Narrator: This is Science Today. Atmospheric methane is the second most important greenhouse gas in the world. Scientists at the University of California, Irvine have been measuring this natural gas for decades and have found that after a rise in emissions during the 1980s, methane levels have stayed nearly flat for over seven years. F. Sherwood Rowland, a professor of chemistry and Earth system science, says these findings suggest that methane emissions can be controlled.
Rowland: If we really make an effort, we may be able to reduce it substantially. We know that two hundred years ago, the amount of methane in the air was around 700 parts per billion and now it's 1700. So, it is possible to think about heading back toward the 700 that existed before we had all of the uses of methane that we have at the present time.
Narrator: Methane emissions are produced by a number of sources including fossil-fuel extraction, cattle, and rice paddies. Leaks connected to oil and gas have also produced atmospheric methane, but Rowland says recent controls of these leaks may have contributed to the lack of change in methane emissions. For Science Today, I'm Larissa Branin.