorial currents. Develop more accurate models of sea ice, which include the effects of salinity and the dynamic and thermodynamic factors governing the distribution of the polar ice packs. The data base being assembled by the Arctic Ice Dynamics Joint Experiment (AIDJEX) in the Beaufort Sea should be useful in the design of models that can predict those properties of the polar ice pack that are important in the surface heat balance, such as the ice thickness and the occurrence of open-water leads. Search for new computational algorithms for predicting oceanic circulation that will provide the greatest accuracy for the least pos- sible cost. At present, the methods used in modeling the ocean are similar to those used in the atmospheric GcMm’s. The presence of lateral boundaries and the need to resolve mesoscale motions may make alternative numerical methods of particular use in numerical ocean models. Coupled Global Atmosphere—Ocean Models Tests of climatic change extending over one or more years are not adequate unless they are made with a model of the coupled ocean—atmosphere system. While the un- coupled atmospheric and oceanic GCM’s are useful for many purposes, the thermal and mechanical coupling between the ocean and atmosphere is fundamental to climatic variation. We note that a global ocean model may require only a fraction of the computational effort needed by an atmospheric GCM of the same resolution but emphasize that care must be taken to avoid erroneous drift in the simulated climate due to sys- | tematic biases in the model or in the oceanic initial state. Assuming that coupled models (CGCM’s) will incorporate the develop- ments and improvements recommended above for the separate at- mospheric and oceanic models, emphasis should be given to the follow- ing research with CGCM’s: Investigation of the simulated climatic variability, on seasonal and annual time scales, of all climatic variables of the coupled system, including the simulated exchange processes at the air—sea interface.

A NATIONAL CLIMATIC RESEARCH PROGRAM 85 Of particular importance in the coupled models is the simulation of the sea-surface temperature, as this has a key role in the evolution of the system. This will require integration over many years of simu- lated time in order to generate adequate climatic statistics and to examine the models’ stability. Particular attention should be given to evidence of climatic trends and intransitivity in the numerical solu- tions. The statistics of such simulations with CGCM’s will also prove valuable in the calibration of statistical climate models. The sensitivity of the climate simulated by coupled models should be systematically examined in experiments extending at least through an annual cycle. These studies should include the climatic consequences of uncertainties in the simulations’ initial state (including random errors), in the parameterization of the various physical processes (such as convection, cloudiness, boundary-layer fluxes, and mesoscale oceanic eddies), and in the computational procedures. Such studies are neces- sary in order to establish the characteristic noise levels of the models and are of great importance in the use of the models for climate ex- periments. A program of climate change hypothesis testing should be under- taken with coupled models, as soon as their stability and calibration are reasonably assured. This should include examination of the various feedback mechanisms among components of the climatic system, such as ice and snow, cloudiness, sea-surface temperature, albedo, radiation, and convection. The coupled models should be used in a program of long-range integrations with observed initial and boundary conditions, in order to assess both their overall fidelity and their usefulness as long-range or climatic forecasting tools. Although not a research task in itself, special efforts should be made to appropriately store, analyze, and display the rather staggering amounts of data generated during the integration of CGCM’s, so that subsequent diagnosis can be performed efficiently. Statistical-Dynamical Climate Models Although the coupled numeri- cal models of the global circulation offer the most comprehensive and detailed solutions available, even with the fastest computers envisaged relatively few century-long climatic simulations will be possible, and it is likely that none will be performed for periods as long as a millenium. Such models will therefore find their greatest use in climatic research in the exploration of the character of relatively short-period (say annual to decadal) climatic variations and in the calibration of other, less- detailed models. We therefore emphasize that statistical-dynamical

86 UNDERSTANDING CLIMATIC CHANGE climate models (defined as those in which the structure and motion of the individual large-scale transient disturbances are not resolved in detail) will have to be used to simulate the longer-period climatic variations. While such models provide less resolution of the details of climatic change, they may display less climatic noise than do the global circulation models. In order to ensure the availability of the hierarchy of models needed in a comprehensive research program on climatic change, the following research should be carried out: Statistical-dynamical models of the coupled time-dependent at- mospheric and oceanic circulation should be constructed and calibrated that embody suitable time- and space-averaged representations of the climatic elements. In their extreme form, such models address the steady-state globally averaged quantities, while others, for example, consider time-dependent zonally averaged variables. Further efforts should be made to represent the climatically important land—sea distri- bution in such models and to calibrate them systematically against observations as well as against other climatic models. Simulation of climatic variation over extended time periods should be made by the integration of suitably calibrated time-dependent statistical-dynamical models. Depending on the time range, appropriate components of the climatic system’s atmosphere, hydrosphere, cryo- sphere, lithosphere, and biosphere should be introduced, along with appropriate variations of the external boundary conditions (see Figures 3.1 and 3.2). ! Coupled time-dependent models in which the global circulation is_ represented by low-order spatial resolution should also be further de- veloped, such as those using a limited number of orthogonal components or spectral modes. Coupled models should be constructed and calibrated that embody new forms of time-averaged representations of the climatic system. We recognize that the parameterization of the effects of the transient eddies poses a difficult problem in statistical hydrodynamics and urge that full use be made of both model-generated and observed statistics, as well as of theory, to develop a variety of such models for different types and ranges of time averaging. . In each type of statistical-dynamical model, particular attention should be given to the inclusion of the ocean and ice. In such models, attention should also be given to the possibility of treating the at- mosphere statistically while simulating the ocean in detail and perhaps of treating both the atmosphere and ocean statistically while simulating

