updated 11/13/2007 3:45:15 PM ET 2007-11-13T20:45:15

Only about a third of the climate-damaging carbon dioxide released into the atmosphere in North America is offset by carbon removing activities, a government report said Tuesday.

Currently, North America produces more than one-fourth of the carbon dioxide released worldwide by burning fossil fuels and other activities, the U.S. Climate Change Science Program said in the report.

The report comes as top climate researchers from around the world meet in Spain to work on a new analysis on climate change, an increasing concern to scientists and policymakers worried about warming temperatures.

According to the new U.S. study, North America released 1,856 million metric tons of carbon into the air in 2003 — 85 percent from the United States, 9 percent from Canada and 6 percent from Mexico.

At the same time, growing vegetation and other sources took in about 500 million metric tons of carbon.

This is the first net carbon report for the region, said Tony King, lead researcher on the report and chief scientist at Oak Ridge National Laboratory.

The amount of carbon taken up by North America had not been closely studied and some reports even suggested that enough was being absorbed to balance emissions, King said.

It is now clear that is not the case and North America is contributing to the worldwide increase in carbon dioxide in the air, he said.

In addition, King said, the main source of carbon dioxide absorption is regrowth of forests that were cut for agriculture or timber about 150 years ago. Because this regrowth is relatively new it is taking in carbon rapidly, but that rate will decline as the forests age, he said.

"Actions to reduce fossil fuel emissions are going to be required if we are interested in mitigating the effects" of climate change, added Lisa Dilling of the University of Colorado, co-lead author of the report.

"More than half of the electricity produced in North America is consumed in buildings, making that single use one of the largest factors in North American emissions," the National Oceanic and Atmospheric Administration said in a press release announcing the report. "In the United States, 67 percent is used in buildings.

"In 2003, the carbon dioxide emissions resulting from energy consumed in United States buildings alone were greater than total carbon dioxide emissions of any country in the world except China," NOAA added. "Energy use in buildings in the United States and Canada, including the use of natural gas, wood, and other fuels as well as electricity, has increased by 30 percent since 1990, corresponding to an annual growth rate of 2.1 percent.

"In the United States, the major drivers of energy consumption in the buildings sector are growth in commercial floor space and increase in the size of the average home," NOAA said. "Carbon emissions from buildings are expected to grow with population and income."

The full report is online at www.climatescience.gov

Copyright 2007 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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