No less a person than the former American President Barak Obama informed the world in 2014, “The debate is settled. Climate change is a fact.” Some sceptics responded to this assertion by claiming that science is never settled; science is a process that continuously evolves, not a set of facts cast in stone. But Obama essentially dismissed this point of view when he said “We don’t have time for a meeting of The Flat Earth Society”.
Is it possible to reconcile these two points of view? If science is never settled how can we use it to formulate a course of action? If new information might change our view tomorrow how are we to make any plans on the basis of current knowledge? This sounds like a council of despair and an excuse to do nothing.
From a strictly objective point of view the sceptics are right – it is always possible that new data might disprove the incumbent theory. Take my own field of geology. When I was a child, students of geology were taught that the Earth’s crust was rigid and that the positions of the continents were fixed. Years later, when I studied geology at university these former students became my teachers. By then the plate tectonic revolution had swept through and I was taught that these formerly fixed continents were now free to drift across the globe, colliding and separating one from the other. It is difficult to imagine two more different views of the same Earth.
How could such a mistaken model for the Earth’s crust hold sway? (I can almost hear President Eisenhower tell the world in 1956 “The Science is settled. Fixed continents are a fact”.) There was no lack of evidence that ‘continental drift’, as it was then called, might be possible. The German scientific polymath Alfred Wegener had proposed as early as 1912 that the Atlantic Ocean had been created by the separation of America from Europe and Africa. Over the next half century geologists amassed substantial evidence from across the globe that supported the theory of mobile continents. The jigsaw like fit of South America with Africa was the iconic example but many other lines of evidence pointed in the same direction: terrestrial animals such as marsupials, and even earthworms are today found in continents far distant from each other; glacial rocks occur in what are now tropical locations; and tropical species such as crocodiles have been found in sediments in the high Arctic. How did they all get there?
All this evidence, though, failed to undermine the implacable resistance of the geophysicists, led by Harold Jeffreys of Cambridge University. Jeffreys dismissed the evidence by demonstrating mathematically, at least to his own satisfaction, that the Earth’s crust was too rigid to allow any significant lateral movement. Many geologists accepted the geophysical arguments and so had to explain away the geological ‘evidence’. ‘Land Bridges’ were a favourite to account for the presence of similar animals on widely separated continents – they were still teaching about these when I was an undergraduate in the mid-70’s! The fit of Africa and South America was dismissed as coincidental, and anyway not that good.
It turned out, of course, that the geological evidence was largely correct and Jeffrey’s objections were mistaken. But the plate tectonic paradigm did not triumph on the basis of the geological evidence. Only when new types of data were brought to bear – especially the discovery of magnetic stripes in oceanic crust and of geophysical ‘low velocity zones’ deep in the Earth’s crust – was the old geological evidence reinterpreted in terms of mobile continents.
The American historian of science Thomas Kuhn proposed in his book ‘The Structure of Scientific Revolutions’ that science at any one time tends to be governed by a ruling ‘paradigm’. The paradigm defines the problems that can be studied and is not generally subject to investigation itself. Results that fail to conform to the paradigm rarely lead immediately to its overthrow; they can be explained away as experimental error, or sub-theories may be constructed to protect the paradigm from refutation. However eventually so many anomalies may arise that the paradigm itself is called into question.
This seems to me a pretty good explanation of how the plate tectonic revolution came about.
Does it have any relevance for modern climate science? There is little doubt that the science today operates within a clearly identifiable paradigm – let’s call it the greenhouse gas theory. This theory maintains that global warming today is caused by the increase of CO2 and other greenhouse gases (GHG’s) that are accumulating in the atmosphere as a result of human activities. Climate scientists, along with Barak Obama, are certain that the paradigm is correct. Moreover, scientists who do not buy in to this paradigm are effectively excluded from working on climate. Is this wise?
Before looking deeper into that issue, let’s consider science and certainty a little further. There are, surely epistemological grounds for claiming that nothing in science can be regarded as a fact. But as I noted earlier, this stance is not very helpful in the real world; if we waited for certainty we would never do anything. In practice most scientists subconsciously subscribe to some version of the celebrated biologist Stephen Jay Gould’s definition:
“In science ‘fact’ can only mean ‘confirmed to such a degree that it would be perverse to withhold provisional assent’. I suppose that apples might start to rise tomorrow, but the possibility does not merit equal time in physics classrooms.”
Does this help? I think it at least allows us to do away with some spurious objections. The example of apples rising rather than, as Newton observed, falling is more useful than abstract statements about settled or non-settled science. We would all agree that flat-earthism is as ridiculous as rising apples. But is Obama justified in using this analogy to dismiss climate sceptics? I’m not so sure.
The argument is not that greenhouse gas theory is wrong; in terms of Gould’s definition I would say that it is a fact. We would not be here to discuss all this if GHG’s were absent from the atmosphere. But it is not as simple as that. To return to the plate tectonic analogy, Jeffreys was correct in his assertion that continental crust could not just plough its way through the oceans. However, neither he, nor anybody else at the time, knew that deep below the crust very different rocks existed that could ‘flow’ extremely slowly and thus carry the upper crustal rocks passively along. The devil is in the detail.
Why might anthropomorphic GHG theory provide an incomplete explanation of current global warming? There are several reasons. An obvious one is that much greater climatic changes have occurred in geologically recent times without man’s influence. Only fifteen thousand years ago the place where I am writing this was uninhabitable because large parts of the Northern Hemisphere were covered in ice. Those ice sheets advanced and receded multiple time in the past two million years as temperature oscillated from cold to warm and back. Scientists have uncovered good circumstantial evidence to relate these changes to so-called ‘Milankovitch Cycles’ – changes in insolation caused by cyclic variations in the Earth’s orbit. But the variation in insolation seems tiny in comparison to the profound changes to the Earth’s climate. Terrestrial factors must amplify the solar signal somehow. Climate scientists have argued that CO2 is the amplifier and thus GHG can account for the ice ages. But others think convincing proof is lacking and other factors are likely to be involved. At the present time this debate is unresolved.
Many climate scientists argue that these ice age cycles are not relevant to the current situation. They claim that since the ice sheets receded from Eurasia and North America (ca 15-10 thousand years ago) climatic variation has been minimal. Therefore, in the jargon, the current temperature increase is portrayed as ‘unprecedented’. This was spectacularly illustrated some 25 years ago when Michael Mann and colleagues produced the first version of what became known as the ‘Hockey Stick’, the graph that featured as poster-child for the IPCC’s 3rd Assessment Report in 2001. The hockey stick portrayed global temperatures as essentially static, or falling slightly over the past 2000 years before a dramatic rise coinciding with 20th Century industrial development.
But the validity of the Hockey Stick reconstruction immediately caused controversy and the argument has hardly abated over the last 25 years. Suffice it to say that despite numerous accusations of poor quality, cherry-picked data and dubious statistics the climate establishment has clung tenaciously to this icon of man-made climate change. It is hard not to see this as ideological commitment to the GHG paradigm. Even the IPCC found it expedient to play down Hockey Stick in later assessment reports.
Prior to the Hockey Stick, earlier workers had identified plentiful variation in historic climate data. Terms such as The Little Ice Age, The Medieval Warm Period or The Roman Warm Period all suggested perceptible climate change during the past 2000 years. But when considered through the prism of the GHG paradigm these all, conveniently, started to fade away. Could it really be that generations of previous researchers were mistaken? To be sure some limited, local change is still allowed, but global climate change it is not.
On a longer time-scale, climate reconstructions once spoke of a post-glacial climate optimum some 8-10,000 years ago (The Holocene Climatic Optimum in the jargon). This too is being called into question because again it cannot be accommodated by the GHG narrative.
