According to data released by NASA and NOAA this week, June 2012 was the 4th warmest June globally on record.  NASA’s analysis produced the 4th warmest June in its dataset; NOAA recorded the 4th warmest May in its dataset.  The two agencies have slightly different analysis techniques, which actually helps to reinforce the results from each other.

The details:

June’s global average temperatures were 0.56°C (1.01°F) above normal (1951-1980), according to NASA, as the following graphic shows.  The warmest regions on Earth coincide with the locations where climate models have been projecting the most warmth to occur for years: high latitudes (especially within the Arctic Circle in June 2012).  The past three months have a +0.59°C temperature anomaly.  And the latest 12-month period (Jul 2011 – Jun 2012) had a +0.52°C temperature anomaly.  The time series graph in the lower-right quadrant shows NASA’s 12-month running mean temperature index.  The recent downturn (post-2010) is largely due to the latest La Niña event (see below for more) that recently ended.  As ENSO conditions return to normal, the temperature trace should track upward again.

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Figure 1. Global mean surface temperature anomaly maps and 12-month running mean time series through June 2012 from NASA.

According to NOAA, June’s global average temperatures were 0.63°C (1.13°F) above the 20th century mean of 15.5°C (59.9°F).  NOAA’s global temperature anomaly map for June (duplicated below) reinforces the message: high latitudes continue to warm at a faster rate than the mid- or low-latitudes.  Unfortunately in June 2012, almost the entire Northern Hemisphere was warmer than normal.

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Figure 2. Global temperature anomaly map for June 2012 from NOAA.

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 over short time-frames (<100y),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.  Indeed, record warmth was observed at a 3200m altitude station earlier this month.  3.6°C may not sound that warm in July, but look at the station’s location:

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Figure 3. Location of Summit Camp, Greenland.

The station is in the middle of the massive Greenland ice sheet at ~10,500ft elevation.  It is difficult to warm this area enough to register above freezing temperatures.  Multiple stations on the top of the ice sheet similarly observed record warm temperatures recently.  What happens when air temperatures are above freezing with the mid-summer sun shining down for most of the day?  Record flooding occurs.

These observations are also worrisome for the following reason: the globe is still exiting the latest La Niña event:

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Figure 4. Time series of weekly SST data from NCEP. (NOAA)  The highest interest region for El Niño/La Niña is NINO 3.4 (2nd time series from top).

As the second time series graph (labeled NINO3.4) shows, the last La Niña event hit its highest (most negative) magnitude more than once between November 2011 and February 2012.  Since then, SSTs have slowly warmed back toward a +0.5°C 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 handful of 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, although other important signals might also occur at any particular point in time).  Looking further into the future, what will next year’s temperatures be as the next El Niño develops (as predicted by a number of methods, see figure below)?

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Figure 5. Set of predictions of ENSO conditions by various models (dynamical and statistical).  To be considered an El Niño event, 3-month temperature anomalies must be measured above +0.5°C for 5 consecutive months.  Approximately 1/2 of the models are predicting a new El Niño event by the end of this year.  The other models predict ENSO-neutral conditions through next spring.

Cross-posted at WeatherDem – the blog.