From ecological economics listserv.  I suspect some of you have seen it.  I
thought it was penned rather eloquently.  The author is an exec at NRDC.

________________________________
Richard Haimann, P.E.
(562) 628-1980
(562) 684-4312 (e-fax)
mailto:[log in to unmask]
http://www.haimann.com


> -----Original Message-----
> From: [log in to unmask]
> [mailto:[log in to unmask]]On Behalf Of Hawkins, Dave
> Sent: Saturday, March 16, 2002 6:06 PM
> To: [log in to unmask]; [log in to unmask]
> Subject: Carbon cycle (was Lomborg...)
>
>
> There seems to be some confusion about stocks and flows of carbon.
>
> There are two basic stocks of carbon in the earth system: the
> "biosphere" carbon stock consisting of carbon in the atmosphere,
> vegetation, soils and the oceans;  and the "isolated" carbon
> stock, consisting of carbon in rocks and fossil fuels.
>
> Flows between the segments of the "biosphere" carbon stock are
> large and occur rapidly--daily, weekly, monthly, seasonally,...
> Prior to the industrial revolution, flows between the "isolated"
> carbon stock to the "biosphere" carbon stock were large but very
> slow--millions of years.  With large scale fossil fuel combustion
> we have greatly accelerated the flow rates FROM the isolated
> carbon stock to the biosphere stock (burning through 75 million
> years of stored carbon in a space of 700 years is a 100,000-fold
> acceleration) but the flows from the biosphere BACK TO the
> isolated stock still remain slow.  Hence, we are systemicatically
> accumulating carbon in the biosphere stock due to transfers from
> the isolated fossil stock.
>
> Over the last 400,000 years (excepting the last 150 years), given
> a constant biosphere stock of carbon, equilibrium conditions with
> fairly constant amounts of carbon in the atmosphere have
> prevailed despite the large annual flows between atmosphere,
> vegetation, soils, and oceans.  But we have changed that.
>
> Estimates are that the atmosphere today has about 750 Gigatonnes
> (Gt) of carbon.  In the past 150 years we have released about 300
> Gt of carbon into the atmosphere.  About half remains in the
> atmosphere, increasing atmospheric concentrations about 30% above
> preindustrial levels.  But all of the 300 Gt has been added to
> the biosphere pool, committing us to a changed equilbrium
> condition in the biosphere until geologic time-scale processes
> put it back into the isolated pool (even this thread will be over
> by then).
>
> Forecasts of additional transfers for the 21st century are more
> ominous.  Moderate reference case forecasts (including large
> increases in renewable energy market share) predict an additional
> 1500 Gt of carbon released by 2100, with about 300 Gt released in
> the next 30 years.
>
> Whatever the climate and ecosystem effects of our rapid and
> large-scale changes to the global carbon cycle may be, we will
> commit many generations to come to those consequences unless we
> act in the next few decades to deploy low-carbon energy systems
> at a huge scale globally.  Since we do not know what these
> consequences may be, our generation must decide whether to accept
> the responsibility of preserving options for future generations.
> If we start now, we can preserve the option of stabilizing
> concentrations at 450ppm (about 60% greater than pre-industrial
> levels) with minimal economic disruption.  If we do not act we
> lose this option or radically increase the cost of achieving it later.
>
> Speculating about unproven feedback mechanisms that might deliver
> us from adverse consequences is little different than Enron
> accountants hoping that the limited partnerships will turn out
> right in time to avert a collapse.
>
> We are not just driving our own passenger car toward the
> fog-shrouded cliff; we are the locomotive pulling a train
> hundreds of cars long, filled with our children, their children,
> their children's children, toward the edge.
>
>
> David
>