Are Our Climate Change Prediction Models Reliable?

March 28, 2023

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On Monday, March 20th, the IPCC published a climate report with advice for policymakers. This advice is partly based on computer models, but criticism of these models is growing. To what extent do the assumptions made in these models accurately reflect our society? And do they still hold when making predictions about 2100?

Detlef van Vuuren is one of the leading climate scientists that use integrated assessment models (IAMs) to show how the goals of the Paris Climate Agreement can be met. He is one of the two primary authors from the Netherlands that worked on the report of the IPCC, the scientific climate panel of the United Nations. He calls the results of his models “possible futures”: climate policy A possibly has future outcome B. He sees them as helpful because they prevent random scenario outlines. The models add knowledge about correlation and technical possibilities.

However, criticism of these kinds of models is growing. Like with any model, you have to make assumptions about how people behave, how quickly technology advances, and how political decision-making works. Furthermore, they can never account for unpredictable developments; take the COVID-19 pandemic and the ongoing war in Ukraine as examples. These two had and continue to have a huge impact on emissions, but we did not see them coming, so they are not in Van Vuuren’s models.

Two years ago, in April 2021, James Dyke, Robert Watson, and Wolfgang Knorr wrote a very critical article on the scientific website The Conversation. At the time, they were Associate Professor in Earth System Science at the University of Exeter, Emeritus Professor in Environmental Sciences at the University of East Anglia, and Senior Research Scientist in Physical Geography and Ecosystem Science at Lund University, respectively, and they were not too satisfied with the computer model-based climate predictions. In their opinion, the IAMs remove “the need for deep critical thinking” (Dyke, Watson, Knorr (2021)). In the models, society is reflected as “a web of idealised, emotionless buyers and sellers”. Complex social and political realities or even the impacts of climate change itself are ignored. The models use data and equations about demand, supply, price elasticity, etc., but in order for them to work, many random assumptions and choices are made, Knorr says to NRC Handelsblad in 2023. An example he gives: a fair division of emission rights and resources is never an option and the use of energy is only demand-based, with no regard to democratic decisions. In other words: people can use as much energy as they can afford. He even compares the models to a game of Monopoly: “you can never win that based on the principle of fair distribution” (Aan de Brugh, Luttikhuis, 2023).

Non-Existent, Highly Ambitious, and Very Experimental Technologies

But there is more Dyke, Watson, and Knorr are unsatisfied with about the climate-economic models. Around the year 2000, it had already become clear that we would not be able to avoid dangerous climate change just by reducing our carbon emissions, therefore, scientists had to incorporate other solutions in their viable pathway designs; more and more examples of carbon capture and storage were included in the models. In principle, this technology, which indefinitely stores carbon dioxide removed from coal-fired power stations deep underground, would be possible; the techniques to remove the CO2 from fossil gas and inject it underground had been used several times since the 1970s. It seemed like the solution for the situation we realised we were in, where just cutting back on emitting carbon dioxide would take CO2 out of the atmosphere (quickly) enough. However, before this carbon capture and storage had ever been brung into practice, the hypothetical process had already been included in many climate-economic models, making them highly dependent on the prospected effectiveness of this technology. Thus, the mere prospect of carbon capture and storage provided a way out for policymakers of bringing greenhouse gas emissions down, even though that is still very much needed (Dyke, Watson, Knorr (2021)).

At the time of the 2009 United Nations Climate Change Conference in Copenhagen, it had become clear that carbon capture and storage was not going to be a sufficient solution to avoid dangerous climate change for two reasons. The undeniable first reason was that it did not exist. There was not even the prospect of having any coal-fired power stations operating with this technology in the foreseeable future, which was primarily because of the higher cost associated with generating electricity in this way. But besides that, it was also apparent that, even if the carbon capture and storage technology were up and running, it would not be possible to make the demanded reductions.

After the 2009 UN Climate Change Conference in Copenhagen, there have been several more Climate Change Conferences, experimental and ambitious climate-change-reducing technologies (that ended up failing or not being effective (enough)), and uncountably many policymakers and businesses still hanging onto them. However, Dyke, Watson, and Knorr (2021) argue that these should be seen as a sort of ejector seat, like one in a jet aircraft, that could propel humanity away from rapid and catastrophic environmental change. As such, it should only be used as a very last resort. They find it problematic that policymakers and businesses seriously view those speculative technologies as a way to “solve” today’s climate change problem, while they say: “In fact, these are no more than fairy tales” (Dyke, Watson, Knorr (2021)).

Political Games

They conclude that the current net-zero policies will not restrict global warming to 1,5 C, “because they were never intended to” (Dyke, Watson, Knorr (2021). These policies were drafted to satisfy the need to “protect business as usual, not the climate”. The models on which these net zero policies are based, provide a false sense of control. They propose that the only viable pathway to refraining from dangerous climate change would be large and sustained cuts to carbon emissions, right now. “The time for wishful thinking is over.” (Dyke, Watson, Knorr (2021).)

Van Vuuren wholeheartedly disagrees with Dyke, Watson, and Knorr’s statement that policymakers don’t feel the urgency of cutting back on greenhouse gas emissions right now because of the IAMs’ suggestions of using speculative technologies. He states that the IAMs explore many different possible futures, but they all conclude that action should be taken quickly. Precisely because the computer models support such far-reaching statements about e.g. the long-term goals, the 1,5 C, or net zero emissions in 2050, the policymakers also dare to reach for them. (Aan de Brugh, Luttikhuis (2023).)

Van Vuuren is aware of the criticism and that the models are not 100% true, but for him, that does not make them any less valuable. Just thinking about and elaborating on all the aspects that should or could be included in the models for different possible futures, including lifestyle changes and reduction of physical growth, gives them their power. However, when thinking about the far future, this gets more difficult, he admits, though this is not just the case for computer models; anyone who is trying to predict the far future, in which not currently existing technologies are in play, encounters the same difficulties.

Furthermore, Van Vuuren also states that the computer models help policymakers to stand strong for CO2 reduction measures. It can be difficult to convince society that there are very costly changes to be made, but if a policymaker can “blame” these ideas on a computer or scientific advice, they are at less risk of being the villain in the eyes of the people.

In the end, however, Van Vuuren admits that climate policy is a political choice. He tries to elaborate on the pros and cons of choices as neutrally as possible, but he sees that more and more scientists are beginning to feel uncomfortable. Like Dyke, Watson, and Knorr, they feel like the climate policies are moving too slowly. Ultimately, of course, everyone wants to see our earth through several centuries of a sustainable and healthy existence. But the way to ensure that? Very debatable.


Brugh, M. aan de, & Luttikhuis, P. (2023, March 20). De Kritiek op klimaatmodellen groeit: ‘Het zijn waanzinnige, futuristische aannames’. NRC. Retrieved March 21, 2023, from 

Dyke, J., Watson, R., & Knorr, W. (2023, January 20). Climate scientists: Concept of net zero is a dangerous trap. The Conversation. Retrieved March 21, 2023, from 

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