We've seen the bankruptcy of many newspapers. We've seen a further erosion of the line between news and entertainment. But I do believe that there is reason to hope that over time we will see the higher-quality journalism rise to the surface.

I understand that being optimistic in this age is challenging, but I am optimistic nonetheless.

All I'm doing, all I have done for 40 years, is spend time with the best scientific experts, gain their confidence, and take advantage of their patience in explaining things to me over and over again in progressively simpler language that I can understand, so that I can read it back to them and get their sign off, where they say, "Yep, that's it, Al. You've got it." When I understand it, I know I can explain it to other people. When the scientists' predictions end up being true, I see that as an opportunity to say to people, "Listen carefully to what they're saying now."

Our new technologies, combined with our numbers, have made us, collectively, a force of nature

We can't negotiate the facts. We can't negotiate the truth about the situation. And for those who are too fearful to finish, it can be done and must be done. Make sure we succeed, . . . It is wrong for this generation to destroy the habitability of our planet and ruin the prospects of every future generation.

Today I challenge our nation to commit to producing 100 percent of our electricity from renewable energy and truly clean carbon-free sources within 10 years.

I will tell you that what gives me a sense of joy is having work to do that justifies pouring every ounce of energy I have into it. That's really a blessing to have in your life. And it gives you energy back when you have the privilege of doing work that makes you feel that way.