A CGD note. Marginal abatement cost curves, which suggest the cheapest approaches to reducing carbon emissions, are out of favor in international climate finance discussions because they are not good tools to use when thinking about systemic and urgent change. On the other hand, international
financing studies based on adding up the investment requirements linked to an emissions path to 1.5 degrees of warming produce historically implausible numbers and endanger existing development finance. To close the gap, we need to push the cost curve down (through technology
advance) and lower the price of finance (through scalable multilateral development bank support) while protecting development finance and focusing it on where it is most needed: the poorest countries suffering the most from climate change.