One criticism of electric cars is that they often just replace one source of carbon pollution with another. Instead of a combustion engine that burns gasoline, you get a plug-in vehicle that depends on electricity from burning coal. In extreme cases, this can look like a dismal trade-off. One recent report from the Innovation Center for Energy and Transportation estimated that, in many parts of China, a Nissan Leaf powered by coal-fired power plants could actually produce more carbon emissions per mile than a comparable gas-powered car. Bad news.I had always assumed (incorrectly, it would seem) that people generally understood that simply switching to electric vehicles would not immediately remedy the vehicular carbon emissions problem. But while they're no panacea, electric cars do broaden the number of ways the problem can be addressed. When gasoline-powered cars are the norm, transportation creates two distinct types of carbon emissions: emissions from producing the fuel and emissions from using the fuel. Electric cars fold the latter category into the former: because they produce no carbon, their entire carbon cost is reflected in the cost of producing the electricity they consume. In either case, of course, the total amount of carbon emitted will be a function of the total amount of energy used for transportation.
The key here is that gasoline-powered cars insulate the carbon emission total from efficiency gains at the production level. If (hypothetically) 30% of carbon emissions from gasoline-powered cars are produced by generating the electricity required to the refine gasoline, and 70% are produced by burning the gasoline in an internal combustion engine, a 33% increase in the efficiency of generating power only creates a 10% drop in emissions. In fact, it would be impossible to generate a 33% drop in transportation emissions by finding more efficient energy sources, even if we could generate power with literally no carbon emissions at all. Reductions past the first 30% could only be achieved by attacking the problem somewhere between the gas pump and the exhaust pipe (i.e., building vehicles with better MPG). In a world in which we only drove electric cars, on the other hand, a 33% improvement in energy production efficiency would reduce emissions by 33%, and emissions-free energy generation would mean transportation would also be emissions-free. And any carbon savings derived from improvements to the actual car would be piled on top of that.
Obviously, this doesn't automatically mean electric cars are the superior option. For instance, if for some reason we expect improvements in the efficiency of fuel use to outstrip improvements in the efficiency of energy generation, then we're better off sticking with gasoline. But it's hard to see how this could be the case, given the necessarily miniature scale of automotive engineering, and the simple fact that we're not going to be mounting nuclear power plants on the backs of cars anytime soon. (An engineering feat helpfully illustrated in the picture above, which, while tangentially-related at best, I deemed more interesting than the obvious choice of "ominous smokestacks.")