Uncertainty: A climate sceptics favourite tool

Climate policy is undoubtedly a complex issue with innumerable factors underpinning which policies make it first to consideration, and then into legislation itself. The portfolios of policies that are enacted are notable for their discrepancy from the actions which experts call for. Understanding the importance of uncertainty, and how different actors respond to it can help us to explain why this discrepancy exists.

Understandings of uncertainty are by no means the only factor contributing to the policy gap between experts and policy makers, a topic to which whole fields of research are dedicated, nevertheless it is an important one. Information can be uncertain in different ways and these differences change the actions that are appropriate. Actors, be they politicians, voters, or other stakeholders such as business leaders, in climate the climate policy discourse do not always properly account for these differences in their responses to information, and this contributes to the gap seen between the actions recommended by experts and the policy that end up being enacted.

Shared trends, different details

Not all uncertainty is the same

Many different kinds of uncertainty about the world around us and how it works have existed since the issue of the world's climate began to be studied in the 1800’s. Firstly, there was uncertainty about what are now very basic facts about the world, such as the heat trapping properties of CO2.

Secondly, there is uncertainty that relates to more detailed quantitative understanding of things. This may manifest as two scientists agreeing broadly about what the answer to a question might look like, but disagreeing on its exact value or the details of an outcome.

Thirdly, there are some phenomena which are intrinsically uncertain, especially at high levels of precision. For example, scientists might be very certain about the trends that they expect to see in the climate, but be uncertain about the exact level of precipitation change, or some other parameter, that they expect to see at a given time.

Uncertainty surrounding basic facts

In the nineteenth century, when scientists began to investigate the global atmospheric system in earnest, there were large uncertainties about the basic dynamics involved and the relative importance of different factors. The physical properties of CO2 and wider importance were poorly understood. It had been shown to trap heat in small scale laboratory studies, but there was no consensus on the consequence of this for the atmospheric system. Svante Arrhenius, the first person to calculate the extent of the greenhouse effect using basic knowledge about the gasses involved, thought that CO2 would have a warming effect that was mild and with a net positive impact on humanity.

Others proposed that the similarity between water vapour and CO2 in their heat trapping abilities would make additional CO2 insignificant because water vapour was trapping the heat anyway. Further support of its insignificance came from the idea that CO2 would be absorbed by the sea. Subsequently, all these ideas have been disproven and the significance of changing levels of CO2 to the dynamics of the atmosphere is well established, but the previous existence of these other theories is evidence of previous uncertainty.

Svante Arrhenius ... thought that CO2 would have a warming effect that was mild and with a net positive impact on humanity.

As late as the 1960’s, long after the warming effects of CO2 were well established, it was still not clear if human impact on the atmosphere would lead to a net warming or cooling effect. It was known that increased greenhouse gases (GHGs) would lead to warming, but that the increase in aerosols would have a cooling effect. Neither of these effects could be quantified well at the global level so it was not clear which would dominate, and therefore unknown if the global trend would be for warming or cooling. Later of course, a strong consensus developed that although some aerosols do have a cooling effect, this is greatly outweighed by the warming caused by increased atmospheric GHG levels.

it was still not clear if human impact on the atmosphere would lead to a net warming or cooling effect

Today, understandings of these aspects of climate science are either complete, or in the cases they are not, much more certain. However, the fact that they were once uncertain allows some to undermine present knowledge by restating the historical controversies as if they are still open questions, ignoring the progress in understanding that has happened in the time in between.

Scientists may broadly agree on an issue, but be uncertain about and disagree on the details.

Sometimes the scientific community is able to come to a broad consensus on an issue, but remain uncertain about the details which may lead to disagreement between scientists on what those details look like.

This type of uncertainty could be seen in 1988 in the aftermath of James Hansen’s testimony to congress that a rise in the global temperature had been detected in the data. He received public criticism from his peers who believed that the assertions he made were too strong. Most of his critics from the climate science community actually agreed with the findings he presented, yet contested that the possibility of being wrong was higher than Hansen made out. Even if on balance the evidence did point in favour of him being right, they wanted to acknowledge the possibility that he could be wrong. Here, the scientists are disagreeing on the certainty with which they know something that they all (mostly) believe to be true. Whether the disagreement is about the findings themselves, or the certainty of the findings, dramatically changes the policies that it is appropriate to base on that evidence. Therefore, it is essential that policy makers and other actions in the policy making process are able to make this distinction.

The same kind of uncertainty had been at the center of a scientific debate early in the 1980’s, this time the controversy was about the climatic effects of a large scale nuclear war. It was feared that the debris created by nuclear explosions and subsequent fires would block out sunlight and lead to a “Nuclear Winter”. Two scientific groups studied the issue, which involved understanding the atmospheric effects of the dust and debris that would result from a nuclear war, using two different models.

The two models broadly agreed; nuclear war of at any scale would incur great risk of hugely damaging climatic effects. However, differences in the models used lead to differences in the details of what was predicted, and developed into a dispute that spilled out into the scientific and popular press. Given the science was not completely settled it would have been best practice for policy makers to maintain an open mind on the matters under dispute, and act with the understanding that the predictions were not yet perfect.

