Watts Up With That? 
Wednesday, April 15, 2009
While I have reservations about the GISS dataset due to the many adjustments it endures, the GISS global temperature anomaly data  for March 2009 has been published.
The March 2009 global anomaly is 0.47 °C, making it the coldest March since the year 2000.
As Luboš Motl  points out:
That is also colder than March 1990 and 1998, That puts March 2009 out of the “top ten”. Also, the March 2009 global mean temperature differed by 0.03 °C only from the March 1981 figure – from a month when the ENSO/ONI index was pretty much equal to the current value. This cherry-picked monthly comparison would suggest that there may have been 0.03 °C of warming in 30 years.
Another blogger, Lucia  plotted long term GISS trends and got some interesting results.
- 20 year (240 month) trends with end points going back in time and
- Trends starting on Jan 1979 and ending “N” months ago. So, N=0 ends in March 09, N=1 ends in February 09 and so on.
Here they are:
(ARTICLE CONTINUES BELOW)
- The trend computed from 1979 to now is higher than the trend computed from 1979 to 2001. (This fact is true as can be seen by comparing the trend represented red square that intersects the yellow line indicating Jan 2001 to the red square representing a trend ending in March 2009.)
- The 20 year trend ending with the month of Dec 2000 is higher than the 20 year trend computed now. (This is a true fact, as seen by comparing the blue diamond intersecting the yellow line to the blue diamond ending representing the trend ending in March 2009.)
- Both facts are supposed to convince us that global warming neither stalled nor ended in 2001.
Well…. I’ve haven’t claimed global warming stopped or stalled in 2001. (In any case I’m not sure precisely what those terms are supposed to mean. If all they mean is temperature trends are down since 2001…. well, they are! If they mean that GHG’s don’t tend to cause warming and warming won’t resume… Well, the data don’t mean that.)
While GISS went up a tiny bit, from 0.41 in February 09 to 0.47 °C in March 09, you could figure that .06 °C to be essentially unchanged month to month and part of the “noise”. The lack of any real increase in trends since 2001 is the most interesting part of the GISS story.