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Temperature Extremes ‘Virtually Certain’ to Rise, UN Draft Says

November 15, 2011

Nov. 15 (Bloomberg) -- Global daily temperature extremes are “virtually certain” to become warmer this century, a panel of about 200 UN scientists said in a draft of their most comprehensive study of weather-related natural disasters.

Extreme weather events such as downpours and storm surges may make parts of the planet “marginal” for inhabitants, and residents may have to leave some low-lying atolls, according to the 18-page draft by the Nobel Prize-winning Intergovernmental Panel on Climate Change that was obtained by Bloomberg. The UN declined to confirm the document’s contents.

“It is very likely that the length, frequency and/or intensity of warm spells, including heat waves, will continue to increase over most land areas,” the scientists wrote. Drought may intensify in the Mediterranean region, central Europe, southern parts of North America, northeast Brazil and southern Africa, they said.

The final report is due for release on Nov. 18 and is aimed at guiding debate at the annual round of climate talks, taking place this year in Durban, South Africa, beginning on Nov. 28. Delegates from more than 190 countries plan to work on ways to limit climate change after average temperatures last year were tied with 2005 for the warmest on record.

Warming Temperatures

By the end of this century, the panel expects more hot days and fewer cold days. The document, dated Aug. 22, is the current draft being debated this week by envoys from 110 countries in Kampala, Uganda, where the final version will be published.

“I can’t comment because they’re still negotiating line by line,” Nick Nuttall, a spokesman for the UN Environment Program, one of the parent agencies of the IPCC, said in a phone interview from the Ugandan capital. “It’s subject to change, and there are four more days of discussions.”

The authors had “low confidence” that the observed long- term trend of increases in cyclone activity is robust because of changes in the way scientists have monitored the storms in the past few decades. They said average maximum wind speed of hurricanes is likely to increase, while their frequency is likely to drop or remain the same.

The researchers said there’s “high confidence” that without new defenses such as sea walls and flood barriers, economic losses from tropical cyclones will rise. Losses couldn’t reliably be attributed to man-made warming.


“Increasing exposure of people and economic assets is the major cause of the long-term changes in economic disaster losses,” the researchers wrote, with “high” confidence. “Long-term trends in normalized economic disaster losses cannot be reliably attributed to natural or anthropogenic (or man-made) change, particularly for cyclones and floods,” they said.

According to IPCC guidelines, “virtually certain” means a 99 percent to 100 percent chance; “very likely” gives a probability of 90 percent to 100 percent, and “likely” means odds of 66 percent or more. The UN didn’t give percentage thresholds for degrees of confidence or agreement in the draft.

The IPCC in 2007 published its most definitive report on climate change, which is used to guide climate treaty negotiations and for which it shared the Nobel Peace prize. The panel has since admitted errors in that study, including exaggerating the melting of Himalayan glaciers.

--Editors: Reed Landberg, Randall Hackley

To contact the reporter on this story: Alex Morales in London at

To contact the editor responsible for this story: Reed Landberg at

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