Temperature changes recorded in the GISP2 ice core from the Greenland Ice Sheet show that the global warming experienced during the past century pales into insignificance when compared to the magnitude of profound climate reversals over the past 25,000 years.
SIGNIFICANCE OF PREVIOUS GLOBAL CLIMATE CHANGES
If CO2 is indeed the cause of global warming, then global temperatures should mirror the rise in CO2. For the past 1000 years, atmospheric CO2 levels remained fairly constant at about 280 ppm (parts per million). Atmospheric CO2 concentrations began to rise during the industrial revolution early in the 20th century but did not exceed about 300 ppm. The climatic warming that occurred between about 1915 and 1945 was not accompanied by significant rise in CO2. In 1945, CO2 emission began to rise sharply and by 1980 atmospheric CO2 had risen to just under 340 ppm. During this time, however, global temperatures fell about 0.9°F (0.5° C) in the Northern Hemisphere and about 0.4°F (0.2° C) globally. Global temperatures suddenly reversed during the Great Climate Shift of 1977 when the Pacific Ocean switched from its cool mode to its warm mode with no change in the rate of CO2 increase. The 1977–1998 warm cycle ended in 1999 and a new cool cycle began. If CO2 is the cause of global warming, why did temperatures rise for 30 years (1915-1945) with no significant increase in CO2? Why did temperatures fall for 30 years (1945-1977) while CO2 was sharply accelerating? Logic dictates that this anomalous cooling cycle during accelerating CO2 levels must mean either (1) rising CO2 is not the cause of global warming or (2) some process other than rising CO2 is capable of strongly overriding its effect on global atmospheric warming.
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