Why 100 authors? If I were wrong, then one would have been enough! - Albert Einstein
Consensus is utterly irrelevant to science. The philosophy of science is devoid of consensus. What concerns science is not weight of numbers on the side of an argument, but what the facts are. What the evidence is.
I have just watched the BBC's latest Horizon program "Science Under Attack". In the program he goes on about overwhelming evidence of AGW, but offers only one tiny piece (tree rings used in spliced data), he talks about consensus (without understanding that consensus is meaningless in science and denying that there are enough professionals who are sceptical of AGW to make such an assertion plainly false), and he mocks 'extreme' scepticism.
Scepticism is the foundation of scientific principles - there is no 'fine line' as Nurse puts it between acceptable levels of scepticism and unacceptable levels. All scepticism is acceptable. When Einstein was in the minority of people against Newton's theory of relativity he would have been seen as going too far, questioning where it was not welcome. The facts were decided, there was 'consensus'. Before Einstein published his work, no contemporary scientist apparently disagreed with Newton's (now disproved) theory. Newton himself was working against the orthodoxy of his peers. Being in a minority dues not mean one is incorrect. Argumentum ad populum (or as used in this case, consensus gentium) is still a logical fallacy whether in the scientific community or within any other group (as is an appeal to authority, for those who keep going 'scientists say...').
Attempting to defend a purely scientific position using non-scientific methods such as attacks on 'sceptics' or 'deniers' (rather politicised language, something Nurse is apparently against) or appealing to logical fallacies is wrong. When debating science, only the science should be under scrutiny - not where money comes from nor what the political position of various groups are. Science and science alone.
I myself, fall into what is often caricatured as a 'climate-sceptic', I do not believe that human greenhouse gases are driving the Earth's climate upwards. Ignoring, for the time-being, all of the other, easily disproved nonsense about other things tacked to the side of the AGW debate (such as the spread of malaria), my belief bases itself on a few well known scientific principles.
1. Historically, CO2 has not driven climate, it has responded to warming centuries later. The greenhouse effect is real, but it is not a climate driver, just part of the conditions of climate. Every study done to date has confirmed this (as far as I am aware).
2. If the theory of Anthropomorphic Global Warming were true, the warming in the stratosphere would be warming at a much faster rate than the surface temperature rise (it is from here that the infra-red radiation is absorbed and transferred to heat energy to be conducted away). Both weather balloon data and satellite data show that this warming is not occurring.
3. The surface temperature record has become inaccurate due to the heat-island effect and other problems, meaning that it should be used with this in mind - it may paint a picture of warming faster than is happening.
I may not be a scientist, but I have read enough to be in an informed opinion, rather more than a large segment of the population.
To return the the BBC program, during the regular attacks on the position of sceptics, Nurse portrays the fight to be between science and sceptics. But he doesn't talk about the green lobby in any capacity, surely they are arguing against the 'sceptics' from an equally unscientific position, are they not? It was the green lobby which took the 'science' out of the labs and into governmental budgets - it was they who politicised the subject. Yet, when Nurse brings up the very same groups (not referred to as green lobby groups but anti-GM groups), he portrays them as in the same camp as the sceptics. Every mainstream book sceptical of global warming that I know of is also supportive of Genetically Modified crops; on this, sceptics are on the side of science, whilst the pro-AGW green lobby groups are against it. Yet it is not portrayed this way. Sceptics are regularly referred to as being anti-science, but in all cases, the majority look at the science, or at least what they can observe (such as the weather). Regularly we are told we are 'flat-earth' believers and that we disagree with everything. But when questioned, we turn to science, not flat-out denial. The opposite is true of believers of AGW and the green groups. They tend to not turn to evidence, but to assert bluntly that there is a consensus, that we should believe it. The data is not important, what matters is what they say scientists believe. It is deeply concerning that people who hold such opinions are listened to in public debates (see the Channel 4 program 'What the Green Movement Got Wrong' and the following televised debate if you wish to see such blunt assertions).
What have we learned from this, well, Nurse isn't a climate scientist, he has no specialism in the subject, he is no better placed to make such a documentary than I. He is an outsider to the science, trying to make sense of it. We have learned that the BBC is still strongly in support of AGW (but we were already aware of their bias here). We have learned that Paul Nurse has a poor understanding of the philosophy of science - he is rationalising his scientific beliefs with his assertion that the globe is warming and that it is caused by man. The only piece of the 'huge weight of evidence' offered up by the program is the widely discredited work on tree ring data. Where's the rest of it? Ice core surveys? Bog plant surveys? The evidence is not present, if the overwhelming weight of evidence does exist, it is yet to be seen.
It is surely time that we gave up with the blank assertions in the debate, I was able to see through them at fourteen, I can see through them now. If there was a consensus, it would be irrelevant. Scepticism is good and the only position a scientist should ever take. Scientists are not always right, especially when they are in a separate field to what is being discussed. Anyone who denies any of those points should not partake in such a debate, their view is surely clouded. The BBC would do well to take these points up, in the name of public service, however, it seems their collective [hive-]mind has already decided that we are guilty and must let the state take over. They have been waiting for the age of planners to come to Britain for far too long.