A NATIONAL CLIMATIC RESEARCH PROGRAM 87 the growth of ice sheets in detail. It is particularly important that such models be calibrated with respect to both the mean and variance of the climatic elements and that their stability and sensitivity be systematically determined. Empirical and Diagnostic Studies of Climatic Variation Although we have recommended some diagnostic and empirical studies in connection with the analysis of instrumental and proxy climatic data, such studies should also be made on a phenomenological basis as part of the climatic analysis and research program. As the record of past climates is made more complete, there will be increased opportunity to carry out such investigations with both instrumental and proxy data. In particular: Studies should be made of the temporal and spatial correlations among various data, including regional and global estimates of the trends of key climatic elements such as temperature and precipitation. Further empirical studies should be made of the surface oceanic variables of temperature, salinity, sea level, and sea ice and of the planetary heat balance, albedo, and cloudiness from satellite-based ob- servations. The studies of Bjerknes (1969), Kukla and Kukla (1974), Namias (1972a), and Wyrtki (1973) are examples of the sort of empirical synthesis that can be achieved and should be systematically extended to other regions of the world and to other climatic variables. In these efforts, particular attention should be given to the various pos- sible climatic feedback processes and to the forcing functions of the general circulation. Here the diagnostic use of climatic models should prove valuable. Further studies should be made of the statistical characteristics of climatic data, both observed and simulated. Power spectrum analyses should be made for as many variables and locations as possible, and with the longest records available, as the spectrum’s “redness” has an important bearing on questions of climatic cycles and climate prediction. Needed Applications of Climatic Studies Although closely related to the climatic data analysis and climatic research recommended above, the needed applications of climatic studies (and of climate models in particular) are so important that they warrant identification as a separate component of the program. It is in these applications that the program reaches its fruition, and if attention to them is delayed until our understanding is complete or our models perfect, they may never be undertaken. With due regard

88 UNDERSTANDING CLIMATIC CHANGE for scientific caution, we believe that the time has come for a vigorous attack on the areas of climate model application described below. Simulation of the Earth’s Climatic History The evidence presented in Appendix A (and summarized in Chapter 4) shows that the climatic history of the earth has been remarkably variable and that this history provides information that is of value in the study of present and possible future climates. The data assembled by paleo- climatologists show conclusively that the flora, fauna, and surface characteristics of many regions of the world have often been markedly different in past times than they are today. Compared with this long- period panorama, instrumental observations provide a frustratingly short record. It is at this juncture that the intersection of paleoclimatic and numeri- cal modeling studies offers the most promise: the global climatic models have the potential ability to simulate at least a near-equilibrium ap- proximation to past climates subject to the appropriate geological boundary conditions, while the paleoclimatic records can be used as verification data. Initial efforts in this direction have already begun (see Chapter 5), and we may expect increasing insight into the nature of past climates as both the models and proxy data base improve. In order to explore the nature of past climates systematically and to lay the foundation for the study of possible future climates, the fol- lowing studies should be made: The geophysical boundary conditions at a number of selected times in the history of the earth should be systematically assembled with a view toward their use in climate models. This should include global data on the continental land-mass positions and elevations, sea-level ice-sheet elevations and margins, sea-ice extent, soil type and vegeta- tive cover, and surface albedo. Estimates should also be made of the earth’s rotation rate and of the solar insolation (due to orbital parameter changes). The selection of the time period might be based on criteria such as the occurrence of an ice age, the distribution of the continents and mountains, the opening or closing of a major oceanic passage, or the large-scale flooding or draining of lowlands. Periods of particular climatic stress such as indicated by the disappearance of species might also be considered. The various proxy records of temperature, salinity, and precipita- tion should also be systematically assembled for the same selected

A NATIONAL CLIMATIC RESEARCH PROGRAM 89 times, to serve as verification data for the coupled climate models’ simu- lations and as possible input or boundary conditions for uncoupled models. Dynamical global models should be used to simulate the quasi- equilibrium paleoclimate at selected times in the past when the boundary conditions external to the ocean—atmosphere system can be reasonably well specified. Such experiments should be focused on times when the global climate might be expected to be in a particularly interesting State (as judged from the available geological and proxy evidence) or when the climate might be expected to be in the process of changing most rapidly from one characteristic regime to another. The simulations should extend long enough to accumulate realistic climatic statistics and should use the assembled paleoclimatic data for vertification. By using part of the paleoclimatic evidence (namely, the sea-surface temperature) as a boundary condition, atmospheric GCM’s may also be used for this purpose. Coupled statistical-dynamical models, or other coupled climate models, should be used to simulate the time-dependent climatic evolu- tion between the various “equilibrium” states identified above. For this application the dynamics of ice sheets should be incorporated into the coupled ocean—atmosphere models and note taken of the possible time dependence of the remaining boundary conditions, such as solar radiation and continental drift. In particular, the astronomical changes of seasonal radiation resulting from the variation of the earth’s orbital parameters should be incorporated in a climate model, and the resulting simulated climatic changes compared with the paleoclimatic evidence. This recommendation parallels one made earlier in connection with the development of the statistical-dynamical models themselves. Studies should be made of possible methods to accelerate the simu- lation of quasi-equilibrium climatic states in the global circulation models, so that realistic statistics can be obtained without integration over long time periods. Exploration of Possible Future Climates One of the most important applications of climate models is the sys- tematic conduct and evaluation of climatic experiments designed to explore the effects of either natural or anthropogenic changes in the system. It is from such model-based experiments, calibrated with respect to observed behavior, that we must draw our conclusions as to how the climatic system operates and on which we should base our projec-

