The algorithm used to produce the AVHRRAerosol demonstration dataset is described inthe doumentation along with links to the processing software. The AVHRR instrument, which was designed for cloud and land observations,is a weak instrument if it is used for the retrieval of a Climate Data Record (CDR) of Aerosol Optical Depth (AOD) over land, because of its small information content with practically only one useful channel with uncertain calibration. However, AVHRR offers a long historic record back to 1978 from the series of instruments flown on NOAA and METOP platforms.AOD can be inverted from top-of-atmosphere (TOA) reflectance measurements in the red band, (directional) surface albedo estimated from the mid-infraredchannel at 3.7 μm and a vegetation index, and byassuming optical properties of atmospheric aerosol (aerosol type) from a multi-model based climatology.