Great Global Warming Swindle FAQ

The great global warming swindle caused a stink when it was screened in the UK and Australia, and it's screening this evening. So before it manages to confuse everyone about the science of global warming, here's a few points:

(thanks to the Australian Meteorological and Oceanographic Society for their summary of the bad science).

1. It was warmer than now in the Middle Ages, so whats the problem?

   The graph which shows the Medieval warm period as being warmer than today is based on an outdated paper from 1990, which itself only considered the temperature in parts of Europe. Years later, good estimates of global temperature for the last 1000 years have been agreed on by amost everyone, which show the last 10 years much warmer than anything before.

   
   

2. Temperatures went down between 1940 and 1980, even though CO2 went up.

   First point, no one ever said higher CO2 one year means higher tenmperatures in the same year. Extra greenhouse gases trap heat year on year, and the full effect of extra CO2 takes 100 of years or more to kick in. Second, their graph is plain wrong. Here's the real one from NASA.

   Finally, Anthropogenic Global Warming (AGW - or global warming caused by humans) is on top of variations in volcanic and solar activity, so you can't expect it to be a smooth relationship.

3. Models suggest that greenhouse gases should warm the lower atmosphere (troposphere, the bit with clouds in) faster than the surface, so any warming today can't be due to AGW.

   Temperature in relation to altitude not fitting in with models was never such a big issue that it would outweigh other evidence for AGW.

   Even so, there had been some debate over the last few years about weather stations ending up in the suburbs surrounded by heated houses, and satellite and balloon measurements being lower than ground measurements and so on. After a while it all got resolved, and some weather stations were adjusted and most satellite measurements were corrected (there was an error making their measurements too low).

   This is all old news now, and pretty much anyone working on climate science agrees the pattern of warming in the atmosphere matches what you would see from AGW.

4. Volcanoes produce more CO2 than humans.

   That's plain wrong. The US Geological survey worked out that volcanoes produce only about 1% as much as the CO2 that humans do per year.

   What you could say is they affect the climate more than humans, but only when there is a particularly massive eruption, and that's a cooling effect from sulphur dioxide (stuff that causes acid rain) and ash blocking the sun.

   So is their point on this one - "humans are causing global warming for certain, year on year, but it's OK because there might be a massive eruption which will cool things down for a while"? Good luck with that one.

5. During ice ages over the past 700,000 years, temperature starts to change first, then CO2, therefore the CO2 we're putting out now wont effect the climate.

   Yes, they're right about the first part. Long term ice ages are caused by gradual (10,000s of years) changes in the earth's orbit affecting the amount of solar energy received by the Earth.

   These changes wouldn't account for the whole switch from warm to cool and back again, and over the years, scientists have come to understand that at the start the heat from the sun changes, then oceans release more CO2, and gradually the combination of solar heat, CO2, water vapour and changes in albedo (ie less ice means more heat from the Sun is absorbed).

   So we're pretty sure CO2 was doing something then, and we have a whole lot more CO2 on our hands now. Secondly, the orbital cycles are 1000 times too slow to be doing what we're seeing now.

6. Recent warming is due to changes in solar activity.

   The graph shown on GGWS stops in the 1970s, which is odd, because, not surprisingly, our best measurements of solar activity are since then (since we invented modern computers and so on). Convinient for them, because although you see an increase in solar activity and increasing temperature before then, after that temperature keeps going up even though solar activity goes down. No wonder they couldn't find any data after 1970, eh? Here's the data they missed out.

   
   

All this interest in the science of global warming is a good thing. It's the science which makes you realise that there is a big problem and we need to do something about it. Skepticism is good; it's only a pity that such sloppy work gets so much air time.