Comparison of Updated Climate Projections for Extreme Temperature and Precipitation

This tool is excerpted from Mid-Atlantic Regional Climate Impacts Summary and Outlook: Fall 2024.

Tool Background

Previous climate summaries have presented updated climate projections for extreme temperature and extreme precipitation. These projections are based on the Coupled Model Intercomparison Project 6 (CMIP6) suite of models that have been downscaled to a finer spatial resolution using the Localized Constructed Analogs 2 (LOCA2) methodology.¹ Previous data tools utilized the CMIP5 suite of models downscaled based on the original LOCA methodology. Understanding how these two datasets differ can be helpful for localities and utilities seeking to update their climate data from to the CMIP6 LOCA2 datasets. The CMIP5 and CMIP6 datasets differ in a number of important ways, including their use of future climate scenarios, model sensitivities to greenhouse gas emissions, and downscaling methodologies. Prior climate summaries have described the differences between the CMIP5 LOCA and CMIP6 LOCA2 datasets in greater detail (see Part 4). The following data tools provide a side-by-side comparison of CMIP5 to CMIP6 LOCA downscaled climate data.

Key Findings

• Precipitation: CMIP6 models generally project wetter conditions compared to CMIP5 models. For example, CMIP6 models project that parts of Western Pennsylvania and Western Virginia will potentially see twice as many extreme precipitation days as was projected by the previous CMIP5 models.
• Temperature: Minimal differences between CMIP5 and CMIP6 projections across the region are within the range of uncertainty expected from an update.

Guidance for Practitioners

• Temperature: CMIP5 projections are likely sufficient and within the range of uncertainty in CMIP6 for the majority of the region but comparing datasets using the tool below could identify any cases in which the datasets differ by more than a few days.
• Precipitation: While uncertainty in precipitation is much greater than temperature, CMIP5 may underestimate extreme precipitation in much of the region. Practitioners should compare CMIP6 projections to assess differences, implications for cost and risk, and the need for adopting updated projections.

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