Tuesday, 20 June 2017

May was the second hottest on record

World Climate Stays in Uncharted Territory as May of 2017 Hits Second Hottest on Record

19 June, 2017

We’re currently in what should be a relatively considerable temperature trough following a strong 2015-2017 El Nino. But the globe hasn’t really cooled off that much.

In contrast, during the two year period following the 1998 super El Nino, annual global temperature averages subsequently cooled by around 0.2 C to about 0.64 C warmer than 1880s averages as a strong La Nina swept in. This post El Nino cooling provided some respite from harmful global conditions like increasingly prevalent droughts, floods, fires and coral bleaching events set off by the 1998 temperature spike. It did not, however, return the world to anything close to average or normal temperature conditions.
Warming Out of Context

(So far, 2017 temperature averages for the first five months have remained disturbingly close to what should have been an El Nino driven peak in 2016. Temperatures remaining so warm post El Nino are providing little respite from this peak warming. Meanwhile, the longer La Nina conditions hold off, the more extreme and out of context the post-2013 period looks from a global weather/climate perspective even relative to the significant warming occurring from the late 1970s through the early 2010s. Note the steep temperature spike following 2013 in the graph above. This should flatten out, step-wise, as La Nina conditions ultimately push against the larger surface warming trend [driven primarily by fossil fuel burning]. We thus await La Nina with baited breath… Image source: NASA.)

During 2015 and 2016, the world was forced to warm much more intensely than during the 1998 event as very high and rising greenhouse gas concentrations (400 ppm CO2 +) met with another strong El Nino and what appeared to be a very widespread ocean surface warming event. Temperatures peaked to a troubling 1.2 C hotter than 1880s averages during 2016. An annual peak nearly 0.4 C warmer than the 1998 temperature spike. But unlike the period following the 1998 event, it appears that 2017 will probably only back off by about 0.1 degrees Celsius at most.

This counter-trend cooling delay is cause for some concern because a larger portion of the global surface heat added in during the 2015-2016 El Nino appears to be remaining in the climate system — which is lengthening some of the impacts of the 2015-2016 temperature spike and putting the world more firmly outside of the weather and climate contexts of the 19th and 20th Centuries.
(2017 temperatures aren’t trailing too far behind 2016’s record spike. A trend that is, so far, considerably warmer than 2015, which was the second hottest year on record. Image source:NASA.)

Record heat, drought, rainfall events, unusual storms, coral bleaching, glacial melt, wildfires, sea ice melt and other effects related to extreme global temperature will, therefore, not abate as much as some would have hoped. Furthermore, though current science does not appear to identify a present perturbation in the ENSO cycle (which may produce more El Ninos as the world warms), monitoring of that cycle for warming-related change at this time seems at least somewhat appropriate.
Second Hottest May on Record

According to NASA, May of 2017 was 0.88 degrees Celsius hotter than its 20th Century baseline — or 1.1 C warmer than 1880s averages when the world first began a considerable warming trend clearly attributable to fossil fuel burning and related human carbon emissions. This reading is just 0.05 C shy of the record warmest May of 2016. It’s also slightly warmer than the now third warmest May (0.01 C warmer) of 2014. And all of the top four warmest Mays in the present NASA record have now occurred since 2014.
(NASA’s second hottest May on record brought above normal temperatures to much of the globe. Disturbingly, the most extreme temperature departures above average occurred in the vulnerable Coastal regions of Antarctica. Small regions including parts of the North Pacific, the Northern Polar Region, the extreme South Atlantic, and the Central U.S. experienced below average temperatures. But these outliers were few and far between. Image source:NASA.)

Add May of 2017 into the present 2017 running average and you get a total of 1.19 C warmer than 1880s conditions. This is the second warmest first five months on record following 2016 at a very considerable 1.38 C above 1880s. It is, however, just about 0.01 C behind 2016’s annual average of 1.2 C above late 19th Century global temperatures.

It’s worth noting that most of the temperature spike attributable to the 2015-2016 El Nino occurred beginning in October of 2015 and ending in April of 2016. Somewhat milder months comparable to April and May 2017 averages followed from June through December of 2016. So a continuation of present trends could leave 2017 rather close to the 2016 spike.
Forecast Trends

GFS model guidance for June shows somewhat cooler global conditions than in May. If this trend continues we will likely see the month range from 0.7 to 0.82 C above NASA’s baseline. If the GFS summary is accurate and this meta-analysis is correct, then June of 2017 will likely range between 1st and 4th warmest on record. Meanwhile, ENSO (El Nino Southern Oscillation) neutral conditions should tend to keep 2017 as a whole in the range of 1.07 C to 1.2 C hotter than 1880s averages — beating out 2015 as the second hottest year on record and keeping the globe in what basically amounts to uncharted climate territory.

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