90 UNDERSTANDING CLIMATIC CHANGE tions of likely future climates. The program in this area should include the determination of the global climatic effects of the following (with both coupled global circulation models and parameterized models): The changes of incoming solar radiation. These experiments should be performed with coupled models, in view of the dominance of the oceans in the planetary heat storage, and should include changes in both the amount and spectral distribution of solar radiation. The changes of land surface character and albedo, as introduced by deforestation, urbanization, irrigation, and changes of agricultural practices. The changes of cloudiness. These experiments should consider the effects of the introduction or removal of both condensation and freezing nuclei and the production of artificial clouds by aircraft. The changes of evaporation, as introduced by reservoirs, irrigation, and transpiration. The disposal of waste heat. These experiments should be made with coupled models and should include a broad range of rates and locations of heat release in both atmosphere and ocean. The introduction of dust and particulates into the troposphere, the stratosphere, or both. These experiments should consider the effects of scattering, absorption, fallout, and scavenging by precipitation and should be designed to simulate the effects of both man-made pollution and volcanic dust. The partial or complete removal of the Arctic sea ice or the Antarctic ice sheet. These experiments should be performed with a coupled model that includes the mass and heat budget of pack ice. The diversion of ocean currents. These experiments should be per- formed with coupled models. In climatic simulations of this kind the physical basis of each experi- ment should be carefully examined in order to ensure the adequacy of the particular model or models to be employed. The experiments sug- gested above are those that we believe should be performed as part of the climatic research program, as they involve processes or areas of likely maximum climatic sensitivity or changes to which the climate’s response is relatively uncertain, and/or they represent conceivable (or in some cases likely) future alterations by nature or by man. It is important in such climatic experiments that the synoptic and statistical significance of the results be carefully examined. This should include the repetition of the experiment under slightly different (but admissible) conditions to determine its stability and noise level and the

A NATIONAL CLIMATIC RESEARCH PROGRAM 91 analysis of independent simulations with other models. Only in this way can we hope to accumulate the necessary experimental knowledge on which to base our expectations of future climatic states. This, together with the knowledge gained from the observational and research por- tions of the program outlined above, will lay the scientific foundation for what might be called climatic engineering. Development of Long-Range or Climatic Forecasting A third important area of application of climatic studies is the problem of long-range or climatic forecasting on time scales of months, seasons, and years. There have been numerous studies of this question almost since the beginning of recorded observations. This research has not solved the problem but has at least identified some of its ingredients. We believe that further efforts should be made to systematically acquire the data and perform the research necessary to attack this problem anew, especially with the aid of climatic models. Clearly the demand for climatic or long-range forecasts greatly exceeds present capability. An accurate prediction of the temperature or rainfall anomaly over, say, the central plains of North America or over the Ukraine a decade, a year, or even a season in advance would be of great value. And even a somewhat less accurate (but reliable) prediction of the likelihood of such anomalies would be of great use to those involved in agriculture, energy supply allocation, and commerce. At present, the skill of the experimental long-range outlooks prepared by the National Weather Service for the 30-day temperature anomaly at some 100 USS. cities is only 11 percent greater than chance and only 2 percent greater than chance for the 30-day precipitation anomaly. These forecasts are principally prepared by a mixture of empirical and statistical methods and have also been applied to the seasonal predic- tion of temperature (Namias, 1968). The ability of numerical models to perform useful long-range or climatic forecasting (i.e., forecasts over monthly, seasonal, or annual periods) has not been systematically examined because of the large amounts of computation involved and the unavailability of suitable models. Such efforts must also contend with the crucial questions of climatic predictability, noted in Chapter 3, and the long-range stability of the models themselves. We believe that further attention should be given to these problems, using the expanded data base, the coupled dynamical models, and the new computer resources called for in the climatic program. We therefore recommend that

92 UNDERSTANDING CLIMATIC CHANGE The coupled global circulation models should be systematically ap- plied to the preparation of a series of long-range forecasts using ob- served initial conditions wherever possible. These integrations should extend over at least several seasons, well beyond the limit of local predictability. Appropriate climatic statistics should be drawn from these integrations and systematically compared with the observed variations of all the climatic elements available and statistically analyzed for pos- sibly significant trends of regional climatic anomalies. The statistical-dynamical models and other appropriate members of the parameterized climate model hierarchy should be used in the preparation of similar long-range forecasts. Systematic empirical and diagnostic studies of longer-period varia- tions in the climatic system should be undertaken with the aid of models and the expanding data base of monitored variables. Assessment of Climate’s Impact on Man While the above efforts are concerned with the physical aspects of the problem of climatic variation, a climatic research program should also include studies of the impact of climate and climatic change on man himself; this is best done with the guidance and insight provided by climate models. While many studies have been made in this important area, such as those of the Department of Transportation’s Climatic Impact Assessment Program (CIAP), more comprehensive research should be undertaken on a long-term basis. These studies may be characterized as seeking answers to such questions as “What is a 1-degree change of mean winter temperature worth, after all?” or even “Climatic variation: so what?” The study of the impacts of climatic variations on man is also a way of establishing priorities for research. Climate and Food, Water, and Energy That climate has a dominant influence on agricultural food production, water supply, and the generation and use of energy is generally recog- nized. The kinds and amounts of crops that may be grown in various regions, the water available for domestic, agricultural, and industrial use, and the consumption of electrical energy and fossil fuels all depend in large measure on the distribution of temperature, rainfall, and sun- shine. During the global warming of the first part of this century, for example, the average length of the growing season in England (as measured by the duration of temperatures above 42°F) increased by

