7 October 2009
A study by CSD scientist Graham Feingold and Max Planck Institute scientist Bjorn Stevens reviewed the work to date on aerosol-cloud-climate interactions, with the aim of shedding light on why the uncertainties remain so large on this topic. They conclude that the complexity of the system means that in some situations, effects of aerosols on clouds and precipitation compensate or cancel each other out (i.e., it is a "buffered system"). Furthermore, these compensating effects vary a lot from place to place on the globe. The study was published on October 1 in the journal Nature.
Significance: The heterogeneity of aerosol-cloud interactions makes it difficult to apply global models and challenging to make sufficiently detailed observations, leading the authors to conclude that current observational approaches and modeling tools used to study the system are not always ideally suited to the task.
Background: Atmospheric particles (aerosols) formed from pollution can cool the climate directly by reflecting sunlight. Soot from biomass burning absorbs sunlight and warms the climate. Aerosols can also affect the formation and properties of clouds, altering their influence on climate. The net effect of all these direct and indirect factors is a cooling by aerosols, which has partially offset the warming by greenhouse gases.
Stevens, B., and G. Feingold, Untangling aerosol effects on clouds and precipitation in a buffered system, Nature, doi:10.1038/nature08281, 2009.