I think the biggest gaping hole in contribution to the world is the absence of leadership. It could very well take 10s of thousands of scientists another hundred years to solve our energy problems, but it only takes one person to stand up and convince us all to drive better cars, turn down our air conditioners, and purchase eco-positive products. Then we'd have 300million people working on the problem, making a difference now. And it would be a BIG difference.
During WWII the president asked the people to make sacrifices in order to win a war against some fairly bad people. If the president today asked people to stop eating meat for a day, the cattle lobby would have a cow (pun intended). They'd start tossing around money and it would be over. That's not leadership, that's middle management at best.
Maybe its too difficult (or impossible) to be a good leader these days, which may explain why most smart people really don't want the job. How can a leader spend 5 minutes on TV and tell everyone to eat better and even hope to compete with an evening full of fast food commercials. I don't think those are bad people, either. They're just another group of people, like many of us, trying to find a way to get ahead in this world so they can finally do some good. We're all a little aimless -- we need a leader.
So here's what I think any and all of us could do today:
1. Start making the sacrifices of a leader and getting people behind you to move the world in a positive direction.
-- or --
Accept that you aren't the person for the job (even for now) and rally your big throbbing brain behind someone who can and will lead.
2. Start working on your todo list.