The most recent report from the Intergovernmental Panel on Climate Change (IPCC) not only shows that urgent and drastic changes will be necessary to avert even more devastating consequences of global warming than those which are already unavoidable, but also mentions, for the first time, the possibility or even necessity of reducing demand, i.e. the use of energy and resources.
This reality, however, is not reflected in the scenarios included in the IPCC report, as climate experts Yamina Saheb and Kai Kuhnhenn point out. Juliane Schumacher spoke with both of them to understand more about how IPCC reports are compiled, whose interests and biases they reflect, and how to address the deep inequalities in funding and access to the scientific process.
The third part of the IPCC report was published in April, with a focus on mitigation scenarios and policies. Yamina and Kai, you’re both familiar with the IPCC process or have even contributed to the report. Was there anything in it that surprised you?
YS: Yes, there was! We succeeded in including the concept of “sufficiency” in the Summary for Policymakers — that’s actually revolutionary. We even have a definition on page 41, footnote 60.
How is sufficiency defined?
YS: Sufficiency denotes all the policy measures and daily practices that avoid the demand for energy, materials, water, and land, while providing wellbeing for all within planetary boundaries. This means putting a cap on the overconsumption of the North to allow the South to develop, with another cap on the overconsumption of the richest in the North to allow low-income communities to access decent living standards.
Yamina Saheb is a Paris-based engineer and economist who works on energy and climate policies. She is the lead author of Chapter 9 of the recent IPCC report on climate mitigation and also contributed to several other chapters of the report.
Kai Kuhnhenn is a Leipzig-based environmental scientist with the Konzeptwerk Neue Ökonomie. Together with Luis Costa, Eva Mahnke, Linda Schneider, und Steffen Lange, he developed the Societal Transformation Scenario to show that a reduction in consumption in the Global North makes it possible to stay within 1.5°C of warming without relying on negative emissions technologies.
KK: I was surprised by Chapter 5, which mentioned the inequality of energy consumption and greenhouse gas emissions. It’s good that this is getting discussed.
If you look at the IPCC reports over the years, there is usually a statement on growth in some part of the report, something like: “economic growth is a driver of emissions”, or “economic growth does not correlate with wellbeing in saturated societies”. But then you have the modelling side, and that side has a very strict bias: “We will model economic growth until the end of times.”
So, there was always a certain kind of schizophrenia between the different parts of the IPCC. That is even stronger in this report, because there is so much talk about reducing demand, sufficiency, or even degrowth, but it’s not reflected at all in the modelling part.
YS: You have to understand that we have 17 chapters, and what ultimately enters a chapter depends a lot on the coordinating lead authors and how much they’re willing to push for. I regret that sufficiency doesn’t appear much in Chapter 5, which is first-ever chapter on services and demand. It’s a chapter I would have loved to be in, but I was the lead author of the chapter on buildings, my primary area of expertise. Then you have Chapter 3 on scenarios, which was led by two scientists from the Integrated Modelling Assessment (IAM) community.
The people in this chapter were responsible for developing the IPCC scenarios?
YS: No, we had a call — or rather, we had three calls — for scenarios. The IPCC doesn’t develop its own scenarios.
This is important to know: people say “IPCC scenarios”, but actually these are scenarios assessed by the IPCC authors. The assessment of long-term scenarios was led by the authors of Chapter 3. So we had three calls for scenarios: one for long-term scenarios, one for short-term, and one for the building sector. We got more than 3,300 scenarios, out of which 700 were Paris-compatible, meaning that you are between 1.5° and 2°C by the end of the century.
If you consider only those aiming for 1.5°C by the end of the century, the number of scenarios drops to 230. I’ve been looking for sufficiency measures, meaning measures to avoid the demand for energy and materials, in those 230 scenarios — you know the expression, “searching for a needle in a haystack”? —and I found just two. And those two scenarios don’t even mention the word sufficiency.
KK: Oh, wow.
YS: This is such a scandal! At the global level, there are two other scenarios that include sufficiency. One of them is the Societal Transformation Scenario developed by Kai and his colleagues, and the other is the one developed by Julia Steinberger and her team in Leeds called “Providing decent living with minimum energy: A global scenario”.
