Huge electric vehicles are far from perfect, but they could still help fight climate change.

But the magnitude of the difference between the scenarios is quite revealing. Take the difference between the worst-case scenario and what the study considers the “status quo,” for example. As far as lithium is concerned, in a business as usual scenario where people drive as much as they do now, we will need 306,000 tonnes in 2050. If batteries get bigger, that number could reach 483,000 tonnes, or 50 % moreover.

We’re not going to run out of materials we need to make batteries, but every mine we have to build has consequences for both people and the environment. Mining often produces pollution, especially of waterways, and the industry has been linked to human rights abuses around the world. So bigger batteries mean bigger consequences to deal with.

Bigger cars will also have a greater climate impact. In the most dramatic example, compare an EV Hummer with a gasoline sedan.

Electric vehicles are not completely zero emissions, even if they do not burn fossil fuels on board. Their construction, especially their batteries, requires energy. And the electricity that powers most electric vehicles today comes from the grid, which is powered at least in part by fossil fuels almost everywhere.

If you consider the lifetime emissions from building a battery and charging an electric vehicle, an electric model of the same car will outperform the gas-powered version in almost every scenario. But comparing different models can be another story. A gas-powered Toyota Corolla is actually responsible for less greenhouse gases per mile than a Hummer EV, according to Quartz Research estimates. So right now this Hummer is worse for the climate.

To be clear, I’m not saying we should all go buy old gas-powered Corollas. Electric vehicles, even the biggest ones, are getting cleaner and cleaner. A grid-charged Hummer EV 2040, which should have more renewables in the power mix, will have fewer emissions than one that’s on the roads today. And hopefully by then we will also have reduced the climate impacts of mining and heavy industry.

And now ?

It would be great if we could drive less in general. I live in a car-free city right now, so I don’t have a car at all, and I love it. If I never had to drive again, it would be too soon. Policy measures could help more cities look more like mine, or at least support public transit and walking and cycling infrastructure to reduce car trips.