Rising methane: A new climate challenge | Science

Rising methane: A new climate challenge | Science: In 2007, the amount of methane in the atmosphere (CH4) began to rise after a 7-year period of near-zero growth ([ 1 ][1]). Recent research shows that a second step change occurred in 2014 ([ 2 ][2]). From 2014 to at least the end of 2018, the amount of CH4 in the atmosphere increased at nearly double the rate observed since 2007 (see the figure). Because CH4 is a potent greenhouse gas, rising atmospheric CH4 presents a major challenge to achieving the goals set out in the Paris Agreement, an international consensus to limit temperature increase to 2°C or, if possible, to 1.5°C above preindustrial levels.

![Figure][3]

Methane trends
Data from U.S. National Oceanic and Atmospheric Administration observing stations show that global mean atmospheric CH4 started to rise in 2007, with a sharper increase beginning in 2014 ([ 2 ][2]).

GRAPHIC: N. CARY/ SCIENCE ; (DATA) HTTPS://WWW.ESRL.NOAA.GOV/GMD/DV/DATA

The causes for the recent rise in atmospheric CH4 remain a subject of scientific debate, even for the initial period of increase from 2007 to 2014 ([ 1 ][1]–[ 8 ][4]). Process-based estimates of CH4 emissions from inventory data, wetland models, and other information offer conf