With slightly above-normal temperatures in the tropical Pacific, the planet's average temperature in September came in at 61.21 degrees, or 1.21 degrees above 20th Century averages, according to the National Climate Data Center.
Thus, September 2012 tied 2005's as the warmest in the period of record, dating to 1880.
The Northern Hemisphere was a shade toastier than the southern half of the planet, which is well into its spring.
Temperatures north of the Equator were 1.39 degrees above the average, the second-warmest after the 1.45 above of September 2005.
In the Southern Hemisphere, it also was the second-warmest, at 1.04 degrees above average. No. 1 remains 1997, at +1.19.
For the Jan. 1-Sept. 30 period, which covered a prolonged period of cooling in the tropical Pacific, the global temperature was 1.03 degrees above the 20th Century average.
The nine months constituted the eighth-warmest such period on record; the warmest occurred in 1998 and 2010, both +1.22.
As with September, the Northern Hemisphere warming has out-paced the Southern Hemisphere's, 1.39 to 1.15.
The climate center reported earlier that Philadelphia and the contiguous United States experienced their warmest first nine months of the year on record.
Not a single month has finished below normal in Philadephia in 2012, but at halftime, the October temperature is quite close to where it should be.