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New data on climate change worries scientists

Earth absorbing more heat than it gives off, they say

NEW YORK -- Climate scientists armed with new data from the ocean depths and from space satellites have found that Earth is absorbing much more heat than it is giving off, which they say validates computer projections of global warming.

Lead scientist James Hansen, a prominent NASA climatologist, described the findings on the planet's out-of-balance energy exchange as a ''smoking gun" that should dispel doubts about forecasts of climate change. A climate specialist from Germany called it a valuable contribution to climate research.

Hansen's team, reporting yesterday in the journal Science, said they also determined that global temperatures will rise by 1 degree Fahrenheit this century even if emissions of greenhouse gases are capped tomorrow.

If carbon dioxide and other heat-trapping emissions instead continue to grow, as expected, things could spin ''out of our control," especially as ocean levels rise from melting Greenland and Antarctic ice sheets, the researchers said. International specialists predict a 10-degree leap in Fahrenheit readings in such a worst-case scenario.

The NASA-led researchers were able to measure Earth's energy imbalance because of more- precise ocean readings collected by 1,800 technology-packed floats deployed in seas worldwide beginning in 2000, in an international monitoring effort called Argo. The robots regularly dive as deep as a mile undersea to take temperature and other readings.

Their measurements are supplemented by better satellite gauging of ocean levels, which rise from meltwater and as the sea warms and expands.

With this data, the scientists calculated the oceans' heat content and the global energy imbalance. They found that for every square meter of surface area, the planet is absorbing almost 1 watt more of the sun's energy than it is radiating back to space as heat -- a historically large imbalance. Such absorbed energy will steadily warm the atmosphere.

The 0.85-watt figure corresponds well with the energy imbalance predicted by the researchers' supercomputer simulations of climate change, the report said.

The computer models factor in greenhouse gases in the atmosphere -- including carbon dioxide and methane -- which are produced by everything from automobiles to pig farms. Those gases keep heat from escaping into space. Significantly, greenhouse emissions have increased at a rate consistent with the detected energy imbalance, the researchers said.

''There can no longer be genuine doubt that human-made gases are the dominant cause of observed warming," said Hansen, director of NASA's Goddard Institute for Space Studies at Columbia University's Earth Institute. ''This energy imbalance is the 'smoking gun' that we have been looking for."

Fourteen other specialists from NASA, Columbia, and the Department of Energy coauthored the study.

Scientists have found other possible ''smoking guns" on global warming in recent years, but Klaus Hasselmann, a leading climatologist from Germany, praised the Hansen report for its innovative work on energy imbalance. ''This is valuable additional supporting evidence" of manmade climate change, he said.

In February, scientists at San Diego's Scripps Institution of Oceanography said their research -- not yet published -- also showed a close correlation between climate models and the observed temperatures of oceans, further defusing skeptics' criticism of uncertainties in modeling.

Average atmospheric temperatures rose by about 1 degree Fahrenheit in the 20th century. The Intergovernmental Panel on Climate Change, a UN-organized network of scientists, says computer modeling predicts temperatures rising between 2.5 degrees and 10.4 degrees Fahrenheit by the year 2100.

Besides raising ocean levels, global warming is expected to intensify storms, spread disease to new areas, and shift climate zones, possibly making farmlands drier and deserts wetter.

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