John Metcalfe was CityLab’s Bay Area bureau chief, covering climate change and the science of cities.
Twenty of the warmest years in known history have now occurred in the last 20 years.
The official tallies are in and—huzzah!—2014 set a record for being the hottest year in known history. What was speculated a short while ago by Japan is now confirmed by both NOAA and NASA: most of the globe sweltered with abnormally high temperatures last year (though the eastern U.S. had a run on cold). Things are now roughly 1.4 degrees hotter than they were a century ago, and most of the warm-up has come since 1980.
This news means the 10 most torrid years on record have arrived since 2002, save for 1998, which was also really hot. Meanwhile, 20 of the record-warmest years have occurred in the (wait for it) last 20 years. Here's NASA on what's causing the atmospheric boil and what to expect in coming years:
"This is the latest in a series of warm years, in a series of warm decades. While the ranking of individual years can be affected by chaotic weather patterns, the long-term trends are attributable to drivers of climate change that right now are dominated by human emissions of greenhouse gases," said GISS Director Gavin Schmidt.
While 2014 temperatures continue the planet’s long-term warming trend, scientists still expect to see year-to-year fluctuations in average global temperature caused by phenomena such as El Niño or La Niña. These phenomena warm or cool the tropical Pacific and are thought to have played a role in the flattening of the long-term warming trend over the past 15 years. However, 2014’s record warmth occurred during an El Niño-neutral year.
May, June, August, September, and December were all record-warm months in 2014. Land temperatures throughout the planet were the fourth warmest on record, while the ocean achieved its most tepid state in known history, leading credence to the theory it's sucking up and storing atmospheric heat. The gradual, then rapid heating of the world is well illustrated in this NOAA animation of historical temperature anomalies: