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Climate: Long-Range Investigation, 

 Mapping.and Prediction (CLIMAP) Study 



CLIMAP research focuses on describing and explaining 

 climatic changes over the last million years. Accurate descrip- 

 tions of climatic change over that time scale will improve the 

 CLIMAP scientists' understanding of transitions between what 

 are considered to be the two stable states of global climate — 

 the ice age and temperate periods. These studies will also 

 increase knowledge about mechanisms of climatic change by 

 comparing global climatic descriptions derived from data col- 

 lection and analyses with those produced by computer models. 



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 since the interchange of heat be- 

 tween the world oceans 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) Their multivariate 

 characteristics make possible a wide range of correlative inter- 

 pretations, including chemical and physical properties, concen- 

 trations of microfossils sensitive to differing combinations of 

 surface or sea-bottom environmental factors, isotopic ratios, and 

 other diverse indicators. 



Recent advances in CLIMAP research relate to the global 



climatic reconstruction programs which assemble synoptic rec- 

 ords of data to reconstruct past changes and near equilibrium 

 states of the global climate. Scientists at several institutions 

 have formulated a model using quantitative geologic evidence 

 to reconstruct the Earth's surface approximately 18,000 years 

 ago, the time of maximum extent of continental glaciation in 

 the last ice age. Climatic boundary conditions for the recon- 

 struction were continental geography at a time of lowest sea 

 levels, the albedo or light reflectance of glaciated and nonglaci- 

 ated areas, the extent and elevation of permanent ice, and the 

 sea-surface temperature pattern of the world ocean. Figure 1 1 

 shows the reconstructed surface for summer of ice-age earth 

 18,000 years ago applying the interpreted boundary conditions. 

 Figure 12 shows the diff'erence between August sea-surface 

 temperatures 18,000 years ago and present measurements. 



From these reconstructions it can be seen that 18,000 

 years ago the Earth's surface differed remarkably from present 

 conditions. Huge land-based ice sheets with a corresponding 

 increase in pack ice and marine-based ice sheets covered large 

 areas in the Northern Hemisphere, while sea ice in the Southern 

 Hemisphere showed a greater contrast in extent. The changes 

 in land vegetation with grasslands and deserts spreading at the 

 expense of forests, joined with the expanded areas of permanent 

 ice to cause an increase in global surface albedo and a marked 

 general cooling of the ocean's surface. 



The determination of the estimated boundary conditions 

 on the Earth's surface during the maximum extent of glaciation 

 1 8,000 years ago has enabled CLIMAP researchers to develop 

 a preliminary model of global atmospheric conditions including 

 such elements as pressure, temperature, wind, cloudiness, and 

 precipitation that enveloped ice-age Earth. The simulation of 

 this model allows preliminary comparisons to be made with 

 available paleoclimatic data, with the result that systematic 

 investigations of paleoclimatic structures can be initiated. 



In addition to estimating boundary conditions and devel- 

 oping global atmospheric models, other accomplishments of 

 CLIMAP in the past year include: 



1. Preparation of material for a second time-level recon- 

 struction — the penultimate interglacial maximum, 120,000 B.P. 

 (before present). 



2. Preparation for final revised 18,000 B.P. reconstruction. 



3. Development of techniques in using benthonic fauna to 

 estimate bottom water characteristics. 



4. Determination of periodicities in the climatic record that 

 match precisely with periodicities of the Earth's orbital param- 

 eters, (eccentricity, obliquity, and precession) during the last 

 half million years. 



5. Establishment of a precise chronology for climatic fluctua- 

 tions in deep-sea cores during the last half million years. 



Future CLIMAP research plans are to improve the 18,000- 

 B.P. August sea surface tempierature map and to complete the 

 first global map of 18,000 B.P. February temperatures and 

 albedos, providing CLIMAP's first look at seasonal contrasts 

 in the ice-age world. This map will then be made available 

 to various modeling groups at several institutions for develop- 

 ment of general circulation models for that time interval. The 

 documentation of global reconstruction of ice sheets at 18,000 

 B.P. and 120,000 B.P. is continuing. 



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