A superb opinion piece published recently in The Australian graphs one scientists conversion from AGW believer to skeptic after failing to find evidence. David Evans is the self-confessed rocket scientist who wrote the custom carbon accounting model (FullCAM) that measures Australia’s carbon credit in the land use change and forestry sector. In disagreeing with mainstream science as represented by the IPCC he is among those that Professor Garnaut indecorously refers to as ‘dissenters’ here or even ‘deniers’ here.
Below are quotes but the full report is well worth reading as an example of the evidential mindset. In this view, climate models are very low on the pecking order of evidential support, and direct evidence for AGW is lacking.
But since 1999 new evidence has seriously weakened the case that carbon emissions are the main cause of global warming, and by 2007 the evidence was pretty conclusive that carbon played only a minor role and was not the main cause of the recent global warming. As Lord Keynes famously said, “When the facts change, I change my mind. What do you do, sir?”
There has not been a public debate about the causes of global warming and most of the public and our decision makers are not aware of the most basic salient facts:
1. The greenhouse signature is missing. We have been looking and measuring for years, and cannot find it.
2. There is no evidence to support the idea that carbon emissions cause significant global warming. None. There is plenty of evidence that global warming has occurred, and theory suggests that carbon emissions should raise temperatures (though by how much is hotly disputed) but there are no observations by anyone that implicate carbon emissions as a significant cause of the recent global warming.
3. The satellites that measure the world’s temperature all say that the warming trend ended in 2001, and that the temperature has dropped about 0.6C in the past year (to the temperature of 1980). Land-based temperature readings are corrupted by the “urban heat island” effect: urban areas encroaching on thermometer stations warm the micro-climate around the thermometer, due to vegetation changes, concrete, cars, houses. Satellite data is the only temperature data we can trust, but it only goes back to 1979. NASA reports only land-based data, and reports a modest warming trend and recent cooling. The other three global temperature records use a mix of satellite and land measurements, or satellite only, and they all show no warming since 2001 and a recent cooling.
4. The new ice cores show that in the past six global warmings over the past half a million years, the temperature rises occurred on average 800 years before the accompanying rise in atmospheric carbon. Which says something important about which was cause and which was effect.
None of these points are controversial. The alarmist scientists agree with them, though they would dispute their relevance.
The world has spent $50 billion on global warming since 1990, and we have not found any actual evidence that carbon emissions cause global warming. Evidence consists of observations made by someone at some time that supports the idea that carbon emissions cause global warming. Computer models and theoretical calculations are not evidence, they are just theory.
Credit to Geoff Sherrington for spotting this.