Methane is one of the most potent greenhouse gases in Earth’s atmosphere and measurements of its atmospheric concentration are vital to the monitoring of climate change.

Methane is emitted from a range of natural and anthropogenic sources. Natural sources are due to anaerobic decomposition of matter, and come from sources such as wetlands, animals, plants, and permafrost. Anthropogenic sources include agricultural livestock, land use change, rice cultivation, waste practices, coal mining, natural gas distribution, and biomass burning.

From the 1800s, to the early 1990s atmospheric methane concentrations increased annually at a rate of about 0.9%. However they “flatlined” from around 1999 to 2006, but since then have been hitting new highs. The National Oceanic and Atmospheric Administration (NOAA) has been measuring atmospheric methane concentrations in air samples from locations around the world since the early 1980s, giving scientists a picture of growth rates at different latitudes over the past 35 years. A hypothesised reason for a decline in the late 1990s to min- 2000s in the Northern Hemisphere has been attributed to industrialized countries, including the United States, gaining better control of “fugitive” methane emissions, which escape during the drilling and pumping of oil and natural gas. The rapid increase in emissions since 2006 is currently a topic of debate amongst scientists, however increased emissions from tropical wetlands are considered to be a likely source.

The SCIAMACHY sensor that was aboard the Envisat satellite performed the first space-based measurements of the global distribution of near-surface methane in 2003. Since then other satellites, such as Metop, GOSAT, and Sentinel-5p are able to take measurements of methane from space.

Featured Educators:

• Dr Anna Agusti-Panareda

Optional mini task

Visit methanelevels.org. On this page you will see an interactive graph displaying global methane measurements for the past 1000 years or so. By hovering over each section with your mouse you can find out how methane levels from that time period compare to present day levels. You can also zoom into each section by highlighting it with your mouse. There is also the added option of extending the time period to the last 800,000 years or inserting an overlay of the historical temperature record using the two icons located on the top left of the screen.

What do you notice about the growth of methane levels over time, and during specific time periods?

Don’t forget you can download the video, transcript and take any quizzes available with the links on the right.