Data and Methodology

Data

Methodology

• All Climate Shift Index (CSI) levels reported in this brief are based on daily average temperatures and ECMWF ERA5 data from Dec. 1, 2024, to Feb. 28, 2025. See the frequently asked questions for details on computing the Climate Shift Index, including a summary of the multi-model approach described in Gilford et al. (2022).

• Risky heat days are days with temperatures hotter than 90% of temperatures observed in a local area over the 1991-2020 period. Heat-related health risks rise when temperatures climb above this local threshold. This is a conservative approximation of the local minimum mortality temperature (MMT), an indicator of the local links between temperature and mortality based on peer-reviewed research by Tobias et al. (2021) and Gasparrini et al. (2015).

• Values shown in maps and tables across this website have been rounded for clarity. For exact data values, please download the full dataset above.

• A detailed methodology can be found in the full report.