Climate policy simulator: The National Determined Contribution policy assessment via C3IAM

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A number of policies have been developed in light of increasing concerns about climate change. One recent strategy to a more ambitious global climate governance is Nationally Determined Contributions (NDCs), which are pledges that each ratified party makes to try to keep the global mean temperature increase to below 2°C or 1.5°C and reduce greenhouse gas emissions. However, whether the committed NDCs are enough to achieve the 2°C target is as yet unknown and difficult to estimate given their dependency on highly dynamic socioeconomic development pathways. Professor Yi-Ming Wei from the Centre for Energy and Environmental Policy Research, Beijing Institute of Technology, focuses on exploring the impact of NDCs under different socioeconomic and technological scenarios to provide climate policy makers and the public with a better understanding about climate change and formulate optimum climate mitigation and adaptation policies.

The Paris Agreement of December 2015 was a defining moment in humanity’s fight against anthropogenic climate change. As countries from around the world came together at the UN Framework Convention on Climate Change (UNFCCC) Conference of the Parties (COP21) to agree a path of action, the world looked on. Countries publicly outlined their intended post-2020 climate actions under the new international agreement, known as their Intended Nationally Determined Contributions (INDCs – now NDCs). The climate actions these NDCs commit to will largely determine whether the world achieves the goals of the Paris Agreement. The aim is to keep the increase in global mean temperature below 2°C compared with pre-industrial levels – but the Agreement goes further: to actively pursue efforts to limit this increase to 1.5°C, and to achieve net zero emissions in the second half of this century. It was an international acknowledgement that failing to do so will have a catastrophic effect on Earth.

Nationally Determined Contributions
One of the key successes of the Paris Agreement was the implementation of the NDCs. Submitted by each country, the NDCs laid out how much and in what ways a country would commit to reducing their greenhouse gas (GHG) emissions up to 2030. The NDCs must be updated every five years, although countries can also amend them at any time.

Melting sea ice and rising sea levels are a concern due to increased global temperatures.

The impact of NDCs is strongly related to dynamic socioecomonic development. To support global climate governance and to anticipate how global and regional climate change and GHG emissions might look in the future following the action plans of the NDCs, Professor Wei and a team of scientists took on a challenge. They made real-world comparisons of NDCs under a range of different socioeconomic and technological pathways in order to assess their impact on climate change. One striking conclusion of their work is the gap between the emission reductions resulting from the NDCs and the level needed to hold to the 2°C, not to mention the 1.5°C, target – i.e. the individual country-based plans don’t add up to the global requirements – so much so that Professor Wei states in his 2018 paper, “it is important for countries to do more than their commitment in NDCs, especially in the near term.”

Shared Socioeconomic Pathway scenarios (SSPs)
The concept of Shared Socioeconomic Pathways scenarios (SSPs) is designed to describe future society. The aim is that they can be used as frameworks for climate change studies: they give researchers the ability to explore a range of future societal circumstances which will pose different challenges to tackling climate change.

In a fossil-fuelled development scenario, the use of fossil fuels increases.

The SSPs are intended to cover all plausible scenarios. They are based on five narratives describing broad socioeconomic trends that will potentially affect climate change in different ways:

  • Sustainability, where the world gradually but pervasively moves towards sustainability, improved human wellbeing and equality and with a view to reducing resource and energy intensity;
  • Middle of the road, where development and income growth proceed unevenly and progress is slow in achieving development goals, and environmental systems experience degradation despite resource and energy use declining;
  • Regional rivalry, with resurgent nationalism and increased focus on domestic or regional issues over global, consumption remains high and inequality worsens;
  • Inequality, where societal stratification increases both between and within countries, conflict and unrest spreads and technological advancement slows in all but the most high-tech sectors, and environmental policies focus on local issues in mid-high-income areas, neglecting developments of low-income regions;
  • Fossil-fuelled development, with its contrasting mixture of increasing faith in competitive markets, innovation to effectively manage social and ecological systems (e.g. geo-engineering), coupled with the exploitation of fossil fuel resources and the adoption of resource- and energy-intensive lifestyles around the world.
Increasingly energy-intensive lifestyles around the world make it difficult to meet the Paris Agreement targets.

The role of the NDCs
Professor Yi-Ming Wei used SSPs to explore different global socioeconomic and technological scenarios and assess the effectiveness of the NDCs in combatting climate change under different SSPs. Specifically, he developed China’s Climate Change Integrated Assessment Model (C3IAM), which couples earth system models with socio-economic models, allowing him to assess climate change impacts under SSPs with and without the NDCs, and to see whether the 2°C or 1.5°C target is achievable by 2100. Beyond these targets, his work makes an important contribution to enhancing our understanding of the relationships between the earth system and man-made socioeconomic systems. Being able to foresee how the world might change by 2100 provides us with insight into the mitigation and adaptation difficulties we may face under climate change and allow better and more effective policies that may help avoid a global climate crisis.

The climate actions communicated in these NDCs largely determine whether the world achieves the goals of the Paris Agreement.

Professor Yi-Ming Wei explored what impact the NDCs would have on the world’s energy, economy, and climate systems, and what would change between 2011–2100 under these different scenarios. As well as validating the power of C3IAM, his findings have important implications for global climate governance. This work helps evaluate the impact of the NDCs on climate change.

