Tens of millions of people in the US, across more than two dozen states, have been living under heat warnings during the past week. The world has already warmed by about 1.1C since the industrial era began and temperatures will keep rising unless governments around the world make steep cuts to emissions. The US climate envoy, John Kerry, says President Joe Biden is considering announcing a climate emergency. The move would give him additional powers to push his renewable energy agenda, which has been held up by lack of support in Congress. Will the declaration really help to cut emissions?