These two scenarios, however, didn’t make it to the IPCC database, because to be able to submit to the database you need to have resources — especially human resources. Realistic scenarios for a liveable planet like the ones developed by Kai and Julia are often developed by very small teams, sometimes on a voluntary basis, putting in lots of hours during their free time.
The IAM models, by contrast, are developed by huge teams — 40, 60 people — and they have plenty of little hands to do the work. The IPCC database has been conceived for this majority. I contacted Kai and his team and Julia and asked them about submitting their scenarios, but it wasn’t possible for either of them.
Because the datasets have to be prepared in a specific format?
YS: Yes, and that’s a lot of work. So Julia’s and Kai’s scenario couldn’t make it into the IPCC report. But even if they made it into the IPCC, this wouldn’t have meant they would be among the five scenarios selected in the end. We were a group of more than 60 people discussing and selecting the scenarios, but the majority of these scientists are all from the IAM community, and IAM scenarios are based on growth — they are driven by continuous growth.
How are these IAM models made?
YS: Integrated Assessment Models have existed for about 30 years. They’re a specific form of scientific computer modelling. A huge community works with these models, with associations in different parts of the world, one of the most important is the International Institute for Applied Systems Analysis (IIASA) in Austria.
All these models anticipate a continuation of growth. At the same time, they’re driven by supply-side decarbonization and not by demand reduction. In our chapter, we clearly show what it means if we ignore the demand side and don’t consider sufficiency measures. Between 1990 and 2019, the improvement of efficiency in the building sector led to reducing emissions by 49 percent. However, the lack of sufficiency measures — people living or working in bigger buildings and using more and larger appliances — has led to an increase of emissions by 52 percent.
It is also highly problematic that these scenarios do not seek convergence between the Global North and Global South in terms of access to decent living standards.
They expect a continuation of economic growth in the North, but less so in the South?
YS: I’ll give you an example from my area of expertise, buildings. Today, the floor area per capita in North America is around 60 square metres, while it’s below 10 square metres in whole of Africa. In some African countries it is even below five, they don’t have proper housing at all. But these scenarios usually expect continuous growth, so in some scenarios, by 2050 they reach 65 square metres per capita in North America, and the Africans reach 10 square metres per capita. Why the hell would I accept this as an African? It’s just not acceptable.
From which disciplines are these modellers coming from, and where are they based?
YS: Most of them are based in the Global North. It’s a very Western vision of the world — neo-colonial, as Jason Hickel wrote. I understand that, today, things are like that. This is the world we inherited. But what’s really shocking for me as an European-African citizen, who is from both sides of the Mediterranean, is to see that they project a world for my son in 2050 that is similarly unequal to my world today.
And the IPCC models are all IAM models?
YS: The IAM models are the only ones to provide projections until 2100 and have the necessary human resources to support the IPCC process, which is quite heavy for small modelling teams. It’s actually all that we have — as you see, other models like the Societal Transformation Scenario developed by Kai and his colleagues couldn’t make it to the database. In the IPCC process, we prioritize all that is published in peer-reviewed journals. But if you look at who the editors of Nature are, for example, you will see that many are from the IAM community.
So the community is reproducing itself, because the reviewers of publication are all from the same community…
YS: Exactly! It’s kind of an incestuous relationship.
KK: You asked what disciplines these modelers come from. My short answer would be: not enough disciplines. Most of them are economists and engineers, and they do what economists always do: they overstep their boundaries in what they can talk about. If you want to talk about how the world should be in 20 or 50 years, you need all kind of disciplines. Like Yamina said: these models are basically about how the world is today. Maybe they can tell what could be in ten years, but they can’t look 30 or 70 years into the future.
YS: These scenarios go until the end of the century.
KK: Until 2100.
KK: And because these are economic models, they need all this data — prices for energy, for technology, from now until 2100. I think it’s ridiculous to have any idea of what the oil price will be in 20 or 40 years. The energy market and energy prices are so influenced by politics and world phenomena that it’s very hard for any mathematical model to predict them.
