Posted: 06/20/2005 | Author: Dennis Avery
California Seal Pups Predict Pacific Ocean Cooling
A new study of California elephant seal pups and their weaning weights predicts that a 25-year Pacific Ocean warming has ended, and the second half of a 50-year cycle has begun to cool the northern Pacific. Historical fish catch data indicate the ocean cooling trend is likely to last until about 2025.
Burney Le Boeuf and David Crocker from the University of California/Santa Cruz monitored central California seal pups’ weaning weights for 29 years, from 1975 to 2004. The ocean’s temperatures generally increased, and the pups’ weaning weights declined 21 percent over the 24 years from the study’s beginning until 2000.
The seal pups’ weight decline coincided with an increase in their mothers’ foraging time of about 36 percent. A decline in the mothers’ own weights confirmed that fish were relatively scarce. After 1999, however, the ocean temperatures began to decline, fish became more abundant, and the pups’ weaning weights abruptly began to rise. By 2004, the pups’ weaning weights had recovered to 90 percent of their 1975 weaning size.
The seal pup weight trends confirm a cycle that is also found in northern Pacific salmon catches. The Columbia River salmon numbers declined sharply after 1977. Columbia River salmon catch data, which date back to 1900, clearly reveal 50-year cycles, with 25 years of salmon abundance interspersed with 25-year periods of salmon scarcity. The Gulf of Alaska salmon catch data show a similar but opposite cycle in salmon numbers. When the Columbia salmon fishery is down, the Alaskan salmon numbers are up.
Dr. Francisco Chavez of the Monterey Bay Aquarium led a 2003 study that found shifts in sardine and anchovy populations across the Pacific followed the same 50-year cycle, and did so in such widely-separate places as California, Peru, and Japan, with sharply different fishing pressures. Chavez’s data show the most recent shift, toward cooler temperatures that favored anchovies over sardines, occurred in the late 1990s. The previous shift toward warmer temperature, which disadvantaged the California seal pups and anchovies, occurred in the mid-70’s.
Researchers have begun to call the 50-year ocean cycle the Pacific Decadal Oscillation. Temperatures rise and fall, fish species wax and wane, the fish are caught in different places, but total ocean productivity remains relatively stable.
Do the seals, salmon, and sardines have something to tell us about man-made global warming? The Earth’s temperatures have definitely increased since 1850—the end of the widely noted Little Ice Age—by about 0.8 degrees Celsius. However, 0.6 degrees C of the warming occurred before 1940, and thus before much human-emitted CO2.
After 1940, the Earth’s temperature declined moderately until the late 1970s, despite huge increases in human CO2 emissions, and in defiance of the Greenhouse Theory. Is it just coincidence that during this period the PDO was cooling the Pacific?
The current surge of public concern about human-caused global warming occurred after the Earth’s average temperatures began to rise again in the late 1970s—which coincided with the PDO’s shift back to its ocean warming phase.
Does the recent shift in the PDO mean that the Earth’s average temperatures will start to cool again? Was the “warmest decade” of the 1990s an artifact of expanding urban heat islands and a 25-year Pacific Ocean warming phase?
We might want the global climate modelers and UN’s Intergovernmental Panel on Climate Change to specifically address the Pacific Decadal Oscillation before we agree to give up 85 percent of society’s energy supply on behalf of man-made global warming.
Ice cores and seabed sediments have already told us that the Earth has a long, moderate natural 1500-year cycle that raises temperatures in New York about 2 degrees C during its warming phase, and drops them about 2 degrees C during its “little ice ages.” The Little Ice Age, from 1300 to 1850 AD, was the most recent of these cooling phases.
Now, seal pups and sardines are instructing us that even temperature trends as long as 25 years can mislead us about cause and effect in the Earth’s climate—which has been cycling constantly for at least the last million years.