Key points

• Current pledges and policies to reduce greenhouse gas emissions put the world on a high-risk climate track. 
• In the most optimistic assessment, where all current climate pledges and policies are delivered, temperatures are projected to rise by 2.0°C over the 21st century. 
• In assessments where only pledges with a high confidence of delivery are included, projections put us on track for temperature increases of 2.7°C over the 21st century. 

Reducing greenhouse gas emissions: pledges or policies?

The Paris Agreement, with its commitment to “pursue efforts to limit the temperature increase to 1.5°C above pre-industrial levels” has been ratified by almost every country in the world. In order to meet this ambition, countries have put forward various pledges (promises of future action) and translate these into policies (where governments have already legislated to affect reductions in emissions).

Pledges:

• Nationally Determined Contributions (NDCs): Under the Paris Agreement, countries are required to develop national climate pledges that set out what their contribution to reducing greenhouse gas emissions will be. These are usually short- to medium-term plans (to 2030) and must be updated and “ratcheted up” at least every five years. For example, the UK’s NDC includes a commitment to reduce emissions by at least 68% by 2030 (compared to 1990 levels). 
• Net Zero targets: More than 70 countries also have longer-term net zero targets. For example, the UK has a target to reach net zero greenhouse gas emissions by 2050.

Policies:

• Emission reduction policies: these are legislative decisions, executive orders or equivalent that represent active steps that countries are taking to reduce emissions. Examples of policies that the UK has implemented include (among many others) the Boiler Upgrade Scheme heat pump grant, Building Regulations minimum energy performance standards and Contracts for Difference to support low-carbon electricity.

How credible are net zero targets?

Although many countries have net zero targets, some are more credible than others. One way of assessing the credibility of climate pledges is to use the following criteria:

1. Is the target legally binding? Legally binding targets are less susceptible to changes resulting from political turnover and tend to promote cross-government coordination.
2. Is the target accompanied by a published implementation plan? Implementation plans are crucial to clarify which changes are needed, identify necessary resources and assign responsibility for action. 
3. Is the country’s current policy trajectory already putting its emissions projections on a clear downward path by 2030? Domestic policies provide a more reliable indication of the level of action a country is likely to make (although even these are still subject to successful implementation). 

In the assessment in Table 1, ‘credible’ net-zero pledges are defined as those that meet criteria 2 and 3 from this list.

What level of temperature rise is expected based on current pledges and policies?

Projections of likely future levels of global warming depend on how much confidence we have that countries will deliver on the pledges they have made. If we are pessimistic and assume that the less credible targets will not be delivered, then we can expect to see more modest reductions in greenhouse gas emissions. If, on the other hand, we are optimistic and assume that everyone delivers on the promises they have made, then we can anticipate a larger reduction in emissions.  

Table 1 shows the results of future global warming projections based on five different scenarios assessed in the UNEP’s most recent Emissions Gap Report. These range from the most pessimistic scenario—where only current near-term domestic policies are delivered—through to the most optimistic view where all net-zero targets and all NDCs come through. 

Table 1: Future global warming scenarios based on current global pledges and policies

Scenario	Peak warming above pre-industrial levels throughout the twenty-first century (°C)*
Current policies continuing (most conservative scenario)  Climate mitigations that have been adopted and implemented as at November 2022	3.0°C
Unconditional NDCs continuing  Current policies plus all NDCs that do not depend on explicit external support	2.9°C
Conditional NDCs continuing  Current policies all NDCs that do not depend on explicit external support plus NDCs for which implementation is contingent on receiving international support such as finance, technology transfer and/or capacity	2.5°C
Unconditional NDCs and credible net-zero pledges Current policies all NDCs that do not depend on explicit external support plus  net-zero pledges after 2030 that have implementation plans and where current policies put short-term emissions on a downward path.	2.5°C
Conditional NDCs and all net-zero pledges (most optimistic case) Current policies   all NDCs that do not depend on explicit external support   NDCs for which implementation is contingent on receiving international support such as finance, technology transfer and/or capacity plus  All net-zero or other long-term low emissions development strategy pledges	2.0°C

*projection with a 66% chance of occuring

Source: United Nations Environment Programme (2023). Emissions Gap Report 2023: Broken Record – Temperatures hit new highs, yet world fails to cut emissions (again). Nairobi.  

The scenarios show that we are on a high-risk climate track. Even under the most optimistic scenario, the projected temperature increase is greater than the 1.5°C goal of the Paris Agreement. More worryingly, only a small number of net-zero pledges currently meet the criteria to be considered as ‘credible’.

The need for credible climate mitigation action 

These results demonstrate that there is no time to lose. Countries must show at COP28 how they plan to cut emissions in line with a 1.5°C pathway, including by setting out ambitious plans to rapidly move away from fossil fuels and scale up clean alternatives to reduce emissions across all parts of the economy.  

Setting, implementing and achieving emissions reduction targets is the best way to hedge against the potential disastrous impacts of climate change. 

The UK’s policies and pledges 

The UK has a legally binding long-term target to reach net zero greenhouse gas emissions by 2050. It also has an NDC commitment to reduce emissions by at least 68% by 2030 (compared to 1990 levels). 

The Carbon Budget Delivery Plan, published in March 2023 sets out the policies for delivering emission reductions to 2037. The independent Climate Change Committee (CCC), in its annual report to Parliament, said that its confidence in the UK meeting its NDC target had decreased. After Prime Minister Rishi Sunak announced further changes to net zero plans in September 2023, the CCC’s updated assessment concluded that UK remains unlikely to meet its NDC target.  

Authors and contacts 

This background briefing was written by:  

• Professor Joeri Rogelj, Director of Research, Grantham Institute, Imperial College  
• Dr Robin Lamboll, Centre for Environmental Policy, Imperial College  
• Jenny Bird, Campaign Manager, Grantham Institute, Imperial College

Media enquiries: grantham.media@imperial.ac.uk   
Policy enquiries: j.bird@imperial.ac.uk 

Further reading

• United Nations Environment Programme (2023). Emissions Gap Report 2023: Broken Record – Temperatures hit new highs, yet world fails to cut emissions (again). Nairobi. 
• Rogelj, J., Fransen, T., den Elzen, M.G., Lamboll, R.D., Schumer, C., Kuramochi, T., Hans, F., Mooldijk, S. and Portugal-Pereira, J., 2023. Credibility gap in net-zero climate targets leaves world at high risk. Science, 380(6649), pp.1014-1016. 
• van de Ven, D.J., Mittal, S., Gambhir, A., Lamboll, R.D., Doukas, H., Giarola, S., Hawkes, A., Koasidis, K., Köberle, A.C., McJeon, H. and Perdana, S., 2023. A multimodel analysis of post-Glasgow climate targets and feasibility challenges. Nature Climate Change, pp.1-9. 
   

 

[Image was taken by Thomas Angus, Imperial College London]