When it comes to greenhouse gases trapping atmospheric heat, excess carbon dioxide is widely considered our greatest enemy. However, methane is also a powerful greenhouse gas that is driving climate change. And we have been broadcasting much more than we thought.
A team of scientists say that we have greatly underestimated the amount of methane that we have released into the atmosphere through the burning of fossil fuels. In the last three centuries, they point out in a study published in the journal Nature, atmospheric levels of the greenhouse gas have increased by 150%. Methane can enter the atmosphere from natural causes, however the increase has been down to human activities, they say.
Methane is present in the atmosphere in two forms: biological methane and fossil methane. Biological methane is released naturally by wetlands, as well as through man-made rice fields, landfills, and flatulence from livestock. Fossil methane, on the other hand, is largely emitted by people through the extraction and use of fossil fuels such as oil, gas, and coal.
Researchers measured the composition of air from the early 18th century before the Industrial Revolution and compared it to current samples. They found that until about 1870 almost all methane emitted into the atmosphere was biological in nature. Then the fossil component of the heat-trapping gas began to increase rapidly just as we began using fossil fuels on a large scale after the mid-19th century.
"We know that the fossil fuel component is one of our largest emissions, but it has been difficult to pin down because in today's atmosphere, the natural and anthropogenic components of fossil emissions look the same, isotopically," explains Vasilii Petrenko, professor of earth and environmental sciences at the University of Rochester in the United States, co-author of the study.
Unlike carbon dioxide, which can stay in the atmosphere for a century, methane stays only for a relatively short time, or nine years on average. That's why we could significantly reduce methane levels in the atmosphere by controlling our burning of fossil fuels, experts say.
“Most of the methane emissions are anthropogenic, so we have more control. If we can reduce our emissions, it will have a greater impact, ”stresses Benjamin Hmiel, a postdoctoral associate who is the lead author. "If we stopped emitting all carbon dioxide today, the high levels of carbon dioxide in the atmosphere would still persist for a long time."
In other words, reducing atmospheric methane levels can be done more easily than addressing CO2 buildup. "The application of stricter methane emission standards in the fossil fuel industry will have the potential to reduce future global warming to a greater extent than previously thought," says Hmiel.