We face the gravest threat that civilization has ever confronted. It's global in nature and requires a global solution. Increased CO2 emissions anywhere, whether from China or the United States or from one of the countries that is burning its forests like Brazil or Indonesia.

The gay rights movement of recent years has been an inspiring victory for humanity and it is in the tradition of the civil rights movement when I was a young boy in the South, the women's suffrage movement when my mother was a young woman in Tennessee, the abolition movement much farther back, and the anti-apartheid movement when I was in the House of Representatives. All of these movements have one thing in common: the opposition to progress was rooted in an outdated understanding of morality.

You know there's an old african proverb that i made up: "If you want to go quickly, go alone. If you want to go far, go together."

Every nation has a moral obligation to safeguard the future.

Remember that the problem is bigger than the car you drive or the types of lightbulbs in city hall. We need a fundamental shift away from dirty fossil fuels that spew carbon pollution. To make that happen, we need to put pressure on our leaders to take the bold actions necessary to move us off dirty sources of energy.

I just think that a much more important part of the problem we face, which was evident 10 years ago and is even more evident now, is that the way we share information among ourselves as American citizens has been radically transformed. The line between news and entertainment has almost dissolved, where ratings now have a big impact on what kinds of stories are covered and not stories.

Winston Churchill aroused this nation in heroic fashion to save civilisation in World War Two. We have everything we need except political will, but political will is a renewable resource.