If you’ve spent any time in the deniersphere in the last decade, you’ve probably seen this graph purporting that according to ice core data, current temperatures in Greenland are much lower than historical ones. We have known this graph is wrong for a while, but considering it's still being used, we thought we’d bring everyone’s attention to a new Carbon Brief factcheck.
The data the graph uses originates from a (totally legitimate and not denier-y) 1997 paper by Professor Kurt Cuffey and Dr. Gary Clow, who used the Greenland Ice Sheet Project 2 (“GISP2”) ice core to estimate historic temperatures in the region. Ice cores are used as a proxy for temperature data because prior to the mid 1700s, thermometers weren’t around. The findings were used by several papers over the next decade. None of the scientists who used the findings made any comparisons to current temperatures or commented on current warming--the uncertainties in Cuffey and Clow’s dataset were too large, and ice cores can’t give information on recent temperatures.
Deniers first got their hands on the data around 2009, but it really blew up in the deniersphere when, 2010, Dr. Don J. Easterbrook wrote a post for Watts Up With That? which included the now-infamous graph. Easterbrook claimed that the ice core data shows that the vast majority of the last 10,000 years were warmer than current years, and therefore climate change is “really much to do about nothing.”
There are several things wrong with the assumptions in the graph-- the first being that the data relies on a single ice core measurement. Obviously it’d be ridiculous to base an argument generalizing about the global climate based on temperature records from one location. Yet a certain set of people, including Easterbrook in his blog post, use this graph to do just that. As Dr. Richard Alley, one of the first to use these GISP2 records, put it to the New York Times in 2010, “no single temperature record from anywhere can prove or disprove global warming, because the temperature is a local record, and one site is not the whole world.”
Perhaps the most misleading part of Easterbrook’s thesis, though, is that the now-viral graphs mislabels the x-axis. The graph claims to show temperatures up until the present time, when really the data ends in 1855. None of the current warming we’ve seen in the last century is represented, despite what the graph insinuates.
The reason the data ends in 1855 is because ice cores can’t give us current temperature measurements, as it takes several decades for the ice to form. But observational temperatures can be used to fill in the blank and get a full picture. Since ice cores are a temperature proxy, combining them with observational temperatures is tricky, but possible if researchers use the same system for averaging the temperatures.
Recently, Carbon Brief combined some new and improved ice core study findings with observational data with the latest ice core results from the 1970s. The analysis found that while temperatures were higher in the Holocene period (7,000+ years ago), Greenland is warmer now than it has been any time in the last 2,000 years. And if emissions continue, even under a modest emissions scenario, by 2050 Greenland’s temperatures will exceed not only the Holocene period but anytime since the last interglacial period 125,000 years ago.
Yet something tells us that even then, whatever deniers are still around (or more likely the bots pretending to be them) in 2050 will still be sharing this graph. Wildfires will rage, the Arctic will melt, and deniers will still post this and exclaim “Here’s the graph those alarmists don’t want Holoseen!”
Top Climate and Clean Energy Stories: