The IPCC Fourth Assessment Report noted that Annex I countries’ targets for 2020 would need to be 25% to 40% below the 1990 level to be in line with the 2° Celsius (C) target. What is the equivalent range for 2030? Over 40 studies that analyse future greenhouse gas emissions allowances or reduction targets for different regions based on a wide range of effort-sharing approaches and long-term concentration stabilization levels have been compared.
This updates previous work undertaken for the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). Regional reduction targets differ significantly for each effort-sharing approach. For example, in the Organisation for Economic Co-operation and Development (OECD) 1990 regions, new proposals that emphasize the equity principles of responsibility, capability, and need, and those based on equal cumulative per capita emissions (carbon budgets), lead to relatively stringent emissions reduction targets.
In order to reach a low concentration stabilization level of 450 parts per million CO2 equivalent, the allowances under all effort sharing approaches in OECD 1990 regions for 2030 would be approximately half of the emissions of 2010 with a large range, roughly two-thirds in the Economies in Transition (EIT), roughly at the 2010 emissions level or slightly below the Asia level, slightly above the 2010 level in the Middle East and Africa and well below the 2010 level in Latin America. For 2050, allowances in OECD 1990 regions and Economies in Transition (EIT) countries would be a fraction of today's emissions, approximately half of 2010 emission levels in Asia, and possibly less than half of the 2010 level in Latin America.