The adequacy of GWPs as indicators of damage costs incurred by global warming

Abstract

This article looks at the ability of Global Warming Potentials (GWPs) to work as indicators of equivalence for temperature development and damage costs. We look at two abatement scenarios that are equivalent when using 100-year GWPs: one scenario reduces short-lived gases, mainly methane (CH4); the other scenario reduces carbon dioxide (CO2). Despite their equivalence in terms of CO2 equivalents, the scenarios do not result in equal rates or levels of temperature change. The disparities continue as we move further down the chain of causality toward damage costs, measured either in terms of rate of climate change or level of climate change. Compared to the CH4 mitigation scenario, the CO2 mitigation scenario gives present value costs 1.3 and 1.5 times higher for level- and rate-dependent damage costs, respectively, assuming a discount rate of 3%. We also test the GWPs for other time horizons and the conclusions remain the same; using GWP as an index to reflect equivalent climate effects and damage costs from emissions is questionable.