2014 and 2015 each set the record for hottest calendar year since we began measuring surface temperatures over 150 years ago, and 2016 is almost certain to break the record once again. It will be without precedent: the first time that we’ve seen three consecutive record-breaking hot years.
But it’s just happenstance that the calendar year begins in January, and so it’s also informative to compare all yearlong periods. In doing so, it becomes clear that we’re living in astonishingly hot times.
June 2015 through May 2016 was the hottest 12-month period on record. That was also true of May 2015 through April 2016, and the 12 months ending in March 2016. In fact, it’s true for every 12 months going all the way back to the period ending in September 2015, according to global surface temperature data compiled by Kevin Cowtan and Robert Way. We just set the record for hottest year in each of the past 9 months.
These record temperatures have been assisted by a very strong El Niño event, which brought warm water to the ocean surface, temporarily warming global surface temperatures. But today’s temperatures are only record-setting because the El Niño was superimposed on top of human-caused global warming.
For comparison, 1997–1998 saw a very similar monster El Niño event. And similarly, the 12-month hottest temperature record was set in each month from October 1997 through August 1998. That was likewise a case of El Niño and global warming teaming up to shatter previous temperature records. (..)