SCIENCE / MEDICINE : Warming Estimates May Be Wrong

Weather changes caused by unusual Pacific ocean currents may have led scientists to overestimate how much the Earth has warmed in recent decades, according to a new study.

Jim Angell of the National Oceanic and Atmospheric Administration has calculated the amount of global warming associated with the El Nino events over the last couple of decades. Subtracting the ocean effects reduces the global warming by one-fourth between the 1960s and the 1980s, according to Angell’s report, published last week.

It may be that part of the increase in global warming is a result of the strength of the El Nino events in the 1980s, but it may also be that the global warming led to more and stronger El Ninos, Angell said. El Nino events involve unusually warm water moving eastward in the Pacific Ocean that can affect weather events worldwide during their lifetime of a year or so.

Scientists have estimated that the layer of air closest to the Earth warmed by 0.33 degrees Celsius (0.59 degrees Fahrenheit) between the 1960s and the 1980s. Angell found that after subtracting the effect of the El Nino warming from the record, the air had warmed by 0.24 degrees Celsius (0.43 degrees Fahrenheit).