Global Environmental Change Research Pathways for the Next Decade (1999) / Chapter Skim
Currently Skimming:
8 Observations
8 Observations
Pages 377-434
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 377... ...
The scientific foundation for each of the six primary science areas -- biology and biogeochemistry of ecosystems, seasonal-to-interannual climate change, decadalto-century climate change, atmospheric chemistry, paleoclimate, and the human dimension of global change -- consists of a statement of the following: scientific character of the problem, selected case studies, key unanswered scientific questions, lessons learned in the course of scientific research over the past decades, and research imperatives. The research imperatives are central.
|
From page 378... ...
Indeed, a parallel activity is taking place (Global Climate Observing System, GCOS) to design a global observing system for climate to satisfy both scientific and monitoring needs.1 Parallel efforts are under way for the ocean (Global Ocean Observing System)
|
From page 379... ...
For example, the need to observe radiatively active gases in the atmosphere is common to atmospheric chemistry, ecosystems, and decadal to centennial climate change research areas. Observations of streamflow, atmospheric and sea surface temperatures, and precipitation are emphasized across science elements.
|
From page 380... ...
Ties of these measurement areas to the research imperatives are shown in Table 2.2. The four key measurement areas are time series observations of ecosystem state; land use and land cover change; site-based networks; and measurements of diversity, functional diversity, and ecosystem function.
|
From page 381... ...
Space-borne sensors with resolutions from a few square meters to tens of square meters have proven to meet these needs.4 Sensors with two to seven spectral bands are adequate for land cover mapping, although new technology employing spectrometers,5 radar, or lidar has great potential. As in measuring ecosystem state, "backwards compatibility" must be preserved to continue existing time series when new technology and capability are introduced.
|
From page 382... ...
It is clear that the functional diversity of the Earth's biota is a first-order control over global ecosystem function, but how changes to the biota will affect global ecosystem function still is a young research topic.8 Designing a global observing system and network of experimental studies, analogous to those described above for biogeochemical fluxes, is premature; the necessary monitoring and manipulations at global scales are currently far from obvious. But a major exploratory effort involving manipulations, studies of ecosystem function in the face of ongoing invasions, extinctions, species range shifts, and global monitoring of species diversity, invasion,
|
From page 383... ...
These tables present examples of issues, measurements, and timescales, but they are not exhaustive. Seasonal to Interannual Climate Chapter 3 sets forth three broad Research Imperatives: ENSO prediction research, global monsoon research, and land surface exchanges, downscaling, and terrestrial hydrology research.
|
From page 384... ...
Land surface effects Water, CO 2, heat, Evapotranspiration, Daily to weekly, Major biomes with Eddy covariance, on physical climate. momentum fluxes, sensible heat, seasonal to replication along micrometeorology.
|
From page 385... ...
Increasing CO2 effects CO2 enrichment Response of Daily to weekly, Major biomes with Open-topped on ecosystem experiments. ecosystem function seasonal to replication along chambers, free air processes.
|
From page 386... ...
Land cover change. Ecosystem type (forests, Seasonal, decadal.
|
From page 387... ...
Not surprisingly, there is virtually complete overlap between these variables and those identified as important in pursuing the other seasonal to interannual research imperatives identified in the following section. Only the variable of land surface energy fluxes is not identified both below and in the following section.
|
From page 388... ...
That Must Be Measured for the GOALS Program Realm State Variables External Variables Ocean • Upper-ocean temperature • Wind stress • Upper-ocean currents • Net surface solar radiation • Sea level • Downwelling longwave radiation • Upper-ocean salinity • Surface air temperature • Optical absorption • Surface humidity • Sea ice extent, concentration, and • Precipitation thickness Atmosphere • Wind structure • Sea surface temperature • Thermal structure • Net radiation at top of the • Surface air temperature atmosphere • Sea level pressure • Land surface variables (see below) • Water vapor structure • Columnar water vapor and liquid water content • Cloud cover and height Land • Soil moisture • Precipitation • Snow cover and depth • Net surface longwave and short • Vegetation type, biomass, and wave radiation vigor • Surface wind • Water runoff • Surface air temperature • Ground temperature • Surface humidity • Evaporation • Evapotranspiration *
|
From page 389... ...
