Lies, damn lies, and statistics.

In his 1954 book “How to lie with statistics,” Darrell Huff devotes a chapter to the “Gee-Whiz” graph. He shows that by truncating figures and altering the proportions between axis that it is possible to create a misleading impression without falsifying any data.

For people who would like you to belive that climate change isn’t a big problem this approach can sometimes be too tempting to avoid. A prominent think tank has a figure similar to the following on their homepage.

I have used data from the UEA Climatic Research Unit to reproduce the figure. There doesn’t seem to have been much in the way of global warming over the last decade, right? But if we want to see if “Global Warming has Halted,” we can use the same data source to take a look.

Borrowing an idea from Tamino, in the below figure I have plotted global mean yearly temperatures from 1975 up to 2000, using the same data source as for the figure above. I have also plotted a trend line (0.0174 °C∙yr-1) estimated by linear regression and dashed lines representing ± twice the standard deviation of the residuals. The idea is that aproximately 95% of the yearly values should fall between the two dashed lines. (Actually, to get things completely right, I need to account for autocorrelation of the residuals, but it shouldn’t make too much difference for our purposes.) By extending the dashed lines forward in time to the present we should be able to see if warming has halted or not.

If when the data points for 2001 – 2009 are included they sit within the two dashed lines, then claims that global warming has halted would seem to be premature. In fact as the below figure shows, the global mean  yearly temperatures for 2001 – 2009 are right where we would expect them to be if global warming were continuing without pause.

 

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5 Responses to Lies, damn lies, and statistics.

  1. theagingfanboy says:

    Excellent post. It’s been claimed that: “Statistics don’t lie, but statisticians do.” If anyone points outside and makes a comment about global warming, then get them to look at http://www.youtube.com/watch?v=g-F8EO3qOVk&sns=em and see that climate cxhange and global warming aren’t the same thing.

  2. Paul Gill says:

    I’ve been to several conferences where presenters have created impressions of significant findings, simply by presenting graphical data carefully. The problem of the climate change debate however is something that frustrates me greatly, largely because of the lack of rational debate on both sides. in fact i suspect that the ground made by the green lobby has now been lost because of the attitudes of some ‘hard liners’ who bordered on the hysterical at times. rationally discussing scientific theory is a fundamental aspect of science, yet this has been in short supply when it comes to climate change and therein lies the rub.

    while i dont dispute the evidence, i question the cause and potential solutions.

  3. jpreed says:

    I think a big part of the problem with discussions about climate change is false-balance or he said/she said journalism. The process of communicating science in that case breaks down and the casual reader/viewer/listener is left not really knowing who to trust.

    The reality is that the vast majority of published literature about climate change (or global warming) as reviewed in the IPCC AR4 points toward the situation that, yes it is happening and yes it is very unlikely to be due to natural forcings alone and that “greenhouse gas forcing has very likely caused most of the observed global warming over the last 50 years.” On top of this, those who are publically “unconvinced of anthropogenic climate change” have been shown to contribute only a small percentage of the publications in the field, implying a lack of expertise in the area.

    I think the evidence points to the cause pretty emphatically and the cause then leads to the obvious solutions. Whether or not those are politically possible is something else.

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