A collection of airborne solid or liquid particles arising from natural and anthropogenic sources (e.g. salt particles, desert dust, soot and charcoal (black carbon), sulphate particles), that reside in the atmosphere and range in size between 0.01 and 10 micrometres (one micrometre is 1/1000000 of a metre). Aerosols may have a direct and indirect effect on climate processes. The direct effect is to scatter and absorb solar radiation; the indirect effect is that they affect a number of cloud processes. The various different types of aerosol affect climate processes in different ways, but the overall net effect of aerosols is that they cool the atmosphere (have a negative radiative forcing).
In developing the UKCP09 probabilistic projections, the effect of sulphate aerosols was considered through the use of a sulphate aerosol PPE. The UKCP09 projections therefore include direct and some indirect effects of sulphate aerosols, and uncertainties in these. Other sources of aerosols are not explicitly included in UKCP09.
- More details about the treatment of sulphate aerosols in UKCP09 are given in Box 2.1 in the UKCP09 Climate change projections report. Table 2.1 provides a list of the constituents included, and not included, in the UKCP09 probabilistic projections.
- A discussion of sources of uncertainty in the UKCP09 probabilistic projections is available in Annex 2.4.
Find out more
- IPCC Fourth Assessment Report, Working Group 1 report The Physical Science Basis , Chapter 7.5
- IPCC Fourth Assessment Report, Working Group 1 report The Physical Science Basis , Chapter 2.4