Human released greenhouse gas pollution continues to warm the surface of the planet. May was thought to be likely a very very warm month but it turns out to be merely very warm (only one “very”) according to data released this morning.
Shockingly, May turned out to be, in the NASA GISS data set, less warm than expected. (I mainly get my cues for what to expect from my friend and colleague John Abraham, who has written up the May NASA GISS results HERE.) At the same time the May data came out (earlier today) the data for April was adjusted by NASA (these adjustments happen all the time, they are always small). So, May 2015 and April 2015 had the same anomaly value in the NASA GISS database, 71. That’s in hundredths of a degree C, which itself doesn’t mean much. The base period is 1951-1980, which is a time period after which considerable surface warming had already occurred. The lowest value in the top 20 warmest months since 1880 is 74, the highest 93, so May 2015 is not quite on that list but still warm compared to the baseline, which averages zero (because it is the baseline).
Using a 12 month moving average based on these data, we’ve had record or near record 12 month periods since some time in 2014. The present 12 month moving average is the fourth highest in the adjusted, updated data, but with all five of the highest periods occurring since the beginning of this year. Here’s a graph of the 12 month moving average:
It is also interesting to look at the year to date. How warm is 2015 compared to previous years through May? Here’s a graph of that too:
Either way you look at it, surface temperatures are rising. What does that mean? This.