Sep 10 2013
The worst lies are those that contain a kernel of truth. This might include all instances of lying with statistics, because they may contain true numbers, simply distorted to tell a deceptive story.
Such lying with numbers is rampant within the global warming debate, mostly on the side of the deniers. Their basic strategy is to cherry pick the duration of time over which they choose to view the data – they are mining large data sets to cherry pick streaks that tell the story they want. This can involve looking at trends over one to a few years, instead of decades, or looking at thousands of years to obscure what is happening over decades.
The hypothesis that man-made activity is warming the globe over the last century, however, occurs over decades. Too long or too short a focus misses or obscures the proper time-frame for this trend.
The latest example of this is the claim, virally spreading around the intertubes, that arctic sea ice has increased by 60% in the last year. This fact this then used to argue that the Earth is not warming, and in fact we may be entering a cooling phase.
It does appear to be true that arctic sea ice increased by about 60% from August 2012 to August 2013. Like all climate, sea ice fluctuates from year to year. The trend over a single year cannot tell us much – it’s just the background noise. If we want to know what the trend in sea ice is over the last few decades, then we need to look at a few decades of data, at least.
Dana Nuccitelli at The Guardian has a nice graphic showing Arctic sea ice trends from 1980 to this year. In this graph you can see the background fluctuation year to year, but also the clear downward trend overall. Another trend is also apparent – following any year with a record low Arctic ice measurement, the following year is likely to have increased total ice. This is simply regression to the mean. In any fluctuating system, extreme values are likely to be followed more average values.
Arctic sea ice hit a record low in 2012, so it is no surprise that total ice regressed to the mean in 2013. It is absurd to consider this a sign of a long term trend.
Dana previously created a similar graphic showing how global warming deniers focus on cherry-picked short trends in global temperature data to argue for stasis, when the long term data over decades show a clear toward steady warming.
They further exploit extreme years (like the Arctic ice minimum in 2012) to skew the appearance of the data. With global temperatures, we had an unusually warm year in 1998 due to short term effects, such as El Nino. If you arbitrarily start your graph at 1998, it might look as if global warming has paused in the last decade, and in fact that is what deniers claim.
However, this is just the latest down fluctuation in the last century of up and down fluctuations in the background of a consistent warming trend. Further, 10 of the 12 hottest years on record have still occurred since 1998. The rate of warming has slowed compared to the average rate, but we are not in a cooling trend or a reversal of the overall global warming trend.
Meanwhile, climate scientists are trying to find explanations for the recent slowing in the warming trend to better understand their climate models. Deniers exploit debate over the details of exactly how and why global warming is occurring in order to cast doubt on the bigger picture that we are warming. This is a typical denialist strategy – creationists, for example, misrepresent debate about the details of evolution as if it calls into question the basic fact of evolution.
We do need to have a healthy scientific debate about the details of global warming, its causes and likely effects, and strategies to deal with it. This debate, however, is hampered by those who insist on abusing the data to sow doubt and confusion.
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