A NATIONAL CLIMATIC RESEARCH PROGRAM 93 two to three weeks and during the more recent cooling trend since the 1940’s has undergone a comparable shortening (Davis, 1972). Al- though Maunder (1970), Johnson and Smith (1965), and others have surveyed the vast literature on the effects of climatic change on man, further quantification of these effects is needed, particularly as a func- tion of the time and space scales of atmospheric variability. Accordingly, we recommend that research be devoted to the following: The systematic assembly from both national and international sources of data on worldwide food production and the analysis of their re- sponse and sensitivity to variations of climate on monthly and seasonal time scales. Such analyses should then be used to model or simulate the total agricultural response to hypothetical climatic variations. We note that in some cases it may be the variance or extremes of climate, rather than the averages themselves, that will prove to be the more important factor. An applied systems study of this problem has been recently initiated by R. A. Bryson and colleagues at the University of Wisconsin, with the aim of developing predictive relationships between climate and food supply, which will be useful for policy decisions. The systematic assembly of worldwide data on available water supply, both from rainfall and snowpack, and its patterns of use and loss. Analysis should then be undertaken of the water supply system’s re- sponse and sensitivity to variations of climate and simulation models constructed. The systematic assembly of worldwide data on the production and use of energy and the determination of its response and sensitivity to climatic variations. As in the cases of food and water, simulation models should be constructed, so that the consequences of various patterns of hypothetical climatic change can be estimated. Social and Economic Impacts Although it is difficult to obtain useful measures of the social and eco- nomic impacts of climatic change, increased attention should be given to this aspect of the problem. This is a problem in which the “noise level” of nonclimatic factors is very high and for which the physical scientist’s knowledge must be supplemented by the skills and methods of social and political scientists. The goal of this research should be the development of an overall model of societal response to climatic change. This is an area in which international cooperation should be sought, and efforts such as those now being proposed by the International

94 UNDERSTANDING CLIMATIC CHANGE Federation of Institutes of Advanced Study should be supported and expanded. THE PLAN Our recommendations for the planning and execution of the climatic research program outlined above are given here in terms of what we believe to be the appropriate subprograms, the necessary facilities and support, and the desirable timetable for both the short-range and long- range phases. We also offer some observations on the program’s ad- ministration and coordination, although we recognize that a program of this scope will require much further planning and that the support and cooperation of many persons and agencies will be necessary for its successful execution. Subprogram Identification In a program as broad as that envisaged here, it is convenient to think in terms of a number of components or subprograms, each concerned with a specific portion of the overall effort. Such subprograms also represent the necessary division of effort for the practical execution of the program. The NcrRP itself should ensure the coordination of the various subprograms and maintain an appropriate balance of effort among them. Climatic Data-Analysis Program (CDAP) In order to promote the extensive assembly and analysis of climatic data outlined above, we recommend that a Climatic Data-Analysis Pro- gram (CDAP) be established as a subprogram of the NcRP. The purposes of this subprogram are to facilitate the exchange of data and informa- tion among the various climatic data depositories and research projects and to support the coordinated preparation, analysis, and dissemination of appropriate climatic statistics. Climatic Index Monitoring Program (CIMP) In order to promote the monitoring of the various climatic indices out- lined above, we recommend that a Climatic Index Monitoring Program (CIMP) be established as a second subprogram of the NCRP. The pur- poses of this subprogram are to support and coordinate the collection of

A NATIONAL CLIMATIC RESEARCH PROGRAM 95 data on selected climatic indices and to ensure their systematic dis- semination on a timely and sustained basis. Climatic Modeling and Applications Program (CMAP) In order to promote the construction and application of the climatic models outlined above, we recommend that a Climatic Modeling and Applications Program (CMAP) be established as a third subprogram of the NCRP. The purposes of this subprogram are to support and co- ordinate the development of a broad range of climatic models, to sup- port necessary background scientific research, and to ensure the sys- tematic application of appropriate models to the problems of climatic reconstruction, climatic prediction, and climatic impacts. Facilities and Support The availability of adequate facilities and support and the design of coordinating mechanisms are necessary to carry out the various sub- programs recommended for the NcRP and should be given careful con- sideration. Of primary importance are the roles of climatic data-analysis facilities and research consortia, the needed high-speed computers, and the required levels of funding. Climatic Data-Analysis Facilities To assist in the implementation of both the Climatic Data Analysis Pro- gram (CDAP) and Climatic Index Monitoring Program (CIMP), we recommend the development of new climatic data-analysis facilities at appropriate locations, including linkage to the various specialized data centers and climatic monitoring agencies by a high-speed data-trans- mission network. Such facilities should have access to machines of the highest speed and capacity available and be staffed by specialists in data analysis, transmission, and display. Collection of certain climatic data by a group of specialized facilities appears more desirable than does collection of all data by a single centralized facility. We envisage these facilities as performing the bulk of the recom- mended cDAP. This would include the inventory, compilation, processing, analysis, and documentation of both conventional and proxy climatic data. Close working cooperation is envisaged with specialized data depositories; for conventional atmospheric and oceanic data these include NOAA’s National Climatic Center and National Oceanographic

