It Is "Virtually Certain" That Climate Change is Causing More Extreme Weather

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There's little to no doubt that climate change will both exacerbate extreme weather events, and cause many kinds to occur more frequently. But there's still debate over which events will be most severely worsened by climate change, and how greatly events like droughts, hurricanes, tropical storms, and floods will be impacted by the climbing global temperature.

These are the basic conclusions of the latest IPCC Special Report, "Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation", which was published today. The IPCC (Intergovernmental Panel on Climate Change), as you know, is an international body of scientists who work together to synthesize the latest climate research into policy recommendations and guidelines for the public.

Heat Waves & Hotter Days

And this time, they've landed with conclusions like this: "It is virtually certain that increases in the frequency and magnitude of warm daily temperature extremes and decreases in cold extremes will occur in the 21st century on the global scale. It is very likely that the length, frequency and/or intensity of warm spells, or heat waves, will increase over most land areas."

In IPCC wonk-speak, that means there's a 90-100% chance that we'll be seeing more heat waves almost everywhere. So that's among the worst news of the report: Citizens of the world, gear up for a near-certain increase in heat waves and dry spells. It is also virtually certain (99% or more) that "on a global scale hot days become even hotter and occur more often." Dr. Thomas Stocker, the other Co-chair of Working Group I wrote that "For the high emissions scenario, it is likely that the frequency of hot days will increase by a factor of 10 in most regions of the world." Bummer.

More Droughts & Rain, Nastier Hurricanes

Elsewhere, we wade into slightly grayer, but still disturbing, territory: “Changes in other extremes, such as more intense and longer droughts are observed in some regions, but the assessment assigns medium confidence due to a lack of direct observations and a lack of agreement in the available scientific studies. Confidence in any long-term trend in tropical cyclone intensity, frequency or duration is assessed to be low,” Stocker writes. “Likewise, heavy precipitation will occur more often, and the wind speed of tropical cyclones will increase while their number will likely remain constant or decrease”.

Which means that there will almost certainly be more intense droughts in many regions, but the IPCC is both unwilling to render wider generalizations about the drought-climate change link or make bolder statements with the currently available data. Physicist and climate writer Joe Romm thinks this is a mistake, and wished the panel would have more thoroughly investigated droughts and 'dust bowlification'. And the jury's still out on hurricanes and cyclones, though the research seems to indicate that the storms will become more intense, with higher wind speeds, but not more frequent -- and potentially even less frequent. Finally, "heavy precipitation" is expected to increase -- meaning harder rains in wet areas.

None of this is particularly revelatory, though it's nice to have a firm, synthesized document signalling agreement on the climate and extreme weather link from the world's most respected scientists. Of course, the naysayers are already sharpening their knives, and getting ready to call IPCC chief Rajendra Pachauri all sorts of nasty names. But, as he told me in an interview last month, the IPCC is stronger than ever, and ready to counter false claims with sound science. And we're going to need to start listening to that sound science ASAP -- with dire changes in extreme weather patterns incipient in a world that's freshly home to 7 billion people, it's time to start taking the necessary actions.

Mitigating the advance of climate change by, say, pricing carbon, would be one. Getting ready for the incoming storm would be another.

It Is "Virtually Certain" That Climate Change is Causing More Extreme Weather
The IPCC's latest Special Report, “Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation" seeks to evaluate the link between extreme weather and climate change.

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