Had Al Gore been president on 9/11, I truly believe he'd have used the unbelievable unity we had in the wake of that tragedy to build support for a massive, New Deal style investment in renewable energy - wind, solar, infrastructure...
It would have done three things: 1) Freed us from our reliance on middle east oil & strengthened our hand in dealing with terrorism; 2) Created millions of jobs; 3) Helped with climate change.
Instead, we had George W. Bush, whose response was 1) to tell us to "go shopping," and 2) to invade the wrong country, at the cost of thousands of lives and trillions of dollars.