In January 2001, the IPCC launched its Third Assessment Report (TAR) in Shanghai. Behind the speakers was a giant projection of what became known as Mann’s Hockey Stick - a temperature-time graph - which purported to represent global temperatures from AD1,000-2,000, and which showed temperatures declining very gradually from AD1,000 to AD1900 and then taking off like a rocket over the next 100 years.
The graph looked like an ice hockey stick lying on its handle (AD1000-1900) with the blade pointing to the sky (AD1900-2000). The inference was that global temperatures had been more or less stable for 900 years and then, because of anthropogenic emissions of carbon dioxide, had increased by an unprecedented 0.9C.
Mann’s Hockey Stick turned out to be fraudulent. The Medieval Warm Period, and the Little Ice Age had been washed out through statistical manipulation of the data. The IPCC spent quite some time and energy in damage control after being exposed.
One of the consequences of that exercise is that the Policy Makers’ Summary (PMS) of the Fourth Assessment Report (AR4), released in Paris on February 2, 2007, is rather more cautious about predictions of temperature and sea level rises than TAR. Instead of the 5.8C temperature rise of 2001, we are back to 3C, and sea level rises have been scaled back to the 500mm range.
This has caused considerable angst among more hard-line members of the anthropogenist movement - the group of radicals who believe passionately that anthropogenic carbon dioxide will bring about the end of the world as we know it, and who demand immediate decarbonisation of the world’s economy. Australia’s Graeme Pearman, formerly head of the CSIRO’s Division of Atmospheric Research, is an adherent of this group.
For example, Robin McKie, science editor of the London Observer wrote (January 18, 2007):
Serious disagreement has broken out among scientists over a United Nations climate report's contention that the world's greatest wilderness - Antarctica - will be largely unaffected by rising world temperatures.
The report, to be published on Friday, will be one of the most comprehensive on climate change to date, and will paint a grim picture of future changes to the planet's weather patterns. Details of the report were first revealed by ‘The Observer’ last weekend.
However, many researchers believe it does not go far enough. In particular, they say it fails to stress that climate change is already having a severe impact on the continent and will continue to do so for the rest of century. At least a quarter of the sea ice around Antarctica will disappear in that time, say the critics, though this forecast is not mentioned in the study.
The IPCC had to steer a difficult course between making a fool of itself - again - as in 2001, and satisfying the demands of the decarbonising radicals. The solution the IPCC chose was to moderate its predictions but to lay the blame more firmly on the shoulders of mankind.
The Policy Makers’ Summary is adamant (90 per cent confidence) that man is responsible for continuing global warming. The fact that the satellite record shows temperature decline since 1998 is ignored. Indeed, the historical record as manifest, for example, in the Greenland Ice Cores, corroborated by sediments from the ocean floors and by cave stalactites, tells us the Medieval Warm Period (AD900-1300), the Roman Warm Period (250BC-AD100), and the Minoan Warm Period (1400BC-1200 BC), were warmer than our present late 20th century Warm Period.
Anthropogenic carbon dioxide cannot explain these warm periods nor can lack of anthropogenic carbon dioxide explain the Little Ice Age which was familiar to the citizens of 17th century London, and indeed to their heirs in the 19th century. The Napoleonic Wars were fought in a period known as the Dalton Minimum when sun spot activity was extremely subdued and temperatures were very low indeed, as La Grande Armée discovered on the retreat from Moscow.
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