2006 Philadelphia Annual Meeting (22–25 October 2006)

Paper No. 2
Presentation Time: 1:45 PM


EASTERBROOK, Don J., Dept. of Geology, Western Washington Univ, Bellingham, WA 98225, dbunny@cc.wwu.edu

At least five abrupt, global climate changes of 4-15° C in the past 16,000 years have implications for understanding present–day global warming: (1) the end of the last glacial maximum (~16,000 yrs. ago), (2) the onset of the Younger Dryas (~12,700 yrs. ago), (3) the end of the Younger Dryas (~11,500 yrs. ago), (4) in the early Holocene (~8,200 yrs. ago), and (5) during the Little Ice Age (~1600–1850 AD). Climatic models that predict soaring of global temperatures in the coming century as a result of increased atmospheric CO2, do not incorporate such geologic data. GISP2 ice cores show that late Pleistocene, abrupt, temperature fluctuations of 8–12° C occurred in only 20–100 years. The GISP2 ice core suggests warming of ~7° C in about a decade at the end of the Younger Dryas. These changes, 10 orders of magnitude greater than the 0.8° C global temperate of the past century, were clearly not caused by changes in atmospheric CO2. During these climatic changes 10Be and 14C production rates varied, suggesting a connection between global climate changes and solar variation. Global warming over the past century has not been constant–glaciers in the Cascade Range show distinct oscillations having a period of ~30 years, dating back to about 1790 AD. Glaciers advanced from about 1890–1920, retreated rapidly from ~1925 to ~1945, readvanced from ~1945 to ~1977, and have been retreating since the present warm cycle began in 1977. Comparable, cyclical, climatic fluctuations occurred in the North Pacific (PDO), the North Atlantic (NAO), Europe, and Greenland. Because the warming periods in these oscillations occurred well before atmospheric CO2 began to rise rapidly in the 1940s, they could not have been caused by increased atmospheric CO2 .and global warming since 1900 could well have happened without any effect of CO2. If the cycles continue as in the past, the current warm cycle should end soon and global temperatures should cool slightly until about 2035, then warm about 0.5° C from ~2035 to ~2065, and cool slightly until 2100. The total increase in global warming for the century should be ~0.3 ° C, rather than the catastrophic warming of 3-6° C (4-11° F) predicted by the IPCC.