Abstract
Citizen science (also referred to as participatory science or community science), in which members of the general public contribute to scientific research, is not a new concept, as early examples of such studies can be found a couple of centuries ago. With the advancement of technology in an increasingly connected world, it has never been easier to engage citizen scientists in research projects. In this paper, we review citizen science initiatives and projects in the fields of atmosphere and space physics, including both early observation campaigns prior to the twenty-first century and recent projects. Ongoing initiatives take a broad range of forms, from the collection of data by citizen scientists to their involvement in the data analysis process and to the hosting of instruments in non-scientific public structures. We also discuss some of the challenges specific to citizen science, such as training citizen scientists, maintaining their engagement, ensuring reciprocity, managing citizen science data, interfacing the academic and citizen scientist communities, and funding citizen science. To these challenges we suggest possible solutions, and we highlight the unique opportunities offered by recent software and hardware developments. These game-changing opportunities are foreshadowing the dawn of a new era for citizen science - and hence for science in general and atmosphere and space physics in particular.