According to new data released this week, May 2014 is officially the warmest May in recorded history.

Both NASA and the Japan Meteorological Agency have tentatively ranked May at the top of historical measurements, though NASA's numbers are preliminary because crucial information is still missing from China.

Warming up: May was another hot month. Credit:NOAA/NASA

Gavin Schmidt, the director of NASA's Goddard Institute for Space Studies, which maintains NASA's global temperature database, explained the Chinese data glitch.

Still, the fact that NASA and the Japan used different calculation methods to arrive at similar results is telling. Another agency, National Oceanographic and Atmospheric Administration, will release its estimate of May global temperatures next week using a third method.