Fwd: Copenhagen Talk

[HighlandWindsLLC Miller]

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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