Hi All
We can see how important climate emulators are by plotting a graph of
days of reliable forecasts against the computing power needed by global
climate models to produce them. Unless there is a dramatic improvement
in computer technology the heat produced by the computer for decade
predictions will itself be affecting the climate.
The paper says that solar reduction is used as a proxy for any approach
that reduces incoming short-wave radiation. Niemeier et al. in
doi:10.1002/2013JD020445 figure 7 showed that thiis was sound for
stratospheric sulphur but not for tropospheric sea salt. Can emulators
sort out the difference?
Stephen
Emeritus Professor of Engineering Design. School of Engineering,
University of Edinburgh, Mayfield Road, Edinburgh EH9 3DW, Scotland
[email protected], Tel +44 (0)131 650 5704, Cell 07795 203 195,
WWW.homepages.ed.ac.uk/shs, YouTube Jamie Taylor Power for Change
On 27/06/2016 07:55, Andrew Lockley wrote:
http://www.atmos-chem-phys-discuss.net/acp-2016-535/
Multi-model dynamic climate emulator for solar geoengineering
: 24 Jun 2016
Abstract. Climate emulators trained on existing simulations can be
used to project the climate effects that would result from different
possible future pathways of anthropogenic forcing, without relying on
general circulation model (GCM) simulations for every possible
pathway. We extend this idea to include different amounts of solar
geoengineering in addition to different pathways of green-house gas
concentrations by training emulators from a multi-model ensemble of
simulations from the Geoengineering Model Intercomparison Project
(GeoMIP). The emulator is trained on the abrupt 4 x CO2 and a
compensating solar reduction simulation (G1), and evaluated by
comparing predictions against a simulated 1 % per year CO2 increase
and a similarly smaller solar reduction (G2). We find reasonable
agreement in most models for predicting changes in temperature and
precipitation (including regional effects), and annual-mean Northern
hemisphere sea ice extent, with the difference between simulation and
prediction typically smaller than natural variability. This verifies
that the linearity assumption used in constructing the emulator is
sufficient for these variables over the range of forcing considered.
Annual-minimum Northern hemisphere sea ice extent is less-well
predicted, indicating the limits of the linearity assumption. For
future pathways involving relatively small forcing from solar
geoengineering, the errors introduced from nonlinear effects may be
smaller than the uncertainty due to natural variability, and the
emulator prediction may be a more accurate estimate of the forced
component of the models' response than an actual simulation would be.
Citation: MacMartin, D. G. and Kravitz, B.: Multi-model dynamic
climate emulator for solar geoengineering, Atmos. Chem. Phys.
Discuss., doi:10.5194/acp-2016-535, in review, 2016.
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