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发表于 2010-7-18 13:11:15 |只看该作者

11-1[7.21]
The controversies in climate science
Science behind closed doors
Two new reports say the science of climate change is fine, but that some scientists and the institutions they work in need to change their attitudes

Jul 8th 2010

THE winter of 2009 was a rough time for climate science. In November, in the run-up to the Copenhagen climate conference, over 1,000 private e-mails from and to researchers at the Climatic Research Unit (CRU), a part of the University of East Anglia (UEA) in Britain, appeared on the internet, presumably after being stolen. At the same time a controversy was bubbling up in India over a claim in the 2007 assessment report by the Intergovernmental Panel on Climate Change (IPCC) that the Himalayas could lose all their glaciers in 25 years, which was wrong. These events seemed to provide evidence of embarrassing incompetence, at the very least.

Explanations were demanded and committees were formed to deliver them. This week two of those committees reported. For the CRU and what became known as “climategate”, an independent panel was created by UEA and chaired by Muir Russell, a former vice-chancellor of the University of Glasgow. The Dutch environmental-assessment agency was asked to look for other errors in the regional analyses of the IPCC’s report. Both the reports conclude that the science of climate is sound and that the professional characters of the scientists involved are unimpeached. But they raise important issues about how to do science in such an argumentative area and under new levels of scrutiny, especially from a largely hostile and sometimes expert blogosphere.

The Dutch agency found a few errors in the relevant chapters of the IPCC’s report, though none amounted to much. It also raised questions about concentrating on bad or worst-case possibilities rather than a range of outcomes. The agency did not say this was a bad thing—policymakers need to have the most critical information flagged up—but it thinks it would be better to explain more clearly what is going on.

Martin Parry, who in 2007 was co-chair of the relevant IPCC working group, says there was not a conscious decision to highlight negative effects, but to highlight important ones, as measured by such things as scale and irreversibility. The important effects are negative ones: this is why people are worried about climate change. A tendency for the IPCC process to produce outputs more worrying, at the margins, than its inputs does not necessarily show bias. It may reflect accurate expert assessment. But the risk that it is a sort of self-reinforcing groupthink merits attention.

Open to criticism

A form of groupthink certainly seems to have been at work in the climategate e-mails. The Russell committee was most exercised by a lack of openness at the CRU, in part explained, but not excused, by a sort of a siege mentality. The committee found that the scientists committed nothing close to fraud. It showed that the data needed to reconstruct CRU’s temperature records were widely available. Informed by a warts-and-all account of peer review from Richard Horton, editor of The Lancet, a medical journal, the committee took the researchers’ harsh behaviour towards critics and leniency towards allies not as unduly partial or aggressive, but as part of the “rough and tumble of interaction in an area of science that has become heavily contested.” As an eminent historian of science put it to a naive scientist when the story first broke, “Everything you believe to be true once looked like this.”

But the committee did criticise the researchers for an unwillingness to pass on data to their critics, for failing to specify which weather stations they were using, for keeping quiet IPCC discussions that should have been public, and so on. This flowed through into “clear incitement” to delete files rather than have them surrendered under Britain’s freedom-of-information act. The committee found UEA’s procedures on freedom of information poor.

Rather remarkably, neither the Russell committee or the university has asked Phil Jones, who ran the CRU, whether he actually deleted e-mails with the intention of foiling subsequent requests under the act. The university says it takes very seriously the need to improve its openness. At the same time it has appointed Dr Jones to a new position as director of research at the CRU—“definitely not a demotion”—while abolishing the role of director and integrating the unit more fully into its school of environmental sciences.

In doing this UEA accepts that Dr Jones’s role in one of the most famous aspects of climategate—his “hide the decline” e-mail—was “misleading”, as the Russell report puts it, without deliberately intending to be so. The growth of some trees, as recorded in their rings, tracks temperature from the 19th century to the 1960s, but then ceases to do so: the two records diverge. In a graph prepared for the World Meteorological Organisation in 1999, Dr Jones cut off the divergent part of one set of tree-ring data and spliced on data from thermometers. The scientific literature contained full discussions about the problems of divergence and various ways of dealing with them, but Dr Jones’s chart had no readily accessible explanations or caveats.

The Russell report is thorough, but it will not satisfy all the critics. Nor does it, in some ways, fulfil its remit. One of the enduring mysteries of climategate is who chose the e-mails released onto the internet and why they did so. These e-mails represented just 0.3% of the material on the university’s backup server, from which they were taken. This larger content has still not really been explored.

And then there is the science. An earlier report on climategate from the House of Commons assumed that a subsequent probe by a panel under Lord Oxburgh, a former academic and chairman of Shell, would deal with the science. The Oxburgh report, though, sought to show only that the science was not fraudulent or systematically flawed, not that it was actually reliable. And nor did Sir Muir, with this third report, think judging the science was his job. So, for verdicts as to whether the way that tree-rings from the Yamal peninsula in Siberia were treated by the CRU produced good results, those following the affair will have to look for future developments in journals and elsewhere. The mode of production has been found acceptable, but the product is for others to judge. Science, in the normal run of things, should do that; and if it does so in a more open, blogosphere-inclusive way some good will have come of the affair.

Science and Technology
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11-2[7.21]

Climate science
A mammoth effect
Hunting large herbivores may have (slightly) contributed to global warming

Jul 8th 2010

CHRISTOPHER FIELD is probably best known as the co-chair of the Intergovermental Panel on Climate Change’s working group on impacts, adaptation and vulnerability. In his day-job, however, he still engages in some serious boffinry. Take the paper soon to be published in Geophysical Research Letters which he wrote with two colleagues from the Carnegie Institution for Science in Stanford. They argue that mankind’s prehistoric penchant for mammoth may have had a discernible effect on climate.

Implausible though this may sound, the theoretical mechanism behind such an effect is pretty well understood. There is plenty of evidence to suggest that early humans were at least in part responsible for driving the woolly megafauna to extinction (the other culprit being natural climate change). Because excavated guts of frozen specimens show them to have grazed on, among other things, small trees such as birch, a reduction in mammoths is likely to have led to a proliferation of deciduous trees. The resulting landscape, being darker, would have absorbed more sunlight, heating up the air above the Earth’s surface.

Still, postulating the effect is one thing; teasing it out from the cobweb of climatic feedback loops and estimating its magnitude is something else altogether. Dr Field’s team set about the task by analysing ancient records of birch pollen preserved in lake sediments from known mammoth breeding grounds like Siberia. They found a spike coinciding with a drop in mammoth numbers some 15,000 years ago. To see how much less land birch would have covered, they used elephants as a proxy. The rate at which present-day pachyderms munch plants and uproot trees was adjusted for the presumed differences in the two species’ behaviour and the variation in vegetation between the mammoths’ tundra and the elephants’ African savannah.

From all this the researchers conclude that the extra area invaded by birch would have been 23% smaller, on average, had mammoths continued grazing. Plugged into a climate model this translates into a 0.13°C temperature rise in Siberian climes over the course of several centuries following the extinction (though some places would have warmed by as much as 1°C).

This may not sound catastrophic; the average global temperature is believed to have risen by 0.74°C in the 20th century alone. But if the model holds up, and if our ancestors really did have a hand in eradicating the hirsute herbivores, then mankind’s climate-meddling may have predated the advent of slash-and-burn agriculture 8,000 years ago, the earliest previous estimate, by as much as seven millennia. If only undoing global warming were as simple as breeding elephants.

Science and Technology

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