A recent UNESCO (United Nations Educational, Scientific, and Cultural Organization) publication and related digital data bank of approximately 1,000 discharge monitoring stations11 represents the last digitized global data bank of river runoff that is freely available to the global change community (at Oak Ridge National Laboratory Data Acquisition and Archive Center)
|
From page 390... ...
Satellite remote sensing algorithms to estimate snow water equivalent in a manner suitable for global studies (e.g., spatial resolutions of tens of kilometers) have been improved and may be suitable for seasonal to interannual timescale studies, notwithstanding problems remaining for forested areas.
|
From page 391... ...
Surface Air and Skin Temperature Observations of surface air temperature are critically important to predict evapotranspiration and snow accumulation and melt. Surface air temperature measurements are routinely collected at NCDC cooperative observer stations, as well as NWS manned observing stations.
|
From page 392... ...
Furthermore, a long-term global archive of seasonal variations in vegetation properties must be preserved, along with sufficient metadata to resolve questions about any effects of changes in instruments. Decadal to Centennial Climate Change The following Research Imperatives (Chapter 4)
|
From page 393... ...
Extend the climate record back through data archeology and paleoclimate records for time series long enough to provide research ers a better database with which to analyze decade-to-century-scale pat terns, specifically to achieve a better understanding of the nature and range of natural variability over these timescales. • Long-term observational system.
|
From page 394... ...
Addressing decadal-to-centennial solar variability, as discussed above, requires a plan for long-term calibrated solar irradiance measurements across the solar spectrum. BOX 8.1 WCRP Message to the Conferences of the Parties to the United Nations Framework Convention on Climate Change and United Nations Convention to Combat Desertification "Well over 300 members of the climate research and policy communities present at the Conference on the World Climate Research Programme (WCRP)
|
From page 395... ...
At this stage, then, it is imperative that we begin (or in a few cases continue) consistent monitoring of the most fundamental state variables (e.g., atmospheric temperature and moisture profiles, ocean surface temperature and salinity values)
|
From page 396... ...
Appropriate parameterization of these phenomena is therefore essential, since modeling efforts are the primary tool we have for forecasting future change. We also need better parameterization of clouds, including their distribution and feedback processes, because their treatment in models may prove crucial in predicting long-term climate responses to changes in radiative forcing, as well as other feedback influences associated with variability and change.
|
From page 397... ...
Sea level change is another important observational challenge. The Intergovernmental Panel on Climate Change (1996)
|
From page 398... ...
Onsite studies that have focused on ice flow, melting, and calving should be continued and extended. Water vapor flux divergence observations will help pin down the source of the ice sheets' mass.
|
From page 399... ...
• Aerosol radiative forcing and climate change. Stratospheric Ozone and Ultraviolet Radiation Research Imperative A central issue of atmospheric chemistry is to define and predict fluctuations and secular trends in the intensity of ultraviolet radiation that the Earth receives.
|
From page 400... ...
Such observations will require high spatial resolution (0.1 km in horizontal and vertical) simultaneous measurements of H2O resolved into its three phases and the isotopes of H2O, O3, CO2, CO, N2O, CH4, upward- and downward-looking lidar for detection of aerosols and cirrus, the upward and downward radiance in the visible and infrared at 1 cm–1 spectral resolution with the ability to scan the view direction to any angle in the plane perpendicular to the platform velocity vector, solar tracking that allows absorption measurements in the visible and infrared, upward- and downwardlooking polarimetry, microwave temperature profiling above and below the platform, and simultaneous observations of meteorological fields and a complete suite of particle measurements.
|
From page 401... ...
As described in Chapter 5, these observations must be obtained with a spatial resolution of 0.1 km, with simultaneous observation of tracers, reservoir species, and ultraviolet flux. It is critical to extend these observations to extreme conditions, such as the polar winter and tropical tropopause.
|
From page 402... ...
