Confirming what many of us have already noted from the anecdotal evidence coming in of a much cooler than normal May, such as late spring snows as far south as Arizona, extended skiing in Colorado, and delays in snow cover melting in many parts of the northern hemisphere, the University of Alabama, Huntsville (UAH) published their satellite derived Advanced Microwave Sounder Unit data set of the Lower Troposphere for May 2008.

It is significantly colder globally, colder even than the significant drop to -0.046°C seen in January 2008.

The global ∆T from April to May 2008 was -.195°C

2008 1 -0.046
2008 2 0.020
2008 3 0.094
2008 4 0.015
2008 5 -0.180

Compared to the May 2007 value of 0.199°C we find a 12 month ∆T is -.379°C.

Global Temperature Anomaly
Reference: UAH lower troposphere data

But even more impressive is the change since the last big peak in global temperature in January 2007 at 0.594°C, giving a 16 month ∆T of -0.774°C which is equal in magnitude to the generally agreed upon "global warming signal" of the last 100 years.