Levin in why INDC studies are reaching different temperature estimates
On Friday, the UNEP Emissions Gap Report joined a series of studies released over the past few weeks assessing how much countries’ recent climate change announcements, or intended nationally determined contributions (INDCs), contribute to combating warming. Collectively, the studies make it clear that the INDCs make a substantial contribution to bending the global emissions trajectory below our current path. However, the studies also show that without additional action, the INDCs are insufficient to limit warming to below 2°C and avoid some of the worst climate impacts. The details of the Paris Agreement are, therefore, very important to help achieve an additional bending of the emissions trajectory before 2020, to support the implementation of the INDCs and to ensure greater ambition after 2030.
While all of the studies support these general conclusions, their numbers differ both in terms of projected temperature increase relative to pre-industrial levels, as well as emissions levels in 2025 and 2030. Below we discuss the results of various studies assessing the INDCs and highlight differences among their underlying assumptions, which can help explain why some details of their findings diverge.