According to data released by NASA and NOAA this month, May 2012 was the 2nd warmest May on record: NASA’s analysis produced the 2nd (tied with 2010) warmest May in its dataset; NOAA recorded the 2nd warmest May in its dataset. The two agencies have slightly different analysis techniques, which actually helps to reinforce the results from each other.
May’s global average temperatures were 0.65°C (1.17°F) above normal (1951-1980), according to NASA. The warmest regions on Earth are exactly where climate models have been projecting the most warmth to occur for years: high latitudes (especially within the Arctic Circle in May 2012). The past three months have a +0.56°C temperature anomaly. And the latest 12-month period (Jun 2011 – May 2012) had a +0.52°C temperature anomaly.
According to NOAA, May’s global average temperatures were 0.66°C (1.19°F) above the 20th century mean of 14.8°C (58.6°F). NOAA’s global temperature anomaly map for May (duplicated below) reinforces the message: high latitudes continue to warm at a faster rate than the mid- or low-latitudes. Unfortunately in May 2012, the Northern Hemisphere was almost entirely warmer than normal. The extreme warmth over Siberia is especially worrisome due to the vast methane reserves locked into the tundra and under the seabed near the region. Methane is a stronger greenhouse gas than carbon dioxide,which is the leading cause of the warmth we’re now witnessing. As I discussed in the comments in a recent post, the warming signal from methane likely hasn’t been captured yet since the yearly natural variability and the CO2-caused warming signals are much stronger. It is likely that we will not detect the methane signal for many more years. Of additional concern are the very warm conditions found over Greenland.
Figure 1. Global temperature anomaly map for May 2012 from NOAA.
These observations are also worrisome for the following reason: the globe is still exiting the latest La Niña event:
As the second time series graph (labeled NINO3.4) shows, the last La Niña event hit its highest (most negative) magnitude in December 2011. Since then, SSTs have slowly warmed back toward a 0C anomaly (y-axis). La Niña is a cooling event of the tropical Pacific Ocean that has effects across the globe. It is therefore significant that the past few months’ global temperatures continued to rank in or near the top-5 warmest in the modern era. You can see the effect on global temperatures that this last La Niña had via this NASA time series.
As the globe returns to ENSO-neutral conditions this summer and early fall, how will global temperatures respond? Remember that global temperatures typically trail ENSO conditions by 3-6 months: the recent tropical Pacific warming trend should therefore help boost global temperatures back to their most natural state (i.e., without an ENSO signal on top of it). Looking further into the future, what will next year’s temperatures be as the next El Niño develops?