* Warning another long global warming post – probably should be ignored by all but enthusiasts.
John Quiggin and Ken Miles are both erudite and generally mild-mannered bloggers, except when it comes to the global warming debate. John Quiggin, for instance, tends to label people who dare to dissent from what he sees as global warming orthodoxy as “hypocrites” and “frauds”; analogises scepticism about any aspect of global warming to “creation science”; and accuses dissenting scientists of “conflict of interest” for having associations with right wing thinktanks, even though those associations are not dissimilar to his own links with the left-leaning Australia Institute (or Christopher Sheil’s association with the Evatt Foundation).
Ken Miles is usually marginally less extreme in his language about global warming sceptics, and is also rather more familiar with the scientific literature. However, he certainly didn’t hesitate to label one of Australia’s most eminent scientists Ian Plimer as intellectually dishonest (“picked the [data] that best suits his case”) and an ideologue (“Ideology 101”) for daring to subject global warming claims to sceptical analysis, when I blogged recently about a sceptically-oriented paper Plimer had delivered at an IPA conference earlier this year. I probably didn’t assist the tone of debate by responding to Miles’ comment with a tactless (if accurate) observation that Ken Miles himself was manifestly an ideologue on this issue. I see Ken now characterises the discussion as a “flame war”. Really? I can only assume Ken never reads blogs like Little Green Footballs or even our own Tim Blair if he thinks this is a flame war.
This post attempts to inject some clarity into the discussion about (1) the satellite temperature record and (2) historical climate proxies (tree rings, ice cores etc), which were the main focus of Quiggin and Miles’ attacks on Ian Plimer.
The satellite temperature record
Ken Miles makes the following criticism:
Plimer claim that a “24 year global coverage of satellite atmosphere temperatures shows only modest warming in the Northern Hemisphere and a slight cooling in the Southern Hemisphere” requires some pretty selective picking of data. There are four different analysis of the satellite data (this is a testament to the difficultly and uncertainties inherent in the satellite atmospheric record), Plimer has picked the one that best suits his case. Additionally, Plimer also gets it wrong. The slight cooling in the Southern Hemisphere, isn’t observed in the lower Troposphere, rather there is a slight warming trend – where the effects of extra CO2 are most felt. This might be good for ideology 101, but it sure isn’t science.
John Quiggin puts it this way:
Your description of the satellite data story is misleading. Christy et al originally claimed that it showed cooling, until it was pointed out (by Wentz and others) that they had failed to take account of orbital decay. When orbital decay is taken into account, there is an upward trend. Christy et al eventually conceded on this point, but came up with other adjustments that reduced the trend to statistical insignificance. The Wentz team has now come up with yet further adjustments that eliminate most of the discrepancy between the satellite and surface records. Given the past history, Wentz et a arel the ones with the best claim to have “the most credible rendering of the data”, and this rendering supports the global warming hypothesis.
Let’s look at the facts. Here’s a useful summary from Wikipedia containing lots of links. Christy and Spencer (the team most commonly cited by warming sceptics) have been compiling a global and hemispherical temperature record from satellite data for the troposphere (lower atmosphere) and stratosphere for over a decade. Until quite recently, they were the only group doing so. Their record showed minimal warming of the lower atmosphere (and even a slight cooling at many points) in the 24 year satellite temperature record. The science and computer models used by the UN IPCC, on the other hand, indicated that the lower atmosphere should have been exhibiting warming at a rate even greater than the surface if global warming was really taking place at the rate indicated by the averaged surface temperature record. The surface temperature record showed warming at approximately 0.18 °C per decade, and the lower atmosphere should have been warming even faster at 0.23 °C per decade. Hence the satellite data presented a puzzling discrepancy for the UN IPCC.
However, in August 1999 Nature published a paper by Wentz and Schabel which (at first) seemed largely to reconcile the surface and satellite records. Wentz and Schabel discovered that the phenomenon of orbital decay had been introducing a false cooling signal into the satellite data. Christy and Spencer immediately (within a week of publication of Wentz and Schabel’s paper) accepted the validity of the orbital decay discovery, but themselves pointed out that Wentz and Schabel had wrongly failed to adjust for orbital decay of each of the 9 satellites individually, and had failed to take into account another phenomenon namely east-west drift of satellites over time. After those adjustments, there is still a major discrepancy between the satellite and surface temperature records. Note the contrast between what actually happened and John Quiggin’s prejudicial and false characterisation of Christy and Spencer as having “eventually” conceded the point on orbital decay. Christy and Spencer make no secret of their sceptical views on global warming, so apparently they’re fair game for character assassination as far as John Quiggin is concerned.
