**Status:**Submitted for Publication
**Citation:**Rose, S.K., 2020. Managing Global Climate Damages: Exploring Trade-Offs. Submitted to Proceedings of the National Academies of Sciences of the United States of America.
The cost of containing climate change rises rapidly with greater ambition to limit global average warming; in particular, for limiting global warming to below 2°C—the goal of The Paris Agreement. Decision-makers and the public need to minimize the full costs to society of climate change, which includes both potential damages from climate change and climate management costs. It is prudent, therefore, to understand and consider the value and trade-offs of pursuing lower global warming levels. Uncertainties, however, make this a difficult question to resolve. Nonetheless, it is a question society cannot ignore. This study considers key uncertainties for managing potential global climate damages and explores the trade-offs in minimizing the full cost to society, which requires a single framework to ensure consistency and coherency in assessing the trade-offs. Specifically, this study uses EPRI’s MERGE model, a global intertemporally optimizing coupled energy-economic and climate model, extended to consider characterizations of potential global climate damages and a range of fundamental global uncertainties from projected socioeconomics to climate to damages. The study evaluates the climate management trade-offs for 180 combinations of assumptions, computing the economically efficient climate pathway that balances marginal mitigation costs and avoided climate damages for each combination. The study evaluates each combination without and with delay in global climate mitigation action, for a total of 360 possible pathways. The study finds a broad range of decision-relevant global emissions and temperature pathways, finding overall that there are important trade-offs and uncertainties to consider in pursuing a global climate goal. In addition, the study evaluates characteristics of pathways to identify the features consistent with efficiently limiting warming to different possible levels, finding, for instance, that efficiently limiting warming to below 2°C is associated with assumptions of more favorable climate system dynamics and relatively extreme damage risk expectations, while delaying climate mitigation to 2030 increases the mitigation trade-offs for society and potentially implies higher levels of warming might be efficient for society, as well as greater mitigation effort. The study’s results raise questions about what we know, likelihoods, and what it might mean when we know more, identifying possibilities and opportunities as knowledge evolves. How uncertainties resolve will impact the trade-offs, options, and planning. Some uncertainties society can control more than others, e.g., mitigation technology, adaptation to lower damage risks, scientific learning to help us understand where we are in the decision space and what trade-offs we need to make. Lastly, there are additional considerations not modeled but informed by this study’s results, including factors affecting mitigation costs (e.g., low carbon R&D, missing costs, and policy design details and coordination), and factors affecting mitigation benefits (e.g., such as adaptation policy, co-benefits, externalities of large deployments, and damage feedbacks). Overall, this study informs strategic planning and stakeholder engagement, as well as research and policy climate risk management deliberations.
**Link to Journal:**See Proceedings of the National Academies of Sciences of the United States of America