Written by Don J. Easterbrook
July 20, 2008
Shifting of the PDO to Cool Mode Assures Global Cooling for the Next Three Decades - Don J. Easterbrook, Dept. of Geology, Western Washington University, Bellingham, WA. Addressing the Washington Policymakers in Seattle, WA, Dr. Don Easterbrook said that shifting of the Pacific Decadal Oscillation (PDO) from its warm mode to its cool mode virtually assures global cooling for the next 25-30 years and means that the global warming of the past 30 years is over.
The cool water anomaly in the center of the image shows the lingering effect of the year-old La Nina. However, the much broader area of cooler-than-average water off the coast of North America from Alaska (top center) to the equator is a classic feature of the cool phase of the Pacific Decadal Oscillation (PDO). The cool waters wrap in a horseshoe shape around a core of warmer-than-average water. (In the warm phase, the pattern is reversed). Unlike El Nino and La Nina, which may occur every 3 to 7 years and last from 6 to 18 months, the PDO can remain in the same phase for 20 to 30 years.
As shown by the historic pattern of PDOs over the past century and by corresponding global warming and cooling, the pattern is part of ongoing warm/cool cycles that last 25-30 years. Each time the PDO mode has shifted from warm to cool or cool to warm, the global climate has changed accordingly. In 1977, the PDO shifted from cool mode to warm mode and set off the global warming from 1977 to 1998, often referred to as the “Great Climate Shift.” The recent shift from PDO warm mode to cool mode is similar to the shift that occurred in the mid-1940’s and resulted in 30 years of global cooling. The global warming from ~1915 to ~1945 was also brought on by a mode shift in the PDO. Every indication points continuation of the PDO patterns of the past century and global cooling for the next 30 years. Thus, the global warming the Earth has experienced since 1977 appears to be over!