Global warming plateau linked to air pollution

Associated Press

WASHINGTON (AP) — China's rapid industrial growth helped ease the pace of global warming in the last decade, according to a new study. But greenhouse gases are heating things up again.

While the decade of the 2000s was one of the hottest on record, the pace of warming had eased until 2009 and 2010, when temperatures lurched upward.

The reason for the seeming plateau, according to the study, was the added sulfur polluting the atmosphere from the sharp increase in coal-burning industrial activity in China.

"What's going on is, human activities do two things: They cool the planet and they warm the planet. People normally just focus on the warming effect of CO2 (carbon dioxide), but during the Chinese economic expansion there was a huge increase in sulfur emissions," which have a cooling effect, explained Robert K. Kaufmann of Boston University, lead author of the new study published Monday in Proceedings of the National Academy of Science.

Chinese coal consumption doubled between 2003 and 2007, and that caused a 26 percent increase in global coal consumption, Kaufmann said. That was about the same as the worldwide increase in coal use in the previous 22 years, he said. "So what took 22 years now took four years, and it started at a higher level."

Now, China has recognized the impacts on their environment and on their citizens' health and are installing equipment to scrub out the sulfur particles, Kaufmann said.

Sulfur quickly drops out of the air if it is not replenished, while CO2 remains for a long time, so the warming from CO2 is beginning to be visible again, he noted.

Indeed, NASA and the National Oceanic and Atmospheric Administration, have listed 2010 as tied for the warmest year on record, while the Hadley Center of the British Meteorological Office lists it as second warmest, after 1998.

Some have even suggested that injecting sulfur compounds into the atmosphere might help ease global warming by increasing clouds and haze that would reflect sunlight, but an earlier study concluded that would be a bad idea.

Injecting enough sulfur to reduce warming would wipe out the Arctic ozone layer and delay recovery of the Antarctic ozone hole by as much as 70 years, according to an analysis by Simone Tilmes of the National Center for Atmospheric Research in Boulder, Colo.

"While climate change is a major threat, more research is required before society attempts global geoengineering solutions," said Tilmes.

Overall, global temperatures have been increasing for more than a century since the industrial revolution began adding gases like carbon dioxide to the air. But there have been similar plateaus, such as during the post-World War II era when industrial production boosted sulfur emissions in several parts of the world, Kaufmann explained.

Atmospheric scientists and environmentalists are concerned that continued rising temperatures could have serious impacts worldwide, ranging from drought in some areas, changes in storm patterns, spread of tropical diseases and rising sea levels.

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Online: http://www.pnas.org

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