However, the pursuit of effective policies was not helped by the use of these disagreements over detail to create the impression that what the science did agree on, that nuclear war posed a great risk to human wellbeing via its effects on the climate, was somehow in doubt. It is this conflation of different kinds of uncertainty that is harmful to the pursuit of effective public policy, because the credibility of good evidence is inappropriately undermined.

Most of [Hansen's] critics from the climate science community actually agreed with the findings he presented

Uncertainty is intrinsic to systems of the size and complexity of the global climate.

One of the reasons that uncertainty is such an important factor in understanding climate change is that the size and the complexity of the climate system makes predicting it intrinsically uncertain. Even with perfect knowledge of the starting conditions and dynamics of the system, predictions of the weather become no better than random after as little as a month because of amplification of random effects. This makes the precise prediction of weather and climate in the medium term impossible, leading some to question how anything can confidently be predicted about the climate.

The limitations having been acknowledged, broad trends in the climate can be predicted with great confidence. There may be great uncertainty in how many degrees the planet will warm over the next 100 years, will it be 1.7 or 3.7? Nobody can be sure of that (although they can make good estimates). Broader predictions, however, can be made with much more certainty. There is a very high degree of confidence that there will be a warming trend. That is known to the same degree as many other scientific facts that are widely accepted. And we can also be highly certain that this temperature increase will be within certain bounds; we know it is almost certain to be more than 0.5°C and less than 10°C.

The coarseness of these predictions can lead people to think, or maliciously create the impression that, all predictions about the climate are simply inaccurate. This isn’t the case. The fact that we can’t predict for certain the average temperature in a given year does nothing to undermine the certainty behind predictions of trends over longer time scales.

There may be great uncertainty in how many degrees the planet will warm over the next 100 years .... Broader predictions, however, can be made with much more certainty.

The credibility of contemporary modelling is also unfairly undermined by references to historical models which contained considerable inaccuracies. Early model predictions would change dramatically as the result of tiny changes in input parameters leading to outputs that bore little resemblance to the real world. The fact is that models today are much more complex, useful, and accurate, able to produce predictions of the long term trends and regional variations in the climate system with a high degree of accuracy. Their inability to predict the precise details of weather represents a completely different type of uncertainty to that seen in historical models which could not even recreate basic climate trends. To undermine modern models by pointing to the flaws in historical models is to misrepresent their abilities.

Misunderstanding and misrepresenting different types of Uncertainty undermines trust in climate science, preventing it from informing policy making effectively.

Contemporary knowledge of the climate and climate change is not complete, but a huge amount of progress has been made in understanding a vastly complex system. International collaboration through organisations like the IPCC has allowed a vast bank of knowledge to be developed, and the holes in that knowledge to be identified allowing work to close those gaps to be pursued.

Despite not knowing everything for certain, we know a great deal and this knowledge gives us the opportunity to act in ways that best favour the achievement of our goals as humanity. By basing policy on this knowledge we give those policies the best chance of working. So far this opportunity has not been fully embraced, partly because people misunderstand and misrepresent the uncertainties in this knowledge undermining the support for policies that it calls for.

The first way in which this is done is to point to repeatedly refer to the uncertainties in knowledge, leading to inappropriate skepticism. Knowledge is never perfect, but this does not prevent it from being useful. However, emphasising imperfections leads to the perception that they are larger and more significant than they really are. This leads to the knowledge being handled as if it is more flawed than it really is, and consequently given less weight than it deserves in decision making, or even being discounted entirely.

Knowledge is undermined by a second route when people mistake one type of uncertainty for another. For example, when they hear that climate scientists still don’t know everything, people may assume this relates to the basic facts about climate, rather than precise predictions and thus not give the advice of climate scientists the credibility it deserves. Alternatively, when presented with two modern models that differ in the local precipitation patterns they predict in 100 years time, people may confuse this uncertainty in detail with the fundamental uncertainty surrounding a warming vs cooling trend present in the 60’s. These different levels of uncertainty have very different implications for which actions should be taken, and thus confusion between them will lead to an inappropriate role, or perhaps more importantly lack of a role, for the given piece of knowledge in the decision making process.

Increasingly the general public is becoming more informed about climate change, and public opinion, for the large part, now mirrors that of scientific experts well. However, the opportunities for misunderstanding highlighted here are still present and this is exploited by those for whom this is convenient. Acknowledging the full implications of modern understandings of the climate would be inconvenient for many large organisations, especially fossil fuel companies. By pointing towards historic errors in climate science, and misrepresenting uncertainties in modern knowledge they are able to create sufficient support to stall climate policies that would be inconvenient for them. Whilst they continue to do this, passing effective climate legislation will be a struggle.

By Louder Than The Storm Political Lead, MacGregor Cox


READ MORE from this series on climate denial:

The Political Origins of Climate Denial

The Climate Denial Timeline

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