When the Nasa climatologist James Hansen testified before Congress in June 1988 about a warming planet, the temperature in Washington DC hit a record 100F. It was a summer of unprecedented heatwaves, and 40 states were grappling with drought.
His warning was seen as a historic wakeup call — but instead of heeding the existential smoke alarm, the US removed the batteries and kept on cooking.
Nearly four decades later, the consequences of a sweltering Earth are hitting home in the US south-west and mountain west — comprising states from California to Colorado. Over the past two decades, extreme heat and dwindling moisture levels have converged to create a “megadrought” deemed the driest period in 1,200 years...