Countries need to be increasingly ambitious in their commitments to renewable energy and to reducing energy-related carbon dioxide (CO2) emissions. The first round of national contributions (NDCs) promised under the Paris Agreement proved insufficient to meet climate targets. Annual costs of mitigating the implementation of National Climate Plans (NDCs) are projected. As part of the Paris climate agreement, countries have submitted national (planned) contributions that contain proposals to reduce greenhouse gases beyond 2020. In this contribution, we apply the IMAGE Integrated Assessment Model to estimate the annual mitigation costs of achieving NPN reduction targets and the additional costs if countries set targets well below 2 degrees Celsius and “continuing efforts” at 1.5 degrees Celsius, in line with continued global warming. We found that mitigation costs are very sensitive to socio-economic assumptions: among the assumptions of the Common Socio-Economic Pathway 3 (SSP3) on slow economic growth, rapid population growth and high inequality, the overall cost of mitigation to reach NDC diehards is estimated at $135 billion by 2030, more than double the sustainable socio-economic assumptions of SSP1. In addition, we estimate that the additional costs associated with the full implementation of conditional NDCs are considerable and range from $40 billion to $55 billion, based on socio-economic assumptions. Among the top ten largest emitting economies, Brazil, Canada and the United States are expected to have the highest share of GDP for the implementation of conditional NCCs, while costs for Japan, China, Russia and India are relatively low. Approval of the Emissions Trading System could significantly reduce overall costs, by more than half for NDC diehards and by almost half for conditional NDCs. Finally, efforts to reduce the cost of achieving emission levels by 2030, which are compatible with 2oC signals, would be at least three times higher than the cost of achieving conditional NDCs – while reductions must be twice as large. At 1.5 degrees Celsius, the cost would be 5-6 times higher. Costs are very sensitive to different socio-economic assumptions.

The new NDC cycle from 2020 is an important opportunity to strengthen renewable energy targets. The letter from the International Renewable Energy Agency (IRENA), published at the COP25 World Climate Conference at the end of 2019, highlights the possibility of combating the climate threat, decarbonising energy consumption while achieving several Sustainable Development Goals (SDGs). In terms of results, there are large differences in the cost of achieving NDCs between countries. The cost of conditional NDCs is estimated to be between $97 billion and $191 billion by 2030. The cost of obtaining 2 degrees Celsius is 3 to 3.5 times the cost of obtaining conditional NDCs.