posted by anthony @ 20:45
Earlier I posted an article on global warming, in which doubt was cast on the view that it caused by man-made CO2 gases. Another blogger, tamino, left a link to an article that he, I assume it’s a he, had written on his own blogsite which seeks to show that the data presented in the made for TV documentary, The Great Global Swindle, is of doubtful accuracy. He has kindly consented to allow me to reproduce it here:
Not too long ago, British TV channel 4 aired a documentary produced by Martin Durkin for production company Wag TV, titled “The Great Global Warming Swindle.” The documentary claims that global warming is not caused by the buildup of greenhouse gases, but by changes in the sun. It specifically attempts to relate temperature change on earth to changes in the length of the solar cycle. It also suggests that the scientific concensus that in fact it’s due to greenhouse gases, is a giant conspiracy perpetrated by scientists who are hoodwinking the world in order to gain access to research funds.
How reliable is this documentary? One of the primary bits of “evidence” put forward is a graph of global average temperature for the last 120 years, attributed to NASA:
I’ve studied temperature time series quite a bit, and this graph looks remarkably different from what I’ve seen from NASA. Here’s the current temperature data from NASA’s Goddard Institude for Space Studies (GISS):
There are dramatic differences between the two pictures. Durkin’s graph indicates that from 1880 to 1940 global temperature increased by more than 0.5 deg.C, while the data from NASA GISS indicates a mere 0.3 deg.C. Durkin’s graph also indicates that from 1940 to 1975 the planet cooled by nearly 0.2 deg.C, while the NASA GISS data indicate a cooling of only 0.1 deg.C. How could these differences arise?
Here’s what the British newspaper The Independent had to say about it:
A Channel 4 documentary that claimed global warming is a swindle was itself flawed with major errors which seriously undermine the programme’s credibility, according to an investigation by The Independent.
…
A graph central to the programme’s thesis, purporting to show variations in global temperatures over the past century, claimed to show that global warming was not linked with industrial emissions of carbon dioxide. Yet the graph was not what it seemed.
…
The programme-makers labelled the source of the world temperature data as “Nasa” but when we inquired about where we could find this information, we received an email through Wag TV’s PR consultant saying that the graph was drawn from a 1998 diagram published in an obscure journal called Medical Sentinel. The authors of the paper are well-known climate sceptics who were funded by the Oregon Institute of Science and Medicine and the George C Marshall Institute, a right-wing Washington think-tank.However, there are no diagrams in the paper that accurately compare with the C4 graph. The nearest comparison is a diagram of “terrestrial northern hemisphere” temperatures – which refers only to data gathered by weather stations in the top one third of the globe.However, further inquiries revealed that the C4 graph was based on a diagram in another paper produced as part of a “petition project” by the same group of climate sceptics. This diagram was itself based on long out-of-date information on terrestrial temperatures compiled by Nasa scientists.However, crucially, the axis along the bottom of the graph has been distorted in the C4 version of the graph, which made it look like the information was up-to-date when in fact the data ended in the early 1980s.Mr Durkin admitted that his graphics team had extended the time axis along the bottom of the graph to the year 2000. “There was a fluff there,” he said.
Durkin now states that updated versions of his documentary will un-adjust the time axis, so that it will be correct. However, this won’t solve the problem that the data are decades out-of-date and only go up to the early 1980s.
Another very important graph in the documentary relates the idea that temperature change is correlated, with stunning accuracy, to the length of the solar cycle. The sun has a roughly 11-year cycle in which the number of sunspots increases and decreases, but the length of that cycle is not constant, it varies slightly. According to the theory, the shorter the sunspot cycle, the higher the global temperature. Durkin’s graph is attributed to Svensmark & Christensen, but actually the solar cycle length data come from Friis-Christensen and Lassen:
The agreement between the graphs is indeed stunning. But are these graphs correct? We’ve already seen that Durkin’s temperature graph is seriously incorrect. I accessed the sunspot data, as well as data for total solar irradiance (TSI), and computed the sunspot cycle length based on each. I then superimposed solar cycle length on the temperature graph, using the same relative scaling between the axes as used by Durkin:
Evidently the supposed “stunning agreement” is not there. In particular, the dramatic rise in global temperature since 1975 does not correspond to any increase in “invers solar cycle length.”
How did this come about? Part of the problem is that the data reported by Friis-Christensen and Lassen were mistaken. As Damon & Laut (2004, Eos, vol. 85, pg 28) reported, their result was due to inconsistent smoothing procedures and simple arithmetic errors:
In a telling episode reflective of Mr. Durkin’s character, the Times Online reports
Two eminent British scientists who questioned the accuracy of a Channel 4 programme that claimed global warming was an unfounded conspiracy theory have received an expletive-filled tirade from the programme maker.In an e-mail exchange leaked to The Times, Martin Durkin, the executive producer of The Great Global Warming Swindle, responded to the concerns of Dr Armand Leroi, from Imperial College, and Simon Singh, the respected scientific author, by telling them to “go and f*** yourself”.
Apparently, Dr. Leroi e-mailed Durkin saying, “To put this bluntly: the data that you showed in your programme were . . . wrong in several different ways,” and copied it to Mr Singh.
Durkin replied to both, saying: “You’re a big daft cock.” Mr Singh replied to Durkin, “I suspect that you will have upset many people (if Armand is right), so it would be great if you could engage in the debate rather than just resorting to one-line replies. That way we could figure out what went wrong/ right and how do things better/ even better in the future.”
Durkin replied nine minutes later with this tirade:
“The BBC is now a force for bigotry and intolerance . . . Since 1940 we have had four decades of cooling, three of warming, and the last decade when temperature has been doing nothing.”“Why have we not heard this in the hours and hours of shit programming on global warming shoved down our throats by the BBC?”“Never mind an irresponsible bit of film-making. Go and f*** yourself.”
Dr. Leroi had been scheduled to make a film with Martin Durkin and [the production company] Wag TV, but is seriously reconsidering now. As Leroi said, “I am no climate scientist, but I was very concerned at the way that flaws in these data were brushed over.”
Me too.
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