National circumstances matter: How climate change vulnerability and political instability affect greenhouse gas coverage in nationally determined contributions

Abstract

Almost 200 countries have submitted their Nationally Determined Contributions (NDCs) in response to the 2015 Paris Agreement's call for net-zero targets. However, critics posit that these collective efforts may fall short of limiting global temperature rise, in part because these countries differ significantly in the scope of greenhouse gases (GHGs) included in their national climate targets. This study investigates why some countries set a narrower set of GHGs in their NDCs than others. Drawing on data from the United Nations Framework Convention on Climate Change (UNFCCC) NDC registry and Climate Watch, we quantify GHG coverage by weighting each gas according to its 100-year Global Warming Potential (GWP-100), thereby capturing relative climate impacts and ensuring alignment with national inventory practices. We then estimate ordinary least squares, ordered logit, and negative binomial regressions to examine the influence of two national-level factors, climate change vulnerability and political instability, on GHG coverage. The results show that both these factors are negatively associated with the scope of GHGs covered in NDCs. These findings underscore that expanding GHG coverage in NDCs requires not only technical capacity building but also institutional conditions that reduce climate change vulnerability and enhance political stability, thereby enabling countries to commit to more comprehensive mitigation goals.