2015 the Warmest Year on Record by a Large Margin

Posted by on Jan 20, 2016

Global temperatures for 2015 reached a new record, whether looking at land temperatures, ocean temperatures, or combined land and ocean data. Source: National Oceanic and Atmospheric Administration

Global temperatures for 2015 reached a new record, whether looking at land temperatures, ocean temperatures, or combined land and ocean data. Source: National Oceanic and Atmospheric Administration

When I wrote in early November that 2015 appeared to be on track to be the warmest year on record, I hadn’t realized just how dramatic the record would be. The National Oceanic and Atmospheric Administration released today their December and yearly data on global temperatures in 2015, and the magnitude of those records is staggering.

Indeed, 2015 had the warmest global average temperatures on record—whether looking at the land data, ocean data, or combined data. Not only was 2015 the warmest year on record, but the margin of that record over the previous warmest (2014) was the largest ever. Global land temperatures in 2015 were 2.39°F above the average temperature for the 20th Century, while global ocean temperatures were 1.33°F above the average and combined land and ocean temperatures were 1.62°F above that 20th Century average.

The 16 warmest years on record, globally. These figures are combined land and ocean temperatures. Source: NOAA

The 16 warmest years on record, globally. These figures are combined land and ocean temperatures. Source: NOAA

When one plots the monthly average global temperature anomalies (compared to the long-term average) for the seven warmest years on record, the graph for 2015 never intersects those of the six previous warmest years (those being, starting with the next warmest, 2014, 2010, 2013, 2005, 2009, and 1998 . That line is consistently above that of the other warmest years—in most cases by at least a tenth of a degree C (and for the last four months by well over a tenth of a degree C).

Even more strikingly, when one looks at the individual months with the greatest deviations from the long-time average global temperatures—a dataset that includes 1,632 monthly temperature records—nine of the ten warmest months on record occurred during 2015!

Average monthly global temperatures for 2015 (in black) compared with monthly global temperatures for the next six-warmest years. Source: NOAA

Average monthly global temperatures for 2015 (in black) compared with monthly global temperatures for the next six-warmest years. Source: NOAA

U.S. temperature records not quite as dramatic

U.S. temperatures in 2015 were also high. The contiguous U.S. had the 2nd highest average temperature on record (first was 2012), going back 121 years; the average temperature was 2.8°F above the 20th Century average. Alaska also had the 2nd warmest year on record (first was 2014), going back to 1925; the average for the state was 4.1°F above the average back to 1925. Being from a state that depends on skiing and snowboarding for a significant chunk of its tourism revenue, this is troubling—though being able to work my garden well into December had its advantages as well.

The NOAA data on record temperatures—where you will find a huge amount of data that one could spend hours pouring over (believe me!)—can be found here.

Chart showing the individual months with the greatest deviations from the 20th Century average temperatures. Nine of the ten greatest anomalies (out of 1,632 months) were in 2015. Source: NOAA

Chart showing the individual months with the greatest deviations from the 20th Century average temperatures. Nine of the ten greatest anomalies (out of 1,632 months) were in 2015. Source: NOAA

The Paris Accord

With the backdrop of 2015’s dramatic temperature records, world leaders made their own history in November with the passage of the most important global agreement to date on global warming. 195 nations came together and agreed to provisions that negotiators had been working on for years and language that was hammered out during an intense two-week period.

Of course, a lot of us would have liked to have seen such an agreement decades earlier, but the forces rejecting the realities of climate change were heretofore too powerful. Indeed, politicians in the U.S. Congress continue to have their heads in the sand, but such positions are increasingly rare in a world that is (to a significant extent) led by learned individuals who listen to their scientists.

If the temperature extremes we’ve seen the past few years continue the upward trajectory for another year or two, I’m predicting that even the most anti-science climate-change-deniers in Washington will finally get on board with the rest of the world.

Then, perhaps we can adopt meaningful policies to spur the transition away from fossil fuels, such as a carbon tax or a national cap-and-trade system.

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Along with founding the Resilient Design Institute in 2012, Alex is founder of BuildingGreen, Inc. To keep up with his latest articles and musings, you can sign up for his Twitter feed. To receive e-mail notices of new blogs, sign up at the top of the page.

2 Comments

  1. The deniers in Washington may individually begin to believe science, but if their funding is from fossil fuel, they’ll have a hard time acting.

  2. Nine of the ten warmest months on record occurred in 2015. Thank you for this compelling post.

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