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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Climatic change 33 (1996), S. 31-62 
    ISSN: 1573-1480
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A terrestrial-biosphere carbon-sink has been included in global carbon-cycle models in order to reproduce past atmospheric CO2, 13C and 14C concentrations. The sink is of large enough magnitude that its effect on projections of future CO2 levels should not be ignored. However, the cause and mechanism of this sink are not well understood, contributing to uncertainty of projections. The estimated magnitude of the biospheric sink is examined with the aid of a global carbon-cycle model. For CO2 emissions scenarios, model estimates are made of the resulting atmospheric CO2 concentration. Next, the response of this model to CO2-emission impulses is broken down to give the fractions of the impulse which reside in the atmosphere, oceans, and terrestrial biosphere - all as a perturbation to background atmospheric CO2 concentration time-profiles that correspond to different emission scenarios. For a biospheric sink driven by the CO2-fertilization effect, we find that the biospheric fraction reaches a maximum of roughly 30% about 50 years after the impulse, which is of the same size as the oceanic fraction at that time. The dependence of these results on emission scenario and the year of the impulse are reported.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-1480
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Analyses of emissions, and consequent chlorine loading, show that projected use of 2,2-dichloro-1,1,1-trifluoroethane (HCFC-123) will result in a virtually indiscernible impact on stratospheric ozone. Parametric scenarios uphold this conclusion, even for extreme levels of emissions far exceeding those of current technologies and practices. Additional scenarios reaffirm the conclusion for continued use – beyond the scheduled phaseout date – as a refrigerant in closed systems. By contrast, use of this compound offers unique opportunities to reduce global warming. Moreover, time-dependent analyses show that the minimal contribution to stratospheric chlorine from HCFC-123 emissions will not peak until more than a decade after the residual peaks of chlorine and bromine, from prior chlorofluorocarbon and halon releases, subside. While no single index exists to compare the relative demerits of ozone depletion and climate change, three conclusions are clear. First, reversal of the buildup of bromine and chlorine (i.e., healing of the ‘ozone layer’) is underway and progressing on target, while sufficient practical remedies for global climate change are far more difficult. Second, the analyses show that phaseout of all chlorinated, and conceptually – but much less probably – all brominated, compounds of anthropogenic origin targets some compounds that provide environmental benefits. Most chlorinated and brominated compounds do warrant phaseout; the exceptions are those with very short atmospheric lifetimes, and consequent low ozone depletion potential (ODP), that also offer offsetting environmental benefits. And third, since new global environmental concerns may, and probably will, be identified in the future, a more scientific approach is needed to determine environmental acceptability or rejection.
    Type of Medium: Electronic Resource
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