After lots of speculation during the year, we can finally call it: 2014 was globally the hottest year on record in both the NASA and NOAA datasets, as well as the Japanese Meteorological Agency’s analysis. NASA and NOAA made the announcement today after tallying the data from December. As seen in the image above, the eastern US had a cooler year—and the western US and pretty much the entire rest of the planet were quite warm—so personal experiences will vary. But that’s why we calculate global averages. Taking land area alone, 2014 wasn’t quite tops (it's #4 in NOAA’s dataset), but warm oceans put the global average over the previous record. NASA measures their temperatures relative to a baseline of the average temperature between 1951 and 1980. By that measure, 2014 has continued a stretch where we haven't seen a month below that average since 1994. The last entire year that was below that average was 1976. In both the NASA and NOAA datasets, 2014 beats out previous record-setters 2010, 2005, and 1998. Those three years all featured El Niño conditions in the eastern tropical Pacific Ocean, where cool, deep water is prevented from surfacing by a lid of warm water. The back-and-forth between El Niño and La Niña (where large amounts of cool, deep water come to the surface there) is a major source of variability in annual averages of global surface temperatures. La Niñas pull the average down, while El Niños push the average up. More via Ars Technica.
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