Antarctic Clouds and Aerosols (ACA) Action Group

About

The IPCC has identified the indirect aerosol effect as the biggest uncertainty in the Earth's climate system. For this reason in many regions worldwide great efforts are being made to measure aerosols and cloud microphysical properties and the associated effect on the climate.

However, in the Antarctic very few measurements have been made of cloud microphysical properties. Climate model representations of the Antarctic climate rely on parameterisations of clouds and cloud properties that based on mid latitude observations and these are likely to be wrong -for example the number nuclei available for the formation of cloud particles will be very different in the pristine air over the Antarctic.

Also the source of many of the cloud nuclei found at high southern latitudes may be either the exposed rock or biological activity in the seas surrounding Antarctica. Climate change will affect both these sources and so they may act as strong climate feedback. Therefore we must understand the process that may be important for the formation of aerosols and Antarctic clouds if we are to successfully model climate change both regionally in Antarctica and globally.