How climate metrics affect global mitigation strategies and costs: a multi-model study

Abstract

In climate policy, substitutions metrics are used to determine exchange ratios for different greenhouse gases as part of a multi-gas strategy. The suitability of the metric depends on the policy goals and considerations regarding its practical use. Here, we present a multimodel comparison study to look at the impact of different metrics on the mitigation strategies and global climate policy costs. The study looks into different Global Warming Potentials (GWP) and the Global Temperature change Potential (GTP). The study shows that for all the models, varying between GWPs -from different IPCC reports, with different integration periods: 20 or 100 years -has a relatively small influence on policy costs (< 2.2 % spread across scenarios with a 2.8 W/m 2 target) and climate outcomes. Metrics with a constant low substitution value for methane (effectively reducing its abatement), in contrast, lead to highercost mitigation pathways (with an average cost increase of 32.8 % in a 2.8 W/m 2 scenario). If implemented efficiently, a time-varying GTP leads to a limited cost reduction compared to GWP. However, under imperfect foresight in combination with inertia of CH 4 abatement options, or if implemented sub-optimally, time-varying GTP can result in higher costs than a 100-year GWP. At the same time, given a long-term radiative forcing target, a time-varying GTP results in slightly higher maximum global temperature change rates.

Robust climate change research: a review on multi-model analysis

“…They indicated that the policy costs for reaching these two policy targets are roughly the same; however, they should be remarkably lower than the corresponding costs for achieving the global warming-rise goal of 2°C warming-rise goal, and this is in agreement with the relative finding in Tavoni et al (2014). Furthermore, climate metrics, like global warming potentials and global temperature change potential, may also play a significant role in the mitigation strategies and policy costs (Harmsen et al 2016).…”

Cost-effective implementation of the Paris Agreement using flexible greenhouse gas metrics

“…Previous studies showed that the use of GWP100 does lead to some but not a strong disadvantage in terms of global total abatement costs under stabilization pathways (including small overshoot pathways) ( 25 – 28 , 53 – 55 ). While we confirm this finding { Fig.…”

“…S9 and S10). The high costs associated with the use of long time horizon metrics including GTP100 are due to the need for more CO 2 abatement at a higher cost to compensate for CH 4 emissions valued low ( 27 , 28 ).…”

“…S12 to S16). Previous studies (25,26,28) reported remarkable regional and sectoral impacts from the choice of metrics, despite relatively small global impacts. Our results imply that these regional and sectoral variations in cost could be larger under overshoot pathways.…”

“…The analysis was performed for a contrasted range of pathways toward the Paris Agreement temperature target levels, including those substantially overshooting the 2°C target level temporarily, which were not assessed in the IPCC Special Report "Global warming of 1.5 °C" (SR15) (24). Low overshoots (i.e., exceedance warming of up to 0.1° or 0.2°C) have been considered in previous related studies (25)(26)(27)(28); however, higher overshoots above 2°C, reflecting the current policy trend [i.e., ~3°C warming by 2100; (29,30)], have not been considered before despite their increasing likelihood. Overshoot pathways are intended to illustrate the relatively unexplored scenarios in which the world would fail to take stronger near-term climate actions that would have been consistent with the Paris Agreement; however, it would later engage in very deep mitigation, allowing a recovery from overshoot.…”