New data in from the Japan Meteorological Agency (JMA) and NASA show that November 2015, like many of the months preceding it this year, was by far the warmest such month on record. In fact, in NASA's database, November narrowly fell short -- by about 0.01 degrees Celsius -- of the record set in October for the largest temperature departure from average for any month since 1880.
The warmth in 2015 is being driven primarily by two factors -- manmade, long-term global warming plus a near-record strong El Niño in the Pacific Ocean. An analysis by the journalism and research group Climate Central found that manmade global warming is the bigger factor out of the two, which is backed up by the fact that 13 of the 15 warmest years have occurred since the year 2000, including many years that did not have El Niño events.
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According to NASA, November had a global average temperature departure of 1.05 degrees Celsius, or 1.89 degrees Fahrenheit, above the 20th-century average. November is the second straight month to average above the 1-degree Celsius threshold, which is significant, since the global goal established in the Paris Climate Agreement is to hold global warming to "well below 2 degrees Celsius above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5 degrees Celsius."
Prior to October 2015, there had not been any month in NASA's database, which dates back to 1880, that had a temperature anomaly of 1-degree Celsius or above.
According to a Climate Central and University of Reading analysis, which has not yet been peer-reviewed, assuming the year will end up with a 1.05ºC temperature departure departure from pre-industrial average temperatures, most of that -- about 1-degree Celsius -- would be due to the anthropogenic forcing, with about 0.05 degrees Celsius to 0.1 degrees Celsius from El Niño.
El Niño events feature unusually mild ocean temperatures in the equatorial Pacific Ocean, and they also add heat into the atmosphere, thereby boosting global average temperatures on top of the already raised levels from global warming.
2015 will be a scorcher relative to all other years in the record. Even with sampling uncertainty: pic.twitter.com/wvTvzA1GC2— Gavin Schmidt (@ClimateOfGavin) December 14, 2015
According to the JMA data, November had a global average surface temperature anomaly of 0.54 degrees Celsius, or 0.92 degrees Fahrenheit, above the 1982-2010 average, which works out to 0.88 degrees Celsius, or 1.54 degrees Fahrenheit, above the 20th century average. On the JMA's graph of November temperatures since 1891, November 2015 stands out as a large spike of heat.