The first five months of 2015 topped the warmest such period on record for the globe, according to a pair of recently released independent analyses from government scientists.
Global temperatures January-May 2015 exceeded 2010's as the warmest first five months of any year, according to NASA's Goddard Institute for Space Studies.
NOAA's National Climatic Data Center noted that the first five months of 2015 nudged ahead of January-May 2010 by 0.09 degrees Celsius.
Record warm sea-surface temperatures in the northeast and equatorial Pacific Ocean, as well as areas of the western North Atlantic Ocean and Barents Sea north of Scandinavia contributed to the anomalous January-May 2015, according to NOAA.
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NOAA's analysis indicates that eastern Canada and parts of the Great Lakes and New England were the only locations much colder than average so far in 2015. Parts of the north Atlantic Ocean, eastern Atlantic Ocean off west Africa, and Southern Ocean off the tip of South America were also somewhat cooler than average in the year's first five months.
This follows a record warm 2014 for the planet.
With the potential for El Nino, a periodic warming of central and eastern equatorial Pacific Ocean water, to strengthen and persist the rest of the year, 2015 may top last year's record warmth.
El Nino doesn't guarantee that happening, but it's worth pointing out the previous two record warm years in NASA's dataset prior to last year, 2010 and 2005, both featured El Ninos that ended early in the year, rather than persisting through an entire year.
January, February and March 2015 were each warmer than 2014. April was roughly comparable, but May was slightly cooler than May 2014, NASA said.
May 2015 tied 2012 for the second-warmest May in the NASA GISTEMP analysis, which merges data from conventional land-based stations and reconstructed sea-surface temperature data from NOAA and dates to 1880.
NASA's analysis found the most pronounced warm anomalies in May 2015 were over the higher latitudes of the northern hemisphere in two zones. One stretched from northern and central Russia into the Kara Sea, Barents Sea, northern Scandinavia westward toward northeast Greenland. Another was centered over northeast Alaska, and Canada's Yukon and Northwest Territories stretching into the Beaufort Sea.
A third, separate analysis from the Japanese Meteorological Agency also found May 2015 to be the globe's hottest May, topping May 2014 in records dating to 1891.
Record May warmth was also observed in parts of equatorial South America, southern Africa and The Middle East, according to NOAA. Spain tallied its second warmest May in records dating to 1961.
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Cooler-than-average May temperatures were noted by NASA in the central and south-central United States, the north Atlantic Ocean, Greenland and much of Antarctica.
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Particularly cold was northern Greenland. A weather station in Danmarkshavn, Greenland tallied its coldest May in records dating to 1949, according to NOAA.
Ultimately, the important takeaway is not whether one particular month or year is a fraction of a degree warmer or cooler than another, but the long-term trend.
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Nine of the ten warmest years in NASA's 134-year database have occurred this century, with the exception of 1998, which featured the tail end of one of the strongest El Ninos on record.
The last year in NASA's dataset globally cooler than average was 1976.
The last cooler-than-average month was over 21 years ago, February 1994. In the 449 months from January 1978 through May 2015, only 11 months have been cooler than average, according to the NASA dataset.
NOAA says nine of 10 warmest 12-month periods have taken place over the past two years. This 12-month record for the globe has been either tied or broken each month from January to April 2015.