Even if you ignore the effects of global warming, there are pollution issues as well... and the differences in that *ARE* readily perceivable in a person's lifetime.
Besides... urgent or not, as the saying goes, why put off until tomorrow what you can do today? Of course I understand that it's really hard right now, quite expensive, and anything but convenient to do, but the reality is that something like this will not get any easier with time until people start caring about trying to do something about it (in fact, it's liable to only get harder as time goes by long as people aren't trying to do something about it, simply because of an ever-growing population and constantly growing energy needs). If we start using alternative energy sources now, then it seems to me there's a much better chance that we will be more ready and able to improve the technologies behind them as the demand grows, while if we just remain oil-based, then any possible advances are much more likely to remain undiscovered for much longer.
And at least this candidate cares enough about the issue to try and make a stand for it... and that much should be applauded, IMO. I am not American, but if I were, this position would weigh heavily among the factors that I would consider when I voted.... not necessarily outweighing everything else, but definitely enough to give the matter some serious consideration.