Perhaps the current climate warriors are right. New and better data often lead to adjustments to old interpretations. But it is hard not to conclude that the questions being asked are indeed framed by the GHG paradigm. And since most researchers in government labs or university departments have to buy into the paradigm it is hard to see them publishing results that will challenge it. All the more so as western governments are committed to vast expenditure on the basis that the GHG theory is fact. Who is going to tell them that it might all be a terrible mistake?
It might be useful to make another diversion into facts and their place in this discussion. Charles Darwin famously wrote that
“False facts are highly injurious to the progress of science, for they often endure long; but false views, if supported by evidence, do little harm, for everyone takes a salutary pleasure in proving their falseness; and when this is done, one path towards error is closed…”
The argument over the Hockey Stick is, in part, about false facts. The Hockey Stick was constructed by combining a large number of proxy data-sets, mainly tree rings, into a statistical model. Critics have argued that much of this data is invalid for a variety of reasons. Some proxies respond to factors other than temperature, such as increased CO2. Some are of dubious quality in that the match to temperature data over a ‘control period’ is poor. Yet others come from sites where alternative tree ring data-sets conflict with those chosen. So the ‘facts’ that have been modelled to produce the Hockey Stick are not unambiguous. Other researchers could have chosen different data sets and reached different conclusions.
Proponents of the Hockey Stick argue that independent reconstructions have validated it time and again. But critics point out that many of the same data sets appear repeatedly in these reconstructions, so they are not really independent at all. I would argue vehemently that this is not simply cavilling by naysayers determined to sabotage GHG theory on behalf of supposedly ‘vested interests’ such as the fossil fuel companies. In fact this debate went all the way to the US Senate in 2006. Both critics and proponents claimed victory in that hearing but the views of Ed Wegman, an eminent statistician, who was involved in the inquiry are worth noting. He concluded, inter alia, that
“In general we found MBH98 and MBH99 [the original Hockey Stick papers] to be somewhat obscure and the criticisms of [McIntyre and McKitrick] (two researchers who questioned the Hockey Stick) to be valid and compelling.” He also observed that
“this group has a self-reinforcing feedback mechanism and moreover, the work has been sufficiently politicized that they can hardly reassess their public positions without losing credibility.”
Hardly a ringing endorsement. I don’t recall the US Government ever being asked to settle a debate with the Flat Earth Society. One does not need to agree with Wegman to appreciate that some aspects of climate science may be less certain than their adherents proclaim.
The rejection of any significant fluctuations in temperature in the post-glacial period is all the more remarkable when one considers the modern data, including that from satellites and weather balloons. In 1998, 2016 and now in 2023/2024, for example, global temperature change of around 1oC occurred within the space of a year. These rapid temperature changes are thought to be caused by the El Niño/La Niña cycles in the Pacific Ocean. The current climate change shibboleth is that we must at all costs avoid an increase in temperature of 1.5oC above pre-industrial. Yet natural change is capable of producing two thirds of this increase in the blink of an eye. There are other natural factors that could produce temperature changes on longer time-frames. Ocean current systems such as the Atlantic Multi-Decadal Oscillation, for example, cycle through warm and cool periods over periods of half a century or more and can have a significant impact on climate.
The existence of these natural factors need not invalidate GHG theory. In fact if natural factors that cool the planet are currently counteracting the rise in temperature caused by GHG’s then the climate crisis might be even worse than we suspect. Surely it is worth trying to find out.
So is President Obama right to say that the science is settled? I leave that for the reader to decide. But I can’t help recalling the possibly apocryphal quote, to the effect that climate scientists blame it all on GHG’s because they cannot think what else it might be. That in turn brings to mind the tortuous words of another American politician:
“There are known knowns; there are things that we know that we know. There are known unknowns; that is to say, there are things that we know we don’t know. But there are also unknown unknowns – the things we do not know we don’t know.”
Scientists should be humble in the face of nature’s complexity. Only if you keep an open mind are you likely to encounter unknown unknowns.
Joe Brannan's Blog 
Science is both a body of knowledge and a process – the process is broken…
LikeLike