NASA Makes It Official: 2015 Was the Hottest Year Ever

Sunday, January 24, 2016

Thanks to a team of worldwide scientists and high-end computer models, it is now official: 2015 was the hottest year on record.

Thanks to the human impacts on climate change, a strong El Niño almost as big as the record-setting one in 1998, and a flywheel effect of what happens from past almost-as-hot years make the next one even hotter, the Earth’s global surface temperatures registered an average +0.87°C (~1.6°F) hotter than the 1951-1980 base years measured in NASA Goddard’s GISSTEMP analysis. That makes it the hottest year ever for any year with temperatures scientifically verified by instrumentation.

2015vs2014+2010_v4In the chart shown above it is perhaps even easier to see both long-term temperature trends as well as how 2015’s El Niño effects began to make their appearance felt. The three graphs showing maps of globe surface temperature anomalies relative to the base period are well-marked, with a color scheme ranging from deep purple and blue at one end (where temperatures were actually lower than the base period) all the way up to a dark blood red for the most extreme variations from the baseline.

In the bottom left quadrant is the 2010 data set. In that one, note that even though the baseline was still significantly higher than normal overall by +0.72°C and coming in at the third hottest year on record, there are areas on the globe with little to no variance above the baseline. Most of those were over larger water regions and in less populated areas over the eastern and higher latitude parts of the Russia/China Asian land masses.

For 2014, the second warmest year on record, the variations are getting bigger and there are few regions where temperatures are close to the baseline figures. In this case the average surface temperature measured in at +0.74°C higher than the baseline.

In 2015, the globe dramatically rose in average temperature, all the way up to +0.87°C beyond the baseline. That’s a 0.13°C jump all in one year.

In the bottom right hand quadrant of this graph, it also possible to see how 2015’s El Niño made its presence felt. For it and the other two years charted here, through mid-year it could be said that temperature variations were following a similar pattern for each year on a month-to-month basis. After mid-year, however, the earth’s heating system kicked into high gear and surface temperatures began to climb quickly. In July 2015, the mean surface temperature measured in at +0.7°C over baseline. By December surface temperatures had risen dramatically, with a new mean value of +1.11°C.

This much change is bad enough, but another piece of climate change data which has only just begun to hit mass media is how it is the upper latitudes that are seeing the biggest temperature changes overall.

In this graph, starting from the bottom up is a good way to go to grasp its implications quickly. The bottom graph shows the long-term surface temperature trends over time for the southernmost latitudes, starting at 23.6°C South Latitude and running to 90° South. Using other descriptors, that is from the Tropic of Capricorn, the southern border of the tropics, to well beyond the southern Arctic Circle (which is located at about 66.5° south latitude. For this region all values have been climbing over time, but even now – in 2015 – the temperature anomaly runs only around +0.5°C relative to baseline.

The next graph, which depicts temperatures on either side of the equator marking the region known as the tropics, the temperature anomaly is a little higher relative to normal, showing a mean overall rise of between +0.8°C and +0.9°C.

When you get to the highest latitudes, from 23.6°N to 90N, running from the Tropic of Cancer, the northernmost part of what is known as the tropics, to well beyond the northern Arctic Circle (around 66.5°C), the temperature change is at its highest level, peaking as of the end of last year at around +1.1°C relative to the baseline. With such high temperatures in this northern region, one can expect faster melting of the ice caps than in the southern region – along with higher temperatures overall, which will impact all manner of animals, birds, and sea life.

With the current El Niño certainly far from finished in doing its best to continue its work well into 2016, and with the top three global greenhouse gas emitters (China, the U.S., and India) dumping more into the atmosphere, it is safe to assume 2015 will not retain its record at the hottest year ever for long. By next December, a number of scientists are already predicting 2016 will set even hotter records everywhere.

For the full report this article was based on, click here. NASA’s full data bank of information behind the graphs shown in this article – along with access to some of the computer programs used to do the analysis them – are available here.

Data included in this article was provided by the NASA Goddard Institute for Space Studies and their GISS Surface Temperature Analysis website and in the following publications:

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