11 March 2007

Channel 4 in Britain recently aired "The Great Global Warming Swindle," a documentary that rehashes the same tired global warming "skeptic" arguments. Basically, the point of the documentary is that climate change is just a worldwide hoax, despite the fact that all of the peer reviewed scientific journals and all the relevant scientific organizations agree that it is indeed real. But people love conspiracy theories, so here is the documentary itself.

Not long after the first showing, one of the experts used in the film (Carl Wunsch) complained that he had been "seriously misrepresented" in the documentary. This is apparently nothing new for the documentary film-maker Martin Durkin, since a previous documentary of his "was roundly condemned by the Independent Television Commission for misleading contributors on the purpose of the programmes, and for editing four interviewees in a way that 'distorted or mispresented their known views'."

Claim #1: CO2 doesn't match the warming of the 20th Century.
Martin Durkin apparently believes that this is damning to the idea that climate change has largely been driven by CO2 emissions. However, nobody is claiming that CO2 is the only forcing agent. In fact, the mid-century cooling period, which was driven by sulfate emissions, fits perfectly into our current models.

Claim #2: The troposphere should warm faster than the surface.
Uh, it does. Their own expert Christy has said:

"Previously reported discrepancies between the amount of warming near the surface and higher in the atmosphere have been used to challenge the reliability of climate models and the reality of human induced global warming. Specifically, surface data showed substantial global-average warming, while early versions of satellite and radiosonde data showed little or no warming above the surface. This significant discrepancy no longer exists because errors in the satellite and radiosonde data have been identified and corrected. New data sets have also been developed that do not show such discrepancies."

Claim #3: Temperature leads CO2 by 800 years in the ice core record.
Durkin believes that since the Vostok ice core record shows temperature changes 800 years ahead of CO2 changes, that this implies that CO2 doesn't actually affect temperature itself. But that claim, made over and over by climate "skeptics", has been refuted over and over. Temperature and CO2 have a feedback relationship where an increase in one results in an increase in the other (albeit in different proportions). What you see in the ice core record is a cyclical increase in temperature (due in part to the orbital variations in the sun) followed by a CO2 amplification of that increase. That's how the feedback works. Increased temperature eventually releases more CO2 from the oceans, which in turn increases the warming. This doesn't cast any doubt on global warming and doesn't even contradict with what the climate experts have been saying.

Claim #4: There were higher temperatures during the "medieval warm period".
To support this claim, Durkin uses a graph that he attributes to the IPCC. No date is given, but here is the graph:

However, this is the graph from the 1990 IPCC report (I think it was also used in AR2). Conspicuously absent are the IPCC graphs used after 1995, showing current temperatures to be higher. Here are the graphs of 10 more recent temperature reconstructions, including one that was used for the 2001 IPCC report:

Claim #5: The sun is really responsible for the recent warming.
Durkin acts as if nobody had ever properly considered the sun before. As evidence that this is responsible for the recent warming, he offers an impressive-looking graph that shows a matching "Temp." plotted against "Solar". However, this graph has been disposed of a long time ago (see Damon and Laut 2004).
the apparent strong correlations displayed on these graphs have been obtained by incorrect handling of the physical data. The graphs are still widely referred to in the literature, and their misleading character has not yet been generally recognized.
More on the sun here and here.

Here's a picture of the man himself, Martin Durkin:

John Houghton of the IPCC responds here.
RealClimate responds here.
Carl Wunsch responds here.
Stoat responds here.
George Monbiot responds for The Guardian here.

1 comment:

Casey said...

WEll done!