Macroeconomic Implications for Decarbonization Policies and Actions: Proceedings of a Workshop (2025)
Chapter: Modeling Opportunities and Challenges
Modeling Opportunities and Challenges
The second day of the workshop focused on how to integrate modeling insights with policy design, as well as how to predict and address global energy interactions. Kate Calvin of the National Aeronautics and Space Administration (NASA) opened the day with a keynote presentation on the strengths and considerations around different approaches for modeling decarbonization and energy transitions.
KEYNOTE: MODELING DECARBONIZATION
Calvin described how modeling generates pathways that illustrate the effects of different policies. Modeling in the 2022 report of the Intergovernmental Panel on Climate Change (IPCC) Working Group III contribution to the Sixth National Climate Assessment report, for example, showed that there is a wide gap between global emissions under existing policies and pledges, and global emissions in pathways that limit warming (Figure 4) (IPCC 2022), she explained. Cautioning that these model-generated pathways are projections, not forecasts or predictions, Calvin described how they can be tailored to a specific country or to help understand potential outcomes based on a set of defined assumptions. She said that the modeling community is actively working to provide insight into sustainable development by incorporating factors such as employment, water quality, and food access in understanding the implications of various emission-mitigation options.
Researchers use models to conduct feasibility assessments for different decarbonization options, economic sectors, and regions that incorporate geophysical, environmental, ecological, technological, economic, institutional, social, and cultural barriers. The results can help to illuminate the plausible benefits, best-case scenarios, or unprecedented outcomes that may result from particular choices, Calvin added. If the option is a new technology, its costs, efficiencies, constraints, and future adaptations are also incorporated into modeling to project its potential impacts, she explained.
SOURCE: Presented by Calvin on September 13, 2024 (Figure SPM.4 in IPCC 2022).
Models are often used to understand the implications of technology deployment, but the research-development-deployment pipeline is more complex, and Calvin highlighted an example focusing on strategies to abate aviation emissions. For this work, NASA has partnered with industry to advance innovative aircraft designs, adjustments in airport operations, and the development of cleaner jet fuels. She emphasized that while many solutions may be technological in nature, their successful deployment requires more than technological success—in this case, the commercial aviation and airport workers who would need to be appropriately trained and equipped to support and adopt new technologies, processes, and infrastructure.
One limitation, Calvin pointed out, is that sustainability and feasibility assessments are typically highly reliant on national or sector-specific models, suggesting a need to better capture the potential interactions that might occur when one country’s actions have impacts in other places. “If you want to understand some of these global implications, you need these global models,” she said. Calvin closed her remarks by emphasizing the importance of future work to understand how to bring together global models with more national or sector-specific models in order to get the detail needed to understand barriers, while capturing
the global interconnectedness that may be needed to understand the implications in one region or another.
DISCUSSION
Following Calvin’s remarks, participants considered various modeling nuances along with opportunities for improving models and how they are interpreted and used. When asked how the modeling community can best assist decision makers, Calvin said that a 2023 IPCC workshop highlighted the need for modelers to communicate more clearly what is and is not represented by the models and their scenarios, and also to characterize changes beyond temperature and better represent equity outcomes (Intergovernmental Panel on Climate Change 2023). She added that communicating the highly technical details of climate models to non-modelers like policymakers and the general public can be an enormous challenge. “I worry a lot about [whether] people understand the information we’re giving them and how we make that easier to understand,” she stated.
In reply to a question from Boushey, Calvin suggested that it would be useful to reframe discussions of barriers—especially when communicating with policymakers and the general public—to reflect the fact that barriers can also be opportunities or enablers. While specific examples of barriers are helpful planning aids, she added that it is important to be sensitive to regional or sectoral differences.
Several participants focused on the issue of feasibility. In reply to a question about modeling feasibility from Jim Stock, Harvard University, Calvin explained that the IPCC has an official definition of “feasible”1 that covers its multidimensional nature and the difference between modeling projections and real-world outcomes. She added that feasibility is related to plausibility and can also have different quantitative and qualitative definitions. Peng asked how feasibility assessments can incorporate long-term policy or technology options in light of the potential for near-term changes. Calvin replied that feasibility assessments typically incorporate multiple short-term and long-term scenarios for different deployment scales and speeds. In fact, she noted that different pathways can have the same cumulative emissions output but very different feasibility challenges in the near- and long-term.
Lori Hunter, University of Colorado Boulder, asked about opportunities to engage or include social science research in climate and decarbonization modeling. Calvin replied that the intersection of modeling and social science is an active area of research with great potential. Social scientists are increasingly being asked to reflect on models’ output to identify feasibility challenges, and in addition, social or behavioral changes are increasingly included in scenarios to project how the output would be different under different assumptions about behavior. In reply
___________________
to a question from Field, Calvin also noted that the next generation of IPCC models will incorporate the work that has been done to address some of the challenges identified during the previous cycle, including around issues such as equity, national and international differences, and social science insights.
