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14 The Climate Record
Pages 117-134

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From page 117...
... Earlier temperature data are available, but their spatial distribution and their sparseness seriously compromise the attempts to infer global averages. Additional difficulties arise because measurements were not taken with an eye to the small and gradual global average changes that are characteristic of climate change.
From page 118...
... Land air temperatures are typically measured 1 to 2 m above ground level. Sea surface temperatures are typically measured in the layer from the ocean's surface to several meters below.
From page 119...
... Additional uncertainties for both land and sea surface temperatures include the following: · The spatial coverage of the data is neither globally comprehensive nor optimally sited, and the degree of coverage changes over time. · Changes have occurred in instruments, exposures of thermometers, observing schedules, observing practices, and other factors including land use, thus introducing artificial changes in the temperature record, some .
From page 120...
... These analyses suggest that changes in spatial coverage have not had a serious impact on our ability to discern changes in the global thermometric record. Because of the large-scale coherence of multidecadal climate variations, especially over the oceans, the sampling problem probably adds less than 0.1°C (0.18°F)
From page 121...
... These simulations generally have a slower rate of temperature increase in the southern hemisphere and over the oceans, especially the circumpolar oceans, than in the northern hemisphere (Stouffer et al., 1989; Washington and Meehl, 1989; Manabe et al., 19901. At this time, however, the large variability in transient climate simulations and the difficulty in linking these simulations to the appropriate part of the climate record prevent unequivocal statements about the consistency or lack thereof between simulations and the climate record.
From page 122...
... . Sea surface temperatures are averages of the U.K.
From page 123...
... N80 60 4n 20 o an 40 S60 THE CLIMATE RECORD 1 950 FIGURE 14.3 Continued 0.2~.43 1970 1 980 Year
From page 124...
... Furthermore, the range of extreme temperatures, especially during summer in the United States and the former USSR, has also decreased (Karl et al., 1991~. Climate models with enhanced greenhouse gases cannot yet reliably predict the expected change in extremes.
From page 125...
... Finally, a recent study has pointed out the danger of overinterpreting midtroposheric temperature trends based on short time series. Whereas previous studies showed current temperature increases compared to 1957, Elms et al.
From page 126...
... 4.3 cC a) 3.7 2.9 min FIGURE 14.4 Changes in the annual mean daily maximum and minimum temperature in the United States (left panels)
From page 127...
... 223 Stations ~1 J 1935 1945 1955 1965 1975 1985 Year USSR National Minimum Temperature Annual (Jan.-Dec.) 223 Stations 1935 1945 1955 1965 1975 1985 Year
From page 128...
... Nonetheless, there have been several large-scale analyses of precipitation variations over the northern and southern hemisphere land masses (Bradley et al., 1987; Diaz et al., 1989; Vinnikov et al., 1990) , which have demonstrated that during the past several decades precipitation has tended to increase in northern hemisphere mid-latitudes and in the southern hemisphere.
From page 129...
... Furthermore, if the rate of change for the increase of winter to summer precipitation ratios suggested by the modeling reported by the IPCC were correct, we probably should have already detected such changes. All in all, the record cannot support persuasively a quantitative relationship between the greenhouse gas accumulation and the precipitation variations of the last century.
From page 130...
... adjusted precipitation measurements over the former USSR based on optimal averaging methods (Groisman et al., 19911.
From page 131...
... In addition, this instrument did not have the ability to retain maximum and minimum temperatures on a midnight-to-midnight basis. As a result, the opportunity was lost to eliminate many of the thermometric biases that had existed in the network because observers were understandably unwilling to remain with a fixed observation schedule over the decades.
From page 132...
... 1988. An interim analysis of the leading covariance eigenvectors of worldwide sea surface temperature anomalies for 195180.
From page 133...
... 1986a. Northern hemisphere surface air temperature variations, 18511984.
From page 134...
... 1990. Precise monitoring of global temperature trends from satellites.


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