Cost-effective implementation of the Paris Agreement using flexible
greenhouse gas metrics
Abstract
Greenhouse gas (GHG) emission metrics, that is, conversion factors to
evaluate the emissions of non-CO2 climate forcers on a common scale with
CO2, serve crucial functions upon the implementation of the Paris
Agreement. While different metrics have been proposed, they have not
been investigated under a range of pathways, including those
significantly overshooting the temperature targets of the Paris
Agreement. Here we show that cost-effective metrics that minimize the
overall cost of climate mitigation are time-dependent, primarily
determined by the period remaining before the eventual stabilization,
and strongly influenced by temperature overshoot. Our study suggests
that flexibility should be maintained to adapt the choice of metrics in
time as the future unfolds, if cost-effectiveness is a key consideration
for global climate policy, instead of hardwiring the 100-year Global
Warming Potential (GWP100) as a permanent feature of the Paris Agreement
implementation as is currently under negotiation.