Ultrafine particles affect both health and climate. In urban areas, road traffic is considered to be the main source of the small particles. However, a long-term measurement campaign of researchers of Karlsruhe Institute of Technology (KIT) outside of cities has now revealed a source that particularly affects regional climate: modern coal-fired power plants. In the Bulletin of the American Meteorological Society, the researchers report how the power plants’ emissions influence the formation of ultrafine particles and which impact these particles have on climate.