Fwd: Copenhagen Talk
Posted by
HighlandWindsLLC Miller on
Mar 27, 2009; 7:06pm
URL: http://friam.383.s1.nabble.com/Fwd-Copenhagen-Talk-tp2546099.html
However,
stabilization of climate becomes a realistic objective if coal emissions
are phased out and unconventional fossil fuels (such as tar sands and oil
shale) are not developed as substitutes for oil and gas as the oil and
gas resources decline. With these assumptions, the
non-CO2 forcings become an important factor in stabilizing
climate. (from below summary of Jim Hansen's (NASA Goddard Space Institute Director) talk, which has a link below also ...) fyi. Peggy Miller
---------- Forwarded message ----------
From:
James Hansen <[hidden email]>Date: Thu, Mar 26, 2009 at 7:53 PM
Subject: Copenhagen Talk
To:
[hidden email]
To be removed from Jim Hansen's e-mail distribution reply
with REMOVE as subject.
My talk on
"Air Pollutant Climate Forcings", given at Copenhagen last
week, is available at
http://www.columbia.edu/~jeh1/2009/Copenhagen_20090311.pdf with the
powerpoint charts at
http://www.columbia.edu/~jeh1/2009/Copenhagen_20090311.ppt
A summary is below.
Jim
Summary
We note that it will be exceedingly
difficult to determine the aerosol climate forcing relative to
pre-industrial climate. However, for policy purposes it may be
sufficient to start with the present situation and consider climate
forcing changes relative to today. The planet’s present energy
imbalance, at least to first order, determines the change of climate
forcings needed to stabilize climate. Climate models, using typical
presumed scenarios of climate forcings for the past century, suggest that
the planet should be out of energy balance by +0.75 ± 0.25
W/m2, but observations of ocean heat content change (averaged
over the 11-year solar cycle) suggest an imbalance of only +0.5 ± 0.25
W/m2 (absorbed solar energy exceeding heat radiation to
space).
If all other forcings were fixed, a
reduction of CO2 amount to 350 ppm would restore the planet’s
energy balance, assuming that the present imbalance is 0.5
W/m2. If fossil fuel emissions continue at anything
approaching “business-as-usual” scenarios, it is not feasible to restore
planetary energy balance and stabilize climate. However,
stabilization of climate becomes a realistic objective if coal emissions
are phased out and unconventional fossil fuels (such as tar sands and oil
shale) are not developed as substitutes for oil and gas as the oil and
gas resources decline. With these assumptions, the
non-CO2 forcings become an important factor in stabilizing
climate.
Of course, all other forcings are not
fixed, but with appropriate directed efforts it is realistic to keep the
net future change of non-CO2 forcings near zero.
N2O will continue to increase, at least in the near future,
but its growth could be slowed with improved fertilization
techniques. An N2O increase could be compensated by a
decrease of CH4. There is a realistic possibility of
decreasing the source strength of CH4 emissions, and thus
CH4 atmospheric amount. However, if global warming
continues, the CH4 source from melting of methane hydrates
could increase. Thus there is a coupling between the need to reduce
CO2 and the possibility of reducing CH4.
Reflective aerosols are likely to decrease, thus adding a warming effect,
but that warming effect may be compensated via an emphasis on reducing
black soot aerosols.
The following charts (from the powerpoint
presentation) include an accurate status report on climate forcings by
greenhouse gases. Unfortunately, such data are not available for
aerosols, but the NASA Glory mission, planned for launch late this year,
promises to provide the first accurate global aerosol measurements.
Comments that accompany the powerpoint charts are included below.
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