Mini-Throughput: Heat Wave Edition

As you may have heard, it’s a little hot out there:

Hundreds of millions of people around the world were sweltering in extreme heat on Wednesday, as record-breaking heat waves set swathes of Europe’s countryside on fire, scorched the US and put dozens of Chinese cities under alert.

Five separate high-pressure weather systems across the northern hemisphere, which are linked by atmospheric waves, have led to unprecedented temperatures on multiple continents. The UK smashed its all-time heat mark on Tuesday, as did several cities in the Texas and Oklahoma, including Wichita Falls, which reached a broiling 115 degrees Fahrenheit (46.1 degrees Celsius) on Tuesday.

As Europe’s heat wave moves eastwards, wildfires have forced tens of thousands of people from their homes, blanketing parts of Italy, Greece and France in smoke. Germany recorded its hottest day of the year as temperatures reached 104.5 F (40.3C) at a measuring station in Bad Mergentheim-Neunkirchen, in the center of the country, while Hungary and Italy have been hit with high temperatures of around 100 F (nearly 38C) in places.

The scale of this heat wave — engulfing almost the entire Northern Hemisphere — is unprecedented. The UK and Canada have set all-time heat records. And last month, an unprecedented heat wave swept through the Arctic.

Of course, the wake of an unprecedented heat wave inevitably comes the debate on whether it is the result of global warming. The answer to that is question is no, but yes.

First, the no part. The temperature on any particular day is affected by both systematic and random factors. Systematic factors are things like seasons — it’s usually warmer in July than December when you live in the Northern hemisphere. Random factors are just that — some days you get a cold day in July or a warm day in December because that’s the way weather works. Extreme weather events have happened throughout history. Every broken record is a reminder of a past year that was almost but not quite as hot as this one, some of them decades ago when the Earth was cooler than it is now. So no, you can’t say that this particular heat wave would never have happened without global warming. It very well might have.

However …

Any place on Earth has an average temperature for any time of the year. My town, for example, has an average July temperature of 72 degrees with an average high of 81 and an average low of 63. But there’s a lot of variation in that and that variation tends to follow a normal distribution or a bell curve.

As with any bell curve, the further you go from the average, the rarer the events get. Let’s put aside temperatures and talk about height as our example. The average man is 5’9″ tall. Most men are somewhere between 5’6″ and 6″. By the time you get out to 5’3″ or 6’4″, you’re only talking about 1% of men. That’s the curve — as you get further and further away from the mean, the frequency drops exponentially. To go back to weather, most July days in my town will be somewhere between 60 and 80. Almost all days will be between 50 and 90. We have, through our history, gotten days as cold as 40 degrees and as warm as 102. Both those were once-a-century things, way out on the bell curve.

Now, back to height: imagine you found some magic elixir that made every man in the country exactly one inch taller. Toward the center of the distribution, things would be largely unchanged. The number of 5’10” men wouldn’t change at all. But the further you go out, the larger the change is. Because it is rare for men to be 6’4″ or taller, even a slight shift means a huge increase in the number of those extremely tall men. The number of men 6’4″ or over would triple. And the same works on the other end. Because so few men are 5’3″ or shorter, the number of very short men would drop equally dramatically. Look again at those extreme ends of the distribution. Imagine pushing that curve to the side and how dramatically things are going to change on those extremes versus the middle.

Now you can see where global warming comes into our picture. If you shift the average temperature of the Earth two degrees Fahrenheit — about what we’ve seen over the last 140 years — extreme events suddenly more common. Just like shifting the average height one inch triples the number of NBA point guards out there, shifting the temperature distribution two degrees produces far more extreme heat events and far fewer extreme cold events. Once-a-decade heat waves become once-a-year heat waves. Once-a-century heat waves becomes once-a-decade. And, on the other end, once-a-decade freezes become once-a-century.

The present heat wave is showing why those shifts in extremes are so concerning. Our society is built for temperatures in the fat part of that distribution. When extreme events happen … well, look at what is happening right now — massive fires, power outages, thousands of deaths, legions of dead cattle. And all this hitting an economy that’s not exactly in the best shape.

In short, you can’t necessarily say that this particular heat wave was caused by global warming. Heat waves happen. But you can say that, over a long enough period of time, those heat waves are going to and have become more common. You can say that such extreme heat waves are extremely damaging and the price of global warming can literally be measured in fire and blood.

I’m generally not hysterical on the subject of global warming. I think we will adapt to even bad scenarios. But that doesn’t mean I can’t realistically look at what is happening and know that it is going to be bad, it is going to be expensive and it is going to cause disruption. And simple prudence dictates that we should do something about it — not necessarily what the greens are suggesting — before we push that bell curve even further to the right and start getting once-a-millennium heat waves.