Saturday, September 5, 2009

Puzzling Graphical Comparisons raise questions of veracity

Dire Predictions” by Michael Mann and Lee Kump, sets out to provide an illustrated guide to the findings of the IPCC. It is a relatively simple volume, full of the promised pictures, small graphs to illustrate points and condensed comments on the different aspects of the climate change debate. In short it is the sort of text that might be provided to a class in the United States to help them understand the prevailing arguments about climate change.

It has some nice initial illustrations of the way in which climate is generated that are easy to follow and which are therefore initially persuasive. But my eye was caught, from the beginning by the different graphs that are scattered throughout the chapters. I was a bit surprised by the first graph, since it didn’t quite look like the graph of the temperature plots given by NOAA, so after looking at the two separately:
From page 20 of the text

Global temperatures from 1880 to 2008 from NCDC

You can see quite a difference in the curves around 1940 – the actual peak back then has disappeared from Dr. Mann’s graph and if I superimpose them you can see how a fluctuating temperature record has been smoothed. (The heavy black line comes from the Mann and Kump curve)

The difference is more than subtle – the peak and stable or declining temperatures between 1940 and 1970 have been magically eliminated. But wait, those of you who have read the book respond – he puts a more detailed temperature plot on page 36.
Here it is:

Mann and Kump – Figure on page 36 – Trends in Global Average Surface Temperature.

But if you look at this figure – relative to the official plot you can see that while the official temperature is “debatably” flat in the official record, here the plot is steadily increasing from 1950.

Skipping forward through the book, let me pick out one more graph that caught my attention – the regional trends shown on Figure 71. Here is the Mann version:
Regional Continental Temperature Trends (after Mann and Kump) Blue are the temperatures taking into account natural trends only, pink includes both human and natural factors). Red is what they say happened.

But this is the official temperature record for North America from NASA.

Again I won’t bother superimposing the pictures, but you can see that the trends that are actually occurring don’t quite follow the curves in the book.
Having discovered which there really isn’t much point in continuing reading it, since it takes such liberties with easily verifiable figures, one is wondering what else has been “quietly adjusted” to make the facts more supportive of the argument.

Now it isn’t as though I completely agree with the official figures, given the corrections that have been imposed on the initial raw data, and that, as a result, trends appear that weren’t there before the “tweaking.’ But I do think that this book is taking the trend of “adjusting” the data just a bit too far in the process of making a point. There comes a point where this stops being Science and becomes Propaganda.


  1. Isn't the graph first above for the 48 US states, not North America?

    A couple of interesting and related items have been in the news this weekend.

    In the first, a crewmember was taken off the cruise ship Bremen in Prudhoe Bay. It's interesting to me because the prospect of a cruise ship venturing into the Beaufort Sea during my youth and yours would have been as unlikely as an oil company drilling a 31,000 ft hole in 4,100 ft of water.

    The second item describes a newly published Arctic temperature reconstruction. The BBC report reproduces a graph putting Arctic temperature rise during the last century into its context over two millenia. The Arctic, like the rest of the northern hemisphere, was in a millenial-scale cooling period until the start of the industrial age and should still be cooling, which it's not.

  2. Grin - that all depends on whether you accept the cyclic Warming Periods, of which there is considerable evidence, and the intervening cold periods, the last of which was The Little Ice Age or not. I believe I have read that it depends on which set of data you pick which set of conclusions you end up coming to.

    There is, to my mind, more than enough evidence that proves the existence of the Warming Periods, which, as with the above, starts to raise other questions.

  3. Oops, and in regard to the cruise ship - it could be that they were a little premature - there is the story in the New Scientist about the prospects of a period of global cooling, which seems to be a more popular thought in the last couple of months.

  4. You used an old version of the NASA series. In 2001, they introduced a major adjustment to US data.

  5. I pulled the figures from the Web sites on the day I wrote the post.

  6. Mannian Math.
    What more needs to be said.

  7. Having followed this issue since we were told we were entering another ice age, 1970s, and man was causing that to happen, I remain skeptical about any quasi-science generated from, at best, questionable data, using correlation of the questionable data to prove an agenda which has become a religion.