A guest post by William Connolley.


There has been a vast amount of back and forth about the recent propaganda film “The Great Global Warming Swindle“. Two things have distressed me: that Channel 4 clearly have no interest in whether they broadcast truth or not; and the number of people prepared to fall for this tripe.

It’s possible to go through and analyse why just about everything they said was wrong or misleading, and I’ll try that in a moment. But if you find that going right over your head, then it may be more convincing to point out that:

Even C4 admits the graphs were faked: see here for a comparison of the version shown on Thursday and the re-run on Monday. In the “Thursday” version, the data has been stretched from 1988 to 2003 – this is simply and utterly impermissible. But even the “corrected” version is dishonest, since its a very old picture omitting the most recent warming period; compare to up to date data.

That is not the end of their misleading: the solar vs temperature graph has been truncated at 1980, because the data properly continued to date show no match to the temperature. And the graph of 400 years of solar correlation appears to have “infilled” missing data to match.

That answers one of the points of the documentary: the claimed excellent correlation of solar variation and climate change. It’s not true if you use proper data. The assertion that there isn’t a good correlation between CO2 and temperature is half true, but irrelevant. The figure (from wikipedia – the link will provide you with some idea of why scientists do indeed think that greenhouse gases are the major drivers of present climate change) shows how if you include CO2, other greenhouse gases, solar (a small part, but not ignored as the film implied), volcanic and ozone forcing then you end up with a good match to the observed temperature change. Oddly enough, the programme choose not to mention this at all: an indication of how partial they were.

The other claim that seems to have impressed many people is that “since temperature rises before CO2 in the ice core record, therefore the CO2 doesn’t affect temperature”. This is a logical non-sequitor: nonsense dressed up as sense. The best explanation of why its wrong that I know of is here but its hard work. In short: the favoured explanation for temperature and CO2 is that they form part of a feedback cycle to end the glacial periods: indeed, without the feedback from CO2 its rather hard to explain how ice ages do end. In the present day, we know we’re pumping CO2 into the atmosphere, so the question of feedbacks doesn’t immediately arise. Its also true that the 800 year lag is not definitively established – but fair to say that most people accept it for now.

Comparisons to Al Gores “An Inconvenient Truth” may be instructive. A defence of TGGWS that I’ve seen is “it may be propaganda, but so was AIT”. While I have some quibbles with AIT, the science is fundamentally correct (though I wasn’t impressed with the images of Manhattan flooding, or the bits about spread of disease). Gore, as far as I can tell, hasn’t faked any of his graphs or mislead any of his interviewees. He ignored the T/CO2 lag stuff, which is probably fair enough as it does little except confuse people.

The ultimate question must be, what does this tawdry little episode tell us about communicating the science of climate change? And the answer is, we’re not doing very well. Showing people pictures of polar bears standing on ice floes does nothing to educate them about the real science, and leaves them undefended when presented with equally convincing looking arguments from the “other side”. One solution is to ban this sort of propaganda, or overwhelm it with more propaganda: not a very pretty idea. The better solution is to effectively communicate the real science. Perhaps we now have an opportunity to do so.

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