Ground based in situ observations of filter_absorption_photometer at Alert (CA0420G). These measurements are gathered as a part of the following projects GAW-WDCA, NOAA-ESRL and they are stored in the EBAS database (http://ebas.nilu.no/). Parameters measured are: aerosol_absorption_coefficient in pm10, aerosol_absorption_coefficient in pm10, aerosol_absorption_coefficient in pm10