World Weather Attribution Pacific Northwest Heatwave Headlines

On July 25, 2021 the Syracuse Post Standard reprinted an opinion piece from the Washington Post “We need to stop fiddling while the world burns” that described the World Weather Attribution analysis of the recent record-breaking heat wave in the Pacific Northwest.  In order to justify the need for massive transformations of the energy system such as New York’s Climate Leadership and Community Protection Act stories like this that claim that the heat wave would have been “virtually impossible without human-based climate change” receive much publicity.  However, upon close examination the claims are hype and exaggeration that do not prove the need to “stop fiddling”.  The fact is that the reason for the heat wave is mostly extreme weather caused by natural variability with a little bit of climate change thrown in.

The difference between weather and climate is constantly mistaken by CLCPA advocates and the July 22 Climate Action Council meeting presentation included a slide that prominently highlighted the Pacific NW heatwave.  This has become such a frequent mis-representation that I have a page that references my evaluations of climatic effects that turned out to be weather events and other similar analyses by other authors.

In this instance there is no need for me to do an evaluation of how climate change affected this extreme weather event.  Dr. Cliff Mass is a meteorology professor at the University of Washington whose has spent his career developing an understanding of the weather and climate of the Pacific NW.  In addition, he is currently doing research running high resolution, state-of-the-science regional climate models of the region.  I do not believe that there is anyone more qualified to address this event and its relationship to climate change.

In a series of three posts, he has discussed this problem and this post summarizes his findings.  In the first post, Was Global Warming the Cause of the Great Northwest Heatwave? Science Says No, he described the causes of the heatwave.  In the second post, Flawed Heatwave Report Leads to False Headlines in Major Media,  he discussed the specific report that was the basis for the Washington Post editorial.  In his last post, Miscommunication in Recent Climate Attribution Studies, he addressed how that report “provided misleading information”.  I will summarize his findings below.

In the first post, Dr. Mass described the heat wave as follows:

The maximum temperatures during the heatwave were as high as 30-40 degrees Fahrenheit above normal.    Seattle had a high of 108F, 35F above the normal high of 73F.  Quilluyte on the Washington Coast zoomed to 109F compared to a normal high of 65 (44F above normal).  Throughout the region, all-time temperature records were broken, representing the hottest day on record at many locations.

He believes that the “Pacific Northwest is warming and human emission of greenhouse gases is probably the origin of much of it” but goes on to explain the specific reasons for the record setting temperatures.  He showed how a persistent high-pressure ridge developed that brought warm air to the area.  The already warm air became “supercharged” because the wind flows caused downslope winds which compress the atmosphere markedly increasing the temperatures.  In both cases the exact conditions needed to cause the high impacts had to align at the same time.  It was a very rare and extreme weather event.  Dr. Mass believes that climate change has increased temperatures in the area 1 to 2 F so that effect is added to the observed temperatures.  As a result, he believes that climate change is only responsible for that amount of the observed 30-40 degrees observed above normal.

The World Weather Attribution analysis of the heat wave claimed that “Based on observations and modeling, the occurrence of a heatwave with maximum temperatures as observed in the area was virtually impossible without human-caused climate change”.  In the second post, Dr. Mass states:

This claim is not supported in the document or by the rigorous science, and, in fact, the material in the attribution report contradicts this assertion.  I will provide substantial evidence that the heatwave attribution report, which has not been submitted for peer-review, is profoundly flawed, with serious technical and interpretative errors.

Dr. Mass points out that their rationale that global warming was the main factor was riddled with contradictions that show no evidence that their conclusion was true.  In his technical explanation of the flaws in the report he examined local data trends and climate model results.  Dr. Mass evaluated local trends of daily high temperatures and found that their analysis was incorrect.  They used a climate model that was not refined enough to capture the factors that affect local weather conditions and improperly used an inaccurate emissions estimate.  Finally, he showed that their evaluation was inconsistent with their conclusion. He sums up: “If anything, much of the material in the report is highly suggestive of a random, black swan event that is slightly enhanced by greenhouse gas warming”.  Exactly Dr. Mass’ conclusion.

In his final article he explains “why their basic framing and approach is problematic, leading readers (and most of the media) to incorrect conclusions” by way of two examples.  He describes a physically meaningful interpretation with an example where the essential event would have happened without any effect from global warming.  He notes that this is “a good example of the golden rule of climate attribution:  the more unusual and extreme the event, the greater the proportion of the event is due to natural variability rather than global warming”.  In contrast the World Weather Attribution analysis focuses only on the headline interpretation.  They ignore the physical situation and actual impacts and the fact that natural variability is dominating the situation.  Instead, they only look at the event itself.  In this case they note that temperatures were up to 40 F higher than normal and say this would not have happened without global warming.  That is true but it ignores the fact that global warming was only responsible for 2 F and 38 F would have been a record-setting heat wave.  This miscommunication leads people to think that global warming was the primary driver rather than natural variability.

He concludes this article with the following:

Many of the climate attribution studies are resulting in headlines that are deceptive and result in people coming to incorrect conclusions about the relative roles of global warming and natural variability in current extreme weather.  Scary headlines and apocalyptic attribution studies needlessly provoke fear.  Furthermore, incorrect and hyped information results in poor decision-making.  


We need to worry about climate change and take steps in both mitigation (reduce greenhouse gas emissions) and adaptation.  But hype and exaggeration of its impacts only undermine the potential for effective action.

I don’t agree with all of his projections for the future because I don’t trust climate models based on my model verification work that found it was possible to get the right answer for the wrong reason.  As a result, I believe it is better to emphasize adaptation over mitigation because the effects of natural variability on extreme weather have devastating impacts which a more resilient society can handle better.  However, we agree that hype and exaggeration of the causes of extreme weather undermine the most effective policies to reduce extreme weather impacts. 

The hype and exaggeration matters to New Yorkers because the politicians who passed New York’s Climate Act based their rationale for mitigating greenhouse gas emissions on the misinterpretation of similar extreme weather events driven primarily by natural variability as evidence that climate change is affecting us now.  As a result, the law’s emission reduction targets will squander state resources that would be better spent on making society more resilient to extreme weather rather than using today’s inefficient, expensive and untested renewable energy “solutions”.

Author: rogercaiazza

I am a meteorologist (BS and MS degrees), was certified as a consulting meteorologist and have worked in the air quality industry for over 40 years. I author two blogs. Environmental staff in any industry have to be pragmatic balancing risks and benefits and ( reflects that outlook. The second blog addresses the New York State Reforming the Energy Vision initiative ( Any of my comments on the web or posts on my blogs are my opinion only. In no way do they reflect the position of any of my past employers or any company I was associated with.

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