Advancing the understanding of the Sun–Earth interaction—the Climate and Weather of the Sun–Earth System (CAWSES) II program

The Scientific Committee on Solar–Terrestrial Physics (SCOSTEP) of the International Council for Science (ICSU) implemented an international collaborative program called Climate and Weather of the Sun–Earth System (CAWSES), which was active from 2004 to 2008; this was followed by the CAWSES II program during the period of 2009–2013. The CAWSES program was aimed at improving the understanding of the coupled solar–terrestrial system, with special emphasis placed on the short-term (weather) and long-term (climate) variability of solar activities and their effects on and responses of Geospace and Earth’s environment. Following the successful implementation of CAWSES, the CAWSES II program pursued four fundamental questions addressing the way in which the coupled Sun–Earth system operates over time scales ranging from minutes to millennia, namely, (1) What are the solar influences on the Earth’s climate? (2) How will Geospace respond to an altered climate? (3) How does short-term solar variability affect the Geospace environment? and (4) What is the Geospace response to variable inputs from the lower atmosphere? In addition to these four major tasks, the SCOSTEP and CAWSES promoted E-science and informatics activities including the creation of scientific databases and their effective utilization in solar–terrestrial physics research. Capacity building activities were also enhanced during CAWSES II, and this represented an important contribution of SCOSTEP to the world’s solar–terrestrial physics community. This introductory paper provides an overview of CAWSES II activities and serves as a preface to the dedicated review papers summarizing the achievements of the program’s four task groups (TGs) and the E-science component.