Sir, We are dismayed by how your Big Read article “ Green driving’s dirty secret” (November 9) turns the fundamental conclusions of our research at Massachusetts Institute of Technology on their head, giving the public a misleading perspective on electric vehicles.
The article makes a legitimate argument about vehicle policy: that emissions regulations should differentiate vehicle models by their full lifecycle greenhouse gas emissions (emissions accruing from both the tailpipe and the production of the vehicle and fuel).
But rather than make this simple point by showing the spread of lifecycle emissions from a representative sample of different electric and petrol car models — data that we made readily available — it instead uses a cherry-picked example. The electric vehicle industry faces a “wake-up call”, the article reads, because the emissions of one petrol car (Mitsubishi Mirage) are slightly lower than the emissions of one electric car (Tesla Model S P100D), in one region of the US. On the basis of this single case, the article broadly critiques policy in Europe, America, and China: “The idea that some combustion engine cars can be greener than some ‘zero-emission’ electric vehicles simply does not make sense in the current regulatory environment [of Europe, America and China] . . . As things stand, a small car like the Mirage could be illegal to drive in cities across Europe, the UK and China by 2030 . . . ”.
There are three fallacies here. First, Tesla-versus-Mirage is an apples-to-oranges comparison, pitting a luxury, high-power electric model against a subcompact, low-power petrol one. (The article glosses over a fairer comparison — between the Tesla and a BMW 7-series — that shows the Tesla has significantly lower carbon emissions.) Second, even if we entertain this comparison, our research shows that the Mirage’s emissions are lower than the Tesla’s only in carbon-intensive electricity grids like the US Midwest, where electricity production emits roughly 40 per cent more CO2 than the US average, and more than twice as much as many European countries (including the UK). The Tesla/Mirage example is attention grabbing, but belies the reality that most electric cars emit considerably less CO2 over their lifetimes than petrol cars. Third, the article assesses policies “as things stand”. This overlooks the main advantage of replacing petrol with electricity: not only do electric cars usually emit less than petrol ones already, but over time, as the carbon footprint of electricity continues to fall, that gap will widen. Electric cars have the potential to reach climate change mitigation targets that petrol cars simply do not.
Deeper in, the article acknowledges some of these conclusions, and focuses instead on distinguishing between electric models. But by this point the damage had been done. As the FT’s second most-read online article of the day, the article’s headline, standfirst and intro spawned grossly misleading reporting in news outlets and auto magazines internationally.
As researchers working to uncover and share accurate information, we are saddened to see our results used in this way.
Jessika Trancik, Geoffrey Supran and Marco Miotti
Trancik Lab, MIT, US
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