This website shows the concentration of particulate matter air pollution (PM2.5) in cities around the world. Very few historical observations of PM2.5 exist before the year 2000 so instead we use data produced from a mix of computer model simulations and satellite observations.
For the most recent years (2000-2021) we use a dataset that combines ground-level and satellite observations of PM2.5 concentrations (from Van Donkelaar et at (2021)), satellite dataset can be found here (V5 0.1 degree resolution). Satellite observations of PM2.5 aren’t available for the years before 1998, so instead we take the historical trend in air pollution from computer models (Turnock 2020); publicly available model data was taken from the Coupled Model Intercomparison Project (CMIP6), these are the climate models used for the IPCC assessment report. We used data from the UKESM submission to CMIP (data is here).
To ensure a smooth time series, we don’t use the model concentrations directly, instead we use them to calculate the historical trend for each city and apply this trend to a three-year average of the observations from 2000-2002. This is a similar approach to that taken by Turnock et al. (2023) and Reddington et al. (2023).
-Because so few historical observations of PM2.5 exist, so it is tricky to evaluate how good this approximation is, but in this approach the historical trend is taken from the computer model and the values are informed by the satellite.
-Both the computer model and the satellite use gridboxes that cover many kilometers, so concentrations from cities will likely be underestimated as the very concentrations in a city center may be mixed with lower concenrations within the same gridbox.
+Because so few historical observations of PM2.5 exist, so it is challenging to evaluate how good this approximation is, but in this approach the historical trend is taken from the computer model and the values are informed by the satellite.
+These images will be updated in the future as improved model simulations and observations become available.
+Both the computer model and the satellite use gridboxes that cover many kilometres, so concentrations from cities will likely be underestimated as the very concentrations in a city center may be mixed with lower concenrations within the same gridbox.
To see the stripes for yourself CLICK HERE
Inspired by the Climate Stripes created by Prof Ed Hawkins from the University of Reading,we have created these Air Quality Stripe images which show the change in particulate matter (PM2.5) air pollution from 1850 to 2021 in cities around the globe.
The PM2.5 data is from the UKESM climate model combined with satellite observations. The colour scale was informed by an artist who analysed google images of air pollution. The light blue colours represent the clean blue sky, with darker red and browns showing increasing amounts of air pollution.
"The images show that it is possible to reduce air pollution; the air in many cities in Europe is much cleaner now than it was 100 years ago, and this is improving our health. We really hope similar improvements can be achieved across the globe."