The heat extremes were especially pervasive in the Arctic, with temperatures in the fall running 20 to 30 degrees Fahrenheit above normal across large stretches of the Arctic Ocean. Sea ice in that region has been in precipitous decline for years, and Arctic communities are already wrestling with enormous problems, such as rapid coastal erosion, caused by the changing climate.
“What’s going on in the Arctic is really very impressive; this year was ridiculously off the chart,” said Gavin A. Schmidt, head of the Goddard Institute for Space Studies in Manhattan, a unit of the National Aeronautics and Space Administration that tracks global temperatures.
But Arctic people were hardly alone in feeling the heat. Drought and starvation afflicted Africa. On May 19, the people in the town of Phalodi lived through the hottest day in the recorded history of India, 123.8 degrees Fahrenheit.
El Niño has now ended, and climate scientists almost universally expect 2017 to be cooler than the year before. But the scale of the heat burst has been startling to many of the experts, and some of them fear an accelerated era of global warming could be at hand over the next few years.