21/08/2013 10:11
U.N. panel says it's more certain that humans drive global warming
Scientists are more convinced that human activity is behind the increase in global temperatures since the 1950s, which has boosted sea levels and the odds of extreme storms, according to a leaked draft of an upcoming U.N. report.
"It is extremely likely that human influence on climate caused more than half of the observed increase in global average surface temperature from 1951 to 2010," according to a summary of the draft obtained by CNN. "There is high confidence that this has warmed the ocean, melted snow and ice, raised global mean sea level and changed some climate extremes in the second half of the 20th century."
Those conclusions come from the upcoming report of the U.N. Intergovernmental Panel on Climate Change, the fifth in a series of multiyear reports seen as a benchmark on the subject. The panel's last report, in 2007, concluded that it was 90% certain that rising temperatures were due to human activity; the new draft raises that figure to 95%.
Increasing concentrations of carbon dioxide and other emissions have driven up global average temperatures by about 0.6 degrees C (1 degree F) since 1950, the report states. That's likely to go up by between 1 and 3.7 degrees C (1.8 to 6.6 F) by 2100, the draft states.
Meanwhile, the rise of sea levels, currently about 3 mm (1/8 inch) per year, is "very likely" to speed up. Global average sea levels are expected to go up between 50 and 97 cm - 20 inches to more than 3 feet - by 2100, according to the draft.
"Emissions at or above current rates would induce changes in all components in the climate system, some of which would very likely be unprecedented in hundreds to thousands of years," it states. Those changes are likely to occur "in all regions of the globe" and affect the water cycle, rising ocean acidity and changes in the water cycle.
"Many of these changes would persist for many centuries," it added.