NASA’s James Hansen just sent around a commentary (in PDF here) on the significance of the 2007 global temperature in the context of the long-term temperature record that he compiles for NASA. After Real Climate went nuts over how misguided it is to engage in a discussion of eight years worth of temperature records, I can”t wait to see them lay into Jim Hansen for asserting that one year’s data is of particular significance (and also for not graphing uncertainty ranges):

The Southern Oscillation and the solar cycle have significant effects on year-to-year global temperature change. Because both of these natural effects were in their cool phases in 2007, the unusual warmth of 2007 is all the more notable.

But maybe it is that data that confirms previously held beliefs is acceptable no matter how short the record, and data that does not is not acceptable, no matter how long the record. But that would be confirmation bias, wouldn’t it?

Anyway, Dr. Hansen does not explain why the 2007 NASA data runs counter to that of UKMET, UAH or RSS, but does manage to note the “incorrect” 2007 UKMET prediction of a record warm year. Dr. Hansen issues his own prediction:

. . . it is unlikely that 2008 will be a year with an unusual global temperature change, i.e., it is likely to remain close to the range of (high) values exhibited in 2002-2007. On the other hand, when the next El Nino occurs it is likely to carry global temperature to a significantly higher level than has occurred in recent centuries, probably higher than any year in recent millennia. Thus we suggest that, barring the unlikely event of a large volcanic eruption, a record global temperature clearly exceeding that of 2005 can be expected within the next 2-3 years.

I wonder if this holds just for the NASA dataset put together by Dr. Hansen or for all of the temperature datasets.