Tim Worstall points readers to a moderate view of global warming from the Stoat at scienceblogs.com.

Unlike most libertarians, Worstall accepts the basic science behind global warming, but disagrees with the policy implications.

William Connolly (Stoat) quotes a list of the main points he made in 2004.

The main points that most would agree on as “the consensus” are:

1. The earth is getting warmer (0.6 +/- 0.2 ^oC in the past century; 0.1 0.17 ^oC /decade over the last 30 years (see update)) [ch 2]
2. People are causing this [ch 12] (see update)
3. If GHG emissions continue, the warming will continue and indeed accelerate [ch 9]
4. (This will be a problem and we ought to do something about it)

These are in descending order of certainty. Further

In the years since I wrote that nothing has come along to overturn any of that, and much has come in to buttress it. 1, 2 and 3 are now strong enough to be considered “essentially true”; the arguments that claim any of them are false are now dull and uninteresting and without scientific validity. Pretty well all of the meaningful scientific skeptics have now given up trying to argue that.  

Let me get really dull and uninteresting, and try to access the scope of scientific validity.

1. The earth got warmer in the last century. It got warmer in spurts, followed by periods of stability.
2. People are highly likely to be contributing this to some extent. It could account (though unlikely) account for greater than 100% of the warming. Certainly, the planet is over 30^oC warmer than it would have been without the natural greenhouse effect, consisting mostly of water vapour. However,

–                 The recent rise in the total level of anthropogenic greenhouse gases has probably added less than 2% to the total, for a 2% rise in temperature. A physicist would expect diminishing temperature rises for incremental rise in the greenhouse blanket, not increasing ones.

–                 Furthermore, then temperature rises have been in spurts – from 1914 to 1940 and from 1977 to 2000. In between global temperatures did not rise. If you look at global growth rates, there was low growth in the inter-war period (with the Great Depression in the middle), high growth from 1945 to 1973 (the year of the oil crisis) and lower growth to 1998, then the greatest level of growth in world history for the next decade. If there is any correlation, it is negative.

–                 The Hockey Stick episode. The great effort that has been put into eliminating the medieval warm period, to demonstrate that the twentieth century warming is unprecedented, should provide strong circumstantial evidence of the doubt that the data engenders. Compare the arguments of the climate sceptic Steve McIntyre (McIntyre S, 2008b is a readable introduction.) with a 2005 consensus view. This is basically a cross-check. If there have been large fluctuations in recent, pre-industrial history. In particular, higher temperatures a few hundred years ago, and an unusually cold period in the 17^th to early 19^th centuries, then it would be more likely that the most of the 20^th century warming was natural.

3. If greenhouse gases keep increasing, then temperatures will, ceteris paribus, also increase. However, that they will accelerate because of positive feedbacks (water vapour – the principle greenhouse gas – is forecast to rise as a result of the temperature rise brought about by the rise in CO2) may contradict, the limited, observed data (Lindzen and Choi 2009 pdf).

The science is much more nuanced. There are large uncertainties in the data and still bigger ones in the forecasts. So a huge range of conclusions is valid. The appointed leaders cover this with dogmatic certainties and untenable forecasts, along with being quick to doubt the motives, competence or even sanity of anyone who stands in their way. Further they still do not see a problem when biased analysis and broken procedures are revealed. Nor manipulation of the data to get the desired results. Nor attempts to block adverse science from being published. Their very lack of humility and dogma is opening the door to those who say it is all a conspiracy or a scam.