The ESM2025 project’s Second Science-to-Policy Briefing: Key climate insights and policy implications

The Earth System Modelling 2025 (ESM2025) project convened its second Science-to-Policy Briefing in November 2023. The project is dedicated to advancing Earth System Models (ESMs) and enhancing their predictive capabilities. This helps refine our understanding of the complex interactions within Earth systems, particularly in the context of a changing climate. 

By improving the precision and reliability of ESMs, ESM2025 supports policymakers in developing informed strategies to mitigate and adapt to climate change. 

This follow-up session was organised to build on the discussions from the first briefing, focusing on the latest scientific findings and their relevance for policy development. 

This second briefing was organised to disseminate new, policy-relevant insights that have emerged from ongoing research and to address critical questions concerning global climate goals.

The event was crucial for connecting recent research outcomes from the 4C, PROVIDE, CONSTRAIN, and ESM2025 projects with the pressing needs of policymakers.

Key insights from the briefing:

• Potential decline in carbon sink efficiency: One of the primary concerns raised during the briefing was the potential reduction in the efficiency of natural carbon sinks—such as forests and oceans—as global temperatures rise. These natural systems currently absorb a significant portion of anthropogenic CO2 emissions, but their capacity may decrease as the climate warms, leading to increased atmospheric CO2 levels and exacerbating climate change.
  
• Revised 1.5°C carbon budget: The briefing underscored the need to reassess the carbon budget necessary to limit global warming to 1.5°C above pre-industrial levels. New research indicates that the remaining carbon budget might be smaller than previously thought, requiring more stringent and immediate reductions in greenhouse gas emissions to meet this target.
  
• Risks associated with climate overshoot: Another significant topic of discussion was the risk of “climate overshoot,” where global temperatures temporarily exceed the target limits before stabilising below the target. Such an overshoot could have profound and potentially irreversible impacts on ecosystems, human health, and economies. The briefing highlighted the necessity of strategies to prevent overshoot or to mitigate its effects if it occurs.
  
• Importance of reducing Non-CO2 greenhouse gases: In addition to CO2, other greenhouse gases like methane and nitrous oxide contribute significantly to global warming. The briefing stressed the importance of addressing these gases due to their higher global warming potential, emphasising that comprehensive climate mitigation strategies must include efforts to reduce all greenhouse gas emissions.

The ESM2025’s Science-to-Policy Briefing underscored the critical need for updated policies that reflect these emerging scientific insights. As the research landscape continues to evolve, initiatives like ESM2025 remain essential in guiding effective climate action and supporting global sustainability efforts.

Read the full policy briefing here.

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