Upgrades to the Climate Shift Index ™
Climate Central has made several improvements to the Climate Shift Index™ (CSI). Beginning in March 2023, you will see in version 2 (see v.2 documentation):
Finer spatial resolution (now 0.25°, ~17 miles). This will be most apparent in the CSI Global Map.
Areas of high uncertainty masked out. This will be visible in the CSI Global Map and occasionally, in the U.S. CSI Map.
These improvements stem from a shift in the observational data behind the CSI. We are now using the ERA5, the fifth generation of atmospheric reanalyses by the Centre for Medium-Range Weather Forecasts (ECMWF), as the basis for our historical climate data and empirical CSI calculations. ERA5 is a reconstruction of the state of the atmosphere that uses a sophisticated weather model to synthesize large volumes of meteorological data. ERA5 is one of the most widely-used datasets for studies of weather and climate. The switch to ERA5 allows us to quadruple the resolution of the CSI and produce more robust attribution estimates.
CSI levels are calculated by taking the latest temperature forecasts from the NOAA Global Forecast System, and comparing them to known temperature distributions from ERA5 climatology. We found that in some regions, the CSI can be sensitive to even small differences between the forecasted temperatures and the temperatures in ERA5 (which are not available until several weeks after real-time CSI levels are calculated). The sensitivity is especially apparent in tropical regions, especially at night. Areas where the sensitivity is very high or where we can not compute a reliable attribution estimate will now be masked, and so will show up as cross-hatched areas on the map
In the near future, daily real-time CSI levels based on GFS forecasts will be updated once ERA5 data is available (after approximately two weeks). This will allow us to calculate the CSI for most of the masked areas, and the updated CSI will be visible in the CSI Global Map.
Additional planned enhancements to the CSI include:
Improvements to the U.S. map to take advantage of the higher spatial resolution
The ability to download real-time CSI data for select locations
A reconstruction (“hindcast”) of CSI values going back to 1970