We can look back through ice-core data and see over 800,000 years, relationships between carbon dioxide and the temperature of the world. So those people who deny the importance of climate change are just wasting their time. They're also being diversionary because if we don't act the risks are enormous.

Science and policy-making thrive on challenge and questioning; they are vital to the health of inquiry and democracy.

This [climate change] is potentially so dangerous that we have to act strongly. Do we want to play Russian roulette with two bullets or one?

Climate change represents the greatest and widest-ranging market failure ever seen

Give up meat to save the planet.

Climate change is a result of the greatest market failure the world has seen...We risk damages on a scale larger than the two world wars of the last century.

Failing to curb the impact of climate change could damage the global economy on the scale of the Great Depression or the world wars by spawning environmental devastation that could cost 5 to 20 percent of the world's annual gross domestic product.