The earth, despite what Jeremy Clarkson and Nigel Lawson might tell you, is getting hotter. And the more we drive around, spitting out carbon-based gases from our old-school cars, the worse it’s going to get.

That’s why, on a very basic level, the move towards electric vehicles, of which there are now around 400,000 on the road worldwide, is a good one – they’re powered by electricity stored in a battery pack, rather than by directly burning polluting fuels. That electricity can come from carbon-free and otherwise clean sources (even if, in practice, it often doesn’t).

But according to a new study, electric cars could keep things cool in other ways, too. That’s because normal cars don’t just produce greenhouse emissions; their internal combustion engines also produce a load of heat.

Electric cars, according to research by scientists from Michigan State University, produce only about one fifth of this heat over the course of an average mile. When you multiply that by the number of cars on the road worldwide, that means an awful lot less heat created on roads. 

So what does this mean for our cites? They’re generally hotter than the surrounding area due to something called the urban heat island effect (basically, more people doing stuff = a generally hotter microclimate). They also tend to be stuffed with cars idling in traffic, and, in hot weather, people blasting air conditioners to counteract the city heat.

If what the researchers have found is true, replacing city cars with electric ones could reduce the urban heat island effect pretty dramatically. The researchers used Beijing’s scorching 2012 summer as an example, and found that the use of electric cars could have reduced the temperature across the city by 0.94°C. This would, in turn, have reduced air conditioning usage by 14.44m kilowatt hours, and reduced daily CO2 emissions by 10,686 tonnes.

Image: “Hidden Benefits of Electric Vehicles for Addressing Climate Change”, Michigan State University.

The study is doubly important because it considers the costs and benefits of replacing conventional vehicles (CVs) with electric ones (EVs) sooner rather than later. Manufacturing an electric car produces more greenhouse gases and is more expensive than a standard car. But the researchers say their findings

….support the imperative acceleration of replacing conventional vehicles with electric vehicles. As EVs emit much less heat than CVs within the same mileage, the replacement can mitigate urban heat island effect (UHIE) to reduce the energy consumption of air conditioners, benefiting local and global climates. 

The researchers’ model takes in lots of assumptions specific to Beijing (the use of air conditioning, cars travelling an average of 30 miles a day, high local temperatures) so it’s difficult to quantify exactly how much we could reduce temperatures and CO2 emissions in cities worldwide by introducing electric cars. But it’s safe to say the difference it would make to emissions, and the city environment in general, would be pretty substantial. 

You can read the paper in full here.