Another day, another pair of studies warning of the dire consequences of inaction on greenhouse gas reduction. This time the admonition is even stronger than the last. On the bright side, they aren't saying we have to cease traveling, just stop emitting greenhouse gases to do it. On the not-so-bright side, according to the article in the Washington Post, even that Herculean effort won't be enough to completely stop the warming trend for several centuries. There still seems to be some time to act though in order to avoid the worst warming effects.

Action of this nature doesn't take place without political impetus and so the Post briefly discusses the CO2 reduction goals of each of the current presidential candidates as well as those of several other political figures. Mr. Obama has the most ambitious intentions: 80 percent by 2050. While that's pretty good, it's not the 100 percent recommended. Maybe some more studies (and your calls and letters) will encourage them to aim higher.

To read abstracts from the two studies for yourself, make the jump.


Abstract from Geophysical Research Letters:

GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L04705, doi:10.1029/2007GL032388, 2008

Stabilizing climate requires near-zero emissions

H. Damon Matthews
Department of Geography, Planning and Environment, Concordia University, Montreal, Quebec, Canada

Ken Caldeira
Department of Global Ecology, Carnegie Institution of Washington, Stanford, California, USA

Abstract
Current international climate mitigation efforts aim to stabilize levels of greenhouse gases in the atmosphere. However, human-induced climate warming will continue for many centuries, even after atmospheric CO
2 levels are stabilized. In this paper, we assess the CO2 emissions requirements for global temperature stabilization within the next several centuries, using an Earth system model of intermediate complexity. We show first that a single pulse of carbon released into the atmosphere increases globally averaged surface temperature by an amount that remains approximately constant for several centuries, even in the absence of additional emissions. We then show that to hold climate constant at a given global temperature requires near-zero future carbon emissions. Our results suggest that future anthropogenic emissions would need to be eliminated in order to stabilize global-mean temperatures. As a consequence, any future anthropogenic emissions will commit the climate system to warming that is essentially irreversible on centennial timescales.

Received 17 October 2007; accepted 11 January 2008; published 27 February 2008.


Abstract from Global Biogeochemical Cycles:

Future changes in climate, ocean circulation, ecosystems, and biogeochemical cycling simulated for a business-as-usual CO2 emission scenario until year 4000 AD

Andreas Schmittner
College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, USA

Andreas Oschlies
Leibniz Institute of Marine Sciences at the Christian-Albrechts University of Kiel (IFM-GEOMAR), Kiel, Germany

H. Damon Matthews
Planning and Environment, Concordia University, Montreal, Quebec, Canada

Eric D. Galbraith
Atmospheric and Oceanic Sciences, Princeton University, Princeton, New Jersey, USA


GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L04705, doi:10.1029/2007GL032388, 2008

Stabilizing climate requires near-zero emissions

H. Damon Matthews
Department of Geography, Planning and Environment, Concordia University, Montreal, Quebec, Canada

Ken Caldeira
Department of Global Ecology, Carnegie Institution of Washington, Stanford, California, USA

Abstract
A new model of global climate, ocean circulation, ecosystems, and biogeochemical cycling, including a fully coupled carbon cycle, is presented and evaluated. The model is consistent with multiple observational data sets from the past 50 years as well as with the observed warming of global surface air and sea temperatures during the last 150 years. It is applied to a simulation of the coming two millennia following a business-as-usual scenario of anthropogenic CO2 emissions (SRES A2 until year 2100 and subsequent linear decrease to zero until year 2300, corresponding to a total release of 5100 GtC). Atmospheric CO2 increases to a peak of more than 2000 ppmv near year 2300 (that is an airborne fraction of 72% of the emissions) followed by a gradual decline to ∼1700 ppmv at year 4000 (airborne fraction of 56%). Forty-four percent of the additional atmospheric CO2 at year 4000 is due to positive carbon cycle–climate feedbacks. Global surface air warms by ∼10°C, sea ice melts back to 10% of its current area, and the circulation of the abyssal ocean collapses. Subsurface oxygen concentrations decrease, tripling the volume of suboxic water and quadrupling the global water column denitrification. We estimate 60 ppb increase in atmospheric N2O concentrations owing to doubling of its oceanic production, leading to a weak positive feedback and contributing about 0.24°C warming at year 4000. Global ocean primary production almost doubles by year 4000. Planktonic biomass increases at high latitudes and in the subtropics whereas it decreases at midlatitudes and in the tropics. In our model, which does not account for possible direct impacts of acidification on ocean biology, production of calcium carbonate in the surface ocean doubles, further increasing surface ocean and atmospheric pCO2. This represents a new positive feedback mechanism and leads to a strengthening of the positive interaction between climate change and the carbon cycle on a multicentennial to millennial timescale. Changes in ocean biology become important for the ocean carbon uptake after year 2600, and at year 4000 they account for 320 ppmv or 22% of the atmospheric CO2 increase since the preindustrial era.

Received 5 February 2007; accepted 6 September 2007; published 14 February 2008.

[Source: Washington Post, journals mentioned]

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