Scientists have modelled thousands of possible futures, and found that different social attitudes could make the difference between a temperature increase of just 1.8C or 3.6C by the end of the 21st century.
Researchers dived into how the complex interactions between social factors, such as public opinion or adherence to the status quo, will affect the global heating trajectory by 2100 and found that there were five main possible outcomes. None of them meet the 1.5C Paris agreement target, but almost all achieve 0.5C less heating than the standard models, which don’t account for changes in social factors.
“This paper looks across a lot of different disciplines in order to try and document some of these relevant feedback processes,” said Frances Moore, assistant professor in environmental science at UC Davis, and lead author of the paper, published in Nature on Wednesday.
“Because these social factors are not independent of each other. If they are connected together, that’s going to lead to different behaviour rather than if you just look at any one piece of the system independently.”
These findings suggest scientists should start making projections which also account for climate policy and social change in their calculations, says Moore. But it is sometimes complicated for scientists to factor elements such as social and political response into their projections. Often each aspect is examined in disciplinary silos, and not as a complex web of interactions which can quickly stymie a change of directions.
“You have a little bit of a change and then there are connections in the system, and they either amplify or dampen that change,” said Moore. “These can drive some complicated dynamics where you can get fairly sudden changes, like these kind of tipping point-type changes, when it suddenly changes in ways that were not necessarily simple extrapolations of what you’ve seen before.”
That’s why standard energy models often miss the mark and underpredict the rate at which renewable energy will grow in the future, for example.
Moore and her team modelled 100,000 possible future global heating scenarios: in some models the researchers set institutions to have higher bias towards the status quo, or more responsiveness from the public, or decreasing costs of policy after policies are implemented, and so forth.
Approximately 48% of the model runs paint a picture of what would happen if we continued on the path we’re on: global emissions would peak in the early 2030s, declining to zero by 2080, and temperatures in 2100 would have risen by 2.3C in comparison with pre-industrialisation temperatures between 1880 and 1910.
Then, just over 5% of model runs represent “too little too late” or “delayed recognition” case scenarios, in which public opinion is too hard to change, political institutions are unresponsive, global emissions peak in 2050 and policies are delayed until after that – temperatures in 2100 are up to 3.6C higher than pre-industrialisation.
In contrast, the “aggressive action” case scenarios, about 28% of model runs, results in a deep support for climate policy and plenty of emission-reduction technologies by the end of the 2020s, leading to zero global emissions by 2060. In 2100, Earth would be just 1.8C warmer than pre-industrialisation.
Although there’s a lot of social science theory to back up these models, there’s still a very wide degree of freedom in the system.
“Part of the problem is that there’s been very little attempt to actually put probabilities over these outcomes, because what typically happens in climate science is you kind of define an emissions trajectory, and you don’t really say how likely is that emissions trajectory over others,” said Moore.
So although even the most aggressive action scenario fails to meet the Paris Agreement target to limit heating to 1.5C, there is a substantial probability of meeting the 2C Paris agreement target. None of these models take into account the growing use of carbon-fixing technologies though, so projecting how those will grow into the future, and adding that to the models, might also help meet some more ambitious targets, Moore said.
“It’s an important scientific question, to understand how society is embedded in this climate system and what these couple feedbacks between society and climate are,” Moore said. “But it’s also important for adaptation planning.”