Alternative energy sources could help combat rising global temperatures.

Although climate change is a global process, each country makes a unique contribution to its course.

Firstly, it was found that under all the NDCs there is no significant change to the total primary energy consumption or its structure, and therefore minimal changes to GHG emissions: “GHG emissions under NDCs steadily increase during this century and almost have the same trend with SSPs without NDCs targets” (Wei et al., 2018).

Secondly, Professor Wei found that even with NDCs in place, temperature rise still occurs in all SSPs. Even under a sustainability scenario, the temperature would increase 1.2°C above the target set out in the Paris Agreement (2°C), indicating that this target is not achievable. If the 2°C level is to be achieved, emissions need to be drastically reduced after 2030. The current NDCs, therefore, do not have sufficient impact on climate change to meet the ambitious targets to minimise global temperature rises.

In a sustainability model, resource and energy intensity is reduced, but temperatures still rise above the 2°C target.

Finally, Professor Wei compared the ambitions of 12 different regions: the strictest carbon targets are set by Japan, Other Branches of the Umbrella Group (OBU), and the European Union (EU) – Professor Wei suggests the NDC targets of these three regions can be rated as ‘sufficient’ to meet the challenge of climate change. In contrast, India, Eastern European CIS excluding Russian Federation (EES), the Middle East and Africa (MAF) and Asia (excluding China, India, and Japan) have set the least restrictive carbon targets, and they can sell additional carbon quota to other regions in all SSPs – their NDC targets are rated as ‘inadequate’. Clearly NDC targets alone are not adequate – there is a need to improve the targets of this group of countries. But there is also plenty of scope for the ‘sufficient’ countries to tighten up their targets. Indeed, if the Paris Agreement is to stand any chance of meeting its 1.5°C or 2°C target, the mitigation commitment of all ratified parties should be urgently upgraded to close the gap.

SSP1_RCP5.5_GHG emissions (Kyoto gases)

Towards global climate governance
Professor Wei’s research suggests that the current NDCs do not have a sufficient impact on climate change to meet the 2°C temperature increase target. Based on these findings, a number of policy recommendations can be made. It is essential for decision makers to bring the climate agenda and development strategies together at both domestic and international levels. Although climate change is a global process, each country makes a unique contribution to its course. Professor Wei’s research highlights that there are long-term challenges associated with keeping temperature increases below the 2°C level, even with NDCs in place. It is thus important for more ambitious reduction targets to be set when countries revise them after 2020. This could also be aided by setting higher carbon prices, thus lowering the dependence upon fossil fuels. Additionally, to combat climate change, the development of low carbon technology and renewable energy should be given priority, including a consideration of the public acceptance of using these fuels.

What have been your most surprising results?

NDCs lead to no evident change in total primary energy supply and GHG emissions compared to the case without NDCs. A temperature rise would occur in all SSPs even with the NDCs in place, which is 3.20°C in SSP1, 3.48°C in SSP2, and 3.59°C in SSP3. Even under a world reigned by a green growth paradigm, the temperature would further increase by 1.2°C compared with 2°C target. All ratified parties should urgently enhance their mitigation commitment to close the emission gap towards the 1.5°C or 2°C target, especially for India, Eastern European CIS excluding Russian Federation (EES), Asia (excluding China, India, and Japan) and the Middle East and Africa (MAF).


  • Wei, Y. M., Han, R., Liang, Q. M., Yu, B. Y., Yao, Y. F., Xue, M. M. & Mi, Z. F. (2018). An integrated assessment of INDCs under Shared Socioeconomic Pathways: an implementation of C3IAM. Natural Hazards, 92(2), 585-618.
Research Objectives
Prof Yi-Ming Wei’s research is focussed on energy economics, climate policy, CO2 emission and energy and climate policy modelling, providing key scientific evidence to tackle the challenges of adapting to and mitigating climate change.

The authors gratefully acknowledge the financial support from China’s National Key R&D Program (2016YFA0602603) issued by the Ministry of Science and Technology of China, and the National Natural Science Foundation of China (Nos. 71521002, 71603020 and 71642004).


  • Department of Economics, State University of New York at Binghamton, Binghamton, NY 13902,USA
  • The National Climate Center of China Meteorological Administration, Beijing 100081, China
  • School of Advanced Agriculture Sciences, Peking University, Beijing 100871, China
  • The National Information Center of National Development and Reform Commission, Beijing 100045, China
  • The Bartlett School of Construction and Project Management, University College London,
    London WC1E 7HB, UK

Yi-Ming Wei is a Distinguished Professor of Energy and Environmental Economics, Beijing Institute of Technology (Top 1% authors in the field of Environmental Economics at IDEAS). His recent research and teaching focus on Energy Policy and Energy Economics, CO2 emission and Climate Policy, Energy and Climate Policy Modelling.

Prof Yi-Ming Wei
Center for Energy and Environmental Policy Research,
Beijing Institute of Technology,
School of Management and Economics,
Beijing Institute of Technology,
No.5 Zhongguancun South Street, Haidian District,
Beijing 100081 P.R. China

T: +86 010 68918009

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