The truth is that climate change is presenting the greatest challenge humanity has ever faced.

We must quickly mobilize our civilization with the urgency and resolve that has previously been seen only when nations mobilized for war. These prior struggles for survival were won when leaders found words at the 11th hour that released a mighty surge of courage, hope and readiness to sacrifice for a protracted and mortal challenge.

We need to put a price on carbon, and that's what cap-and-trade does and that's also what a CO2 tax does. As long as our current valuation in the marketplace tells us every minute of every day that it's perfectly all right to dump 90 million tons of global warming into the thin atmosphere surrounding the planet every 24 hours as if that atmosphere is an open sewer, then the individual actions are not going to solve the problem.

As many of you know, I was very instrumental in the founding of the Internet

Fifteen per cent of the population believe the moon landing was actually staged in a movie lot in Arizona and somewhat fewer still believe the Earth is flat. I think they all get together with the global warming deniers on a Saturday night and party

My plan to put Social Security in an ironclad lockbox has gotten a lot of attention recently, and I'm glad about that. But I'm afraid that it's overshadowing some vitally important proposals. For instance, I'll put Medicaid in a walk-in closet. I'll put the Community Reinvestment Act in a secured gym locker. I'll put NASA funding in a hermetically sealed Ziploc bag.

When our founders created America, it was in the age of the printing press, when individuals could freely join the conversation. And that robust, democratic dialogue more often than not lifted up the best available evidence and asserted what was more likely to be true than not.