摘要：Greenhouse gases other than CO2 make a significant contribution to human-induced climate change, and multi-gas
mitigation strategies are cheaper to implement than those which limit
CO2 emissions
alone. Most practical multi-gas mitigation strategies require metrics to relate the climate warming effects
of CO2 and other greenhouse gases. Global warming potential (GWP), defined as
the ratio of time-integrated radiative forcing of a particular gas to that of
CO2 following a unit mass emission, is the metric used in the Kyoto Protocol, and
we define mean global temperature change potential (MGTP) as an equivalent
metric of the temperature response. Here we show that carbon–climate
feedbacks inflate the GWPs and MGTPs of methane and nitrous oxide by ~ 20% in coupled carbon–climate model simulations of the response to a pulse of
50 × 1990 emissions, due to a warming-induced release of
CO2 from the land biosphere and ocean. The magnitude of this effect is expected to be
dependent on the model, but it is not captured at all by the analytical models usually used
to calculate metrics such as GWP. We argue that the omission of carbon cycle dynamics
has led to a low bias of uncertain but potentially substantial magnitude in metrics of the
global warming effect of other greenhouse gases, and we suggest that the carbon–climate
feedback should be considered when greenhouse gas metrics are calculated and applied.
