WASHINGTONWhile the rest of the world is getting hotter, the continental United States has become just a smidge cooler and a lot wetter in the past third of a century, according to a new federal study.
The latest data, which detected a shift in the climate in the lower 48 states since 1966, runs counter to what many Americans have been feeling and what scientists have been theorizing. Conducted by two researchers at the Climate Prediction Center, the study concludes the cooling has been subtle, variable and quite likely not statistically significant.
Its barely 1/30th of a degree cooler per decade for the lower 48 states as a whole. In the northern Midwest and west of the Rockies, it has gotten hotter, and much hotter in Southern California. But it is cooler in the Eastespecially the Southeastand the lower Midwest.
Its cooler nationwide mostly because late summers and falls have been cooler. Winters have been warmer.
Theres been nothing subtle or variable about precipitation in the nation. Its been hard to miss. Nearly the entire countryexcept for slivers of Idaho, Washington state and Oregonhas been wetter. Much wetter. The United States has been getting 9/lOths of an inch more precipitation every decade since 1966. And each month is more moist than it used to be, with autumn far wetter.
We cant really pin any of this on a definite physical cause, said study co-author Rich Tinker, a meteorologist at the Climate Prediction Center, a division of the National Oceanic and Atmospheric Administration.
Theres disagreement about what this means in the continuing debate about the greenhouse effect, a theory that pegs a gradual warming of the planet to the excesses of an industrial age.
Skeptics of global warming say the study confirms what they thought: The world isnt getting hotter; maybe parts of it are, but not the globe as a whole.
Global warming doesnt mean that everywhere warms up at once, but rather theres complicated changes in weather, said Kevin Trenberth, head of c1imate analysis at the nonprofit National Center for Atmospheric Research. He said the Arctic (including Alaska), Russia and Europe are warming tremendously.
Thats why Europeans are more active in efforts to combat global warming: They feel it more than people in Washington, where the temperature hasnt changed much.
The National Center for Atmospheric Research released the results of a new computer model that forecasts that rain in the American Southwest and Great Plains will increase 40 percent and world temperatures will rise by 3 degrees during the next century because of increases in carbon dioxide emissions.
Climate change skeptic and former National Weather Service official Fred Singer, president of the environmental Policy Project, said the two studies highlight the differences in climate change theory.
It depends on who you believe, Singer said. Should you believe in the atmosphere or should you believe in the (computer) models? I prefer to believe in the atmosphere.
Singer said the U.S. weather trend study confirms earlier research.
But not all studies agree. David Easterling, principal scientist at the National Climatic Data Center (which, like the Climate Prediction Center, is part of NOAA) said his agencys studies show that only the American Southeast is getting cooler. He said his study is based on longer-term data than Tinkers is; his goes back to 1900 instead of 1941.
But some of Tinkers findings jibe with what other researchers have found. They all tend to agree its getting wetter, the winters are warmer and the falls are cooler.
Easterling and Trenberth said the most significant finding from Tinkers study is that the lower 48 states are getting much wetter.
Rain is natures air conditioner, and this increase in precipitation fits in with global warming theory, Trenberth said. And moisture is what really determines how the weather feels to people and how crops survive.
To global warming skeptic Pat Michaels, a professor at the University of Virginia and Virginias state climatologist, the key from Tinkers study is that people are beginning to realize that Tip ONeills dictum works in climate too: All climate is local.
But Tinker said theres been an even more solid use of his study by forecasters at the Climate Prediction Center who put out long-range prognostications. Using his research, he said, the weather service devised this years winter and spring predictions. They were the most accurate on record.