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Climate: Long-Range Investigation, Mapping, and 

 Prediction (CLIMAP) Study 



CLIMAP research is designed to describe and explain 

 the major changes in global climate that have occurred in the 

 past million years. These changes involve transitions between 

 two partly stable states of global climate — ice ages and tem- 

 perate periods. The fundamental objective is to improve our 

 understanding of the physical mechanisms that cause these 

 major variations in the atmosphere, ocean, and ice sheets. 

 Because these changes have simpler geographic patterns and 

 occur more slowly than climatic changes taking place on a year- 

 to-year or decade-to-decade scale, they are in many ways 

 easier to understand than the higher-frequency events. CLI 

 map's central strategy is to view the geological record of the 

 ice-age cycle as a huge, natural experiment to gain new cli- 

 matic insights. These insights will help improve our ability to 

 understand and forecast the economically important variations 

 in climate that occur on human time scales. CLIMAP studies 

 are jointly funded by NSF's Office of Climate Dynamics and 

 Office for the IDOE. CLIMAP scientists are listed in table 12 

 and CLIMAP task groups in table 13. 



A unique aspect of the CLIMAP study is that analyses of 

 deep-sea sediments are used as the primary source of data. 

 Deep-sea sediments are particularly useful as indicators of past 

 climatic conditions for a variety of reasons. 1) They are not 

 geographically restricted, and their global extent adds to their 

 value as climatic indicators because the interchange between 

 the ocean and the atmosphere plays a dominant role in climatic 

 variations. 2) Deep-sea sediments accumulate at a relatively 

 constant and continuous rate that is uninterrupted for perhaps 

 hundreds of thousands of years. 3) The chemical, physical, 

 and biological characteristics leave a permanent record of many 

 aspects of the ocean, including the temperature and circula- 

 tion pattern of the surface waters, the chemical nature of the 

 bottom waters, and the extent of sea ice. In addition, isotopic 

 studies of marine sediments make it possible to calculate his- 

 torical changes in the volume of terrestrial ice sheets. Each 

 sediment core is thus a multipurpose recorder monitoring past 

 climatic changes. 



Modeling of Ice Age Climale. One recent advance in 

 CLIMAP research is the publication of a numerical model of 

 the global atmosphere at the maximum extent of the last ice 

 age, 18,000 years ago (fig. 22). This work is part of a larger 

 program directed to reconstruct the geographic pattern of 

 selected past chmatic states — and to learn from these recon- 

 structions how winds and the ocean currents balance the 

 Earth's radiation budgets during climatic regimes quite differ- 

 ent from today. The results shown in figure 22 were obtained 

 by CLIMAP corresponding member W. L. Gates as follows: 



CLIMAP paleo-oceanographers first assembled synoptic rec- 

 ords of the Earth's surface 18,000 years ago (fig. 23). These 

 records include the extent and elevation of the ice sheets, the 

 extent of sea ice, the temperature of the sea surface, and the 

 albedo (reflectivity) of the land surface. This information is 

 assembled and used as the set of boundary conditions for 

 running a numerical model of the atmosphere. The surface air 

 temperatures (fig. 22) and other properties of the ice age at- 

 mosphere are then calculated by the model. When averaged 

 globally, and compared to temperatures calculated for the 

 climate today, the mean air temperature decrease during the 

 ice age was only 5°C. This result is one of the most important 

 CLIMAP contributions to date. For the first time, we have 

 an accurate estimate of the magnitude of the largest climatic 

 change ever to occur during the past million years. Thus, we 

 have a basis for judging the impact of any change in future 

 climate that might occur either naturally or as the result of 

 man's activities. 



Solar Control of Climate. Another important advance in 

 recent CLIMAP research is the publication of evidence that 

 changes in the geometry of the Earth's orbit are a major 

 cause of the ice ages. This theory, which was developed origin- 

 ally a century ago and has come to be known as the Milanko- 

 vich theory, assumes that ice ages are caused by changes in the 

 seasonal and latitudinal distribution of solar energy that must 

 result when the geometry of the Earth's solar orbit changes 

 (fig. 24). 



Three periodic variations in the orbit occur as a result of 

 changes in the position of planets in the solar system — varia- 

 tions in the eccentricity of the orbit, with an average period of 

 about 100,000 years; in the tih of the Earth's axis with a period 

 of about 41,000 years; and a 22,000-year cycle in the position 

 of the orbital path at which a given season occurs. According 

 to a modified version of the Milankovich theory, each of these 

 periodicities should be found in climatic records — if, in fact, 

 the orbital changes are the fundamental cause of the ice ages. 

 CLIMAP researchers assembled long climatic records from 

 two deep-sea cores from the southern Indian Ocean, and dis- 

 covered climatic periodicities so close to those predicted that 

 the Milankovich theory is confirmed as the primary cause of the 

 ice age cycle. The effect of the longest cycle is schematically 

 shown in figure 25. 



Other Accomplishments. Other accomplishments of CLI 

 MAP during the past year include: 



1. An interactive system of computer programs called the 

 CLIMAP Update System has been designed to store paleo- 

 oceanographic data. Over 11,000 carbonate, 4,000 isotope, and 

 140 radioisotope analyses will soon be added to the CLIMAP 

 data file presently archived with EDS' National Geophysical 

 and Solar-Terrestrial Data Center (NGSDC) in Boulder, 

 Colorado. 



2. A volume of 17 scientific papers published in 1976 re- 

 flects the multi-disciplinary efforts of the CLIMAP project. 

 (Geographical Society of America Memoir 145, edited by 

 R. M. Cline and J. D. Hays, Investigation of Late Quaternary 

 Paleo-oceanography and Paleoclintatology, x + 446 pages, 

 245 figures, 66 tables, 26 appendices on three 98-frame micro- 

 fiche for use on 24x readers. ) 



3. Studies of the movement of the North Atlantic Polar 

 Front during the last major climatic cycle (127,000 to 12,000 



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