Q: What’s the difference between a rise in global temperature of 2 degrees C and 4 degrees?

A: Human civilisation.

Who says? John Schellnhuber, one of the world’s most influential climate scientists, quoted in Paul Kingsnorth’s LRB Review of George Marshall’s new book, Don’t Even Think About It: Why Our Brains Are Wired to Ignore Climate Change.

According to Kingsnorth’s summary of Marshall’s thinking, four degrees of warming is likely

“to bring heatwaves of magnitudes never experienced before, and temperatures not seen on Earth in the last five million years. Forty per cent of plant and animal species would be at risk of extinction, a third of Asian rainforests would be under threat and most of the Amazon would be at high risk of burning down. Crop yields would collapse, possibly by a third in Africa. US production of corn, soy beans and cotton would fall by up to 82 per cent. Four degrees guarantees the total melting of the Greenland ice sheet and probably the Western Antarctic ice sheet, which would raise sea levels by more than thirty feet. Two thirds of the world’s major cities would wind up underwater. And we aren’t looking at a multigenerational time-scale: we may see a four degree rise over the next sixty years.”