NPR logo Was 2014 The Hottest Year On Record — Or Not?


Was 2014 The Hottest Year On Record — Or Not?

Icebergs float in Iceland's Jökulsárlón glacial lake, where the Vatnajökull glacier is retreating quickly due to global warming. iStockphoto hide caption

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Icebergs float in Iceland's Jökulsárlón glacial lake, where the Vatnajökull glacier is retreating quickly due to global warming.


Since the Jan. 16 release of findings by NASA's Goddard Institute for Space Studies (GISS) indicating that 2014 has been the hottest year on record, naysayers have criticized the report as being exaggerated and distorted.

According to the NASA data collected from more than 3,000 weather stations around the globe, "The year 2014 ranks as Earth's warmest since 1880." NASA's results were backed by analyses of data gathered from more than 6,000 weather stations belonging to the National Oceanic and Atmospheric Administration (NOAA) and the Japan Meteorological Agency.

So, what's going on?

According to NASA scientists, since 1880 — the year such global temperature averages started to be analyzed — the global temperature has risen on average by 1.4 degrees Fahrenheit (about 0.8 degrees Celsius), a trend that correlates directly to an increase in the release of carbon dioxide to the atmosphere. This release is largely from the burning of fossil fuels that sustains the increased industrialization of the global economy. We know this from a very clear correlation between the global temperature increase and the amounts of carbon dioxide in the atmosphere as a function of time.

The problem is that the NASA news release didn't include the error bars in the data. And, as we know, every scientific measurement is subject to a margin of error. For example, if you claim you weigh 170 lbs. on a scale with half a pound gradation, the measurement has an error of a quarter of a pound, half of the smallest gradation.

However, if one has the patience to look at the sources, in particular the paper by Prof. James Hansen from Columbia University and collaborators — responsible for the data analysis — one finds that there is no controversy at all. According to the authors, 2014 was the warmest year compared to the previous record held by 2010. The authors make clear, however, that the difference of only 0.02 degrees Celsius "is within the uncertainty of the measurement." That is, the actual scientific study that NASA based its statement on does, of course, take care of error bars. Furthermore, the authors go on to claim, "The three warmest years in the GISS temperature analysis, 2014, 2010, and 2005 in that order, can be considered to be in a statistical tie because of several sources of uncertainty, the largest source being incomplete spatial coverage of the data." [My italics.]

Clearly, the scientists in charge know what they are doing.

There are three points worth making here. First, NASA officials should be more careful with their public statements, in particular on a topic as politically and economically sensitive as global warming. Given the amount of controversy in the public sphere, this should be obvious by now. Second, if someone wants to criticize scientific results, he should read to the bottom of the research and not rely on superficial media statements. Third, and most important, the data ties 2005, 2010 and 2014 as the three hottest years on record. Even within the margin of error and the occasional yearly fluctuation, our planet is getting steadily warmer. Ignoring this fact is like stepping in front of a train and hoping that, if we close our eyes, the train won't hit us.

Marcelo Gleiser is a theoretical physicist and cosmologist — and professor of natural philosophy, physics and astronomy at Dartmouth College. He is the co-founder of 13.7, prolific author of papers and essays, and active promoter of science to the general public. His latest book is The Island of Knowledge: The Limits of Science and the Search for Meaning. You can keep up with Marcelo on Facebook and Twitter: @mgleiser