Soot Particles and Global Warming
A team of researchers from ETH Zurich has for the first time used simulations on the CSCS supercomputer Piz Daint to investigate how certain aging mechanisms of soot particles in the atmosphere affect cloud formation. The results show that the influence of ozone and sulfuric acid on soot aging alters cloud formation and, ultimately, the climate.
Burning wood, petroleum products or other organic materials releases soot particles into the atmosphere that consist mainly of carbon. This soot is considered the second most important anthropogenic climate forcing agent after carbon dioxide. In the atmosphere or as deposits on snow and ice surfaces, soot particles absorb the short-wave radiation of the sun and thus contribute to global warming. In the atmosphere, soot particles also have an indirect effect on the climate by altering the formation, development and properties of clouds.
When soot particles combine with ozone or sulfuric acid, their physical and chemical properties change. Simulations of ozone-aged soot show that when the carbon dioxide content of the atmosphere doubles compared to the pre-industrial era, fewer low clouds form and more short-wave radiation reaches the earth and warms it.
The soot particles aged by sulfuric acid, on the other hand, cause more ice crystals to form and make cirrus clouds optically thicker, i.e. they are less permeable to radiation. As a result, cirrus clouds absorb more of the long-wave thermal radiation emitted by the Earth and allow less of it to escape into space also warming the earth.