Guest post by Paul Homewood
The HADCRUT data has now been released for September, so we can have a look at the latest figures for the four main global temperature datasets. I have now switched to HADCRUT4, although the Hadley Centre are still producing numbers for HADCRUT3.
|September 2012 anomaly||0.38||0.52||0.34||0.60|
|Increase/Decrease From Last Month||+0.12||-0.01||+0.14||+0.03|
|12 Month Running Average||0.16||0.42||0.11||0.50|
Global Temperature Anomalies – Degree Centigrade
The pattern is similar across all datasets, with September temperatures above both long term and 12 month averages, although, interestingly, both satellite sets have picked up a bigger spike than the other two. We are currently seeing the lagged effect on temperature from the mild El Nino, which began in April and has now pretty much fizzled out, as can be seen below. Purely thinking aloud, but is this an indication that atmospheric warming is slower to dissipate than surface warming?
My guess is that temperatures will settle back slightly by the end of the year. If ENSO conditions remain fairly neutral in the next few months, we should get a good indication of underlying temperatures, for the first time for a while.
The following graphs show 12-month running averages for each set. As I mentioned before, we often get fixated with calendar year figures, which obviously change a good deal from year to year. It therefore seems much more sensible to look at 12 month averages on a monthly basis, rather than wait till December.
In all cases, the 12 month averages are lower than they were at the start of the year.
Finally, I mentioned last month that UAH had just brought out a new Version 5.5, which corrected for spurious warming from the Aqua satellite. (Roy Spencer has the full technical stuff here). The new version is now incorporated and backdated in my analysis above. I have also plotted the difference between the old and new versions below.
As can be seen, the divergence really started to be noticeable towards the end of last year, and has steadily grown wider over the last few months.
Remember that all monthly updates can be accessed on my “Global Temperature Updates” page, at