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Climate Change Will Worsen Extreme Weather

Changes in extreme weather will require governments to change how they cope with natural disasters, a new report from the U.N. Intergovernmental Panel on Climate Change warns



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Climate change is shifting weather extremes, increasing the frequency of drought and heat waves and the intensity of rainstorms -- changes that will require the world's governments to change how they cope with natural disasters, the Intergovernmental Panel on Climate Change (IPCC) said today.

The report, written by more than 100 of the world's top scientists, recommends taking steps now to increase the world's ability to adapt and cope with climate extremes.

"The report finds much to be positive about, as far as the chance to make the world a better place at the same time we reduce risk and disaster losses," said Christopher Field, a Stanford University professor who leads the IPCC's working group on climate change impacts.

The key, according to the report, is to focus on what Field called "low-regret" strategies to help reduce future disaster risk while improving people's current livelihoods and well-being.

The report, the IPCC's first in-depth examination of extreme weather, was released in Kampala, Uganda, where researchers gathered this week to finalize their analysis.

IPCC chief Rajendra Pachauri said he hoped governments gathering later this month in Durban, South Africa, for U.N. climate talks would pay heed to the report's conclusions.

"We need to sensitize the global community to the scientific reality of climate change, because therein lies the basis by which society can take action," Pachauri said. "If we do not give science the primacy it deserves ... I'm afraid you're not likely to get any action."

Tracking human-driven changes since the 1950s
The analysis describes wide-ranging changes in climate extremes since the middle of the last century, and says there is good evidence that some of those changes have been driven by human activities.

Those changes include an overall decrease in the number of cold days and nights, and an overall increase in the number of warm days and nights, worldwide -- a shift that researchers said was "very likely," which in IPCC terms signifies 99-100 percent confidence in that conclusion.

The report says it is "likely" -- or a 66-100 percent chance -- that human activities have contributed to that shift.

There have been "statistically significant" changes in the number of heavy precipitation events in some areas, with more areas experiencing increases than decreases.

Researchers say they have "medium confidence" that humans have influenced those changes, and "medium confidence" that parts of the world, including southern Europe and West Africa, have seen more intense and longer droughts. Other areas, like central North America and northwestern Australia, have seen droughts becomes less frequent, less intense or shorter.

Researchers say they have low confidence of any long-term shifts in hurricane and tornado activity, and there is sparse evidence available to determine whether climate change has altered the magnitude and frequency of flooding.

Those trends are likely to continue and intensify through the end of the century, [without efforts to cut the world's output of greenhouse gases], the report says.

It predicts "substantial warming" of temperature extremes by 2100, with the length, frequency and intensity of heat waves increasing over most land areas.

Extreme heat expected by century's end
Extreme heat now considered a 1-in-20-year event will occur every 1-2 years by the end of the century in most parts of the world. In high northern latitudes, such heat waves will occur every 1-5 years by 2100, the report says.

Very hot days now considered 1-in-20-year extremes will grow 1.8-5.4 degrees Fahrenheit warmer by mid-century and 3.6-9 degrees Fahrenheit warmer by the end of the century.

The number of heavy rainfall events and the proportion of annual rainfall that falls during those events will also increase, the report says. Very rainy days that now occur once every 20 years will occur once every five to 15 years by the end of the century.

Even in places that appear likely to become drier as the planet warms, there is "medium confidence" that individual rainstorms will become more intense, the report says.

There is also "medium confidence" that droughts will grow more severe in a broad swath of the globe, including southern and central Europe, the Mediterranean, central North America, Central America and Mexico, northeastern Brazil and southern Africa.

Hurricanes' average maximum winds will grow stronger in many ocean basins, although the number of storms will remain steady or decrease slightly. That change in wind speed, coupled with a "very likely" increase in average sea level, is a concern for small tropical island nations, the report says.

The analysis also says there is "high confidence" that changing rainfall and temperature extremes will increase the likelihood of landslides in high mountain regions and flooding caused by the rapid release of glacial meltwater from mountain glaciers.

Scientists are less certain about climate change-driven shifts in flooding and natural climate patterns like El Niño, the report says.

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500

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