LONDON — My youngest daughter is 17, so she will have lived most of her life before the worst of the warming hits. But her later years will not be easy, and her kids will have it very hard from the start. As for their kids, I just don't know.

It is the Met Office's job to make forecasts, and its forecast for the 2060s is an average global temperature that is as much as 4 degrees (Celsius) warmer. Speaking last week at a conference called "4 degrees and beyond" at Oxford University, Dr. Richard Betts, head of Climate Impacts at the Meteorological Office's Hadley Center, one of the world's most important centers for climate research, laid it all out.

"We've always talked about these very severe impacts only affecting future generations," said Betts, "but people alive today could live to see a four-degree (C) rise. People will say it's an extreme scenario, and it is an extreme scenario, but it's also a plausible scenario."