Many people are attracted to either all-electric or hybrid cars because they believe they are helping the environment by doing so – they are “green” cars. There are other reasons as well, but for many buyers of “green” cars, their green-ness is the major factor.
However, when you take into account the additional carbon footprint and other pollutants produced in the manufacture of both hybrid and all-electric cars, and the indirect carbon footprint and pollution increase from all-electric cars (because they're recharged with electricity produced most often in a non-nuclear power plant), then they don't look quite so green. Over the average lifetime of a green car, both the carbon footprint and the pollution are worse than the average gasoline-powered car – and there's nothing on the horizon that would change that. Massive conversion of power plants to nuclear or fusion power would help a lot, but that's not very likely. Massive conversion to wind or solar doesn't work because there is no known way to store power produced during the daytime for use at night. Lithium mining is notoriously polluting and energy intensive, but no replacement technology for lithium-ion batteries is even in the laboratory, much less in production.
None of this information is a secret, nor is it hidden or hard to access. Do a little googling and you can find all you want. Green cars are a myth (albeit a popular myth!). They really should be called brown cars.
Bjorn Lomberg (of The Skeptical Environmentalist fame) has a nice summary of this in today's Wall Street Journal)...