Honestly? In the short term, the smartest answer is probably nuclear power, but there are other alternatives depending on how ambitious we are. The anti-scientific left (which does exist, it's just not as loud as the anti-scientific right--which is to say, almost all of the current GOP lawmakers)--hysterically opposes nuclear power, genetic modification of food (which is critical to averting widespread famine, especially in the increasingly warm climate), etc.
Before the financial crisis (and Egypt's implosion), the EU was seriously considering a continent-wide energy grid that would've been fed from huge solar farms in Egypt. http://www.nytimes.com/cwire/2011/06...pagewanted=all The US could conceivably do something similar in Arizona/etc, but there are logistical difficulties in terms of energy loss transmitting power over a land mass as large as ours (and the high cost of the infrastructure).
Germany's proved that on a small scale, solar is viable even in their cloud-ridden climate that isn't particularly conducive to solar. In any case, nuclear would be the best short-term plan, but the scientific community has done a piss-poor job advocating the technology to environmentalists, who seem content to maintain the status quo until they get their precious 100% green options rather than accept a no-carbon alternative like nuclear.