Atmospheric aerosols in the earth system: a review of interactions and feedbacks

Abstract

The natural environment is a major source of atmospheric aerosols, including dust, secondar y organic material from terrestrial biogenic emissions, carbonaceous par ti- cles from wildfires, and sulphate from marine phytoplankton dimethyl sulphide emis- sions. These aerosols also have a significant effect on many components of the Ear th system such as the atmospheric radiative balance and photosynthetically available ra- diation entering the biosphere, the supply of nutrients to the ocean, and the albedo of snow and ice. The physical and biological systems that produce these aerosols can be highly susceptible to modification due to climate change so there is the poten- tial for impor tant climate feedbacks. We review the impact of these natural systems on atmospheric aerosol based on obser vations and models, including the potential for long term changes in emissions and the feedbacks on climate. The number of drivers of change is ver y large and the various systems are strongly coupled. There have therefore been ver y few studies that integrate the various effects to estimate climate feedback factors. Never theless, available obser vations and model studies suggest that the regional radiative forcings are potentially several Watts per square metre due to changes in these natural aerosol emissions in a future climate. The level of scientific understanding of the climate drivers, interactions and impacts is very low.