96 UNDERSTANDING CLIMATIC CHANGE Data Center, for satellite data the National Environmental Satellite Service, for glaciological data the Geological Survey’s Data Center A in Tacoma, for ice-core data the Army’s Cold Regions Research and Engi- neering Laboratory, for marine cores Columbia University’s Lamont- Doherty Geological Observatory, and for pollen and tree-ring data the universities of Wisconsin and Arizona. We also envisage the data-analysis facilities as playing a prominent role in the CIMP and in the processing, analysis, and dissemination of the results on as nearly a real-time basis as possible. Certain of the facilities could serve as global climatic “watchdogs” and might have a resident scientific staff to perform diagnostic research as appropriate. Climatic Research Consortia and Manpower Needs We envisage the broad range of research and analysis recommended here as being best performed by a number of institutions and groups. This is desirable in order to ensure the breadth of viewpoint and diversity of approach necessary in a problem as close to the unknown as is cli- matic variation. An attempt to carry out all the recommended activities and research by a single institution would in any case be a practical impossibility. Research on climate and climatic variation at the present time is principally performed in governmental laboratories and in a variety of research projects in universities and other institutions, usually with the support of the federal government. Chief among the laboratories con- cerned with elements of the climatic problem are NOAA’s Geophysical Fluid Dynamics Laboratory, NoAa’s National Environmental Satellite Service and Environmental Data Service, NSF’s National Center for Atmospheric Research, and Nasa’s Goddard Institute for Space Studies. More specialized research on problems related to climate is also per- formed by the U.S. Geological Survey and by the operational services and laboratories of the U.S. Army, Navy, and Air Force. Many of the climate-related research projects in universities and other institu- tions are supported by the National Science Foundation through its programs for atmospheric, oceanic, and polar research; by DOT’s Cli- matic Impact Assessment Program; and by ARPA’s Climate Dynamics Program. These include the various Quaternary research groups, geo- logical and oceanographic laboratories, numerical modeling groups, and polar studies and environmental institutes. Each of these efforts makes a contribution to the national climatic research picture, and they represent a valuable reservoir of experience

A NATIONAL CLIMATIC RESEARCH PROGRAM 97 and talent. In order to promote greater cooperation and exchange, to ensure an appropriate balance of effort, and to give such research the needed stability and coherence, we recommend that efforts be made to coordinate present research more effectively as parts of a national climatic research program. We believe that this can be achieved best by the formation of cooperative associations of existing climatic research groups and the initiation of whatever new research efforts may be re- quired as parts of such associations. We accordingly recommend the formation of a number of climatic research consortia among various research groups as appropriate to their interests, with each such con- sortium having links to computing facilities of the highest speed and capacity available. Such research consortia would serve as valuable coordinating mechanisms for the broad range of climatic research en- visaged in the Climatic Modeling and Applications Program (CMAP), as well as giving both coherence and flexibility to the NCRP as a whole. The present MODE, NORPAX, and CLIMAP programs may serve as useful examples for such consortia. As the national program develops, the possible need for new institutional structures or facilities should be- come clear. Our recommendations reflect the consensus that maximum use should be made of existing institutions while further consideration is given to the possible need for their expansion. Aside from institutional arrangements, however, we believe that the proposed research program unquestionably calls for the initiation and support of new mechanisms to provide an expanded base of appro- priately trained scientific and technical manpower. We accordingly recommend that programs for technical training be developed and that both predoctoral and postdoctoral fellowships in the broad area of climatic research be established as soon as possible. Computer Requirements The required access to high-speed computers has been alluded to several times in the discussion of the recommended program. Although it is difficult to make precise projections, the volume of data processing involved in the analysis and monitoring portions of the program alone indicate that a dedicated machine of at least the cpc 7600 class is required for the implementation of the cDAP and cimp. The computer needs of the research consortia and of the other research groups involved in the modeling portions of the program are even more demanding, in view of the variety of the needed climatic models and tests and the number and the length of the necessary climatic simulation experiments

98 UNDERSTANDING CLIMATIC CHANGE and applications. Our estimates of the NCRP’s overall computer require- ments are given in Table 6.2 and call for a very significant increase over present levels of computer usage. If anything, these estimates may be too low. In its computer planning, NCAR has estimated a climate-related usage of several coc 7600 units by 1980 for the needs of NCAR and the university community it serves (W. M. Washington, personal communication), while the installation of the TI-ASC system at GFDL in 1974 will likely significantly raise their machine usage for climatic studies. As shown in Table 6.2, it is estimated that climatic data analysis and monitoring will require the full-time use of at least one fourth-generation machine, and that climatic modeling and applications will require the full-time use of at least one fifth-genera- tion machine. We therefore recommend that machines of the cpc-7600 class be secured as soon as possible for the use of the data-analysis facilities and the associated elements of the CDAP and CIMP and that planning begin for the acquisition of computers of the TI-ASC or ILLIAC-4 class for the use of the climatic research consortia and the associated elements of the CMAP. It will also be necessary to provide broadband communication links among the various facilities and cooperating groups and with the climatic research community as a whole. TABLE 6.2 Estimated Computing Needs for the National Climatic Research Program * Present Use ° Projected Use ° Climatic data analysis and monitoring 0.2 1.54 Atmospheric GcM development 0.8 ° 3.0 Oceanic GCM development 0.2 2.0 Coupled Gcm’s (climate models) Development and tests 0.1 3.0! Climatic reconstructions ~0 2.0° Climatic experiments and projections 0.1 3.0! Other models and studies 0.1 2.0 TOTAL 1.5 16.5 In units of coc 7600 years. > Estimated 1973 national total, exclusive of operational agencies. ¢ For the program year circa 1980. ¢ Envisaged as use by climatic data-analysis facilities. ¢ Estimating 0.2 usage at NCAR, 0.5 usage at GFDL, and 0.1 total usage elsewhere. f Envisaged as use by cooperative climatic research consortia.

