Was 2014 Really the Warmest Year?

• The media is widely reporting 2014 as the warmest year on record, yet the underlying data don't support that conclusion.
• The data actually lead to a different finding, of 2014 tied with 2010 and 2005 within the margin of error, reflecting little warming since 2005.

When I opened today's Washington Post and turned to the Opinion section, I found two op-eds that began almost identically: Eugene Robinson's column stated, "We now know that 2014 was the hottest year in recorded history," while Catherine Rampell announced, "Last year, government scientists tell us, was the hottest year on record." The President even repeated this in his State of the Union address. However, that is not really what the figures in question indicate.

I suppose it's understandable that the Post's editors and those of many other media reporting the same finding might rely on the expertise of the government agencies involved, rather than digging deeper. The Post's columnists apparently based their comments on information provided to the media by NASA's Goddard Space Flight Center. The NASA press release, entitled, "NASA, NOAA Find 2014 Warmest Year in Modern Record," included links enabling one to scrutinize the raw data upon which this conclusion was based. I've reproduced the relevant portion below in picture form as of noon today, since this data is subject to periodic revisions.

NASA's dataset displays the differences between measured temperatures and the 14.0°C average from 1951-80. On this basis it confirms that the average recorded temperature in 2014 was 0.02°C higher than the average for the previous warmest year, 2010, which was in turn 0.01°C higher than 2005's. Unfortunately, neither that page nor the press release includes any information about the uncertainty inherent in these figures, which turns out to be larger than the increase from 2010-14.

All physical measurements, including those from the weather stations providing data to NASA, are plus-or-minus some error. Averaging them doesn't entirely negate that. Within the accuracy of these temperatures, it's not possible to distinguish among 2005, 2010 and 2014; they represent a statistical tie. That fact was explained more clearly than I have done in a report on January 14, 2015, from the team of scientists at Berkeley Earth. Hardly climate skeptics, this is the same group that made headlines a couple of years ago with a comprehensive study of existing climate data.

Why does this distinction matter? After all, measured temperatures have warmed nearly 2° Fahrenheit since the early 20th century, as shown in the graph above. Whether last year or 2010 was warmer might seem like more of an academic point than a practical one. However, the refrain of "record temperature" reports gives a false sense that the warming is accelerating. Instead, as the Berkeley Earth report found, "the Earth's average temperature for the last decade has changed very little." That's a very different impression than the one created by the stories I saw, with implications for how we respond to the risks of climate change.