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Medientyp:
E-Artikel
Titel:
If Anthropogenic CO2 Emissions Cease, Will Atmospheric CO2 Concentration Continue to Increase?
Beteiligte:
MacDougall, Andrew H.;
Eby, Michael;
Weaver, Andrew J.
Erschienen:
American Meteorological Society, 2013
Erschienen in:Journal of Climate
Sprache:
Englisch
DOI:
10.1175/jcli-d-12-00751.1
ISSN:
0894-8755;
1520-0442
Entstehung:
Anmerkungen:
Beschreibung:
<jats:p> If anthropogenic CO<jats:sub>2</jats:sub> emissions were to suddenly cease, the evolution of the atmospheric CO<jats:sub>2</jats:sub> concentration would depend on the magnitude and sign of natural carbon sources and sinks. Experiments using Earth system models indicate that the overall carbon sinks dominate, such that upon the cessation of anthropogenic emissions, atmospheric CO<jats:sub>2</jats:sub> levels decrease over time. However, these models have typically neglected the permafrost carbon pool, which has the potential to introduce an additional terrestrial source of carbon to the atmosphere. Here, the authors use the University of Victoria Earth System Climate Model (UVic ESCM), which has recently been expanded to include permafrost carbon stocks and exchanges with the atmosphere. In a scenario of zeroed CO<jats:sub>2</jats:sub> and sulfate aerosol emissions, whether the warming induced by specified constant concentrations of non-CO<jats:sub>2</jats:sub> greenhouse gases could slow the CO<jats:sub>2</jats:sub> decline following zero emissions or even reverse this trend and cause CO<jats:sub>2</jats:sub> to increase over time is assessed. It is found that a radiative forcing from non-CO<jats:sub>2</jats:sub> gases of approximately 0.6 W m<jats:sup>−2</jats:sup> results in a near balance of CO<jats:sub>2</jats:sub> emissions from the terrestrial biosphere and uptake of CO<jats:sub>2</jats:sub> by the oceans, resulting in near-constant atmospheric CO<jats:sub>2</jats:sub> concentrations for at least a century after emissions are eliminated. At higher values of non-CO<jats:sub>2</jats:sub> radiative forcing, CO<jats:sub>2</jats:sub> concentrations increase over time, regardless of when emissions cease during the twenty-first century. Given that the present-day radiative forcing from non-CO<jats:sub>2</jats:sub> greenhouse gases is about 0.95 W m<jats:sup>−2</jats:sup>, the results suggest that if all CO<jats:sub>2</jats:sub> and aerosols emissions were eliminated without also decreasing non-CO<jats:sub>2</jats:sub> greenhouse gas emissions CO<jats:sub>2</jats:sub> levels would increase over time, resulting in a small increase in climate warming associated with this positive permafrost–carbon feedback. </jats:p>