About that Northwestern European Heat Wave

Steve has mentioned the brief heat wave that brought unprecedented high temperatures to much of England, and elsewhere in Northwestern Europe. The heat wave didn’t last long–the high today in London was 79 degrees–but it prompted an outpouring of global warming hysteria.

I was reminded of visiting London around 27 years ago, in April. Then, too, the city was in the midst of an unprecedented heat wave–in April! With temperatures in the 90s and no air conditioning, everyone was sweltering. We stayed at the East India Club, and as I recall the Club, for the first time, relaxed its centuries-old requirement that coats and ties be worn in all public areas. It was hot then, too; the difference is that no one claimed it was our fault.

Watts Up With That has a useful antidote to “green” hysteria:

The high this week for central England was absolutely unparalleled, particularly regarding the deviation from the previous record high. Also note that the heat wave was very short.

As you can see in this chart:

Ironically, such an extraordinarily extreme event is a sign that global warming played a very small role in this event. This reflects the

Golden Rule of Climate Extremes:

The more extreme a climate or weather record is, the greater the contribution of natural variability and the smaller the contribution of human-caused global warming.

British temperatures have indeed been rising, around 1 degree Centigrade over the past 50 years:

So you can call that 1 degree rise “global warming,” and human activity may have something to do with it. But that doesn’t explain the brief heat wave of a few days ago:

That background warming of around 1°C is absolutely dwarfed by the magnitude of the heatwave, in which maximum temperatures were as much as 20C above normal (as shown by the figure above).

So why were the temperatures so extreme this week?

The reason is the development of a large ridge of high pressure, something called a ridge, which produces warming by sinking and moving air northwards on its western flanks.

Here is the upper level (500-hPa pressure level, about 18,000 ft) at 5 PM PDT July 17th. The ridging (high heights or pressure) are indicated by the red-orange colors. Note there was a trough (blue colors) of lower pressure on its southwest side. This feature increases southerly flow that brings up warmer air.

One feature of this rather freakish weather pattern is that the areas around the super-warm zone were colder than normal:

Ironically such a pattern also produces enhanced cooling to the east and west, something shown by the temperature anomalies (difference from normal) six hours later (red/brown above normal, blue below normal).


The bottom line is that the recent European heat wave was caused by an amplification of the northern hemisphere wave pattern, with global warming contributing perhaps 5-10% of the warmth. Natural variability of the atmosphere was the proximate cause of the warmth and does not represent an existential threat to the population of Europe.

One obvious point is that weather events get lots of attention if they occur in the U.S. or in Western Europe. They often go unnoticed elsewhere. When it gets cold, climate alarmists like to tell us that it isn’t climate, it is only weather. What happened in England for a few days this month wasn’t climate, it was weather. Like the heat wave I endured in London many years ago.

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