ANNOUNCER: Can you explain to our listeners how you had this – well, was it a road to Damascus conversion? Or- what’s gone on, in your thinking, over the issue of greenhouse gases over the last few years.Read it all here at Bolt's.
EVANS Well, when I started the job in ‘99, the evidence that greenhouse gases, and particularly carbon emissions, caused global warming was fairly good. At that stage, as exhibited in Al Gore’s movie, we knew that from the old ice core data, that in previous warmings over the last half a million years, temperature and carbon moved in lockstep. So we assumed that carbon was causing the temperature rises. Since 1998 or so, the science has changed a fair bit. Unfortunately the public and the decision makers are still caught back in the pre-1998 situation. First of all, the new ice core data that came through from about 1998 through to 2003 was a high resolution and the data points were only a couple of hundred years apart, instead of a couple of thousand years apart, and that new ice core data shows that the rise in temperature preceded the rise in carbon dioxide by, on average, about 800 years. So we know that the temperature rises cause the CO2 rises, not the other way round as previously assumed. Now, if you look carefully at Al Gore’s movie, you’ll find that’s the only evidence offered for why carbon emissions cause global warming. He shows
lots of evidence that global warming’s occurring, but that’s the only evidence he offered for the causes – that carbon emissions cause global warming. And it gets worse than that. Turns out that there is no other evidence, and by evidence you mean that someone saw something on a particular date or there was some observations made that implicated or implied that carbon emissions cause global warming. The case that carbon emissions cause global warming is now entirely theoretical and it’s all driven by computer models and computer models and theory aren’t evidence. But it’s worse than that - something else happened. By 2006 we had a new result. You see, each cause of global warming heats the atmosphere in a dfferent pattern, a so-called signature. The pattern for increased greenhouse warming, which would be what you’d get if you had carbon emissions causing global warming, would be an increase in the heat above the tropics at about eight to 12 kilometres up. That is to say, you’d get a hot spot there. Now, people have been looking for several decades now sending up radio sones - which are weather balloons with thermometers attached - into that region, to try and detect the hot spot. They never found it. In fact, they’re quite sure that it isn’t there. So, by 2006, we had the result that the hot spot is missing. The signature of increased greenhouse warming is missing, and therefore, we know that carbon emissions aren’t the main cause of the recent global warming.
Tuesday, July 22, 2008
More David Evans: interview ABC Adelaide - via A Bolt
Andrew Bolt has a transcript of a radio interview ABC Adelaide: