From a climate change perspective, 2015 had all the elements of a good drama: suspense, a surprise twist and a (somewhat) happy ending. It turned out to be the hottest year on record, but ended with new hope for turning down the thermostat: In December, nations are expected to enter into negotiations for a plan to cut greenhouse gas emissions. Throughout the year, a series of scientific revelations underscored its necessity — and overturned some long-standing assumptions.
Two reports, published in February and July, upended the widespread belief that warming had stalled the past 15 years. They revealed that Earth had continued warming as quickly as ever — shifts in ocean circulation had simply cloaked this trend by pulling some extra heat into deep waters for a few years. “This year will be the warmest — it’s so far ahead of any other year,” Phil Jones, a climatologist at the ...