Extending the Cumulative Emissions Framework to Non-CO2 Gases: Can This Inform the Allocation of National Emissions Allowances?

Abstract:

It is now well established that global temperature responds approximately linearly to cumulative CO2 emissions, allowing a finite carbon emissions budget to be defined and associated with a given global temperature target. However, it is less obvious how to incorporate into this framework the other greenhouse gases and aerosol emissions, owing largely to their widely varying atmospheric lifetimes and consequent climate effect. In this presentation, I will propose a new way to compare the climate effect of a range of greenhouse gases and aerosols. I will first assess the lifetime of the temperature response to different types of emissions, which depends on the atmospheric lifetime of the gas in question, as well as the timescale of the climate system response to forcing. I will then use this timescale of temperature decay to weight emissions of a given gas over time, generating an estimate of the effective cumulative emissions that produce a given amount of temperature change at a particular time. Finally, I will illustrate the application of this method to the question of quantifying historical national contributions to global warming and determine future emission allowances for a given climate target.