Scientists looking at nearly a century of records say they can't discern any warming trend to confirm the threat of a greenhouse-like heating of the earth.
The heat and drought of last summer helped fuel concern about the greenhouse theory of climate change, even though scientists cautioned that one unusual season didn't necessarily prove a long-term trend.Now, researchers at the National Oceanic and Atmospheric Administration report that they have been unable to find evidence of any overall temperature increase for the United States.
"The most important result of this study is that there is no statistically significant evidence of an overall increase in annual temperature or change in annual precipitation for the contiguous U.S., 1895-1987," concluded the authors of the new analysis.
Another leading climate expert, however, cautioned that the findings don't necessarily knock down the greenhouse theory.
James E. Hansen of the Goddard Institute for Space Studies in New York said that the new analysis is limited to the United States.
It's not inconsistent with the greenhouse theory for some parts of the world to be warmer, others cooler and some to show no change at this point, he said in a telephone interview. By the mid-1990s, he went on, the data should show a clearer trend.
"Assuming the numbers are right, they are not inconsistent" with the greenhouse warming theory, responded John Topping of the Climate Institute, also pointing out that the study covers only the United States.
The new study, published in the January edition of Geophysical Research Letters, showed no significant change in the nation's average temperature or precipitation between 1895 and 1987.