摘要：Equivalence metrics used to quantify the relative climate impacts of different atmospheric forcers serve an essential function in policy and economic discussions about global climate change. The 100-year global warming potential (GWP-100), the most established greenhouse gas (GHG) equivalence metric, is used within the Kyoto Protocol, and in most emissions inventory, trading and offset mechanisms, to assign the mitigation value of non-carbon dioxide greenhouse gases relative to carbon dioxide. In recent literature the GWP-100 and alternative metrics have been used to compare various anthropogenic climate forcers with respect to a wide range of environmental and economic goals. Building on this work, we examine how 16 different static and time-varying CO2-equivalence schemes might influence GHG mitigation across sectors and gases in a perfect and fluid global mitigation regime. This mitigation regime is guided by achieving a global mean radiative forcing (RF) of 5.7 Wm−2 in 2100 from 1765 levels through a mitigation policy of prescribed emissions reductions in each decade. It was found that static metrics defined on 20- instead of 100-year time horizons favor mitigation strategies that maximize the abatement of short-lived gases (e.g. methane), on average resulting in an RF from methane in 2100 of 0.5 Wm−2 instead of 1.1 Wm−2 from 100-year metrics. Similarly, metrics that consider integrated rather than end-point climate impacts imply mitigation strategies that maximize mitigation of shorter-lived GHGs, resulting in higher abatement of agriculture and waste emissions. Comparing extreme scenarios, these mitigation shifts across gases and sectors result in a nearly 30% difference in the representation of methane in global cumulative emissions reductions. This shift across gases and sectors to mitigate shorter-lived GHGs, in lieu of longer-lived GHGs like carbon dioxide, has implications for the long-term warming commitment due to 21st century emissions.
