Methane and the Paris Agreement temperature goals

Abstract

Meeting the Paris Agreement temperature goal necessitates limiting methane (CH₄)-induced warming, in addition to achieving net-zero or (net-negative) carbon dioxide (CO₂) emissions. In our model, for the median 1.5°C scenario between 2020 and 2050, CH₄ mitigation lowers temperatures by 0.1°C; CO₂ increases it by 0.2°C. CO₂ emissions continue increasing global mean temperature until net-zero emissions are reached, with potential for lowering temperatures with net-negative emissions. By contrast, reducing CH₄ emissions starts to reverse CH₄-induced warming within a few decades. These differences are hidden when framing climate mitigation using annual 'CO₂-equivalent' emissions, including targets based on aggregated annual emission rates. We show how the different warming responses to CO₂ and CH₄ emissions can be accurately aggregated to estimate warming by using 'warming-equivalent emissions', which provide a transparent and convenient method to inform policies and measures for mitigation, or demonstrate progress towards a temperature goal. The method presented (GWP*) uses well-established climate science concepts to relate GWP100 to temperature, as a simple proxy for a climate model. The use of warming-equivalent emissions for nationally determined contributions and long-term strategies would enhance the transparency of stocktakes of progress towards a long-term temperature goal, compared to the use of standard equivalence methods. This article is part of a discussion meeting issue 'Rising methane: is warming feeding warming? (part 2)'.