How were the sea level scenarios in the 2022 Technical Report created?

The 2022 Interagency Technical Report uses the foundational knowledge and projections from the IPCC AR6 to develop specific sea level rise scenarios tailored for practical use in the United States. This report is produced by multiple U.S. federal agencies and aims to provide actionable information for policy-makers, planners, and stakeholders. The 2022 Interagency Technical Report adapts these projections to a more localized context, providing detailed scenarios for different regions and communities in the U.S. It includes site-specific vertical land motion and other localized factors to create relevant sea level scenarios. While the IPCC AR6 provides a global scientific foundation, the 2022 Interagency Technical Report translates this knowledge into practical scientific information for U.S. policy-makers and planners. This helps bridge the gap between global scientific assessments and local implementation needs.

To create the sea level scenarios, the following process is followed:

1. Determine Range: Assess IPCC AR6 projections to establish a plausible global mean sea level rise range from 1 ft (0.3 m) to 6.6 ft (2.0 m) by 2100, representing the best and worst cases.

2. Collect Projections: Use medium confidence sea level projections and low confidence projections for rapid ice-sheet loss processes from multiple SSPs from IPCC AR6. Thousands of samples for each SSP from 2020 to 2150 are used to cover a range of possibilities.

3. Define Targets: Set five global mean sea level targets ("gates") for 2100, spanning from 1 ft (0.3 m) to 6.6 ft (2.0 m). Filter samples to fit through these gates, with lower emissions SSPs forming lower scenarios and higher emissions plus rapid ice loss scenarios forming higher ones.

4. Construct Scenarios: Collect samples that fit through each gate to create five time-varying Sea Level Scenarios. Intermediate scenarios include the most samples, while others have fewer. These scenarios provide context with varying warming levels and emissions pathways. Though direct probabilities can't be assigned, probabilities can be estimated based on additional future assumptions

For more information and additional detail, see the Dive Deeper section of the Future Sea Level Section in Sea Level 101.