The Concept of Commitment - The Changing Arctic Environment: The Arctic Messenger - page 384

to have already absorbed about 48% of the carbon emitted to the atmosphere from an-
thropogenic sources between 1800 and 1994. However, carbon dioxide absorption by the
oceans is a slow process. There are major bottlenecks in the route to the deep ocean (me-
ridional overturning circulations), a warm ocean can hold less carbon dioxide than a cold
ocean, and the depletion of carbonate in the surface waters will slow the conversion of car-
bon dioxide into bicarbonate. Although it makes up only 15% of the total world ocean sur-
face, theNorthAtlantic contains nearly 25%ofthecarbonreleased byhumanactivity since
1800. The net result of all this bad news is that over time, the ocean will become saturated
with CO 2 , beginning first with its surface waters. As this state is approached, the ocean's
ability to absorb “excess” carbon dioxide will decline and atmospheric concentrations will
increase. Some studies have already reported regional saturation of CO 2 in the ocean.
The stark implication is that even if we could stabilize our carbon dioxide emissions
at current levels, we will simply be adding to the CO 2 stockpile we have already dumped
into the atmosphere. Therefore, we are “committed” to seeing a continuous increase of at-
mospheric carbon dioxide concentrations for centuries to come (and of increasing temper-
atures). To make matters worse, we all know we are far from achieving even a stabilization
of current levels. The rate at which we are adding carbon dioxide to the atmosphere greatly
exceeds its rate of removal. Combine this with our knowledge about the slow atmospheric
removal processes of the carbon cycle and we can foresee that even moderate reductions
in global emissions will only reduce the rate of increase of atmospheric concentrations in
coming decades. The practical importance in terms of climate policy of this huge “stock-
pile” of carbon dioxide that now resides in our atmosphere/ocean system was shown in
a 2007 study by Montenegro and colleagues. They estimated how long anthropogenically
produced carbon dioxide will stay in the atmosphere following one of the emission scenari-
os used by the Intergovernmental Panel on Climate Change (IPCC). The scenario chosen
was the A2 scenario until the end of the twenty-first century, followed by a linear decline
in emissions until zero emissions are reached in 2300. It was found that 75% of all anthro-
pogenic carbon dioxide will remain in the atmosphere for an average of 1,800 years and