[asa] Effect of CO2-Induced Global Warming on Antarctic Surface Mass Balance a Hundred Years Hence

"I don't trust ANYBODY's predictions on sea level. There are two many
free variables most specifically how much anthropogenic CO2 there is
going to be. The climate sensitivity numbers from the 2001 report
have been confirmed by more recent research. We don't know how
successful or unsuccessful we will be at controlling CO2 emissions or
external factors such as possibly running out oil might have. We are
discovering different negative (and positive!) feedback mechanisms
that also affect the CO2 levels. Since 2001 we have better models
where given the right inputs we can predict the effects but it is
still GIGO (garbage in garbage out) because we still do not have
accurate prediction of CO2 levels and probably never will." ~ Rich
Blinne Mon, 11 Dec 2006 11:49:39 -0700

~ Janice :)

Effect of CO2-Induced Global Warming on Antarctic Surface Mass
Balance a Hundred Years Hence

Reference
Krinner, G., Magand, O., Simmonds, I., Genthon, C. and Dufresne,
J.-L. 2007. Simulated Antarctic precipitation and surface mass
balance at the end of the twentieth and twenty-first centuries.
Climate Dynamics 28: 215-230.

What was done
The authors used the LMDZ4 atmospheric general circulation model
(Hourdin et al., 2006) to simulate Antarctic climate for the periods
1981-2000 (to test the model's ability to adequately simulate present
conditions) and 2081-2100 (to see what the future might hold for the
mass balance of the Antarctic Ice Sheet and its impact on global sea level).

What was learned
Krinner et al. report, first of all, that "the simulated present-day
surface mass balance is skilful on continental scales," giving them
confidence that their results for the end of the 21st century would
be reasonably skilful as well. Of that latter period a full century
from now, they determined that "the simulated Antarctic surface mass
balance increases by 32 mm water equivalent per year," which
corresponds "to a sea level decrease of 1.2 mm per year by the end of
the twenty-first century," which would in turn "lead to a cumulated
sea level decrease of about 6 cm." This result, in their words,
occurs because the simulated temperature increase "leads to an
increased moisture transport towards the interior of the continent
because of the higher moisture holding capacity of warmer air," where
the extra moisture falls as precipitation, causing the continent's
ice sheet to grow.

What it means
The results of this study - based on sea surface boundary conditions
taken from IPCC 4th assessment report simulations (Dufresne et al.,
2005) that were carried out with the IPSL-CM4 coupled
atmosphere-ocean general circulation model (Marti et al., 2005), of
which the LMDZ4 model is the atmospheric component - argue strongly
against climate-alarmist predictions of future catastrophic sea level
rise due to the mass wastage of the Antarctic Ice Sheet caused by
CO2-induced global warming. In fact, they suggest just the opposite,
i.e., that CO2-induced global warming would tend to buffer the planet
against such an outcome.

References
Dufresne, J.L., Quaas, J., Boucher, O., Denvil, S. and Fairhead, L.
2005. Contrasts in the effects on climate of anthropogenic sulfate
aerosols between the 20th and the 21st century. Geophysical Research
Letters 32: 10.1029/2005GL023619.

Hourdin, F., Musat, I., Bony, S., Braconnot, P., Codron, F.,
Dufresne, J.L., Fairhead, L., Filiberti, M.A., Friedlingstein, P.,
Grandpeix, J.Y., Krinner, G., Le Van, P., Li, Z.X. and Lott, F. 2006.
The LMDZ4 general circulation model: climate performance and
sensitivity to parameterized physics with emphasis on tropical
convection. Climate Dynamics 27: 787-813.

Marti, O., Braconnot, P., Bellier, J., Benshila, R., Bony, S.,
Brockmann, P., Cadule, P., Caubel, A., Denvil, S., Dufresne, J.L.,
Fairhead, L., Filiberti, M.A., Foujols, M.A., Fichefet, T.,
Friedlingstein, P., Grandpeix, J.Y., Hourdin, F., Krinner, G., Levy,
C., Madec, G., Musat, I., de Noblet-Ducoudre, N., Polcher, J. and
Talandier, C. 2005. The new IPSL climate system model: IPSL-CM4. Note
du Pole de Modelisation n. 26, IPSL, ISSN 1288-1619.

Reviewed 31 January
2007 http://www.co2science.org/scripts/CO2ScienceB2C/articles/V10/N5/C2.jsp

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Received on Sun Feb 4 16:21:43 2007