The Stern Review examines the financial, human and other costs of failing to tackle climate change and concludes that this could amount to trillions of pounds, equivalent to shrinking the global economy by a fifth by 2050.

More importantly:

• Floods from rising sea levels could displace up to 100 million people
• Melting glaciers could cause water shortages for 1 in 6 of the world's population
• Wildlife will be harmed; at worst up to 40% of species could become extinct
• Droughts may create tens or even hundreds of millions of climate refugees

In all, without action, up to 200 million people could become refugees as their homes are hit by drought or flood.

Taking action now, on the other hand, would cost only 1% of global GDP. Stern's calculations are based on the assumption that the concentration of GHGs in the atmosphere will need to be stablised at around 500 to 550 parts per million by 2050. This has been acknowledged elsewhere as still too high – 450ppm is safer (although the impacts will still be felt) and we are at 430ppm today.

The Stern Review has been given extra attention following the leaking of a letter from David Miliband to the Chancellor, arguing for stronger green taxes to tackle climate change. You can read the letter here.

For media coverage of the Stern report and the Miliband letter see here.