Geoscience Reference
In-Depth Information
.
Primary boundary conditions for the LGM climate, such as continental
geography, orbital configurations, and atmospheric pCO
2
are well known.
Other factors, such as sea level, ice area, and ice sheet heights are reasonably
well known.
The CLIMAP project in the early 1970s attempted to describe the state of the
Earth at the time of the LGM using all the data available at that time. The
CLIMAP project culminated in a series of maps that emphasized seasonal sea
surface temperatures, but also included the distribution of ice on land and in the
ocean, as well as vegetation and albedo of the land surface.
Mix et al. (2001) provided an update to the CLIMAP study based on more
recent work, mainly with advanced climate models. Their estimate of sea surface
temperatures during the LGM is shown in
Figure 1.5
.
A number of investigators used climate models to describe the climate at the
LGM. Kim et al. (2008) and Oglesby and Maasch (2009) provide reviews.
Schneider von Deimling et al. (2006) analyzed the LGM using climate models.
In their model, they estimated the global distribution of various forcings (change
in vegetation, effect of dust, CO
2
, and ice sheet albedo) at the LGM relative to
modern pre-industrial times. Unfortunately, despite a great deal of verbiage in the
paper (''
the main glacial forcings are relatively well known''), they did not
actually specify their best estimates of the global average forcings for these
factors, although they did mention that dust and vegetation were estimated to
contribute a total of about 2W/m
2
, and the total of all forcings was in the range
8.0 to 8.5W/m
2
. This suggests that CO
2
and ice sheet albedo were each roughly
3W/m
2
although that was not explicitly stated. Having estimated the forcing, they
proceeded to estimate the temperature difference from modern pre-industrial
times. For the tropics, they estimated a cooling of 2.7
C and for the global
...
Figure 1.5. Estimates of sea surface temperatures during the LGM (Mix et al., 2001; Woillez et
al. 2011).
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