A NATIONAL CLIMATIC RESEARCH PROGRAM 99 Estimated Costs The cost of the recommended national climatic research program is difficult to determine accurately without a great deal of information on observational, computing, and support costs from the various agencies and institutions presently engaged in the many aspects of climatic re- search. Rather than seeking such detailed data, we have restricted our- selves to gross projections on the basis of estimates of the costs of present efforts. Our estimates of the expenditures for climatic research (not including the costs of instruments, observing platforms, or opera- tional and service-related activities) are given in Table 6.3. Our pro- jections of the growth of these (direct) costs during the early phases of the program (i.e., to the year 1980) are shown in Figure 6.1, along with the percentage increases over the preceding year; these estimates, of course, depend directly on the base figures that are used and are sub- ject to further refinement. These figures are intended for order-of- magnitude guidance only and will require revision as the program develops. We recognize that the ultimate distribution of resources among the various subprograms of the NcCRP will be determined by the sense of priorities of the government and by the capabilities of the research community. The estimates shown in Figure 6.1 for the year 1980 are based on our preception of the needed increases over present efforts in the areas of data analysis and monitoring (CDAP and CIMP), especially those concerning satellite data and the monitoring of oceanic climatic indices. In the area of climatic modeling and applications (CMAP), the largest increases over present efforts are envisaged for the develop- TABLE 6.3 Estimated Expenditures for Climatic Research’ (in $10°/yr) Present Projected (1974) (c.1980) Climatic data assembly and analysis 5 18 Climatic index monitoring ° 4 12 Climatic modeling and applications 9 37 18 67 * Based on estimates of the climate-related research sponsored by the NSF, DOT, and pop and that conducted by GFDL, NCAR, NASA, and NOAA but not including essentially operational or service- related activities. >’ Not including costs of instruments or observing platforms.

100 UNDERSTANDING CLIMATIC CHANGE 70 67 60 - 61 50 - 51 CMAP > SO 40 “ 39 £ ¢ 8 30 = SN _ _ =3 28 - CIMP 20 - 22 6® | fo Foo fof Pe CDAP 10- (20%) (30%) (40%) (30%) (20%) (10%) 1974 1975 1976 1977 1978 1979 1980 (present) FIGURE 6.1 Projected costs of the National Climatic Research Program (NCRP). The numbers in parentheses are the percent increase over the preceding year’s expenditures. ment and application of coupled global climate models and climatic impact studies. The relatively rapid growth rate during the program’s third and fourth years are projected to include the acquisition of the necessary computers and networks. Overall, the recommended pro- gram calls for an approximate fourfold expansion of the support of research on climatic variation by the year 1980; the program’s costs beyond this time are more difficult to estimate and will depend on the progress and opportunities developed prior to that time. It is useful to compare these cost projections with the direct and indirect costs of present GARP efforts and those of closely related pro- grams. In fiscal year 1973 the direct GARP expenditures totaled $13.2 million, about 54 percent of which represented expenditures by the De-

A NATIONAL CLIMATIC RESEARCH PROGRAM 101 partment of Commerce and Nasa directed toward the improvement of weather forecasting, with the remainder expended by NsF for research on both forecasting and general circulation studies. Some of these costs are included in the estimates in Table 6.3, insofar as they can be identi- fied as directed toward climatic research. The indirect costs associated with GARP amounted to $29.0 million in fiscal year 1973 and are not reflected in the present climatic research estimates. In addition to these efforts, there are other current programs that contribute to GARP and whose costs should not be overlooked. The implementation of the World Weather Watch (www) and its satellite system represented $1.5 million direct costs and $54.5 million indirect costs in fiscal year 1973, while systems design and technological de- velopment represented $2.4 million direct costs and $50.1 million in- direct costs in the same period. The extent to which elements of the recommended cCDAP and cIMP subprograms of the NCRP may be con- sidered as add-ons to such existing programs needs further considera- tion, as does the extent to which the future costs of GARP itself may be merged with those envisaged for the NCRP. Also in need of further study are the United States’ contributions to the costs of the various subprograms recommended as part of the In- ternational Climatic Research Program (icRP) described below, as well as the impacts of inflation. We also note that funds will be required for the training of additional scientific manpower in all aspects of the research program. Timetable and Priorities within the Program We recognize the need for flexibility in a research program of this kind, and that future technological and research discoveries may have important impacts on the direction of climatic research. In spite of these unknown factors, however, some consideration of goals and priorities is useful. Here we present our recommendations for the ob- jectives of the initial phase of the program (1974-1980) and the necessary sequence of planning activities for both these goals and those of the long-term phase (1980-2000). Our recommendations for a coordinated international program are considered subsequently. The Initial Phase (1974-1980) Once the decision is made to develop a national climatic research pro- gram, we recommend that planning begin immediately for the implemen- tation of its component activities and subprograms. Our specific recom-

102 UNDERSTANDING CLIMATIC CHANGE mendations for both the immediate and subsequent objectives during this phase of the program are shown in Table 6.4 in terms of the data- analysis, index-monitoring, and modeling subprograms identified earlier. Here our sense of relative priorities is given implicitly by the ranking into immediate and subsequent objectives; these time scales refer to the expected times of the achievement of first useful results, with the recognition that initial development must in some cases begin earlier TABLE 6.4 Goals for the Initial Phase of the NCRP (1974—-1980) Immediate Objectives Subsequent Objectives Subprogram (1974-1976) (1976-1980) Climatic data 1. Development of climatic data- 1. Development of global analysis analysis facilities climatic data-analysis (CDAP ) 2. Statistical analysis of climatic system (FGGE) variability, predictability, 2. Assembly and process- feedback processes ing of global climatic 3. Statistical climatic-impact data (conventional, studies (crops, human affairs) satellite, historical, proxy data) 3. Development of cli- matic impact models Climatic index 1. Monitoring of oceanic mixed- 1. Satellite monitoring of monitoring layer global heat-balance (CIMP ) 2. Monitoring of ice, snow, and components cloud cover 2. Monitoring selected 3. Expansion of proxy data physical processes sources (FGGE) 4. Monitoring system simulation 3. Development of global studies climatic index monitor- ing system Climatic model- 1. Development of oceanic 1. Development of fully ing and appli- mixed-layer models coupled atmosphere— cations 2. Development and analysis of ocean—ice GCM’S (CMAP) provisionally coupled Gcm’s 2. Development of statis- (sensitivity, predictability tical-dynamical cli- studies) mate models 3. Development of simplified cli- 3. Parameterization of matic models and related mesoscale. processes, theoretical studies simulation of climatic 4. Selected paleoclimatic recon- feedback mechanisms structions (FGGE) 4. Experimental seasonal climatic forecasts by dynamical models

