AGU: Geophysical Research Letters

 

Editors' Highlight

Renewed growth of atmospheric methane

Methane, an important greenhouse gas, plays a significant role in ozone layer chemistry. Its average concentration in the atmosphere is determined largely by a balance between free emission from the surface (from outgassing wetlands and anthropogenic activity) and destruction by hydroxyl free radicals in the troposphere. Previous measurements of atmospheric methane show persistent increases in concentrations through the latter part of the twentieth century, followed by a period of little change since 1999. However, networks show increasing methane concentrations starting near the beginning of 2007. Using a simple model of atmospheric chemistry and transport, Rigby et al. (2008) investigated what caused this rise. Through simulating the behavior of hydroxyl free radicals, the authors concluded that if the annual mean hydroxyl free radical concentrations did not change, a substantial increase in methane emissions was required simultaneously in both hemispheres between 2006 and 2007 to explain current observations. However, if a small drop in the hydroxyl radical concentration occurred, as is implied by observations, the methane emissions increase is more strongly biased to the Northern Hemisphere.

View abstract

View full article (Subscription required)