Relative Contributions of Global Warming to Various Climate Sensitive Risks, and Their Implications for Adaptation and Mitigation

A rationale for mitigating global warming (GW) is that warming might exacerbate many of today’s urgent problems — hunger, malaria, water shortage, coastal flooding, and habitat conversion — which could be particularly problematic for developing countries. Recent assessments of the global impacts of climate change indicate that into the 2080s, except for coastal flooding, GW’s contribution to these problems [∆P(GW)] would be small compared to P(BASELINE), the problem’s magnitude in the absence of warming, i.e., under baseline conditions. Hence, mitigation can, at best, reduce only the smaller portion of the total problem [= ∆P(GW) + P(BASELINE)]. To compound matters, costs of markedly reducing ∆P(GW) through mitigation are high; moreover, because of the inertia of the climate system, its benefits are backloaded while costs have to be borne up front for decades. Discounting further magnifies this asymmetry between costs and benefits. By contrast, approaches that would help societies cope with or reduce vulnerabilities to the urgent problems noted above would, by reducing both P(BASELINE) and ∆P(GW), deliver greater benefits. Devising and/or using such approaches now would allow benefits to accrue in relatively short order, and help societies adapt to GW’s future impacts, if and when those impacts become significant. With regard to coastal flooding, the exception to the rule that ∆P(GW) < P(BASELINE), protecting against such flooding (i.e., adaptation) is, into the 2080s, substantially cheaper than the Kyoto Protocol despite the latter’s comparatively modest reduction requirements. Thus, relative to mitigation, for the next several decades the benefits of such adaptation are likely to be larger, occur sooner, more certainly, and more contemporaneously with costs. Hence, over this period adaptation is probably more costeffective than mitigation. In particular, the Kyoto Protocol delivers too little too late, and costs too much. Importantly, by reducing hunger, malaria, water shortage, and habitat loss now, such adaptation approaches would enable sustainable development and improve human well-being in its various dimensions, especially in developing countries. In turn, that would further enhance their ability to adapt to or mitigate climate change. ∗ Views expressed in this paper are not necessarily those of the U.S. government or any of its parts.