Climate models are complicated things. They must consider a staggering number of mathematical and physical variables to predict, for instance, how emitting a given amount of carbon dioxide will change the flows of air, water and heat between the atmosphere and the oceans. More sophisticated projections go further, showing how temperature changes will affect rainfall in a certain region, which in turn will affect crop yields and, as a result, the carbon cycle.
Integrated assessment models widen the analysis yet further, including links between the climate system and the economy; for example, simulating how changes in population growth or fuel demand will affect the climate. It is also possible to add social and political variables: The models used in the latest report by the U.N. Intergovernmental Panel on Climate Change rely on narratives of future development, or “shared socioeconomic pathways.” One narrative depicts the world developing in a way that respects planetary boundaries and reduces inequality along with emissions; another shows a world where resurgent nationalism and environmental degradation make mitigation and adaptation difficult. There are big unanswered questions here; for example, once they can afford to, will people in the global south consume as much meat as Westerners currently do? An integrated assessment model puts out different results based on which storyline it’s fed.
As useful as these models are, though, nearly all of them treat the human decisions that determine greenhouse gas emissions as external: Political choices are inputs, not outputs. Modelers generally don’t have a way of accounting for the complex interactions between the energy system and human decisions. For instance, extreme heat waves like the one that baked Europe in July tend to drive support for green parties, but the heat has also pushed sweaty British and French people to buy air conditioners, which can increase the cost of electricity, leading some politicians to blame carbon pricing for the high cost of living. The thousands of Britons pledging to boycott their energy bills this winter are unlikely to support any climate policies that cut emissions by raising the cost of their energy, and it’s very tricky for a typical climate model to capture these dynamics.
And yet these shifts — in which climate change generates political responses that, among other things, make climate action more or less likely — act as distortions that undermine the accuracy of models’ projections. This isn’t just an academic point. At a global level, political dynamics in one country affect the climate outcomes for others, some disproportionately so. At a local level, policymakers need a true sense of what kind of ecological and climate change is coming so they can make the right preparations — for example, to inform decisions on which neighborhoods are at risk of flooding and might need to be protected with a new sea wall.
Some scientists are trying to address these limitations — to show how social factors and biophysical changes influence each other. In a February article in Nature, a group of scholars described a new model they called the “coupled climate-social system.” It includes feedback processes involving policy, public opinion, emissions and the climate. One feedback process takes into account social conformity: the pressure to fit in, for example, by conserving energy when gasoline is expensive or installing solar panels to match the neighbors’. Another feedback process involves political interest; think of how America’s new Inflation Reduction Act promises to create millions of jobs installing green technologies such as solar panels, and how those workers might then support policies that boost clean energy even further. One of the most interesting mechanisms is the “expressive force of law” feedback loop, the idea that changes to laws can shape broader social norms, the way smoking bans in restaurants helped reduce smoking throughout society. For example, in the grip of a megadrought, Nevada is banning most lawns to save water. People from parts of the parched American West where lawns remain legal might visit Las Vegas and decide that rock gardens aren’t so bad, especially if saving water helps the state keep producing low-emissions hydropower from the Hoover Dam.
The Nature article’s authors argue that integrating these social phenomena into their perspective allows them to explain emissions trajectories as a product not only of the price of wind power or the rate of deforestation, but also of the social and political changes that will be shaped by (and themselves shape) humanity’s path to a lower-carbon future. Bringing sociopolitical dynamics into scientific models of climate change, they say, makes the models more robust.
The social-climate system article builds on other recent efforts to link climate models with social models, such as a 2021 Nature commentary calling for climate models to “get real about people.” As The Washington Post recently reported, in an article about the energy economics models used in calculating how the Inflation Reduction Act might benefit the climate, it’s clear that humans are not purely rational actors who make decisions solely by weighing costs and benefits. It’s time for modelers of climate change — which, after all, is a product of human behavior — to recognize that too.
Kids are living with climate catastrophe. That doesn’t mean they believe in it.
What these early attempts at an integrated model drive home is that neither physical scientists on the one hand, nor economists, political scientists and international relations scholars on the other, can responsibly assume that the other sphere will proceed in a straight or predictable line. If the world is to successfully address climate change, the path will proceed in steps, many of which will be driven by human decisions in response to climate impacts.
Admittedly, no model can be comprehensive. The social-climate model, for one, does not account for geopolitical shocks such as Russia’s invasion of Ukraine and the ensuing restrictions on Russian fuel exports, nor how those shocks might be shaped or even caused by climate action or inaction. But the point isn’t that social-climate models have to keep expanding to include every possible feedback loop in all its complexity. That’s impossible.
The scientists behind the social-climate model have begun to do their part to consider how sociopolitical phenomena manifest as dependent variables. But are policymakers and political analysts doing enough to integrate climate science into their own models and theories, which are built on their understandings of social and political dynamics? Political scientists could build models and theoretical frames that take into account climate science, making their side of the feedback loop more robust. They can help clarify how geopolitical shifts could be shaped by and in turn shape climate action, focusing on the effects of climate change and the responses to it.
For example, if the richest, most polluting nations continue to fall short on their promises to share climate-related financial aid and technology with developing nations, and the U.N. Security Council remains unable to agree to address climate security risks, won’t the United Nations — if it still exists — be a less-effective actor in 2040 than it is today? China plans to double its wind and solar capacity over the next five years, and electric vehicles already make up a quarter of the cars produced there. What, then, would be the geostrategic implications of China reducing its dependence on foreign oil imported through the Strait of Malacca? Or, to take another example, might those suffering from historic heat waves be radicalized and turn to violence, sabotaging oil and gas pipelines or committing violent attacks on the governments they perceive to have failed them? And how would any of this then affect decisions about climate policy? Here, too, there are feedback loops, between the climate impacts, the perceptions of those suffering from them, and the reactions of governments and international organizations.
To the extent that policymakers pay attention to the geopolitical implications of climate change, they mostly focus on constraints and opportunities in their existing worldviews — such as Arctic ice melting and opening up new sea routes — rather than reevaluating their theories of global security: The United States’ Interim National Security Strategic Guidance from 2021 repeats the term “climate crisis” without considering how it interacts with other threats. The Defense Department’s Climate Risk Analysis from 2021 goes deeper, with an encouraging focus on second-order effects of climate change, such as migration and civil unrest. Most forward-looking and holistic is the 2021 National Intelligence Estimate on climate security challenges, which warns that rich countries’ failure to uphold the Paris agreement could raise geopolitical tensions in ways that threaten the United States and the institutions it co-leads. But such thinking is not widespread enough. A climate-change-worsened hurricane in the Caribbean is a geopolitical event as well as a humanitarian crisis.
Now that the scientists have lobbed it over the net, the ball is in the court of the political, international relations and foreign policy community. Our task is to ensure that we treat climate change and environmental crises not as troubling developments that run parallel to human-driven international politics, but as threads that cannot be disentangled from them.