YS: There is another problems with the IAMs that I see in my field: one sector like building is just one point for them, one indicator — the energy consumption for the overall building stock. They don’t have any idea how the building stock evolves. Many assumptions in their models are not based on data, so they come to very strange conclusions — some of the scenarios project negative emissions in the building stock in countries like Indonesia by 2030. Who could believe for one second that by 2030 negative emissions will decarbonize the building stock in a country like Indonesia!
KK: I tried to figure out what the welfare function of the IAMs is, or their utility function. Because what they actually do is tell the model, “Please stay within this or that emission budget by employing options A–Z” — such as renewables, nuclear energy, or sufficiency — but they usually don’t include this last option. Then, the model tries to figure out the cheapest way to stay within these emissions budgets. Or, more specifically, it tries to optimize consumption per capita within the given emission budget.
Then some adjustments are made: it is more useful that poor people increase their consumption than rich people, for example, so there are some good parts in there. But the basic problem is that what the models try to optimize — or rather, maximize — is consumption per person. They’re presenting their scenarios as the best paths, but it’s just the past with the most consumption per capita. What about working hours, or how many resources are used for this lifestyle? That isn’t factored in.
And all models work that way?
KK: That’s the foundation. Then they employ the cheapest technology first, followed by the second-cheapest. For this they need a lot of data. They need to figure out how much all of the ways to produce electricity and mitigate emissions will cost from now until 2100.
So, the problem is that it’s mainly mainstream economists who work on these models and bring in their neoliberal ideas.
KK: Definitely. I had a conversation with one modeler who said, “We are just employing the normal theory, the normal economic theory. This is not our idea, this is how it is.” There are so many ethics involved in these models that are not made public, not debated, and that is my main concern.
There’s an issue of transparency?
Are the codes and algorithms accessible? Or do only the modelers themselves know how the model actually works?
KK: The data is not public, of course, because that’s their most valuable resource — their bread and butter. Sometimes, you find documentation that’s good enough to figure out more or less how the models work, like in the case of the Remind model from the Potsdam Institute of Climate Research (PIK). When I looked at it three or four years ago, it was the only model where I found documentation that really showed the utility function in a mathematical sense.
How much influence do these models have? Why is it problematic that they’re so homogenous?
YS: I’ll give you an example. These models all work with continuous economic growth, and economic growth means more emissions. We have a limitation for the temperature at the end of the century, but because the economy cannot be decarbonized under these conditions, all the models end up putting in negative emissions to keep that limit.
But negative emission technology — technology that captures carbon out of the atmosphere — is still very speculative, it doesn’t exist on that scale. When I was presenting the IPCC report to the minister in Paris in April, we were directly asked about negative emissions. What people take from the IPCC report is that we need negative emissions!
We had to explain that even among us IPCC authors, we don’t agree on that. I explained to her that we have two options: option 1 with the scenarios assessed is the IAMs — we do need negative emissions. With option 2, with models like the one from Kai or Julia, we don’t need negative emissions to maintain the temperature limit because they model the world differently. But the message that came out of the IPCC, unfortunately, is that we need negative emissions.
It has a huge impact if the IPCC only shows models relying on negative emissions.
KK: Exactly. Because then people only talk about negative emission technologies, and that’s where the money goes instead of talking about what the world could look like and how we want to change it. It closes the political debate and brings it onto a very narrow path, without showing other solutions, because there’s no relativation. The IPCC doesn’t say, “With our approach, with our models, we did not come up with other options.” They say: “These are the scenarios, these are the possibilities we can choose between, there are no others.”
Are there interests behind this strong focus on growth-driven models and negative emission technologies?
KK: There is a general interest in a world with continued economic growth among governments, companies, and corporations, and some of those are also the ones that finance climate scenarios, such as the German government. As a result, researchers are asked to produce scenarios with continued economic growth.
I would’ve liked to create a scenario like the Societal Transformation Scenario on a national level — a scenario that would actually be quite helpful in the situation now with Ukraine, because we would have a scenario on how we could reduce fossil fuel use by reducing consumption and production — but it’s hard to get that financed.
Maybe funders were also reluctant because they didn’t want to criticize the IPCC?
