IAMC Advisory Council Meeting – March 18th, 2024

Detlef van Vuuren briefed the AC on work by the Scenarios Scientific Working Group (SWG) on the latest developments in new Shared Socioeconomic Pathways (SSPs). The Scenarios SWG have embarked on an update of the SSP projections. The SWG decided not to undertake a fundamental revision of the SSP structure. Rather it focused on updates to models and parameters. To date update to population and economic development have been completed. Updates to urbanization is on fast-track review. Spatial downscaling is forthcoming. New poverty and equity elements are to be added as well as an extension explorer. The IAMC SWG is coordinating with climate modelers to inform Climate Model Intercomparison Project 7 (CMIP7). In contrast to earlier SSP scenarios, which provided CMIP with atmospheric concentrations of relevant atmospheric constituents, CMIP7 will be given emissions and not concentrations. Both processes are on accelerated timelines to inform IPCC assessments.

The AC expressed enthusiasm for the SSP updates. The AC also expressed a desire for more frequent updates. One proposed path forward was the development of a parallel process in which annual updates would be released based on the prior major update. However, in parallel, an overall review of the SSPs, their architecture, number, and definition would proceed on a longer time step with regular major releases.

There was also interest in the development of scenarios that included the impacts of climate change as well as the drivers of climate change. Similarly, there was a desire for closer integration between the scenario developers and the climate impacts community.

Finally, there was interest in extending the SSPs to include a broader suite of issues including for example, equity, convergence, and biodiversity.

The AC was asked for comment on the topics that might be the basis for keynote speakers and for research sessions. Recommendations included:

• Equity, income distribution, convergence as applied to a wide range of considerations including income, energy, health and water.
• Governance
• Geopolitics, including assessments of the current state of politics, with an emphasis on how they affect climate change. It was noted that the IAMC meeting would occur immediately after the U.S. national elections and would be an opportunity for stock taking.
• Negative emissions and the role of carbon dioxide removal technologies

The AC recommended engaging with user communities such as the private sector, and/or city mayors.

The AC also noted the importance of the IAMC community’s work for informing the Global Stocktake process.

IAMC Advisory Council Liaison Jae Edmonds