How bad was Donald Trump for the planet - and can Joe Biden turn things around?

When Donald Trump responded to the California wildfires by saying it would “start getting cooler”, it was a prime example of the president’s climate change scepticism that has partly defined his tenure in the White House.  Our chief correspondent, Alex Thomson, explains how far Trump set the country back, and whether President-elect Biden - who calls the climate crisis an “urgent national security issue” - can buy America - and the planet - back some time.