Aerosols dominate chemistry in the troposphere and influence radiative forcing, both directly by scattering or absorbing light, and indirectly by serving as Cloud Condensation Nuclei (CCN). In terms of their net influence on global climate, aerosols are thought to represent the greatest uncertainty, yet computer climate models estimate that over the last century human-produced aerosols have offset global warming due to greenhouse gases by about 40 percent. Determining the contribution of aerosols to the global radiation budget is critical to better modelling of future climate change.
Some aerosols come from natural sources, such as volcanic eruptions, dessert sand, dust storms, forest and grassland fires, living vegetation, and salt from sea spray. Volcanic ash aerosols contribute to the chemistry in the atmosphere since they become coated in sulphuric acid after a volcanic eruption, providing a surface for further chemical reactions. Volcanic Ash aerosols are also damaging to aircraft, made largely of silicate, they can enter aeroplane engines and melt, causing a reduction in engine performance and sometimes even engine failure. Many busy air traffic corridors pass over volcanoes so it is important that better detection of volcanic ash clouds is achieved. Remote sensing is vital for detection of these aerosols in the atmosphere, although the characterisation has been limited by the lack of detailed knowledge of the chemical and spectroscopic properties of aerosols.
Successful laboratory measurements of aerosol spectra have proven to be problematic due to the difficulties involved in the dispersion of small particles. Achieving a high enough particle density and residence time with respect to the length of measurement has therefore proven to be a major barrier in recording infrared absorptions in the laboratory.
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