A first-of-its-kind model—that measures the effects of human behavior on climate—provides new insight into the range of temperatures the planet may face in the coming century. And it provides “a rational basis for hope”—one of the co-authors says—that people, as the dominant cause of global temperature rise, may also be a crucial factor in helping to reduce it.
The results, published January 1 in the journal Nature Climate Change, demonstrate the importance of factoring human behavior into models of climate change.
Combining climate projections and social processes, the model predicts global temperature change ranging from 3.4 to 6.2°C by 2100, compared to 4.9°C from the climate model alone.
“A better understanding of the human perception of risk from climate change and the behavioral responses are key to curbing future climate change,” said lead author Brian Beckage, a professor of plant biology and computer science at the University of Vermont.
Drawing from both social psychology and climate science, the new model investigates how human behavioral changes evolve in response to extreme climate events and affect global temperature change.
The model accounts for the dynamic feedbacks that occur naturally in the Earth’s climate system—temperature projections determine the likelihood of extreme weather events, which in turn influence human behavior. Human behavioral changes, such as installing solar panels or investing in public transportation, alter greenhouse gas emissions, which change the global temperature and thus the frequency of extreme events, leading to new behaviors, and the cycle continues.
Due to the complexity of physical processes, climate models have uncertainties in global temperature prediction. The new model found that temperature uncertainty associated with the social component was of a similar magnitude to that of the physical processes, which implies that a better understanding of the human social component is important but often overlooked.
The model found that long-term, less easily reversed behavioral changes, such as insulating homes or purchasing hybrid cars, had by far the most impact in mitigating greenhouse gas emissions and thus reducing climate change, versus more short-term adjustments, such as adjusting thermostats or driving fewer miles.
Basis for hope
“It is easy to lose confidence in the capacity for societies to make sufficient changes to reduce future temperatures. When we started this project, we simply wanted to address the question as to whether there was any rational basis for ‘hope’—that is a rational basis to expect that human behavioral changes can sufficiently impact climate to significantly reduce future global temperatures,” said co-author Louis J. Gross, director of the National Institute for Mathematical and Biological Synthesis (NIMBioS) at the University of Tennessee, Knoxville, who co-organized the working group that produced the new study.
“Climate models can easily make assumptions about reductions in future greenhouse gas emissions and project the implications, but they do this with no rational basis for human responses,” Gross said. “The key result from this paper is that there is indeed some rational basis for hope.”
That basis for hope can be the foundation which communities can build on in adopting policies to reduce emissions, said co-author Katherine Lacasse, an assistant professor of psychology at Rhode Island College. “We may notice more hurricanes and heat waves than usual and become concerned about climate change, but we don’t always know the best ways to reduce our emissions,” she said. Programs that help reduce the cost and difficulty of making long-term changes or that bring in whole communities, Lacasse says, can help support people to take big steps that have a meaningful impact on the climate.
The new study was supported by the National Science Foundation and was a result of combined efforts of the joint Working Group on Human Risk Perception and Climate Change at the National Institute for Mathematical and Biological Synthesis (NIMBioS) at the University of Tennessee, Knoxville, and the National Socio-Environmental Synthesis Center (SESYNC) at the University of Maryland, where UVM's Brian Beckage has been a long-time collaborator. Asim Zia, a UVM professor in Community Development and Applied Economics and computer science, was also a co-author on the new study.
"Our paper shifts the focus from the uncertainty in the physical climate system to the social components of the system—the human behavior," says Beckage, "and how to best invest resources into the social components that are most likely to have the largest impacts on reducing future climate change."