Climate Change

DOI: 10.53289/TFAW4050

The role of science in delivering international progress

Jim Skea

Jim Skea CBE is Professor of Sustainable Energy at Imperial College London, with research interests in energy, climate change and technological innovation. His current main role is as Co-Chair of IPCC Working Group III for the 6th assessment cycle. He was Research Director of the UK Energy Research Centre 2004-12 and Director of the Policy Studies Institute 1998-2004. He was a member of the UK Committee on Climate Change from its inception in 2008 until 2018 and is currently the Chair of Scotland’s Just Transition Commission.


  • Science plays a crucial role in underpinning intergovernmental action on climate
  • There is still work to be done simplifying and clarifying scientific messages
  • Lifestyle and behaviour are explicitly included in an IPCC report for the first time
  • The consequences of overshoot need to be better addressed
  • A global stocktake of progress towards meeting the Paris Agreement goals, supported by scientific evidence, will be completed in 2023.

Science is absolutely crucial at COP27. The Intergovernmental Panel on Climate Change (IPCC) has regular meetings with the UNFCCC Secretariat through its Subsidiary Body for Scientific and Technological Advice. One priority has been to map out the way that science (and IPCC in particular) could interface with the negotiations during the conference. There would be a Science Day maintaining the tradition established in Glasgow, but also an Earth Information Day focussing on atmospheric observations and the contribution these can make to climate action.

The sessions at the IPCC pavilion are the result of negotiations between IPCC, the World Meteorological Organisation (WMO) and the MERI Foundation. IPCC ended up with 20 slots – eight for Working Group II on inputs, eight for WG III on mitigation, then two each for WG I and the Task Force on Inventories.


The mitigation sessions in the IPCC pavilion are all of importance to policymakers. To take two in particular – scenarios and the reconciliation of different estimates of emissions – both play into the negotiations.

It has been said that scientists have done a great job of confusing policymakers about scenarios. The IPCC does not develop its own scenarios, it assesses those produced by others and there are thousands of them. It is the IPCC’s task to distil them and present clear messages to policymakers. However, with the WG I report, the policymakers cut through the maze of terminology and said they wanted a simpler classification into ‘very low, low, intermediate, high and very high’ categories of emissions.

There are two sessions on scenarios at the pavilion. The first simply presents what has been done in order to help people to understand the work. The second focusses more on engagement with

policymakers, asking them what they want us to do and how they want scientists to construct scenario architectures in ways that are meaningful. That will then lead to an IPCC workshop in April 2023, where recommendations will be made for the next assessment cycle.

On reconciling different greenhouse gas emission estimates, there is a 5 Gigatonne difference between the emissions estimates submitted by countries under the Framework Convention on the one hand and the emissions estimates used in global models on the other. Note that 5Gt is 10% of global emissions. This is troubling.

The discrepancy is related primarily to carbon dioxide fluxes from land. Developing countries that are trying to produce net zero commitments may struggle to understand what net zero means because of that 5Gt difference. There is, therefore, a session with policymakers to try and explain what the differences are and how they can be reconciled.

The main differences are the distinction between managed and unmanaged land, as well as between direct human intervention as opposed to indirect natural effects. The inventories estimate these differently from the global models. The difference is understood but it is not easy to communicate: however, it does have a significance for the setting of net zero targets.

Other mitigation events on the pavilion include issues around economics and social aspects. For the first time in an IPCC report, lifestyle and behavioural issues have been explicitly highlighted: there is currently a great deal of interest in these.

While IPCC is also hosting a session on managing just transitions, the International Labour Organisation has a separate pavilion solely devoted to this issue.

Colleagues in WG II are hosting events on impacts, adaptation and vulnerability. These include nature-based solutions, as well as specific concerns about, for example, the situation of small island states.

Science has been core to the sessions at COP27 


One event, which features collaboration between working groups, is on the question of overshoot. Many of the projections for the 21st century envisaged 1.6-1.7 degrees of warming, while taking carbon dioxide out of the atmosphere and so cooling down again. So the consequences of overshoot for impacts, adaptation and vulnerable systems still need to be explored. Dealing with the impacts when temperature reaches a peak and then comes down again is also something that needs to be better understood.

On Earth Information Day, there is a session on observations for adaptation and early warning systems – and, interestingly, a session on Earth observation for mitigation. That is designed to help measure the impact of mitigation measures and emission inventories by earth observation, rather than simply multiplying activity by an emission factor to arrive at an estimate. There is a special event on gender-related aspects of the latest Assessment Report, including ways that gender balance could be improved within negotiations and scientific processes.

A high-level ministerial roundtable is being held on ‘pre-2030 ambition’. It is clear that there is an emissions gap: the pledges made to date do not limit warming to 1.5˚C and there is also an implementation gap because the policies on the ground do not even allow these pledges to be met. Both issues have to be addressed.

Global stocktake

Under the Paris Agreement, a global stocktake has to take place every five years, with the first one due in 2023. The first technical phase is already under way, making a big demand on IPCC and other scientific programmes to provide evidence to that process.

A set of roundtables at COP27 cover mitigation, adaptation and means of implementation. The UNFCC has managed to get the term ‘transformation’ into the agenda of the mitigation roundtable. This is a major triumph: in IPCC we have struggled to include this term in agreed texts.

COP27 will have some focussed exchanges on ‘intersections’. These are, essentially, points at which mitigation, adaptation and means of implementation cut across each other. There are many responses to climate change that have mitigation and adaptation outcomes.

The organisers have created a ‘World Café’ session where people move between about 20 tables to talk about specific topics. This has worked really well in the past. It is a way of getting insights from policymakers, where they are not constrained by the formal nature of the negotiation sessions.

One big conclusion from all the work that has been going on is that negotiators are hungry for scientific advice. One quote, that came out of a preparatory meeting was that the process was not just about keeping 1.5 alive, it was also about keeping the science alive.