Today we're dumping 70 million tons of global-warming pollution into the environment, and tomorrow we will dump more, and there is no effective worldwide response. Until we start sharply reducing global-warming pollution, I will feel that I have failed.

What changed in the United States with Hurricane Katrina was a feeling that we have entered a period of consequences.

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.

In order to solve the climate crisis, we need to solve the democracy crisis.

We have arrived at a moment of decision. Our home - Earth - is in grave danger. What is at risk of being destroyed is not the planet itself, of course, but the conditions that have made it hospitable for human beings.

We all know the leopard can't change his stripes.

Science has a culture that is inherently cautious and that is normally not a bad thing. You could even say conservative, because of the peer review process and because the scientific method prizes uncertainty and penalises anyone who goes out on any sort of a limb that is not held in place by abundant and well-documented evidence.