Houghton Lecture Series - Ray Pierrehumbert (University of Oxford)

Methane vs. CO2 in climate policy: The problem with global warming potenials

Greenhouse gases differ amongst each other in two primary characteristics: their atmospheric

lifetime and their radiative efficiency. These lead to dramatically different kinds of relations

between emissions rate and warming, with great implications for climate policy. The widely

used family of metrics, n-year Global Warming Potentials, do not adequately reflect the actual

consequences of emission control strategies embracing both short-lived and long-lived gases,

and in typical cases exaggerate the urgency of methane emissions abatement. The stock

phrase typically used in most recent journalism, that “Methane is 80X worse than CO2 over a 20

year period” is particularly misleading. This issue has particularly important consequences for

the impact of livestock-based agriculture on climate.

About this Series: Supported by the Houghton Fund, Houghton Lecturers are distinguished visitors from outside MIT invited by the EAPS Program in Atmospheres, Oceans and Climate to spend a period of time, ranging from a week to several months, as scientists-in-residence within our Program. For more information and Zoom password please contact Kayla Bauer: kbauer@mit.edu