Priority: Determine the flux of CO2 from the primary systems (ocean, tropical, temperate, high-latitude terrestrial, Arctic, Antarctic, industrial, agricultural) as a function of season, with spatial resolution of 0.5 km.
|
From page 403... ...
, Cl, O3, Br) in various regions of the troposphere (e.g., boundary layer, continental regions, industrial regions, biomass-burning regions, western tropical Pacific, Arctic)
|
From page 404... ...
Production of Infrared Active Gases that Control Climate Ozone is recognized to be an important component in the radiative balance of the Earth in the critical region of the tropopause.14 It is also recognized to be increasing in the upper troposphere15 and to be strongly linked to photochemical production via hydrogen and nitrogen radicals.16 The upper troposphere is thus central to the link between the production of infrared gases and climate. From the perspective of scientific strategy, the upper troposphere is ideally suited for critical photochemical experiments because it provides an in situ laboratory with chemistry representative of the troposphere and yet is simple enough to reach closure on a range of experiments testing key hypotheses.
|
From page 405... ...
. These observations are required with a spatial resolution of 0.1 km in both vertical and horizontal dimensions, over trajectories that scan from sea level to the lower stratosphere.
|
From page 406... ...
Aerosol Radiative Forcing and Climate Change Research Imperative This imperative requires definition of the production and loss mechanisms, distribution, and optical properties of aerosols. Observations must be directed at processes that control aerosols from the fine scale to the global scale.
|
From page 407... ...
For example, point measurements of aerosol number concentration and chemical composition as a function of particle size can be used to calculate simultaneously observed aerosol light scattering and absorption coefficients and the number concentration of CCN; and column measurements of the vertical profile of aerosol light scattering and absorption coefficients with simultaneously observed radiative fluxes that can be tested against measurements of aerosol optical thickness of the entire column and aerosol optical properties and with radiative fluxes at the top of the atmosphere.18 Priority: Pursuit of vertical column experiments that link nadir-viewing satellite observations of spectrally resolved absolute radiance with surfaced-based, column-integrated radiation measurements and in situ observations of aerosol chemical composition as a function of size, spectrally resolved upwelling and downwelling radiance (solar and infrared) , light scattering (total and hemispheric backscatter)
|
From page 408... ...
These fields in turn are tied to both planetary albedo in the lowertroposphere boundary layer and the genesis of subvisible cirrus and visible cirrus, which are critical to the trapping of thermal infrared in the middle/upper troposphere. A nested set of hypotheses constitute the foundation of our understanding of marine sulfur chemistry: • Climate is substantially affected by the radiation budget.
|
From page 409... ...
in a Lagrangian experiment would permit testing of the key hypotheses that DMS oxidation leads to new particle formation: OH, HO2, NO, NO2, DMS, DMSO, SO2, H2SO4, CH3S(O2) OH, CH4, CO, HOOH, O3, H2O, CH3OOH, CH2O, CH3O2, ultraviolet spectrum, aerosol size and compo sition as a function of size, Lagrangian tracers, and DMS eddy flux for MBL exper iments.
|
From page 410... ...
Research Imperatives • Global changes of the past. Document how the global climate and the Earth's environment have changed in the past and determine the factors that caused the changes.
|
From page 411... ...
This has been designated a core research topic by the IGBP and the International Human Dimensions Programme on Global Environmental Change and was a NASA research initiative in 1998. Most land use research teams are using satellite data to provide biophysical measures of land cover.
|
From page 412... ...
As the above examples and others in Chapter 7 indicate, efforts are increasing to link social, economic, and health data to biophysical data to improve understanding of the human dimensions of global change. However, a number of important observational issues must be addressed in the next decade.
|
From page 413... ...
What are the costs and benefits of bringing the federal agencies responsible for the bulk of the social, economic, and health data into the USGCRP? What human dimensions of global change research needs are not being met by current observational strategies?
|
From page 414... ...
At present, relevant human dimensions data are being collected locally. Sometimes, local data are being used for local case studies; sometimes, local data are aggregated to the global scale, with various forms of imputation for those local areas not providing the relevant data.
|
From page 415... ...
