A recent screed by a denier claims that none of the expected unhappy consequences of global warming has happened, not even any increase in heat waves. That claim is not only false, it’s ridiculous. One of the consequences of global warming is an increase in heat waves, and in extreme hot days — which isn’t a future consequence, it has happened already.
Let’s take another look at daily high temperature from ECA&D, the European Climate Assessment and Dataset Project. It has recently updated its daily data holdings through August of 2015, so we’ll have very current data, including this year. We’ll study the summer months of June, July, and August, and count how many “hot days” occur each year. In order for a year to be included, it had to have data for at least 85 of the 92 summer-month days. In order for a station to be included, it had to have data for at least 100 years since 1900, including at least one year in the 2010’s.
“Hot” is defined relative to what was normal for that location prior to 1980. The cutoff limit was chosen as the 99th percentile (of summer days), so we’re looking at extremely hot days — ordinarily we would expect an average of slightly less than one per year. Then we can compare how many occured at each location from 1900 through 1979, to how many each year since 1980.
Here’s a “map” of the change in the total number of hot days from the 1900-1979 time span, to years since 1980. Red circles show places with more hot days, blue circles those with fewer, the size of the cirlce indicating how much the number changed:
There are a few scattered places where the average number of very hot days has decreased — but few indeed, and not by much. There are, however, many places where very hots days are more frequent, and by a lot. Only about 11% of locations have suffered less extreme heat while 89% have suffered more.
In some places the number of very hot days has exploded, and this year (2015) was a helluva scorcher in Europe. Kremsmuenster, Austria, for instance, sweltered through 32 very hot days this year — the kind of heat you would have expected to happen, before 1980, slightly less than once per year. But this year it happened 32 times. That’s a whopper of a heat problem — and yes, it’s a problem.
But let’s not judge the whole set by one extreme location. Here’s the number of very hot days per year for each location, with different places plotted in different colors:
From this it’s evident that the severe heat problem in Europe really kicked off with the killer heat wave in 2003 — and that it has kept coming since then. In fact it’s gotten worse; if we plot the average for all stations, we see that this year has been the worst yet:
Bear in mind that by definition — since “very hot days” is defined by the 99th percentile at each location — what used to be a “slightly less than once a year on average” event has already gotten about four times more common. And that’s the average over all ECA&D stations — some places have been hit even harder.
And it’s going to get worse. Maybe not next year, maybe not the next, but soon, and for the rest of our lives.
Not only will such very hot days get more frequent than they already have, they’ll get hotter too. The impact of all that extra heat isn’t just the number of days it happens, it’s how hot the days get. And that too is on the increase.
Anybody who says that heat waves aren’t already worse than they were, is either a fool or a liar or both. Anybody who denies that they’re going to get worse, is selling something.