The joint dataset ATMEL2007A (Tammet, 2009) provides scientists with a tool for studying the correlations and trends in fair-weather atmospheric electricity, air pollution effects, and trends in global climate on a broader basis. It includes hourly averages of digitally available data from 12 stations including 7 stations of the former World Data Centre network. Additional stations are Wank Peak (Germany), Marsta (Sweden), Tahkuse (Estonia), Tartu (Estonia), and Hyytiälä (Finland). The atmospheric electric measurements are accompanied with meteorological and air pollution data. The total amount of included hourly average values is about 12,000,000. New data can easily be imported into the dataset and the excerpts of the data can be exported as traditional tables using the included free software.

Fresh data is the property of scientists who have carried out the measurements. As a rule, the data are not made public until it has been analyzed and the first scientific papers have been published. The dataset ATMEL2007A contains only the data which have been decided to make public by the copyright owners. The most important source of the initially public data is the collection of files of the WDC/AE at the MGO. The collection was compiled due to the efforts of Dr. Ya.M. Shvarts and delivered to the University of Tartu, together with the data publishing rights. An essential complement to the WDC data is the Wank Peak data collection by Reinhold Reiter, which contains 9½ years of continuous measurements. The Wank Peak data were reconditioned at the Max Planck Institute for Aeronomy, Katlenburg-Lindau, Germany, and published on CD-ROM by Prof. K. Schlegel. Some additional information required for the data interpretation was kindly presented by Dr. W. Carnuth as a personal communication. A 4½ year subset of atmospheric electric measurements at the Marsta Observatory of the University of Uppsala is for the first time published in ATMEL2007A. This data was digitally recorded during 1994-1998 (Israelsson and Tammet, 2001). The Wank Peak and Marsta datasets additionally include the measurements of background meteorological parameters. Today, the air ion mobility distribution is routinely measured at Tahkuse, Estonia (Hõrrak et al., 2003), at Tartu, Estonia, and at Hyytiälä, Finland (Kulmala and Tammet, 2007). The data are available since 2003 for Tahkuse and Hyytiälä, and since 2004 for Tartu. Hourly averages of air conductivity and ion concentrations are made public in ATMEL2007A for the first time. However, the dataset includes only the integral parameters of air ions: air conductivity, concentrations of wide ion groups, and average mobility of cluster ions. The original 10-minute records of detailed mobility distributions at Tartu, Tahkuse and Hyytiälä were still not opened for public access when compiling ATMEL2007A. A small but important part of ATMEL2007A is the classic data of electric field measurements made during the Carnegie cruises 4–7 (Mauchly, 1926). The digitized data were presented for ATMEL2007A by Dr. E.R. Williams (Williams, 2007).