2015: A High Temperature Record-Breaker Like None Before It?

With the cold winter just behind us, the return to ‘normal warmth’ in the Northeast in April was a relief.  But at a global level, temperatures continue to be not just warm, but record-breaking.

2014 was considered by several weather authorities to be the hottest year on record, while a few ranked it second.In any case, it was a photo-finish still on a par with other years in the record-breaking hot decade in which it occurred.

2015 is on track to break that 2014 record and might even create a new high-temperature bar that lifts itself above all past contenders from the period of instrumental records.  This year may show us what the next decade has to offer!

The first four months of 2015 have been well above the previous cluster of records, and there is reason to think this could actually intensify in the year ahead.

noaa-graph-jan-april-2015

Source: NOAA https://www.ncdc.noaa.gov/cag/time-series/global/globe/land_ocean/ytd/4/1880-2015

Each bar on this graph represents just the first four months, January to April, of each respective year.  2015 has already set a new height for the global red mercury column. So one-third of the way through the year, it has a dramatic lead. Will this lead hold in the months ahead?

Weather predictions are never certain, but some experts predict that it will. That’s because in 2015, El Nino, which feinted and teased all through 2014 with a predicted arrival date that kept being pushed back and pushed back, is now fully developed.  El Nino is recognized by a band of hotter than usual sea surface temperatures (SST) in the Equatorial Pacific.  SST there are currently surpassing the diagnostic threshold by a factor of two, and the anomaly is predicted to get stronger as the year progresses.  Predictions now give it a 90% chance of lasting through the whole summer, and a greater than 80% chance of lasting the entire year of 2015 (NOAA’s Climate Prediction Center (CPC)).  While the future intensity of the El Nino is difficult to predict, many of the models indicate a continuously increasing SST throughout the summer.  El Nino’s are generally associated with higher than average global temperatures and altered rainfall patterns.  This is why many are predicting that 2015’s global annual temperature will be no near-tie among recent decade contenders, but will leave the others behind in the hot dust and mud.

But that is still just a medium-term weather prediction, and we will have to wait and see if it is fully accurate.  Right now, the globe is more than hot enough already.

noaa map april 2015

NOAA National Climatic Data Center, State of the Climate: Global Analysis for April 2015, published online May 2015, retrieved on May 27, 2015 from http://www.ncdc.noaa.gov/sotc/global/201504.

Two regions stand out on this global map of April 2015 temperature anomalies. Look at the reddest and bluest colors! The reddest colors are indicating that the equatorial Pacific Ocean, among other regions, currently has high temperatures that break all records of the instrumental period (1880-2015). This is the defining region for El Nino (see right and left edges of the map at the greatest bulge) and contributes strongly to the expectation of a 2015 scorcher.

There is also one spot on the globe breaking all records for being cold. This is the Atlantic Ocean just south of Greenland. These cold temperatures are not just a one month fluke either, but occur in the only region of the globe that has a convincing record lasting for recent decades of being colder than the hundred year average. This is a source of great interest among climate scientists. A recent article in Nature Climate change (Ramstorf et al) suggested that this was due to a reduction in the strength of the Atlantic Meridian Overturning Current (AMOC). They found that the effect was unprecedented in the last 1100 years. Ramstorf and his colleagues suggested this was due to freshwater inputs from melting Greenland glaciers decreasing salinity in the Northern Atlantic and, because fresher water is lighter than saltier water, inhibiting the subsidence of cold surface waters to the deeps. Normally cold salty water would sink in this region and be replenished with warmer waters coming north in the Gulf Stream. Some even draw links between this and our recent cold winters in the NE, but that is a topic that is still speculative and much debated.

Rahmstorf, S., Box, J., Feulner, G., Mann, M., Robinson, A., Rutherford, S., Schaffernicht, E. (2015): Exceptional twentieth-Century slowdown in Atlantic Ocean overturning circulation. Nature Climate Change, Vol. 5, pages 475-480, May 2015 (http://www.nature.com/nclimate/journal/v5/n5/full/nclimate2554.html).

See more at: http://www.realclimate.org/index.php/archives/2015/03/whats-going-on-in-the-north-atlantic/?wpmp_tp=1#sthash.2TWQgXGZ.dpuf



Category: What's With the Weather

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