Marginal Emissions Pathways: Drivers and Implications

.g., amount of clean technology in the baseline and/or added , policy driving the expansion) can give rise to significant prediction errors. Similarly, with respect to decentralized efforts to address climate change such as the Paris Agreement, simple estimates of collective mitigation, such as the sum of all countries’ mitigation pledges, are unlikely to be accurate which, in turn, may make it difficult to attribute each country’s mitigation contribution. Numerically, we show that failing to account for non-constant marginal emissions can give rise to predicted changes in emissions that are of the wrong sign and/or that diverge by an order of magnitude from true estimates. Due to differences in the shapes of the marginal emissions pathways, these errors differ drastically across policies. Taken together our findings illustrate the potential for sizeable harm from implicitly or explicitly ignoring non-constancy in marginal emissions pathways when predicting or attributing mitigation from non-marginal changes in a clean technology.