Carbon dioxide level in atmosphere at high

WASHINGTON – The concentration of carbon dioxide in the atmosphere climbed to a record 381 parts per million last year, an increase sure to spark further debate on global warming.

The reading was up 2.6 parts per million, according to preliminary calculations, David J. Hofmann, of the Office of Atmospheric Research at the National Oceanic and Atmospheric Administration, said Tuesday.

Final calculations from reporting stations around the world won’t be available until the spring, Hofmann said, but the preliminary numbers are usually quite close.

Carbon dioxide is a major greenhouse gas. Those are chemicals that have been increasing in the atmosphere since the Industrial Revolution, raising fears of altering the planet’s climate by trapping heat from the sun.

In Geneva, meanwhile, the World Meteorological Organization issued its own report for 2004, in which Secretary-General Michel Jarraud said, “Global observations coordinated by WMO show that levels of carbon dioxide, the most abundant greenhouse gas in the atmosphere, continue to increase steadily and show no signs of leveling off.”

While the total of carbon dioxide in the atmosphere goes up every year, the amount of increase varies from year to year, Hofmann said.

The ocean absorbs carbon dioxide at a fairly steady rate, he explained, but some years plants are more active in taking it up as they grow while other years they use less. And years when there are large forest fires can release increased amounts of the gas into the air, he said.

“The real question is how long will the Earth continue to adjust itself to take up the additional carbon dioxide,” he said. “That’s one of the major questions.”

In addition to carbon dioxide, the 2004 data from WMO calculated that nitrous oxide, which has been rising steadily since 1988, totaled 318.6 parts per billion. Methane has risen the most dramatically over the past two centuries, with the total amount in 2004 at 1,783 parts per billion, but its growth has been slowing, WMO said.

Hans Verolme, director of climate change for the World Wildlife Fund in the United States, welcomed the report as providing an authoritative measurement of the change.