Science is about testing hypotheses

[This is a response to Peter Smith’s essay "Sceptics losing clarity"]

Peter Smith writes that “I am not a climate scientist therefore I have no first hand knowledge of, or insight into, the scientific evidence” [relevant to possibly dangerous global warming]. My sympathy is entirely with him. For the gargantuan amount of propaganda that has been pumped out by global warming devotees over the last 10 years has confused or fooled many expert scientists, let alone lay folk or politicians.

The nub of the problem lies with the concept of “official” or “consensus” scientific advice, which for climate science is claimed to be rendered by the Intergovernmental Panel on Climate Change (IPCC), i.e., by an unaccountable, political branch of the United Nations. Whilst some able scientists do act as IPCC advisors, the outcomes of the IPCC’s pivotal Advice for Policymakers are dictated by political considerations, and that to a degree that required the 2007 science volume of the 4^th Assessment Report to be edited to bring its content into line with the prior, politically moderated conclusions of the Advice for Policymakers.

The advice dispensed by the IPCC represents, then, the nub of the alarmist case that human carbon dioxide emissions are causing dangerous global warming, a conclusion that is drawn almost exclusively from unvalidated computer modelling. On the other side of the argument are to be found many thousands of independent scientists who owe their allegiance to no comparable organisation, but rather are committed to the use of evidence-based science for setting public policy. Peter Smith writes “Can the sceptics [his term for independent scientists] please get get their story straight”, thereby failing to appreciate that it is precisely the point that the sceptics have no story to tell! Rather, they are committed to good scientific technique, which is married to the consideration of empirical evidence (not computer models), however messy and indeterminate that evidence might turn out to be.

For example, Mr. Smith is concerned that there is “a mind-numbing array of different interpretations” as to why some glacial ice masses are increasing in volume, and others shrinking, all at the same time – expecting that if warming is occurring then all glaciers should be uniformly retreating. Alas, the natural world is not that simple, and it is entirely characteristic both that some glaciers advance whilst others retreat and that scientists will in turn be advancing many different reasons for this type of complex behaviour.

It is also precisely to the point, and entirely correct, that Peter perceives the IPCC to be “telling a story” – at which point his bullshit detector should be ringing loudly. For science is not about telling stories, especially neat, tidy and politically correct ones, but about testing hypotheses against factual and experimental evidence and in the light of established theoretical precepts.

The hypothesis of the day, which requires testing, is that dangerous global warming is being caused by human carbon dioxide emissions. This was a sensible query to raise in the late 1980s, but 20 years, $100 billion and tens of thousands of scientist-years later we now know that the hypothesis is wrong, amongst other reasons for the one alluded to by Mr Smith.

Which was (modified so as to avoid Mr Smith’s disliked year of 1998 as the starting point) that since 1995 the global temperature has not increased within the bounds of its estimated error. Over the same 15 years, the carbon dioxide content of the atmosphere has increased by more than 5%. It follows that increased carbon dioxide is not causing dangerous warming, or, indeed, any measurable warming at all. Thus this test provides a direct invalidation of the global warming hypothesis.

Note, at the same time, that this test does not challenge the fact that carbon dioxide is indeed a greenhouse gas. Rather, it shows only that the warming effect produced by human emissions is so small that it cannot be disentangled from the noise and natural variation of the climate system. To those familiar with the physics of the matter, and with the fact that the relationship between increasing carbon dioxide and increasing temperature is a decreasing logarithmic one (i.e. less warming bang for every invested carbon dioxide buck), this result is entirely unsurprising.

Peter Smith is also troubled by the fact that:

temperatures since satellite data have been collected (1979) show an upward trend to the naked eye. What is the point in not acknowledging that evident fact? It is plain silly in my view and detracts from the sceptic’s case.

But the sceptics “case”, to the limited degree that they are united behind one, is that tests of the global warming hypothesis show it to be invalid. Whether or not temperature warmed or cooled over a particular time span (in this case, the span of the satellite record) is, on its own, simply an inconsequential fact. For example, it is just as true, and probably more relevant, to note that over the last 10,000 years temperature has cooled by an amount at least twice as great as the gentle late 20^th century warming, which represents just one of many modulating wiggles on the long term downward temperature trend. That a small part of the warming wiggle may result from human influence in no way detracts from the pivotal fact that the wiggle is small, well within natural variation, and therefore not dangerous.

Peter Smith writes further that:

There is no substitute for clarity of thought and communicating the results plainly and consistently. The sceptics are not doing that. They might have truth on their side. It is being lost in the blather. I invite sceptical scientists to write under four headings – temperature, sea levels, quantity of ice, and untoward weather events; to compare notes; to write in an accessible way; and to leave peripheral things out.

Yet this interesting paragraph includes mostly peripheral things and omits another (carbon dioxide) that is pivotal to the whole argument, thus destroying any possibility of clarity of thought.

First, temperature change on its own provides no information about the effect of human emissions on climate. Judgements about possible human-caused warming can only be arrived at by considering both temperature change and carbon dioxide change over similar periods of time, as was done in the validation test of the global warming theory described above.

Second, the other three headings that Peter Smith suggests for material worthy of discussion all comprise circumstantial matters that, on their own, are quite peripheral to testing the global warming hypothesis. As explained in Chapter 6 of my book, Climate: the Counter Consensus, sea-level, ice quantity, extreme weather events and, yes, even the numbers of polar bears, all vary all the time – for the very good reason that we live on a dynamic planet. Such changes are only relevant to the global warming hypothesis if they can be shown to lie outside of the range of previous natural variation, or if some direct evidence exists that indicates a human causation. In fact, there is no such evidence.

Given the wide range of natural environmental variation that we (but not, apparently, Mr Al Gore) observe around us, the null hypothesis regarding changes that we observe on the planet today is that they are natural, unless and until evidence emerges otherwise. In this regard, global sea-level change is proceeding along the same lines that it has for the last 100 years (gentle rise of between 1 and 2 mm/yr), the area of sea-ice on our planet currently equates to the estimated long term average, and no compelling evidence exists for a significant increase in extreme weather events. Amongst the tens of thousands of refereed scientific papers that address these matters, not one yet provides data that invalidate the null hypothesis of natural change.

Peter Smith concludes that unless the independent scientists stop blathering, compare notes and write clearly then “they will surely lose the debate as they are most assuredly doing”.

Well, if losing the debate means that the United Kingdom adopts a sensible policy of adaptation to climate change, Canada rejects emissions limitation legislation, Japan rejects absolutely any continuation of Kyoto-style international action, and the Cancun meeting ends in disarray, then I for one shall be quite happy to keep right on blathering.

Bob Carter is a geologist from Townsville and the author of Climate: the Counter Consensus

See also:

Alex Stuart’s “Debating physics”

Peter Smith’s “Climate riposte”