World Weather Attribution

Cold Waves in North America Are Not As Cold Now As a Century Ago

Over the last week of 2017 and first week of 2018, a cold wave gripped the northeastern U.S. and southeastern Canada, with temperatures over 18ºF (10ºC) colder than is typical at this time of year over this area, setting records at many sites. We show that the temperature of North American cold waves has increased substantially over the last century due to global warming. So, although this cold spell would not have been unusual before global warming, it is now a relatively rare event in any one region. The chance of a cold wave anywhere in North America is much larger than in this specific location. We do not find any evidence for an intensification of these types of cold waves due to the Arctic warming faster than the midlatitudes. On the contrary, they seem to be warming faster than the winter mean as the Arctic air coming south is less cold now.

Read the full analysis here.

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Climate Change Fingerprints Confirmed in Hurricane Harvey’s Record-Shattering Rainfall

Scientists with World Weather Attribution (WWA) find that human-caused climate change made the record rainfall that fell over Houston during Hurricane Harvey roughly three times more likely and 15 percent more intense.  WWA is releasing the findings of its new analysis regarding the role of human-induced climate change on Hurricane Harvey’s devastating rains that is published in the peer-reviewed journal, Environmental Research Letters (ERL). The findings are being released jointly with the American Geophysical Union (AGU) in a joint press release and at a press conference on Wednesday, December 13 at 2:30 p.m. CT at the annual AGU Fall Meeting in New Orleans.  The paper can be found on our website and in Environmental Research Letters.

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Two Year Anniversary of UK’s Storm Desmond: New Paper Confirms WWA’s Prior Rapid Analysis Findings

Two years have passed since Storm Desmond caused large disruption in the UK. On December 5, 2015, heavy rainfall and high winds led to devastating flooding in Northern England, Southern Scotland and Ireland, and left many families with damaged homes. Desmond was the first of three storms to bring heavy rain to the region; December 2015 would go in the books as the wettest December on record in that part of the UK.

At the time, WWA scientists performed a rapid attribution analysis within five days after the storm, and found that human-caused climate change made a rainfall event like Storm Desmond more likely now than in preindustrial times. This analysis was based on provisional observations available soon after the event and pre-existing climate model experiments.

Now that more time has passed, all measurements from those days have been made available and more climate model experiments have been performed. WWA scientists have revisited their original attribution analysis and show in a new scientific article that rapid analyses, of which the Desmond rapid attribution is an example, can stand the test of time: the results in the revisited analysis were essentially the same as in the rapid analysis.

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Photo: REUTERS