Map (IMAGE) Paul Scherrer Institute Caption The data for the new scientific publication come from 22 measuring stations in 14 countries, spread across the European continent. A protocol developed at PSI for the standardised evaluation of the different data sets ensured their comparability. Credit Paul Scherrer Institute/Mahir Dzambegovic Usage Restrictions PSI provides image and/or video material free of charge for media coverage of the content of the above text. Use of this material for other purposes is not permitted. This also includes the transfer of the image and video material into databases as well as sale by third parties. License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.