It is official: According to both NASA and the National Oceanic and Atmospheric Administration, the year 2014 was the hottest ever measured, based on records going back to the year 1880.
Perhaps the most surprising thing about the new record is that it occurred even though 2014 was not an El Niño year, of the sort that usually powers the already up-trending global average temperature to new highs.
"This is the first year since 1997 that the record warmest year was not an El Niño year at the beginning of the year, because the last three have been," says Gavin Schmidt, who directs NASA's Goddard Institute for Space Studies, which collaborated on the analysis.
Note: For scientists' reactions to the new record, see this post at Capital Weather Gang.
The two agencies released a joint announcement this morning, following a careful collaborative effort in which experts closely compared analyses. Last year, NASA and NOAA also collaborated on an analysis of 2013, which wasn't as warm but still ranks within the top 10 hottest years on record.
The agencies' joint presentation shows that despite some differences, overall NASA's and NOAA's temperature records are overwhelmingly similar:
The new findings are also consistent with an earlier, preliminary analysis by the Japan Meteorological Agency, which also pronounced 2014 the hottest year in its records, which go back to 1891. Another leading agency that keeps temperature records, Britain's Hadley Center, has not yet released its 2014 results.
The 2014 record, say the agencies, was driven by the world ocean, the planet's great repository of heat. Temperatures at the sea surface have never been hotter than in 2014, in recorded human history. Temperatures over land were not actually record breaking (although they were in some places, such as Britain), but the ocean's warmth overwhelmed that.
There were, to be sure, a few scattered cold anomalies in 2014 -- including over the eastern United States.
The 2014 record was not a blowout -- statistically speaking, the year surpassed the next runners-up by only a few hundredths of a degree Centigrade, averaged across the globe. That means that if an El Niño emerges early this year, as some are forecasting, yet another record could be possible.
For NASA's Schmidt, the new record is precisely what we would expect to see on a warming planet. "If you’ve got a long-term warming trend, you’re going to get new records every so often — in fact, on a pretty regular basis," says Schmidt. "This is what you’re expecting, and this is going to continue to happen because the underlying rate of global warming really hasn’t changed."
That would stand in contrast to the assertions of many climate "skeptics," who often assert that the rate of global warming has paused or slowed down since the year 1998.
They are expected to point to other analyses, including one from Berkeley Earth, which suggested that while 2014 is "nominally" the hottest year, "within the margin of error, it is tied with 2005 and 2010." Another analysis based on satellite temperature recordings of the lower atmosphere or "troposphere," conducted at the University of Alabama in Huntsville, found that 2014 was only the third-warmest year for this part of the planet.
However, NASA's and NOAA's joint statement will likely carry the most force. We can expect it to be cited almost constantly throughout this year, leading up to December, when countries of the world gather in Paris to negotiate a new global agreement to ratchet down the greenhouse gas emissions that lie behind one record-setting temperature year after another.
More: For a summary of scientists' reactions to the new temperature record, see this post at Capital Weather Gang.