Will 'extreme weather attribution' become the next cultural wars bogeyman?
Prestigious global science collective study says extreme Pacific heatwave "virtually impossible" without climate change.
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For years most climate researchers have resisted being dragged into the increasingly political peril of attributing a particular extreme weather event to climate change. That is, generally, a good thing. Healthy skepticism is an essential trait for researchers and journalists and others for whom letting the cards fall where they may are the defined mission. But, at what point does prudence become foolhardy or outright cowardly?
We may be about to find out. World Weather Attribution (WWA), a blue ribbon international scientific collective, headquartered at Oxford University has released a “rapid attribution analysis” of the recent extreme heatwaves in the Pacific Northwest conducted by 27 researchers around the world with the virtually unambiguous (snark intended) title “Western North American extreme heat virtually impossible without human-caused climate change.”
Among the conclusions of the report:
Based on observations and modeling, the occurrence of a heatwave with maximum daily temperatures (TXx) as observed in the area 45–52 ºN, 119–123 ºW, was virtually impossible without human-caused climate change.
The observed temperatures were so extreme that they lie far outside the range of historically observed temperatures. This makes it hard to quantify with confidence how rare the event was. In the most realistic statistical analysis the event is estimated to be about a 1 in 1000 year event in today’s climate.
There are two possible sources of this extreme jump in peak temperatures. The first is that this is a very low probability event, even in the current climate which already includes about 1.2°C of global warming — the statistical equivalent of really bad luck, albeit aggravated by climate change. The second option is that nonlinear interactions in the climate have substantially increased the probability of such extreme heat, much beyond the gradual increase in heat extremes that has been observed up to now. We need to investigate the second possibility further, although we note the climate models do not show it. All numbers below assume that the heatwave was a very low probability event that was not caused by new nonlinearities.
With this assumption and combining the results from the analysis of climate models and weather observations, an event, defined as daily maximum temperatures (TXx) in the heatwave region, as rare as 1 in a 1000 years would have been at least 150 times rarer without human-induced climate change.
WWA was started in late 2014 after several influential members of the scientific community concluded that the emerging science of extreme event attribution could be operationalized. It is hosted at the Environmental Change Institute, University of Oxford, and co-led by Dr Geert Jan van Oldenborgh (KNMI) and Dr Friederike Otto (ECI).
In making attributions, climate scientists create and assess data simulations of how weather systems might behave if humans had never started producing carbon dioxide, and compare that with current weather and meteorological data. They also factor in direct weather observations made over the last century or more.
Scientists from the US, Canada, the UK, the Netherlands, France, Germany and Switzerland collaborated to assess to what extent human-induced climate change made this heatwave hotter and more likely.
Using published peer-reviewed methods, they analyzed how human-induced climate change affected the maximum temperatures in the region where most people have been affected by the heat (45–52 ºN, 119–123 ºW) including the cities of Seattle, Portland, and Vancouver (with more than 9 million people in their combined metropolitan areas). For a better explanation of attribution science, see the “Pathways and Pitfalls in extreme event attribution” link in Dig Deeper below.
From the report:
Multiple cities in the U.S. states of Oregon and Washington and the western provinces of Canada recorded temperatures far above 40ºC (104 ºF), including setting a new all-time Canadian temperature record of 49.6ºC in the village of Lytton. Shortly after setting the record, Lytton was largely destroyed in a wildfire. The exceptionally high temperatures led to spikes in sudden deaths, and sharp increases in hospital visits for heat-related illnesses and emergency calls. Heatwaves are one of the deadliest natural hazards and this heatwave affected a population unaccustomed and unprepared for such extreme temperatures, for instance with most homes lacking air-conditioning. Currently available mortality estimates of at least several hundred additional deaths are almost certainly an underestimate. The full extent of the impact of this exceptional heat on population health will not be known for several months.
The heatwaves are becoming so much more frequent and deadly, that decisionmakers need information faster than the the traditional route can provide. Co-author and WWA co-leader Friederike Otto, a climate scientist at the University of Oxford told Reuters:
"People need to realize that heatwaves are killers, and they are by far the deadliest extreme event. Heatwaves are really changing so much more and so much faster than all other extreme events. "Heat preparation and preventing death during heatwaves need to be a No. 1 priority for every city authority.”
Alas, our collective experience during the deadliest pandemic in 100-years is that there are certain segments of our fellow citizens who cannot ever be convinced or scared into getting a shot or wearing a mask, or taking climate change seriously. Wait until Tucker Carlson gets the “extreme weather attribution” memo and turns it into the next Critical Race Theory misinformation meme. The older I get the more inclined I am to believe Walt Kelly’s Pogo was right: “We have met the enemy and he is us.”
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Dig Deeper
Pathways and Pitfalls in extreme event attribution (WWA)
Pacific Northwest heat wave 'virtually impossible' without climate change -research (Reuters)
The Environmental Change Institute (Oxford)
Northwest Heatwave is 'historic,' 'unprecedented,' but not unexpected (EarthWatch)
Never Turn Your Back on Mother Earth (Sparks, 1974)
How worried should we be about “virtually impossible” becoming a measurement in scientific research?