UN Climate Panel Amends CO2 Estimates for Policy Makers

A United Nations climate panel that was criticized after a 2007 study overstated the rate of glacial melting backtracked on global carbon-emissions estimates.

The UN Intergovernmental Panel on Climate Change cut its estimate of total emissions since 1870 to 515 billion metric tons, or 515 gigatons, from 531 gigatons, according to a document released this week. It raised its calculation of total carbon emissions since 1750 to 555 gigatons from 545 gigatons.

The Summary for Policy Makers document is designed to guide envoys from 195 nations as they devise a climate agreement by 2015 to limit emissions after 2020. Since some figures were revised up and others down, nations have less or more leeway to emit in the future depending on the scenario.

“Errors can always occur in a human endeavor even if you do a very thorough revision,” Thomas Stocker, co-chairman of the group that drafted the report, said today in Warsaw, where climate envoys are gathered for two weeks of talks. “Addressing these errors expeditiously and transparently adds to the credibility of the process.”

The UN panel came under scrutiny following its last major report in 2007, which exaggerated the rate of melting of glaciers in the Himalayas and overstated the risk of floods in the Netherlands. Since then, the panel has changed the way it deals with errors.

Warming Target

The Summary for Policy Makers document was released in draft form on Sept. 27 and was then subject to editing. The revisions are included in the final version and will inform climate envoys working toward a new treaty to ensure global temperatures don’t rise by more than the UN target of 2 degrees Celsius (3.6 Fahrenheit) since industrialization.

The original report also provided the total carbon emissions permissible under various scenarios. Releasing 900 gigatons would give the world a 33 percent chance of meeting the 2-degree goal, the panel said in the latest document, raising its estimate from 880 gigatons.

Emissions must be kept to 820 gigatons for a 50 percent chance of meeting the target, and 790 gigatons for a 66 percent chance, it said, reducing both figures from previous estimates.

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