LONDON Increases in the amount of the greenhouse gas carbon dioxide in the atmosphere accelerated last year, the U.S. National Oceanic and Atmospheric Administration (NOAA) told Reuters on Wednesday.
The new data may dampen hopes that a slowdown in industrial output and carbon emissions, which started at the end of last year, will temporarily deflect climate change.
Some analysts had hoped that recession would give the world breathing space to reverse its impact on the climate. The new NOAA data showed that levels of carbon dioxide accelerated slightly last year.
"For us to see (the impact) in the atmosphere it would take a large drop in emissions, but it hasn't happened yet and that's very clear from this data," said Thomas Conway, a NOAA climate scientist who helped compile the figures.
"If the change in emissions is only a few percent we're not going to see that in the atmosphere," Conway told Reuters, explaining that natural processes, whereby for example forests and oceans mop up carbon dioxide, masked small changes in manmade emissions in the short-term at least.
Recession means that developed nations' greenhouse gas emissions will fall by about 2 percent this year, some analysts estimate, although that effect could be much greater if the world slipped into a wider slump or depression.
Emissions are expected to continue to rise in China, which analysts say is the world's biggest carbon emitter.
Levels of carbon dioxide last year reached a global average of 384.9 parts per million (ppm) in the atmosphere, up 2.2 ppm on 2007, compared with a previous annual increase of 1.8 ppm, the NOAA data showed.
Annual increases had been greater in the past decade compared with the 1980s and 1990s, said Conway.
That acceleration was mostly due to increases in emissions, he added, but may also support an unproven theory that oceans, which currently mop up a large part of excess manmade carbon emissions, were becoming saturated.
"There is some evidence that a sink in the southern (Antarctic) ocean is not keeping up ... has been saturated."
Rising global carbon emissions are stoking global warming, most scientists agree. One threshold for dangerous climate change adopted by the European Union is 2 degrees centigrade warming above pre-industrial levels.
"Levels of CO2 at 385 ppm are already approaching a level which in the long-term we have to stay below to have a likely chance of staying below 2 degrees," said Malte Meinshausen, a climate scientist at the Germany-based Potsdam Institute.
It was possible for levels of carbon in the atmosphere to peak and then fall again, however, if people adopted low-carbon sources of energy and technologies which suck carbon dioxide out of the air by burying it underground, Meinshausen added.