Behind the UN Climate Pledge Analysis
Calculations for the Climate Scoreboard are made by taking the Nationally Determined Contributions (NDCs) received to date by the UN and analyzing them with C-ROADS, a scientifically reviewed climate simulator that is designed to aggregate the proposals of countries and country groups to calculate long-term global climate impacts such as carbon dioxide concentration and temperature. C-ROADS was built by Climate Interactive, Ventana Systems, and the MIT Sloan School of Management and is available to download for free. C-ROADS is calibrated to the Intergovernmental Panel on Climate Change’s (IPCC) Fifth Assessment Report results.
Graphical summary of climate pledges and additional scenarios
Below is the summary graph and table that shows calculations behind the Climate Scoreboard as well as other important climate indicators.
- NDC Strict – No change after national contribution pledge period: 3.5°C (6.3°F);
- Ratchet 1 – Plus, pledged reductions continue after pledges end (2025 or 2030): 3.2°C (5.7°F);
- Ratchet 2 – Plus, China includes other GHGs and reduces emissions after they peak in 2030 at up to 2%/year: 3.0°C (5.4°F);
- Ratchet 3 – Plus, other developing countries without commitment also peak by 2035: 2.7°C (4.8°F);
- Ratchet Success – Plus, all countries peak before just 2030 and then reduce steadily: 1.8°C (3.2°F).
- 1.5°C – Plus, developed countries make deeper cuts and all others peak no later than 2025 and then reduce steadily: 1.5°C (2.7°F).
Assumptions about the UN climate pledges:
In order to assess the cumulative impact of all the pledges and offer a projected temperature in 2100, we had to make some assumptions that are highlighted below. Many points are also explained in our FAQs.
- We only include Nationally Determined Contributions (NDCs) submitted to the UNFCCC that are unconditional.
- For the “NDCs Strict” scenario, which is the one displayed on the Scoreboard, we assume no continued reductions by developed countries and no further action from developing countries post end of 2025-2030 pledge period. Specifically, there are four primary types of pledges, and we make the following assumptions for them:
- Absolute reductions – For countries that are making absolute emissions reductions, we assume that emissions stay constant after 2025-2030 (the end of the pledge period), unless an NDC states otherwise. For example, Canada has offered to reduce their greenhouse gas emissions 30% below 2005 levels by 2030. After that, given there is no formal post-2030 pledge, we assume that Canada’s emissions do not increase nor continue to decrease, but stay constant at that new level.
- Relative to a reference scenario – For countries that are reducing emissions from a reference scenario or business as usual (BAU) level, we assume they stay at the target level below the reference scenario after the pledge period. For example, Kenya has pledged to reduce their emissions 30% below their BAU by 2030. After 2030, we assumed that the emissions would continue to stay 30% below their Reference Scenario. Since the Reference Scenario is increasing, however, emissions increase at the same rate as the Reference Scenario.
- Peaking – Emissions grow until year target peak year. For example, China has said they will peak their CO2 emissions by 2030. We assumed that the rate of growth in emissions would slow starting in 2015, approaching a flat trajectory gradually. After the peaking date, emissions would stay level. (Note: other greenhouse gas emissions continue to increase given they were not covered by China’s pledge).
- Emissions intensity reduction – Change in emissions relative to the GDP of the country. For example, India reducing emissions intensity 40% (we took the low end of the pledge, which was 35-40%) by 2030. Up to 2030, we calculate emissions by using the GDP growth. After 2030, emissions intensity stays 40% below the growing GDP.
- In the “Ratchet 1” case, we assume some continued action and reductions after the period for current NDCs end:
- Absolute reductions – Countries with absolute reductions will continue to reduce emissions post-pledge period at the same annual fractional rate as in their previous pledge period. For example, U.S. GHG emissions would continue to drop 3% per year after 2025.
- Relative to a reference scenario or BAU – Emissions stay flat at the level achieved at the end of the pledge period.
- Peaking – Same as “NDCs Strict.” Emissions stay level.
- Emissions intensity reduction – Same as “NDCs Strict.” Emissions stay at that percentage below the BAU.
- The regional distribution of emissions reductions in the ratchet scenarios is one representation of many possible approaches.
- We assume that proposals will be fully implemented, in accordance with the dates specified in the NDC.
- Some countries have made proposals for specific actions (rather than for emissions targets). If we don’t have a good estimate for the impact of those actions on emissions then we don’t include the action in our analysis.
- We assume emission reductions cover all GHG emissions unless specified otherwise. In some cases for smaller countries, the structure of the model requires us to assume that they take proportional action on other greenhouse gases.
- Read more about the assumptions behind the Ratchet Success Scenario.
Assumptions inherent in C-ROADS:
- The C-ROADS “reference scenario” (often called “business as usual”) is based on the RCP 8.5 scenario from the Intergovernmental Panel on Climate Change’s (IPCC) Fifth Assessment Report (AR5) report.
- C-ROADS uses a climate sensitivity of 3 (that is 3°C of temperature increase for a doubling of CO2 concentration.)
- There are positive feedback loops in the real climate system that are not modeled in the current version of C-ROADS. Additionally, C-ROADS is based upon and calibrated to the results of models from the IPCC’s AR5.
- C-ROADS allows inputs of emissions reductions targets for 12 countries (U.S., Japan, Russia, Canada, Australia, South Korea, China, India, Brazil, Mexico, South Africa, Indonesia) and three blocs of countries (EU, “other developed” and “other developing”). For the 12 countries with individual controls, we adjust that country’s modeled emissions from a reference scenario (based on the IPCCs RCP 8.5 scenario).
- NDCs accounted for in “other developed” or “other developing” were calculated in accordance with that country’s percentage of emissions from the entire group. In other words, each nation’s proposals are scaled to their actual share of emissions within their bloc.
- For more information on C-ROADS, please consult the peer-reviewed journal article or C-ROADS Reference Guide.
Credits and Contact Information
The Climate Scoreboard and associated images are copyright 2015 by Climate Interactive, but you are welcome to use the unaltered Scoreboard image, data, and Flash animation in any form.
Inquiries, contact info [at] climateinteractive.org.
Resources on the tools behind the Climate Scoreboard analysis:
- Request a C-ROADS download
- Watch a video about the scenarios
- C-ROADS Frequently Asked Questions (FAQs)
- Comments from C-ROADS users
- C-ROADS Scientific Review one-page summary
- C-ROADS Technical Reference Guide on the simulator, including simulation purpose, structure, parameters, test results, and bibliography
- A peer-reviewed journal article on C-ROADS. Sterman, John, Thomas Fiddaman, Travis Franck, Andrew Jones, Stephanie McCauley, Philip Rice, Elizabeth Sawin, Lori Siegel. (2013) Management Flight Simulators to Support Climate Negotiations. Environmental Modelling and Software.
- A second Journal article on C-ROADS published in System Dynamics Review July 2012. (translated into Chinese)
- Press coverage of C-ROADS and other Climate Interactive tools.
We are fortunate to have many colleagues in the field of adding up climate mitigation proposals to assess their sufficiency, aggregate their contributions, and see what more is needed. Explore other climate trackers.