Introduction to special section on Global Dimming and Brightening

Global dimming and brightening is a popular expression which refers to the recent observational evidence for substantial decadal variations in solar radiation reaching the Earth's surface. For the first time, a special section is dedicated to this rapidly growing field of research. A comprehensive collection of more than 20 papers sheds new light on the phenomenon of global dimming and brightening. Here I provide a brief introduction and guideline to the special section and place the individual papers into context. To facilitate orientation in this special section, the papers are grouped according to the specific aspects of global dimming and brightening that they address.