THE NEXT 25 YEARS: GLOBAL WARMING OR GLOBAL COOLING?—GEOLOGIC AND OCEANOGRAPHIC EVIDENCE FOR CYCLICAL CLIMATIC OSCILLATIONS

Paper presented at the The Geological Society of America (GSA) Annual Meeting, 5-8 November 2001

EASTERBROOK, Don J., Geology, Western Washington Univ, Bellingham, WA 98225, dbunny@cc.wwu.edu and KOVANEN, Dori J., 3117 Chandler Parkway, Bellingham, WA 98226

Global temperatures have been predicted to soar in the next several decades from increase in atmospheric CO2. Such a temperature increase could be catastrophic.

However, evidence of past climatic changes over the past century from glaciers and the oceans suggest another possibility. Advance and retreat of glaciers in the Pacific Northwest show three distinct oscillations, each having a period of ~25 years. Glaciers retreated rapidly from ~1930 to ~1950-55 (warm cycle), readvanced from ~1955 to ~1977 (cool cycle), then retreated rapidly from ~1977 to the present (warm cycle). Evidence in the Northern Hemisphere temperate latitudes shows comparable, cyclical, oscillation patterns in the North Pacific (PDO), the North Atlantic (NAO), European alpine glaciers, and Greenland ice cores (GISP2). If the trend continues, the current warm cycle should end soon.

Global warming curves show a temperature reversal during the last cool cycle (~1950 to 1980) at a time when large amounts of CO2 were introduced into the atmosphere. This infers that global temperatures then were not driven solely by atmospheric CO2 but responded in the same fashion as the Northern Hemisphere, temperate, glacial and oceanic cycles. The present global warming occurs during a warm climatic cycle, suggesting that only part of it can be attributed to increased atmospheric CO2 If the cycles continue as in the past, the current warm cycle should end in the next few years, and global warming should abate, rather than increase, in the coming decades.

GSA Annual Meeting, November 5-8, 2001