Mind the Gap: Applying Integrated Assessment Models to Inform International and National Climate Policy on Bridging the Emissions Gap

World leaders signed the Paris Agreement in 2015 to combat climate change. They agreed to limit global warming to ‘well below’ 2 °C relative to pre-industrial levels and strive to limit it further to 1.5 °C. The Agreement has a bottom-up architecture: it is up to the 192 Parties (191 countries plus the European Union) to formulate their targets and policies. At the moment, the sum of these individual targets for 2030 is not enough to reach the global emissions needed to meet the Paris climate goals. This difference is called the ambition gap. Moreover, current policies implemented by the countries are not yet sufficient to meet their pledged ambitions, which is called the implementation gap. This thesis addresses three main questions: 1) How large are the ambition and implementation gaps?; 2) When can countries achieve net-zero greenhouse gas emissions?; and 3) How can the gaps be bridged? Integrated Assessment Models were used at both the global level and the level of individual countries to answer these questions. We found that the global ambition and implementation gaps are roughly similar in size, so both need closing. To close the ambition gap, net-zero emission targets could be, if fully implemented, an important step in the right direction. However, they will need to be aligned with ambitious, short-term targets and backed up by climate policies to avoid widening of the implementation gap. To that end, replicating policies that have been successful in some countries (good practice policies) could be a stepping stone.