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Global warming: carbon dioxide emissions worldwide fell in 2009

That's the good news heading into Cancun global warming talks Nov. 29. The bad news is that the carbon dioxide emissions aren't likely to stay down for long.

By Staff writer / November 22, 2010

Mayor of Paris Bertrand Delanoe (l.) and Mexico City Mayor Marcelo Ebrard display the signed agreements during the World Mayors Summit on Climate Change in Mexico City Sunday. Mayors from around the world signed an agreement to address global warming at the summit and the agreement will be presented to the United Nations Framework Convention for Climate Change in Cancun.

Eliana Aponte/Reuters

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Industrial carbon-dioxide emissions, the driver behind a new round of global climate talks set to begin in Cancun, Mexico, Nov. 29, eased in 2009, according to a group of scientists monitoring atmospheric CO2.

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Emissions from burning coal, oil, and natural gas fell 1.3 percent compared with emissions in 2008, notes in the team from the Global Carbon Project, set up in 2001 to keep track of CO2 emissions as well as conduct research on Earth's carbon cycle.

Even so, concentrations of CO2 rose last year to a level where, for every 1 million molecules of gases in the atmosphere, 387 of them were carbon dioxide. By contrast, the average level for 2008 was 385 ppm.

Concentrations continued to rise even as emissions slipped because even at the reduced pace, humans are pumping CO2 into the atmosphere faster than natural processes can scrub the gas, meaning that human emissions can stay in the atmosphere for centuries, if not longer.

“More CO2 is staying in the atmosphere instead of being absorbed by the ocean and land sinks, like trees and other vegetation,” said Richard Feely, an oceanographer at the National Oceanic and Atmospheric Administration's Marine Environmental Laboratory in Seattle and a member of the team producing the report.

“We’re concerned that if the natural sinks can't keep pace with the increased CO2 emissions, then the physical and biological impacts of global warming will accelerate over the next century.”

The rising concentration highlights the challenge negotiators headed to Cancun face in confronting global warming.

Many countries have agreed in principle to try to stabilize emissions at 350 parts-per-million by century's end. That would result in a 50 percent chance of holding the increase in global average temperatures to about 2 degrees C over preindustrial levels. Yet stabilizing concentrations at any level essentially means ceasing emissions once the desired level is achieved. Global CO2 concentrations already have passed the 350 mark.

La Niña

Among the factors the team cites for lower emissions last year: the global economic downturn and an increase in carbon-dioxide uptake by the oceans and by plants on land, encouraged by La Niña. La Niña is one-half of a natural seesaw shift in climate that takes place across the tropical Pacific every three to seven years.

This swing "has a very clear impact on global carbon cycle," says Pierre Friedlingstein, an atmospheric scientist at the University of Exeter in Britain and the lead author of a summary of the reports findings that appears in the current issue of the journal Nature Geoscience.

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