In any debate over Global Warming,
Michael Mann and his
"hockey stick" graph come up. This is of course the graph that shows a reconstruction of global temperatures from about 1,000 AD to the mid 1990s. You occasionally hear, from
GW skeptics, that the graph has been "refuted" by Stephen McIntyre and
Ross McKitrick, although the U.S. National Academy of Sciences concluded last year that:
The basic conclusion of Mann et al. (1998, 1999) was that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years. This conclusion has subsequently been supported by an array of evidence...What's more interesting to me, however, is the additional claim, which many climate scientists have made, to the effect that any methodological short-comings in Mann's work are
irrelevant, because his main findings have been replicated by alternative methods.
Which brings us to the graph top-left. It provides 500 years worth of average temperatures in the Ottawa, Ontario region and has been produced using one of these alternative methods. Specifically, it has been produced by
dropping thermometers down pre-dug boreholes and recording the temperature change that occurs as this measuring device plunges deeper into the Earth. How the results are calculated from data-points gathered in this way, and some of the drawbacks to the method, can be found in this terrific (and only somewhat technical) post at
Open Mind.
The
original data can be found
here.
Note the important thing: the graph pretty much replicates Mann's result.
This reveals...just how wrong it is to claim that “global warming stopped in 1998.” Temperatures since then have been perfectly consistent with the preceding trend. In fact they really have been a little warmer, although the extra warmth post-2000 is not yet statistically significant.
Ultra deniers Anthony Watts and Steve McIntyre have been hard at work. Anthony Watts has ranked about one third of U.S. surface stations according to the new CRN siting guidelines. Meanwhile, Steve McIntyre and several of his commenters have graphed the resulting temperature trends from the "good" (CRN class 1 and 2) stations as well as the "bad" (CRN5) stations. It would be fair to say that both expected the warming trend apparent in the GISSTEMP (Goddard Institute For Space Studies) data set to disappear once this had been done. As Anthony has written, "you have to wonder if the whole house of cards isn't about to start falling down". It would be fair to say, however, that they have both been disappointed. Their preliminary results are given in the above graph, provided by one John V (a frequent poster on Climate Audit), who writes:
If the Deniers can't deny it, then I think we're on pretty solid ground. But McIntyre's not giving up yet. He's standing on his head and looking at the data all squinty eyed, to see if he can't make the numbers go in another direction. So far, however, the resemblance is astonishing.
In any debate over Global Warming, Michael Mann and his "hockey stick" graph come up. This is of course the graph that shows a reconstruction of global temperatures from about 1,000 AD to the mid 1990s. You occasionally hear, from GW skeptics, that the graph has been "refuted" by Stephen McIntyre and Ross McKitrick, although the U.S. National Academy of Sciences concluded last year that:
