Addressing Uncertainty in Developing Long-Term Greenhouse Gas Emission Reduction Strategies

The Paris Agreement invites individual countries to "formulate and communicate long-term low greenhouse gas emissions development strategies" consistent with the agreement's global goal of reducing net human greenhouse gas (GHG) emissions to zero by the second half of the 21st century. These long-term strategies (LTSs), also known as Midcentury Strategies (MCSs), generally focus on pathways to 2050 and aim to complement each nation's nationally determined contributions (NDCs). NDCs have a much shorter five-year time horizon and must be updated every five years. In principle, a nation might meet its long-term Paris commitments without an LTS by just stringing together a sequence of short-term NDCs. But such an approach seems unlikely to succeed. Without being part of an envisioned pathway into the longer-term future, a series of short-term steps may prove insufficiently ambitious, may get stuck in blind alleys, and fail to take advantage of unexpectedly promising opportunities.