Overview of the various models for ice ages in the recent past (3 MYBP to present) - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 231

Figure 8.6. Comparison of the Greenland temperature profile (from Figure 4.6 ) with the

methane profile at Vostok, Antarctica (Petit et al., 1999).

is important to understand natural variability in cloud climate forcing (Kernthaler
et al., 1999).
Cloud cover has a strong effect on the Earth's climate by reflecting incident
sunlight and absorbing outgoing IR emitted by the Earth. With an average solar
input to Earth of 342W/m 2 , even a change of only 1% in the Earth's average
albedo generates a climate forcing of 3.4W/m 2 . The effect is even greater in the
equatorial zone. Cloud formation provides a strong positive feedback mechanism
that can amplify other climatological variations that change the distribution of
clouds. However, the effects of clouds are complex. Some clouds predominantly
reflect incident sunlight, causing cooling. Other clouds predominantly absorb and
re-emit IR radiation and, thereby, produce a heating effect. M&M provided the
summary given in Table 8.1 , based on estimates from the Earth Radiation Budget
Experiment (ERBE).