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Ask an Expert: How Does Methane Play a Role in Climate Change?
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While carbon dioxide dominates the climate change conversation, a growing body of research has revealed that methane functions as a powerful greenhouse gas. But how does methane play a role in climate change? And what can we do to reduce the methane in our atmosphere?
Prof. Yuzhong Zhang—who heads the Atmospheric Environment Research Lab at Westlake University and served as a postdoctoral fellow at Harvard University—has spent years studying and quantifying methane emissions. We asked him to explain the science behind methane and its effects on the Earth’s climate.
What is methane and how does it play a role in climate change?
Methane is a greenhouse gas, like carbon dioxide. It can trap heat in the atmosphere by absorbing infrared radiation.
Methane is a very strong infrared absorber, at least an order of magnitude stronger than carbon dioxide on a per molecule basis.
In addition to this direct radiative effect, methane can also react chemically in the atmosphere to produce carbon dioxide, water vapor, and ozone. All these are greenhouse gases, which result in indirect climate effects.
By combining the direct and indirect effects, scientists have estimated that methane emissions from human activities are responsible for about 40% of the warming we have seen, which is not an insignificant portion.
Where do methane emissions come from?
Methane comes from many sources, including manmade sources such as the oil and gas industry, coal mining, livestock, rice cultivation, landfills, and wastewater treatment.
It also comes from natural sources—an important one is wetlands.
As you can see, methane emissions are intricately related to many aspects of our society and environment. The provision of food and energy. The management of waste, and more broadly, our cities. Changes in land use and how natural environments, such as wetlands, can respond to climate change.
This makes it a very exciting research area.
In your research into methane emissions, what growth trends have you observed?
Methane concentrations in the atmosphere have increased from a preindustrial level of 700 parts per billion, based on the ice core records, to a current level of about 1,900 parts per billion. This is a rise of about a factor of three, which is huge.
More importantly, in the last few decades, we have seen a very rapid upswing in the methane concentration in the atmosphere.
The increases in 2021 and 2020 constitute record highs since the 1980s, when we started to have a global monitoring network.
The reasons behind these recent rapid increases are not very well understood, so this is a very active research area that our group is working on.
How much methane in the atmosphere is too much? Is there an upper limit?
Every bit of methane contributes to warming, so we want there to be less. The less, the better.
People have realized that we need to substantially slow down the rise in methane or even reverse the trend by rapidly taking action to reduce methane emissions across all sectors.
If we want to get serious about lowering methane emissions in the atmosphere, how much do we need to cut and what should we target?
The current goal is a 30% reduction of anthropogenic emissions by 2030, relative to the 2020 level.
This is not an easy task, given that our demands for food and energy as well as waste treatment are all projected to increase in the next 10 years.
So, this requires immediate action across all sectors.
The fossil fuel sector is considered low-hanging fruit, because for a large part of it, the technology is already there to mitigate methane emissions.
Agricultural and waste emissions are more challenging. But things can still be done by improving the management in these areas and by building infrastructure for less-developed regions, so measures can be implemented.
If we take all these suggested actions quickly, a 30% reduction is possible to achieve, though not without difficulty.