Complaint to Ofcom Regarding “The Great Global Warming Swindle”

[Comment 47: These comments are highly misleading, and apparently intentionally so, in a number of ways.

First, the notion that, because greenhouse gases, and especially carbon dioxide, make up only a small part of the atmosphere they must have only a small effect, is false: without greenhouse gases the Earth’s surface would be around 33 degrees Celsius colder than it is (see: http://tinyurl.com/2pjoge).

Second, although it is true that water vapour is the most important greenhouse gas, carbon dioxide is the second most important, accounting for around 20% of the natural greenhouse effect (see Kiehl and Trenberth, 1997, Bulletin of the American Meteorological Society, at http://tinyurl.com/zpzel (PDF) and Realclimate: http://tinyurl.com/8no28).

Third, water vapour does not directly drive climate change, although it does amplify existing temperature trends (in climate science terminology it is a “feedback” rather than a “forcing”). The reason for this is that, whereas carbon dioxide remains in the atmosphere for an average of more than 100 years after entering it, water vapour only remains in the atmosphere for around 10 days on average, before condensing again. Average atmospheric water vapour levels are therefore determined solely by the temperature: pumping extra water vapour into the atmosphere (as happens, for instance following a volcanic eruption) does not increase atmospheric water vapour levels for long enough for its “greenhouse” properties to be a driver of climate change – within days, the extra water vapour condenses again. Water vapour is therefore extremely important in amplifying CO₂–driven global warming (because warmer air holds more water vapour, thus increasing the greenhouse effect); but it does not drive global warming (see also Realclimate: http://tinyurl.com/8no28).

Carbon dioxide therefore has a very significant effect on the climate, which is reinforced by water vapour, contrary to the impression given by the narrator and interviewees.

Continued …