As far as I can see from reading this very complex research, Wentz and Schabel accept the validity of the additional corrections (to their own corrections) made by Christy and Spencer, although there remain small (indeed almost statistically insignificant) differences between the (now) three separate formulations of the satellite data, because each of the three teams undertakes necessary adjustments of the raw data in slightly different ways. All the research teams working in this area are going to meet at the end of October to see if they can reach complete consensus on the most appropriate methodology for adjustment of the raw satellite data. However, even now, the increasing length of the satellite record and the intense focus by three separate high-powered research teams has achieved a high level of concordance. The most recent update of Christy and Spencer’s data set generates a temperature trend of 0.074 °C per decade, the data set of the Mears team generates 0.097 °C per decade, and Wentz and Schabel’s most recent (so far unpublished as far as I know) data set generates 0.1 °C per decade. All three data sets are therefore very close together, and all three show markedly less cooling than the 0.18 °C shown by the surface record, let alone the 0.23 °C per decade that the IPCC’s favoured computer models say they should be exhibiting.
Interestingly, Ken Miles himself blogged a couple of days ago about a study of the huge quantity of (notoriously difficult to adjust and interpret accurately) radiosonde weather balloon data. Like the 3 mainstream satellite teams, the study appears to generate a decadal global warming trend of around 0.1 °C, almost identical to the 3 mainstream satellite data sets.
Very recently (September 2003), a fourth team led by Vinnikov and Grody published a paper on the online supplement to Science, which global warming devotees are again touting (as they did with Wentz and Schabel for a short while back in 1999) as removing the discrepancy between the surface and satellite records. It purports to extract a warming trend from the satellite data of 0.22-0.26 °C (exactly what the computer models claim should be happening). Ken Miles gleefully and uncritically blogged a report of the Vinnikov and Grody paper under the title The Global Warming Skeptics Won’t Like This One. However Ken conspicuously failed to mention that the other teams researching in the area have dismissed the Vinnikov and Grody paper as arrant nonsense:
The findings have been attacked not only by John Christy of the University of Alabama at Huntsville, who along with colleague Roy Spencer produces the generally-accepted satellite temperature data, but also by Frank Wentz of Remote Sensing Systems in California, which has published data that finds more of a warming trend than Christy’s data. Wentz told the Wall Street Journal (Sep. 12), “It just adds noise to the whole debate.”
Christy went further, saying, “I think it’s a paper that should not have been published “¦ There are many fatal problems with it.” The principal objection is that Vinnikov and Grody did not correct the measurements for inaccuracies introduced by the heating up of the satellites by the sun. “They allowed it to remain in the data,” he told Cox News (Sept. 12), “and it corrupted all of their calculations, like a computer virus.” Grody responded that he did not think Christy should have made the adjustments.
And Ken Miles wonders why I label him a ideologue! I suppose it’s barely conceivable that Vinnikov and Grody might be correct, and the three other teams completely wrong. But it’s hardly reasonable to accuse Ian Plimer, one of Australia’s leading scientists, of selective use of data (let alone the “pot calling the kettle black” accusation of being an ideologue) in the circumstances, especially when Plimer’s IPA paper was presented months before Vinnikov and Grody’s research (for what it’s worth) was published. Moreover, when we examine Plimer’s words on which both Quiggin and Miles build their character assassination, we find he didn’t even mention any specific satellite temperature data set. Here’s what Plimer actually said:
To put such measurements into perspective over the history of time, changes in atmospheric temperature in the 20th Century can only be considered small and slow. A 24 year global coverage of satellite atmosphere temperatures shows only modest warming in the Northern Hemisphere and a slight cooling in the Southern Hemisphere. Temperature measurements from balloons agree with the satellite measurements for the period of overlap. Because greenhouse warming is a phenomenon of the atmosphere, significant changes should have been recorded. They have not.
Except for the relatively minor error about slight cooling in the southern hemisphere, everything Plimer says here is manifestly correct, whether based on Christy and Spencer’s, Wentz and Schabel’s or Mears’ version of the satellite record. Plimer’s statements simply don’t justify the relatively extreme ad hominem abuse employed against him by both Quiggin and Miles.