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Updated 11 October, 2003

Strategic Plan for the Climate Change Science Program Final Report, July 2003

Figure 3-2
from Annex C
(Graphics and Photography Source Information)

Figure 3-2: Schematic illustrating a comparison among several factors that influence Earth's climate. These factors can be broadly compared using the concept of radiative forcing. The principal forcings arise from changes in atmospheric composition of gases, aerosols, clouds, land use, and solar output. The rectangular bars represent best estimates of the contributions of these forcings, some of which yield warming and some cooling. The forcing contributions are shown for different aerosol types and for those produced or emitted by aviation. The indirect effect shown for aerosols is their effect on the size and number of cloud droplets. A second indirect effect, namely the effect on cloud lifetime, which would lead to a negative forcing, is not shown. The vertical line about the rectangular bars indicates the range of estimates. A vertical line without a rectangular bar denotes a forcing for which no best estimate can be given owing to large uncertainties. Aerosol forcings are generally not uniform over the globe, unlike those of well-mixed greenhouse gases (e.g., CO₂). A more detailed description of this schematic and its interpretation is provided by the IPCC (IPCC, 2001a,d).

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