Earth’s climate is chiefly driven by its energy and water cycles that are mobilized by the earth’s radiation budget altered mostly by clouds and aerosols. Cloud processes have been recognized as the largest sources of uncertainty in projecting future climate changes in response to increasing greenhouse gases, while the aerosol-radiation-interaction (ARI) and aerosol-cloud-interaction (ACI) exert the most uncertain forcing to the climate system. As such, the CAR is the most complicated vehicle driving our earth’s climate system.
In this lecture, I’ll provide both a historical perspective and a landscape overview of the frontiers associated with the CAR dated to 1990s, the beginning of a golden era brought up by the emerging earth system sciences thanks partially to the NASA’s Earth Observation System (EOS), offering unprecedented opportunities to monitor all the parts of the CAR (aerosol, cloud and radiation) and their interactions, and some major milestones achieved concerning the breakdown of radiation budget or energy disposition and the roles of clouds and aerosols through global observation from space and ground (cloud microphysics and vertical structure), the ARI and ACI and their impact on weather and climate by altering the energy and water cycles. Besides, they also play important roles in extreme weather events (drought and floods, heat waves, lightning and thunderstorms, etc.). As such, all three key parts of the CAR have been identified as the central thrusts of high priority in the US Decadal Survey in geosciences.