KK: It’s important to make clear that I don’t mean to say that the IPCC is lying and there is no climate change. The whole natural scientific basis — that is all very good science. It’s not a critique of the IPCC as such, but of a specific part of it — the scenarios — and of how they are made.
YS: The IPCC itself is a very interesting process because you have authors from different regions of the world, selected based on their publications. But for sure, the chances to contribute to the IPCC are very unequal. If you work as a scientist in the Global North, you have access to funding, publications, tools, and conferences. People from the South don’t have access to all that.
In my group we had a colleague from Africa. He couldn’t really participate because all our work was done online, and his internet connection wasn’t working well enough. He didn’t have access to publications, because they’re usually behind expensive paywalls and you need a university or a well-funded institute to provide access. So he was lagging behind compared to us.
Another interesting part of the IPCC process is the fact that the Summary for Policymakers — which is very influential — is approved line-by-line by governments, and scientists have to clarify each single statement included in the summary for policymakers.
This is often criticized, because in that way it’s more a political document than a purely scientific one.
YS: But it also has some advantages. If governments approve the document, they also have to act accordingly. This allows NGOs to apply pressure on them to do so.
The IPCC is an interesting process, but there’s definitely room to improve it. One major issue for improvement is how to deal with the scenarios. That they are all so homogenous is not the fault of the IPCC — these are the scenarios that are available at the moment. Other types of scenarios need to be developed, but to develop them you would need money and resources.
Let’s talk about alternatives. What would a better model or scenario look like?
KK: I could imagine having a global model that’s relatively simple and easy to understand and can be used and changed by everyone. We could then put that out there and use it for all kinds of exercises.
An open-source model that can be used, for example, in education.
KK: Exactly. So people can add things — for example, someone who is an expert in the building sector may add a part to make it more realistic with regard to what can be built within a certain timeframe. And so, bit-by-bit, this open-source model would become the gold standard and could be used for different scenarios. That would be really nice.
YS: This would also better reflect the vision of the South. People could use and contribute more easily. You need people from all over the world to build these models. That people sit here in Paris and imagine the future of billions of people all over the world — this is just not possible.
Kai, was the scenario you developed going in this direction?
KK: Our model is very simple, it’s basically a big slide ruler. You have to put everything in there: what are the average kilometres driven per year, how much of that is driven by car, how much by bike, by train, and how many people sit in a car? You do this for every sector, and then you come up with, let’s say, ten to 20 consumption parameters.
Then you do the same on the supply side. You have to assume, for example, the share of renewables and their increase over time. Then it calculates the result. It’s a very simple model, basically one big spreadsheet file. You can even download it, it’s all open. But the data is already a bit outdated, and it only distinguishes between Global North and South on the consumption side, so it would need more geographical differentiation.
But you showed that it can be done that way.
KK: In a way, it’s kind of ridiculous to do a scenario like this and compare it with what people do with their IAMs. But we compared ours to the Low Energy Demand or LED scenario, the most sustainable scenario in the IPCC, and they were quite close with regard to the results. So its quality seems to be not much worse, and we just worked with the tools we had at hand.
If you could make one change to improve the IPCC process in relation to scenarios or the modelling community, what would it be?
KK: I would like to have all those social scientists in there contributing. Feminist economists, progressive sociologists, experts on colonialism — people who think very differently about economics and society.
YS: Today, in the IPCC process, we collect numbers about people contributing to the chapters, about their gender and whether they come from the Global North or South. But we don’t have figures about the disciplines of the authors. My impression is that most of them are economists — mainstream economists — or engineers. The other disciplines are missing in that process, and it would be good to have them in there.
The other thing is how to ensure the participation of the Global South. We have to make sure that people from the Global South have access to publications like we have in the Global North, that they have access to the tools we have. And just as the research community usually only accepts peer-reviewed journal publications, we need to find a way for people from the Global South to publish and get cited.
Actually, it would be good to have a number of citations from the Global South in the IPCC, for example, and a number of citations from women. I don’t know the figures, but I wouldn’t be surprised if they’re extremely low compared to the number of citations of men from the Global North. These kinds of differences keep the same development model going — and are also reflected in the models used today.