by Unity

As anthropogenic global warming is currently a hot topic, thanks to the CRU e-mail hack and the Copenhagen summit, I figured it was long past time that someone (me) sorted out this whole business of how to correctly identify the difference between climate change sceptics and climate change deniers.

The problem is a fairly straightforward one.

On the one hand you have genuine climate change sceptics who are often unfairly labelled as deniers for voicing what are wholly legitimate scientific and economic concerns about the validity of certain aspects of the main climate change narrative.

On the other, you have a loose coteries of flat-earthers and wackaloons who use the terms ‘sceptic’ and ‘scepticism’ as cover for the fact that they haven’t got the first clue about climate science and are, not to put too fine a point on it, talking out of their collective arses.

So far as helpful resources go, the Denialism blog at Scienceblogs has a long, but very interesting and helpful, generic guide to denialism which covers the main tactics deployed by genuine deniers; conspiracy, selectivity (cherry-picking), fake experts, impossible expectations (i.e. moving the goal posts) and fallacies of logic. Do take the time to read the full article as it will arm you with many of the tools you need when spotting deniers, not just in the climate change debate but more generally as the tactics set out in the article apply just as readily to creationists/ID-ers, HIV/AIDS deniers, 9/11 conspiracists, the anti-vaccination lobby and an assortment of other wackaloons.

So, bringing the subject back to climate change, what can we say about the position adopted by genuine sceptics?Well, for starters, sceptics accepts as a matter of fact that the earth’s climate is currently getting warmer and that average global temperatures have been rising, pretty consistently, for at least the last 50-100 years. They also accept that human activity, particularly industrial activity, is at least a significant contributory factor if not the primary cause of this trend.

Their scepticism comes in two main varieties.

1. Scientific scepticism about, specifically, catastrophic AGW theories – i.e. ‘runaway’ global warming. The suggestion here is that in something as complex as the global climate there are negative feedback mechanisms that may be string enough to counteract the positive feedback mechanisms that proponents of catastrophic AGW (i.e. the ‘tipping point’ theory) believe may push the earth’s climate over the edge and seriously screw things up for us humans.

This is complex, fascinating and legitimate area of scientific debate, but not I’d recommend you get into unless you have a decent grasp of thermodynamics and non-linear physics because it is frightening complex. Currently the evidence does comes down on the side of there being enough of a risk of catastrophic AGW to warrant taking action to try and limit emissions of carbon dioxide and other greenhouse gases but there are still enough uncertainities to keep this debate going for a good while yet and, indeed, it may never produce a definitive answer one way or another unless something actually happens and either the planet’s climate goes tits-up or a clear and observable negative feedback mechanism kicks in powerfully enough to avoid a catastrophy.

2. Economic scepticism. Here the central issue is whether the or not the measures being proposed to counter AGW are either genuinely viable or likely to have such a deleterious impact on the global economy as to create as many, if not more problems, than they actually solve. The heart of this debate tends to revolve around the relative economic merits of measures to limit emissions of greenhouse gases against the development of technological solutions, such as geoengineering.

Again, its a complex debate and, because it deals in the main with political and economic issue, a debate that often fractious and polemical in character, but it is nevertheless a legitimate debate in which there is genuine room for scepticism.

Moving on to the deniers, their signature belief is the earth’s climate is, at most, warming within the parameters of and due to natural cycles of warming and cooling in which human activity plays little or no part, with many being firmly of the belief that the earth’s climate is, in fact, currently cooling and that this being covered up by a global conspiracy involving politicians, scientists, industrialists, climate change activists and their lizard overlords, or some other bullshit to that effect.

The core ‘evidence’ they cite in support of this belief is called the ‘hockey stick’ controversy and stems from methodological problems that were found to exist in a particular longitudinal temperature model called MBH98, which featured heavily in IPCC reports published around the turn of the current decade.

MBH98 is a reconstruction of temperatures in the Northern Hemisphere between 1000AD and the late 1990’s based on evidence from tree rings, a new and very immature field of science called dendroclimatology. This is the field that researchers at the Climate Research Unit and University of East Anglia have been working on and, consequently, the field to which the current controversy over the hacking of its webmail server relates.

