The first group focuses on climate change science. In the opening chapter of this section, Jerry Mahlman (Senior Research Fellow at the National Center for Atmospheric Research) describes what he terms the “global warming dilemma.” According to Mahlman, the scientific community has reached an effective consensus that immediate and quite aggressive steps would be required to avoid climatic changes that are large in comparison with those observed in the Earth's geological record. Stabilizing atmospheric concentrations of carbon dioxide, for example, would require permanent emissions reductions of roughly 60–80%. Moreover, the long lags in the Earth's response to changes in the composition of the atmosphere suggests that even this stringent scenario would be insufficient to prevent moderate temperature increases in the coming decades. Based on his reading of the scientific literature, Mahlman concludes that deferring action until climate change has broadly recognized deleterious effects would most likely “lock in” quite profound environmental impacts with effects lasting for centuries and even millennia. In terms of mechanisms, this argument appeals to the view that today's greenhouse gas emissions might use up the Earth's assimilative capacity, thus increasing the length of time that greenhouse gases remain in the atmosphere. On top of this, Mahlman notes that most scientific studies have emphasized time scales of one century or less in evaluating climate impacts. But impacts such as sea-level rise, which would be strongly affected by the melting and breakup of glacial formations such as the West Antarctic Ice Sheet, occur over much longer time horizons with a high degree of irreversibility. This makes climate change an issue of intergenerational fairness that pits present society's willingness to bear significant economic costs against the goal of protecting future generations from environmental harms that are hypothetical and yet potentially catastrophic.
Howarth, R.B. and Sinnott-Armstrong, W. (2005), "Introduction", Sinnott-Armstrong, W. and Howarth, R.B. (Ed.) Perspectives on Climate Change: Science, Economics, Politics, Ethics (Advances in the Economics of Environmental Resources, Vol. 5), Emerald Group Publishing Limited, Bingley, pp. xi-xx. https://doi.org/10.1016/S1569-3740(05)05016-9
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