Options Magazine, Winter 2022: Equitably sharing the costs of mitigation is vital to ensure a just transition to a net-zero world. By calculating the impact of national policies on global emissions and exploring different effort-sharing schemes, the ENGAGE Project is at the forefront of developing feasible solutions.

While the number of countries with net-zero emissions targets has grown to more than 70, current national plans still fall short of what is required to meet the Paris climate goals. Governments need to ramp up their commitments significantly to limit global warming to well below 2°C compared to pre-industrial levels. However, developing nations frequently lack the resources to implement effective mitigation measures, despite bearing the brunt of the effects of climate change.

The Exploring National and Global Actions to Reduce Greenhouse Gas Emissions (ENGAGE) Project, a consortium comprising nearly 30 partners and coordinated by IIASA, has developed a standardized modeling framework to assess the impact of national commitments on global emissions and identify policy mixes that maximize co-benefits and minimize tradeoffs. Two IIASA policy briefs highlight the most important findings thus far.

Based on four different models, the researchers calculated global emission pathways for five broad scenarios until the end of the century, ranging from maintaining current policies – thereby further driving up emissions – to globally reaching the 1.5°C temperature goal in a cost-optimal way, ignoring all stated policy. The latter scenario entails a coal phaseout and a rapid cut in oil and gas, coupled with substantially extending renewables. However, different
national economies and resource availabilities require different strategies.

The policy briefs highlight that deep decarbonization requires international burden-sharing. To develop solutions that are fair, affordable, and feasible, the researchers are modeling several sharing approaches based on different ethical principles. These include mitigation depending on per-capita GDP, future national emissions that are proportional to historical emissions, as well as a formula that includes past emissions, GDP per capita, and income distribution. Each approach was first modeled at the national level and subsequently examined in an international scenario.

The model results show that most effort-sharing schemes imply only a slight global GDP reduction by 2050. While fairness-based emissions trading might cut costs even further, the scale of international money transfers might be a hindrance. A combined approach might be the best solution: a climate club of willing nations takes ambitious action, trading emissions among themselves, while countries outside of the club make a least-effort contribution. In sum, the analyses show that every effort-sharing scheme reduces the unfair burden on developing nations. Countries nonetheless need to increase their nationally determined contributions in order to meet the Paris goals.

“In earlier ENGAGE research we found that faster near-term emission reductions avoid feasibility concerns in the long run and can even be economically beneficial. Ratcheting up climate ambition now really helps to achieve targets later. However, ambition alone is not enough. Improving the quality of institutions could make an essential contribution to the implementation of climate policies,” concludes Bas van Ruijven, one of the project coordinators and Research Group leader of the IIASA Sustainable Service Systems Group.

by Jakob Angeli