The term ‘hockey stick’ was coined Jerry Mahlman of the National Oceanic and Atmospheric Administration (NOAA) to describe the shape of the graph, a broadly stable and slightly declining linear trend from 1000AD to around 1900 followed by a sharply rising trend (the ‘foot’ of the hockey stick – and being an American, he’s referring to the stick used in ice hockey) covering the last century. What the graph shows is the accepted figure of a 0.6 degree rise in average global temperature in the last century.

There are two main issues with MBH98 that need to be understood.

One, and this is the one that the deniers have latched on to, is that from 1960 onwards, the tree ring samples used to compile MBH98 show an apparent cooling trend. This is called the ‘divergence’ problem and is the subject of much of the current research in the field of dendroclimatology, which is directed toward trying to understand and account for the full range of causes behind it.

What is, however, fully understood is that the apparent cooling effect in tree ring data from 1960 onwards is not evidence of actual cooling; the data is entirely at odds with the real world evidence from surface, sea and atmospheric temperature records collected by meteorologists in considerable detail over this same period, but of the impact of a range of other, non-temperature related, confounding factors.

This is where the ‘trick’ referred to in the CRU emails comes into play. What the research did to try and correct their model was adjust the data for the period after 1960 using the real world data from other reliable sources. This still resulted in errors in the model, specifically it over-estimated global temperatures in the mid 1990s but, overall, this had no effect on the weight of scientific evidence for the warming trend for this century because the evidence for that trend comes from a wide range of other models and sources, all of which show the trend to be real.

While attempts have been made to try and knock over these other temperature records, particular by TV weatherman Anthony Watts and his survey of US surface weather stations, all of them have proved to be laughable failures. In Watts’ case, researchers took his study, used it to exclude all the weather stations he argued were inappropriately sited and, therefore, giving false readings, a recalculated the temperature trend using only the weather stations Watts approved of. The trend line on this graph was near enough identical to that for the full range of weather stations, including the one’s Watts claimed were compromised.

The second problem with MBH98 relates to a number of confounding factors discovered since it was published which call into question the reliability of the reconstructed trends in model for the pre-industrial period (i.e. 1000AD to around 1750AD). This has no impact, whatsoever, on the key evidence in the model, which is found in the ‘blade’ of the hockey stick (1900 onwards) but it did call into question the general validity of using the dendroclimatological models of the time with the IPCC’s reports.

As a result, the MBH98 model has been dropped from recent IPCC reports without it having any significant impact at all on their main findings. Recent reports are more cautious in the reporting the results of proxy data from tree-ring samples, particularly in including qualifying remarks which indicate that there are uncertainties, but this has no affected its conclusions, which are buttressed by the weigh of evidence from other sources.

Finally, it should be noted that in 2008, Michael Mann and his colleagues, who produced the original MBH98 model, published a new reconstruction based on a much larger dataset than the original model. This also showed that temperatures in the Northern Hemisphere over that last 100 years are anomalous when compared to reconstructions of the temperature record for the last 1,300 years (i.e. the same warming trend that appeared in MBH98) and, crucially, that these result are robust regardless of whether you include or exclude the tree-ring data used in the original model.

The denier’s claim that the earth’s climate has actually been cooling, as voice by Mad Mel Phillips on Question Time only a couple of weeks ago, is a complete and utter crock of shit.

Why?

Because the scientific evidence say so, and does so clearly and unequivocally based on evidence drawn from a wide range of different sources, all of which verify the trends show in the original ‘hockey stick’ graph.

What Mann and others, including researchers at the CRU, did was arrive at the right answers but by methods which ultimately didn’t stand up fully to scrutiny, forcing them to go back are revise their work in light of the problems that had been found in the original model and the methodology behind it. That, if you understand how science ‘works’ shows the broad peer review process doing exactly what it should.

So, people who raise scientific questions about negative feedback mechanisms or raise doubt about the economic viability of political and economic measures designed to reduce emission in the absence of investment and research into the potential technological solutions are sceptics and deserve to be taken seriously.

People who claim that the ‘hockey stick’ graph is a fake and that the earth’s climate is actually cooling, not warming, are deniers and deserve to be laughed at and ridiculed for the wackloons they are.