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, (here and here), 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.
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.
Click for a larger image
Reference: UAH lower troposphere data
I’m betting that RSS (expected soon) will also be below the zero anomaly line, since it tends to agree well with UAH. HadCRUT will likely show a significant drop, I’m going to make a SWAG and say it will end up around 0.05 to -0.15°C. GISS; I’m not going to try a SWAG, as it could be anything. Of course anomalies can change to positive on the next El Nino, but this one seems to be deepening.
Update 06/05/08: Per MattN’s suggestion, changed link above for snow melt to news stories from previous link to National Snow and Ice Center