"are ANY weather events made more "tame" by global warming,"
Of course.
=
“Pleasant Weather” Through A Glass Darkly
Today, just two days after devastating floods rolled through the city of Houston leaving nine dead in their wake, a pair of climate scientists have released a study making a truly astonishing claim about weather in the United States: “from 1974 to 2013, the weather conditions experienced by the vast majority of the population improved.”
Promotional tweet by Nature, featuring Egan and Mullin study on magazine’s front cover
The study, authored by Patrick Egan and Megan Mullin, is published in the esteemed journal Nature and as such, is sure to stir up a hornet’s nest of debate. However, the pending academic dust-up will likely center not on the data in the study. Rather, the focus of the criticism will be on some extraordinary assumptions made by the authors regarding the kind of weather Americans “prefer.” According to Egan and Mullin, extreme events such as heat waves and torrential rains should not be considered when evaluating Americans’ weather preferences.
Of course heat waves and torrential rains have been on the increase over recent decades in the United States. In fact, these trends are perhaps the clearest signals of climate change that we witness in our day-to-day lives. Extreme precipitation is up 20% in the United States, and heat waves are increasingly blanketing the country. The percentage of land area in the United States with unusually hot summer nights has increased from an average under 10% in the 1970s to over 40% in recent years.
It’s hard to see any of this as “improved” weather. Nevertheless the author’s claim that “80% of Americans live in counties that are experiencing more pleasant weather than they did four decades ago.”
So, how did the Egan and Mullin wind up where they did? To begin, Egan and Mullin make a very particular choice in looking at temperature trends. Rather than looking at the frequency or severity of extreme temperatures, Egan and Mullin focused just on the changes in average temperatures for the months of January and July. Yes, that means short-term temperatures extremes were mostly left out of their analysis. Daily and weekly temperature extremes (i.e. heat waves) are missed entirely.
Not surprisingly Egan and Mullin found a moderate increase in average temperatures, concentrated more in January than in July. This finding on changes in average seasonal temperatures is entirely in line with similar findings by larger, more authoritative assessments such as the recent National Academies report on extreme weather and the U.S. National Climate Assessment.
Egan and Mullin then pair rising average winter temperatures with summers that they describe as “not markedly more uncomfortable”to claim that weather has shifted toward a temperate year-round climate that Americans have been demonstrated to prefer.
Similarly, when Egan and Mullin look at precipitation, they look only at annual precipitation totals and the number of days on which precipitation occurs annually. And not surprisingly, they didn’t find significant changes. However, by looking at annual totals the authors exclude the trend toward concentration of precipitation into extreme downpours. A warmer atmosphere holds more water vapor. And like a bigger bucket, a warmer atmosphere both holds and dumps more water when it rains. By averaging out the extremes, Egan and Mullin do not include the kind of rain and snowfall that makes peoples lives miserable, like the suffering just witnessed in Houston.
For their final step, Egan and Mullin devised their own metric for measuring the weather called “WPI” or weather preference index. The metric was based entirely on their measurement of monthly and annual averages. The authors argue that their metric measures the trend in “pleasant weather.”
Of course, extreme weather was excluded entirely from their metric, a point on which Egan and Mullin were refreshingly transparent, noting that their analysis focuses “only on preferences for long-term weather conditions, not on less predictable public responses to extreme weather events.”
It should be noted that Egan and Mullin also exclude many other trends related to extreme weather such as increasing drought and wildfire, none of which could be seen as “pleasant.”
Egan and Mullin even exclude important changes directly connected to the average monthly changes that are the focus of their analysis. For instance, gradually warming seasonal temperatures are playing a role in contributing to asthma, lengthening the allergy season and raising pollen counts. Between 1995 and 2011, hotter temperatures caused the ragweed pollen season to increase by anywhere from 11 to 27 days in parts of the U.S. and the rate of people diagnosed with asthma has gone up from 7.3 percent of the population to 8.4 percent over the last decade. Not pleasant at all.
A promotional tweet of Egan and Mullin article by Nature News and Views Twitter feed
All this of this raises the question, why did Nature publish this study as is? The short, snarky answer is click bait. The longer, more nuanced answer isn’t much different, but that’s a post for another day.
medium.com@huntercutting/pleasant-weather-through-a-glass-darkly-10b3686e8412#.8l8hb350w |
