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OK, but if we want a second example, it would be best to use the second largest forcing, not the third |
m Gasses -> gases (see prev) |
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'''Climate commitment studies''' attempt to assess the amount of future warming that is "committed" by the present levels of climate forcings, even assuming no further increase. This is by no means a new idea [http://www.agu.org/pubs/crossref/2001/2000GL011786.shtml]; the concept is discussed in the [[IPCC]] [[TAR]] [http://www.grida.no/climate/ipcc_tar/wg1/008.htm] and in the [[SAR]] in 1995, although even at the time of the TAR there were no studies of the levels of unrealized climate commitment from past increases in the greenhouse
The basic idea is that if a perturbation - such as an increase in [[greenhouse gas]]es or sulphate aerosols - is applied to the climate system the response will not be immediate, principally because of the large thermal inertia of the oceans. As an analogue, consider the heating of a thick metal block by the sun, or by a flame: the block will warm, more or less slowly, until the entire block has reached equilibrium with the imposed heating. If a thin plate is heated instead, the plate will warm far more quickly because of its lower heat capacity. The oceans, being to some extent vertically mobile, are able to store heat within their depth. Over the land, by contrast, heat penetration beyond the top few meters is very slow because of the lack of mobility. This is why the land surface is observed to warm more than the oceans, and it is predicted that this should continue in the future. It also explains the very large difference in response between "transient" climate prediction runs (in which a full ocean is used) and the climate is out of balance, and "equilibrium" runs in which only a shallow ocean is used and it is assumed that the climate has come to equilibrium.
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