Methane may not stay in the air for long, but it still warms the planet quickly. A tiny chemical in the air helps clean it up every day.
Scientists now want to know what will happen to this natural cleaning system as Earth gets hotter.
Methane is a strong greenhouse gas. It traps heat much faster than carbon dioxide, even though it does not stay in the air as long.
Over time, human activities have increased methane levels in the atmosphere. This is concerning because if methane stays longer in the air, it can make global warming worse.
The air’s natural cleaner
The hydroxyl radical is a highly reactive molecule that helps clean the air. Often described as the atmosphere’s “detergent,” it reacts with methane and breaks it down.
“Hydroxyl radicals are important in determining the lifetime of methane and other reactive greenhouse gases, as well as gases that affect public health, including ozone and certain other air pollutants,” said study lead author Qindan Zhu.
This tiny molecule plays a huge role. It removes most of the methane present in the atmosphere.
Many things affect this system
The cleaning process is not simple. Many factors control how much hydroxyl radical is present in the air.
Temperature, sunlight, and water vapor all affect it. Different gases in the atmosphere can either help create it or destroy it. Natural changes in weather patterns also play a role.
Because so many things affect it, scientists find it hard to predict what will happen in the future.
Scientists from the Massachusetts Institute of Technology, the Columbia Climate School, and the National Center for Atmospheric Research built a model to study this system.
The model, called AquaChem, simplifies the Earth so scientists can focus only on the atmosphere. It helps them understand how different factors affect the air’s cleaning ability.
What happens when Earth warms
When the planet gets warmer, the air holds more water vapor. This helps create more hydroxyl radicals, which is good for cleaning methane.
But warming also causes plants to release more natural gases into the air. These gases react with hydroxyl radicals and reduce their amount.
So warming creates two opposite effects at the same time.
Plants release natural gases as part of their normal activity. When temperatures rise, this release increases.
These gases use up hydroxyl radicals faster. This reduces the air’s ability to clean methane.
So even though warmer air helps produce more cleaning molecules, plant emissions cancel out some of that benefit.
The role of plant emissions
Scientists studied what happens if global temperatures rise by 2 degrees Celsius (3.6°F). They found that water vapor increases the cleaning power of the atmosphere.
At the same time, plant gases reduce it. In the end, the atmosphere may only become slightly better at removing methane.
“For methane, the reaction with OH is considered the most important loss pathway,” said Zhu. “About 90 percent of the methane that’s removed from the atmosphere is due to the reaction with OH.”
Even small changes in this system are important. A tiny increase or decrease can change how long methane stays in the air.
This makes it harder to predict future climate changes. Scientists also found that natural emissions from plants are still uncertain, which adds to the challenge.
“There’s a whole range of environmental reasons why we want to understand what’s going on with this molecule,” said study co-author Arlene Fiore from Massachusetts Institute of Technology (MIT).
“We want to make sure it’s around to chemically remove all these gases and pollutants.”
What comes next
Scientists plan to improve their models and include more real-world factors. They want to better understand how plants and other natural systems will respond to warming.
“We know that changes in atmospheric OH, even of a few percent, can actually matter for interpreting how methane might accumulate in the atmosphere,” said Zhu. “Understanding future trends of OH will allow us to determine future trends of methane.”
Ultimately, the research shows that even tiny molecules can have a big impact on Earth’s climate.
The study is published in the Journal of Advances in Modeling Earth Systems.
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