Linking glacial and future climates through an ensemble of GCM simulations J. C. Hargreaves1, A. Abe-Ouchi1,2, and J. D. Annan1 1FRCGC/JAMSTEC, Yokohama, Japan 2CCSR, Tokyo, Japan
Abstract. In this paper we explore the relationships between the modelled climate of
the Last Glacial Maximum (LGM) and that for doubled atmospheric carbon
dioxide compared to the pre-industrial climate by analysing the output from
an ensemble of runs from the MIROC3.2 GCM.
Our results lend support to the idea in other recent work that the Antarctic
is a useful place to look for historical data which can be used to validate
models used for climate forecasting of future greenhouse gas induced climate
changes, at local, regional and global scales. Good results may also be
obtainable using tropical temperatures, particularly those over the ocean.
While the greater area in the tropics makes them an attractive area for
seeking data, polar amplification of temperature changes may mean that the
Antarctic provides a clearer signal relative to the uncertainties in data and
model results. Our result for Greenland is not so strong, possibly due to
difficulties in accurately modelling the sea ice extent.
The MIROC3.2 model shows an asymmetry in climate sensitivity calculated by
decreasing rather than increasing the greenhouse gases, with 80% of the
ensemble having a weaker cooling than warming. This asymmetry, if confirmed
by other studies would mean that direct estimates of climate sensitivity from
the LGM are likely to be underestimated by the order of half a degree. Our
suspicion is, however, that this result may be highly model dependent.
Analysis of the parameters varied in the model suggest the asymmetrical
response may be linked to the ice in the clouds, which is therefore indicated
as an important area for future research.
Citation: Hargreaves, J. C., Abe-Ouchi, A., and Annan, J. D.: Linking glacial and future climates through an ensemble of GCM simulations, Clim. Past, 3, 77-87, doi:10.5194/cp-3-77-2007, 2007.