For example, census takers need addresses of dwelling units in order to conduct the census. By georeferencing social, economic, and health data, such human dimensions data could be more meaningfully linked to biophysical data.
|
From page 416... ...
The time is now ripe for a systematic assessment of the role and needs for social, economic, and health data in global change research. Such an assessment should pay particular attention to issues of comparability, georeferencing, confidentiality, and relevance.
|
From page 417... ...
A measurement can be made to document the secular change of some relevant climatic quantity, such as global surface temperature or upper-tropospheric humidity, for the purpose of documenting some aspect of global change and for providing the data to compare to models. Such a measurement could be critical if a prediction of such changes has been precise and unambiguous, but this rarely happens in geophysics because it is hardly possible to control the surroundings of a measurement.
|
From page 418... ...
A research measurement is usually designed to answer a specific scientific question and is usually finite in duration. What distinguishes an operational measurement from a research measurement is the absolute operational need to deliver a measurement regularly in a given time.
|
From page 419... ...
The complexity of the design increases as the objectives and number of users increase. Without such a design, it is likely that large amounts of money will be invested in taking observations, with no guarantee that the research objectives of the USGCRP are fulfilled or that the community of users feels satisfied in having their needs respected.
|
From page 420... ...
The quantities to be measured for the science areas of the USGCRP must be identified, and the accuracies to which they must be measured must be stated in terms of the scientific questions and objectives. A specific scientific rationale must be given for each mea surement proposed, so that the scientific importance of the measurements can be recognized.
|
From page 421... ...
, variations on the order of a few tenths of a degree of global temperature can be forced by solar output variations on decadal timescales. Because globally averaged temperature is of this order, one cannot exclude the possibility that solar variability is the cause of decadal climate variations.
|
From page 422... ...
Long-Term Variations and Changes of Clouds in the United States Few elements of the atmosphere are more fundamental to understanding climate and its impacts on ecosystems and human systems than cloud amount and height. The specification of cloud cover is one of the most sensitive parameters in general circulation models, which are used to study climate.
|
From page 423... ...
Automated lidar measurements were replacing human observers. These automated measurements were unable to detect clouds above 12,000 feet, which introduced a major discontinuity in the cloud observing network.
|
From page 424... ...
There are also some indications that many of the same problems may continue to appear in both ground-based and satellite observations relied on by virtually all of the science elements. For example, support for NOAA's Cooperative Observing Network, which is the basis for many of the longest surface temperature and precipitation records, continues to be a matter of concern.
|
From page 425... ...
11) • A Decade of International Climate Research: The First Ten Years of the World Climate Research Program, National Academy Press, 1992, 55 pp.
|
From page 426... ...
"For future progress in the study of climate variations, it is essential to main tain what we already have, including the upper-air observing network, satel lite altimetry, and the upper-ocean and surface-meteorological measure ments made routinely in and over the ocean." (p.
|
From page 427... ...
This step is particularly important because most observing systems have been de signed for purposes other than long-term climate monitoring. Instru ments must have adequate accuracy, with biases small enough to docu ment climate variations and changes.
|
From page 428... ...
International cooperation is critical for successful manage ment of data used to monitor long-term climate change and variability. The remainder of this section concentrates on the transition from a researchfocused observing system to a permanent operational component within the observing system of the USGCRP for global environmental monitoring.
|
From page 429... ...
The current designs for a global observing system by the GCOS and the Global Ocean Observing System33 seem unattainable in practice because of the lack of such an operational mandate for any existing agency or the USGCRP. The prospects for a permanent observing system therefore seem to rest on three possibilities: • The USGCRP accepts environmental global change-focused monitoring as an operational necessity and makes the institutional changes needed to enforce the discipline that operational requirements demand.
|
From page 430... ...
. It is crucial for global change research and monitoring that future operational satellites should, to the extent practical, have the qualities necessary for global change science identified in this report.
|
From page 431... ...
1997. The response of global terrestrial ecosystems to interannual temperature variability.
|
From page 432... ...
1996. Aerosol Radiative Forcing and Climate Change.
|
From page 433... ...
1982. Variations in tropical sea surface temperature and surface wind fields associated with the Southern Oscillation/El Niño.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.