In science, there's cause and effect -- do something and you'll get a certain result. What does this tell us about electric cars and this summer's warm weather in Europe?

Well, consider the fact that this summer's European heat wave was immediately preceded by a sharp increase in electric-car sales there over the past 12 months. Specifically, sales of the Model 3 from Tesla (TSLA - Get Report) increased from barely north of zero before mid-2018 to 247,749 units over the past four quarters.

As you can see in the table below, that's an eight-fold increase over the previous four quarters -- 247,749 units compared to 28,390:

What about Tesla's Model 3 sales specifically in Europe? Let's check that out:

As you can see in the table above, initial Model 3 European deliveries only took place in January, but a ramp-up was in full swing by March.

Meanwhile, some Europeans are freaking out about this summer being warmer than average, believing that there must be a man-made culprit for this "problem." (Why is it suddenly bad that it's nice and warm in summer? Isn't that why most of us travel to warm locations for our vacations?)

Mercedes parent Daimler (DDAIF) even took a lot of flak recently for having tweeted about releasing a "red-hot" new car this summer:

[Kraftstoffverbrauch kombiniert: 8,5 l/ 100 km | CO₂-Emissionen kombiniert: 193 g/km | https://t.co/NCNjWnA238] If this summer wasn't warm enough already, the Mercedes-AMG GLA 45 4MATIC will heat things up even more with this red-hot finish. �� �� Mercedes-Benz Kundencerter pic.twitter.com/2xfcKAb85f — Mercedes-Benz (@MercedesBenz) August 1, 2019

Defensive and feckless, Mercedes ended up apologizing:

Folks, that was really not our finest hour. We apologize sincerely. We're working hard on the transformation of our car fleet. We aim for CO2-neutral mobility: https://t.co/eM89zLEp4I — Mercedes-Benz (@MercedesBenz) August 2, 2019

Unfortunately, this just feeds into what I consider a myth -- that it's gas-powered cars that are causing warmer summers in Europe. In my view, here's what Mercedes (and all other automakers) should have said: "Actually, European sales of gas and diesel cars are on the decline. Not a lot, but ever so slightly -- 3% or so thus far in 2019."

But what is on the rise -- and sharply so -- are European sales of electric cars. Sales of plug-in cars in Europe rose 34% in 2019's first half.

Most of that increase comes from the Tesla Model 3, with 37,786 units sold in Europe during the first half. That's essentially half of the 74,577 units sold by the top-20 plug-in cars in Europe during 2019's first six months.

In other words, the European car market's only major change during the first half was the rise in Tesla Model 3 sales from zero to more than 37,000 for the six-month period.

Presumably, those Model 3 sales came at the expense of fewer sales for gas and diesel cars. That's the only real change for car sales -- and so, that must be the cause of Europe's heat wave, right?

The Bottom Line

You might be wondering by now: "Does this guy really believe that electric cars cause global temperatures to rise?" Of course not, but I'm trying to illustrate the well-known saying that "correlation does not prove causation."

Just because we recently saw a huge increase in European electric-car sales (and Tesla Model 3 sales in particular) doesn't mean that EVs caused Europe's warmer weather. But the opposite is also true -- you can't conclude that gas-powered car sales caused Europe's warmer weather, either.

A fair analyst might say that the matter is simply inconclusive based on the available evidence. That should cause those who argue the opposite to be more humble about their assertions.

There's simply no more evidence that gas/diesel cars cause warm weather than there is that electric cars do. Let's just call that an inconvenient truth.