A NATIONAL CLIMATIC RESEARCH PROGRAM 103 and that further development and application will continue later. This ranking also reflects a balance between the relative ease of accomplish- ment and the relative potential for initial practical usefulness. We believe that progress toward the subsequent objectives will require the support of all immediate objectives of the program, with new priorities evolving as a function of achievement and opportunity. Relationship to the FGGE (1978-1979) The First GARP Global Experiment (FGGE), now planned for 1978- 1979, is primarily an attempt to collect a definitive global data set for use in the improvement of weather prediction by numerical atmospheric models. The potential value of these data for climatic research lies not so much in their display of seasonal and interhemispheric variations, valuable as that will be, but in the fact that many of the short-period physical processes to be intensely measured or parameterized in FGGE are also important for the understanding of climate. Among these are the processes of convection, boundary-layer dynamics, and the at- mosphere’s interaction with the surface of the ocean. The observational requirements during the FGGE call for measurement of the atmospheric temperature, water vapor, cloud cover and eleva- tion, wind, and surface pressure, together with the surface boundary variables of sea-surface temperature, soil moisture, precipitation, snow depth, and sea-ice distribution. To enhance their value for climatic studies, we recommend that these data be supplemented during FGGE insofar as possible by observations of the global distributions of ozone, particulates, surface and planetary albedo, incoming solar and outgoing terrestrial radiation, vegetal cover, and the continental freshwater runoff. We recommend that special observations also be made in con- junction with regional programs, such as NORPAX and POLEX, which are expected to be in operation during the FGGE. The Long-Term Phase (1980-2000) The long-range goals and full-scale operation of the NCRP in the period beyond 1980 are portrayed in the upper part of Figure 6.2. During this period, the full interaction among the observational, analysis, modeling, and theoretical components of the program will occur, leading to the development of an operational global climatic data system and, it is hoped, to the acquisition of an increasingly accurate theory of climatic variation. Although priorities cannot be set at such long range, the eventual practical payoffs of this program will be the determination of

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A NATIONAL CLIMATIC RESEARCH PROGRAM 105 the degree to which climatic variations on seasonal, annual, decadal, and longer times scales may be predicted and the degree to which they may be controlled by man. Administration and Coordination The administrative structure and coordination of the recommended program are the responsibility of the federal government and were not given extensive consideration. However, noting the concern with the problem of climatic variation in many parts of the government, and the widespread participation of many governmental and nongovernmental groups in climatic research, we believe that the program should be ad- ministered in such a way that the interests of all are effectively repre- sented and coordinated. It is particularly important that the advice of the scientific community be used in the design and development of the major elements of the research program. Both the short-term and long-term goals of the NCRP are also shared by the International Climatic Research Program (ICRP) recommended below. The development of this international program should proceed in parallel with the NCRP and should be closely coordinated with GARP. The principal activities within GARP up to the present time have focused on the problem of improving the accuracy and extending the range of weather forecasts, and the United States’ contributions to GARP in par- ticular have emphasized the development and use of numerical models for this purpose. These efforts are necessary steps in the development of an adequate modeling capability for both weather prediction and climate, and were they not already under way as part of GARP they would have had to be undertaken through some other means as a prelude to the climatic research program. A COORDINATED INTERNATIONAL CLIMATIC RESEARCH PROGRAM (ICRP) Many of the efforts envisaged within the NcRP are of an obvious inter- national character, and the degree to which these should be regarded as national as opposed to international activities is not of critical im- portance for our purposes. The important point is that there are inter- national efforts now under way within GARP of direct relevance to the climatic problem, of which we note especially the International Study Conference on the Physical Basis of Climate and Climate Modeling held in Sweden in July and August 1974 under the auspices of the ICSU/WMO GARP Joint Organizing Committee. The recommendations

106 UNDERSTANDING CLIMATIC CHANGE and programs resulting from this and subsequent planning conferences should be closely coordinated with the U.S. national program. We offer here our recommendations for an appropriate international climatic re- search program and some observations on how such a program might best be coordinated with GARP itself. Program Motivation and Structure The observational programs planned in support of GARP offer an un- paralleled opportunity to observe the global atmosphere, and every effort should be made to use these data for climatic purposes as well as for the purposes of weather prediction. The climatic system, how- ever, consists of important nonatmospheric components, including the world’s oceans, ice masses, and land surfaces, together with elements of the biosphere. While it is not necessary to measure all of these com- ponents in the same detail with which we observe the atmosphere, their roles in climatic variation must not be overlooked. In addition to the fundamental physical differences discussed in Chapter 3, the problem of climatic variation also differs from that of weather forecasting by the nature of the data sets required. The primary data needs of weather prediction are accurate and dense synoptic observations of the atmosphere’s present (and future) states, while the data needed for studies of climatic variation are longer-term statistics of a much wider variety of variables. When climatic variations over long time scales are considered, these variables must be supplied from fields outside of observational meteorology. Thus, an essential characteristic of climate studies is its involvement of a wide range of nonatmospheric scientific disciplines. The types of numerical models needed for climatic research also differ from those of weather prediction. The atmospheric GCM’s (which represent the ultimate in weather models) do not need a time-dependent ocean for weather-forecasting purposes over periods of a week or two. For climatic change purposes, on the other hand, such numerical models must include the changes of the oceanic heat storage. Such a slowly varying feature may be regarded as a boundary or external condition for weather prediction but becomes an internal part of the system for climatic variation. International Climatic Research and GARP In view of these characteristics, we suggest that while the GARP concern with climate is a natural one, as indicated above the problem of climate

A NATIONAL CLIMATIC RESEARCH PROGRAM 107 goes much beyond the present basis and emphasis of GARP. Accordingly, we recommend that the global climate studies that are under way within GARP be viewed as leading to the organization of a new and long-term international program devoted specifically to the study of climate and climatic variation, which we suggest be called the International Climatic Research Program (ICRP). International Climatic Decades (1980-2000) We suggest that the observational programs of GARP, and especially those of the FGGE, be viewed as preliminary efforts, later to be expanded and maintained on a long-term basis. In particular, we recommend that the special data needs of climatic studies be supported on an inter- national scale through the designation of the period 1980-2000 as the International Climatic Decades (IcD), during which intensive efforts would be made to secure as complete a global climatic data base as possible. The general outline of the envisaged international program (ICRP) is sketched in the lower part of Figure 6:2, and the program’s scientific elements are discussed in more detail below. Program Elements Climatic Data Analysis The main thrust of the international climatic program should be the collection and analysis of climatic data during the Icp’s, 1980-2000. During this period, the participation of all nations should be sought in order to develop global climatic statistics for a broad set of climatic variables. We urge that these efforts include international cooperation in the systematic summary of all available meteorological observations of climatic value, including oceanographic observations in the waters of coastal nations. International Paleoclimatic Data Network (IPDN) We urge the development of an international cooperative program for the monitoring of selected climatic indices and the extraction of histori- cal and proxy climatic data unique to each nation, such as indices of glaciers, rain forest precipitation, lake levels, local desert history, tree rings, and soil records. Specifically, we recommend that this take the form of an International Paleoclimatic Data Network (IPDN), as a

108 UNDERSTANDING CLIMATIC CHANGE subprogram of the IcrRP. The cooperation of such organizations as SCAR, SCOR, and the International Union for Quaternary Research (INQUA) should be sought in this program. The contents of these international observational efforts might possibly broadly follow those recommended for the U.S. national effort, with modifications as appropriate to each nation’s needs and capabilities. In addition, we recommend that the icrP undertake the following: The international collection of special climatic data sets on such events as widespread drought and floods and following major environ- mental disturbances such as volcanic eruptions; Programs to encourage international exchange of climatic data and analyses. Climatic Research Although cooperative research studies are desirable, we recognize that the large-scale numerical simulation of climate with CGCM’s can now be carried out in only a relatively few countries. To promote wider international participation in climatic research, we therefore recommend that the IcrP include the following: Programs and activities to encourage international cooperation in climatic research and to facilitate the participation of developing na- tions that do not yet have adequate training or research facilities. Internationally supported regional climatic studies in order to describe and model local climatic anomalies of special interest. The contents of these and other research activities of the ICRP might also broadly follow those recommended for the U.S. national effort, with appropriate modifications for each nation’s interests and capabilities. Global Climatic Impacts While all nations are tied in some fashion to the world pattern of climate, some are more vulnerable to climatic variations than others by virtue of their locations and the delicacy of their climatic balance. We therefore recommend that the IcrP include the following: International cooperative programs to assess the impacts of observed climatic changes on the economies of the world’s nations, including

A NATIONAL CLIMATIC RESEARCH PROGRAM 109 the effects on the water supply, food production, and energy utilization. This should include the impacts of variations of oceanic climate for those nations whose economies are dependent on the sea. The coopera- tion of appropriate international agencies of the United Nations and of other groups such as the International Federation of Institutes of Ad- vanced Study should be sought. Cooperative analyses of the regional impacts of possible future cli- mates. Such studies could be of great importance to many countries, particularly emerging nations making long-range policy decisions con- cerning the development of their resources. Program Support The question of the details of support of the ICRP was not dealt with. It seems clear, however, that an appropriate balance of effort should be maintained among ICRP, the various national climatic research pro- grams, and other international programs such as the World Weather Watch (www) and the United Nations Environment Program (UNEP). The services of groups performing the function of the present GARP Joint Organizing Committee and its Joint Planning Staff will also be necessary for the success of the international program. In order to assist in the coordination of the ICRP, we urge that sup- port be made available by the appropriate agencies of the United Na- tions on a scale commensurate with the breadth and importance of the problem. This should include a budget adequate for the effective inter- national coordination of the ICRP on a scale significantly greater than that of GARP and on a continuing long-term basis. We also urge that scientific assistance be sought from the International Council of Scientific Unions in support of selected ICRP subprograms.

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he increasing realization that man’s activities may be changing the climate, and mounting evidence that the earth’s climates have undergone a long series of complex natural changes in the past, have brought new interest and concern to the problem of climatic variation. The importance of the problem has also been underscored by new recognition of the continuing vulnerability of man’s economic and social structure to climatic variations. Our response to these concerns is the proposal of a major new program of research designed to increase our understanding of climatic change and to lay the foundation for its prediction.

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