David Evans, greenhouse sceptic debates his views on Troppo

The ETS: completely unnecessary

Rudd has failed to see through the vested interests that promote anthropogenic global warming (AGW), the theory that human emissions of carbon cause global warming. Though masquerading as “science based”, the promoters of AGW have a medieval outlook and are in fact anti-science. Meanwhile carbon is innocent, and the political class is plunging ahead with making us poorer because they do not understand what science really is or what the real science is.

The Renaissance began when the absolute authority of the church and ancient texts was overthrown. Science then evolved as our most reliable method for acquiring knowledge, free of superstition and political authority. Suppose you wanted to know whether big cannonballs or small cannonballs fell faster. In medieval times you argued theoretically with what could be gleaned from the Bible, the works of Aristotle, or maybe a Papal announcement. In the Renaissance you ignored the authorities and simply dropped cannon balls from a tower and observed what happened - this was science, where empirical evidence trumps theory.

From 1975 to 2001 the global temperature trended up. How do you empirically determine the cause of this global warming? It turns out we can learn a lot simply by observing where the warming occurred: each possible cause of global warming heats the atmosphere differently, heating some parts before others. The pattern of warming is the cause’s “signature”.

The signature of an increased greenhouse effect consists of two features: a hotspot about 10 km up in the atmosphere over the tropics, and a combination of broad stratospheric cooling and broad tropospheric warming. The signature of ozone depletion consists just of the second feature. These signatures are theoretically derived by the Intergovernmental Panel on Climate Change (IPCC), and are integral to our understanding of how the atmosphere works. [1]

We have been observing temperatures in the atmosphere for decades using radiosondes - weather balloons with thermometers that radio back the temperature as the balloon ascends through the atmosphere. The radiosonde measurements for 1979-1999 show broad stratospheric cooling and broad tropospheric warming, but they show no tropical hotspot. Not even a small one. [2]

Empirically, we therefore know that an increased greenhouse effect was not a significant cause of the recent global warming. (Either that or the signatures from the IPCC are wrong, so its climate models and predictions are rubbish anyway.)

Human carbon emissions were occurring at the time but the greenhouse effect did not increase. Therefore human carbon emissions did not increase the greenhouse effect, and did not cause global warming. So AGW is wrong, and carbon is innocent. Suspect exonerated - wrong signature.

Alarmist scientists (supporters of AGW) objected that the radiosonde thermometers were not accurate and maybe the hotspot was there but went undetected. But there were hundreds of radiosondes, so statistically this is unlikely. They have also suggested we ignore the radiosonde thermometers, and use the radiosonde wind measurements instead. When combined with a theory about wind shear they estimated the temperatures on their computers - and say that the results show that we cannot rule out the presence of a hotspot. But thermometers are designed to measure temperature, so it’s a bit of a stretch to claim that wind gauges are accidentally better at it. Serious alarmist scientists do not claim that the hotspot was found, only that we might have missed it. The obvious conclusion is that the hotspot was too weak to be easily detected. We cannot collect any more data from the past warming, and there is no sign of the hotspot in the data that was collected - so the occasional claims that appear on the Internet that the hotspot has been found are simply wrong. [3]

So can we tell from the observed warming pattern what did cause the global warming? Unfortunately we have little idea of the signatures of some of the suspects, such as cosmic rays or the Pacific Decadal Oscillation, so we cannot say except to note that ozone depletion was one of the causes.

Is there any observational evidence in favour of AGW? As of 2003, none at all.

The only supporting evidence for AGW was the old ice core data. The old ice core data, gathered from 1985, showed that in the past half million years, through several global warmings and coolings, the earth’s temperature and atmospheric carbon levels rose and fell in lockstep. AGW was coming into vogue in the 1980s, so it was widely assumed that it was the carbon changes causing the temperature changes.

By the late 1990s ice core techniques had improved. In the old ice cores the data points were a few thousand years apart, but in the new ice core data they were only a few hundred years apart. In the early 1990s, New Scientist magazine anticipated that the higher-resolution data would seal the case for AGW.