In his most recent book, ""The Vanishing Face of Gaia"", he suggests that we may already be beyond the tipping point of terrestrial climate into a permanently hot state. Given these conditions, Lovelock expects human civilization will be hard pressed to survive. He expects the change to be similar to the PaleoceneEocene Thermal Maximum when atmospheric concentration of CO was 450 ppm. At that point the Arctic Ocean was 23 °C and had crocodiles in it, with the rest of the world mostly scrub and desert.