On a sweltering night this February, the world’s No. 2 exporter of liquefied natural gas didn’t have enough energy left to keep its own citizens cool. A nationwide heat wave in Australia drove temperatures above 105 degrees Fahrenheit around the city of Adelaide on the southern coast. As air-conditioning demand soared, regulators called on Pelican Point, a local gas-fueled power station running at half capacity, to crank up. …