Methane and the Paris Agreement temperature goals
Michelle Cain, Stuart Jenkins, Myles Allen, John Lynch, David J. Frame, Adrian Macey, Glen P. Peters
Abstract
Meeting the Paris Agreement temperature goal necessitates limiting methane (CH 4 )-induced warming, in addition to achieving net-zero or (net-negative) carbon dioxide (CO 2 ) emissions. In our model, for the median 1.5°C scenario between 2020 and 2050, CH 4 mitigation lowers temperatures by 0.1°C; CO 2 increases it by 0.2°C. CO 2 emissions continue increasing global mean temperature until net-zero emissions are reached, with potential for lowering temperatures with net-negative emissions. By contrast, reducing CH 4 emissions starts to reverse CH 4 -induced warming within a few decades. These differences are hidden when framing climate mitigation using annual ‘CO 2 -equivalent’ emissions, including targets based on aggregated annual emission rates. We show how the different warming responses to CO 2 and CH 4 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)’.