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Worldwide increase in methane bubbles due to climate change

Researchers have found that a rise in temperatures due to global warming causes more frequent emissions from methane bubbles. When these methane bubbles burst, they release methane gas into the atmosphere that contributes to climate change.

While most attention has been given to carbon dioxide, it isn’t the only greenhouse gas that scientists are worried about. Carbon dioxide is the most important human-emitted greenhouse gas, but methane has also increased in the atmosphere and it adds to our concerns.

While methane is not currently as important as carbon dioxide, it has a hidden danger. Molecule for molecule, methane traps more heat than carbon dioxide; approximately 30 times more, depending on the time frame under consideration. However, because methane is present in much smaller concentrations (compared to carbon dioxide), its aggregate effect is less.

But what has scientists focusing on methane is the way it is released into the atmosphere. Unlike carbon dioxide, which is emitted primarily through burning of fossil fuels, methane has a large natural emission component. Now, researchers from Radboud University in the Netherlands have shown that rising temperatures increase the numbers of methane bubbles produced.

 “Never before have such unequivocal, strong relationships between temperature and emissions of methane bubbles been shown on such a wide, continent-spanning scale,” said study co-author Sarian Kosten of Radboud University.

The study closely examined the impacts of aquatic environments on greenhouse gas emissions, focusing on shallow lakes, ponds, rivers, and wetlands. These marine environments are responsible for a substantial amount of emissions, much of which comes from methane bubbles.

These bubbles filled with methane gas develop in the sediment at the bottom of bodies of water. When the bubbles reach the surface, the gas is released into the atmosphere.

The international research team collaborated with researchers at Netherlands Institute of Ecology (NIOO-KNAW) for a massive experiment. First, they collected existing data on methane bubbles, ranging from forest ponds in Canada to postglacial lakes in northern Sweden.

“Next, we simulated methane bubble production in 1000-litre ‘mini-lakes’ at the NIOO, where we could accurately control temperature and other conditions,” said co-author Ralf Aben. “In this way we excluded causes other than the rise in temperature.”

The scientists used open tanks filled with water and sediment to mimic an annual cycle. Four tanks had an average Dutch climate, while four other tanks contained temperatures which were up to 4 degrees Celsius higher than average.

The researchers found that the higher temperatures led to 50 percent higher emission of methane bubbles. They estimated that a temperature rise of 1 degree Celsius caused up to 20 percent higher methane emission. This leads to additional greenhouse gases in the atmosphere and to an additional temperature increase.

Methane is produced more frequently in nutrient-rich sediments, which means that methane production can be slowed down by reducing the amount of fertilizer being used.

The experts say that global warming will not be easy to stop, but that it is still possible.

“Every tonne of greenhouse gas that we emit leads to additional emissions from natural sources such as methane bubbles,” said Kosten. “Luckily, the opposite is also true: if we emit less greenhouse gas and the temperature drops, we gain a bonus in the form of less methane production. This bonus from nature should be our motivation to reduce greenhouse gas emissions even further.”

                                                Source: Science Daily

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