Variability of the Earth’s climate - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 46

All of these calculations suffer from a lack of understanding of changes in
lapse rate, cloudiness, and humidity in the LGM ) pre-industrial transition.
Kohler et al. (2009) also performed an estimate of climate sensitivity based on
glacial-interglacial cycles. They said: ''Although water vapor is the most important
GHG, the following compilation does not consider any changes in water vapor in
the past due to missing constraints on its variability.'' In other words, they more
or less said: Water vapor may be the biggest factor, but since we have no data on it,
we will neglect it! Some of the data used by Kohler et al. (2009) are compared with
data used by C&L and Hansen and Sato (2011) in Table 2.2 .
It is noteworthy that Hansen and Sato (2011), which came along three years
after Chylek and Lohmann (2008) and two years after Kohler et al. (2009), did

Table 2.2. Parameters for analyzing LGM-pre-industrial transitions. Forcings are in W/m 2 .
Blank elements are not available. Elements with dashes represent items that were not included.

Chylek and Kohler et al. Hansen and Sato

Lohmann (2008) (2009) (2011)

CO 2 forcing 2.4 2.1 2.25

CH 4 forcing 0.27 0.4 0.43

N 2 O forcing — 0.3 0.32

Total GHG forcing 2.67 2.8 3.0

Land cryosphere 4.54

Land ice 3.17

Sea ice 0.55

Snow cover 0.82

Sea ice 2.13

Sea ice—north 0.42

Sea ice—south 1.71

Vegetation 1.09

Total albedo 3.5 7.76 3.5

Dust/Aerosols 3.2 1.88

Water vapor, lapse rate, and clouds — — —

Total forcing 9.4 12.43 6.5

D T G ( C) 5.8 a

4.6 5.0

a Kohler et al. (2009) emphasized at considerable length that although reasonable estimates can be made for
the D T at Antarctica, the value of D T G is far more elusive. They suggested that 5.8 C was perhaps one of
the better estimates but emphasized that D T G is not well pinned down.