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ensure accuracy. Surface Temperature Reconstructions for the
last 2,000 Years FIGURE 10-1 Evolution of atmospheric carbon
dioxide and methane over the last 22,000 years. Left-hand axes
show atmospheric concentrations (note the carbon dioxide scale
does not start from zero), and right-hand axes show the
radiative forcing relative to 1750 as calculated using the
formulas given by Myhre et al. (1998) and Ramaswamy et al.
(2001). Red arrows indicate the theoretical detection limit of a
forcing (relative to Last Glacial Maximum and preindustrial
conditions) within a climate system model, assuming an internal
climate variability or detection threshold of 0.2°C, climate
equilibrium, and a midrange climate sensitivity of 3°C for a
carbon dioxide doubling. Dashed red lines indicate the
uncertainty of the detection threshold associated wit