Global methane emissions may be underestimated

Methane is 25 times more perilous for global warming than CO₂, and scientists’ understanding of its dynamics has changed in recent years, researchers warned at the São Paulo School of Advanced Methane Science.

By André Julião in Ilhabela (Brazil)  |  Agência FAPESP – Global methane emissions may have been underestimated, judging by recent changes in scientists’ understanding of how methane behaves on Earth, in conjunction with the difficulty of measuring emissions from the oceans. Methane molecules retain 25 times more heat than carbon dioxide molecules.

If methane emissions are indeed substantially larger than previously estimated, the consequences range from an even sharper rise in global temperatures to the possible triggering of a “clathrate bomb”.

Methane clathrates are unstable water/methane compounds that apparently form large deposits in various places below the seafloor, often in ice. According to the “clathrate bomb” hypothesis, rising sea temperatures could rapidly release these deposits into the atmosphere, leading to a mass extinction event similar to the Permian-Triassic or Paleocene-Eocene extinction events (which occurred approximately 250 million and 55 million years ago, respectively).

“As the Arctic and Antarctic ice sheets melt owing to global warming, much of the methane trapped under the ice in the form of gas hydrate is starting to seep out,” said Antje Boetius, a researcher at the Max Planck Institute for Marine Microbiology in Bremen, Germany.

Boetius was one of the participants in the São Paulo School of Advanced Methane Science, which was held from October 16-23, 2018 in Ilhabela (São Paulo State, Brazil) and concluded on October 26 at the University of São Paulo’s Luiz de Queiroz College of Agriculture (ESALQ-USP) in Piracicaba.

“The School aimed to survey the new knowledge frontiers in this area of science, especially with regard to the microorganisms that produce methane in nature,” said Vivian Pellizari, a professor at the University of São Paulo’s Oceanographic Institute (IO-USP) and an organizer of the event. In addition to Brazilian and foreign speakers, 73 graduate students and postdoctoral researchers from 13 countries other than Brazil attended the event.

“In order to be able to control methane emissions, we need to know more about the basic metabolism of the microorganisms and their hosts,” Pellizari told Agência FAPESP. “New groups of these microorganisms have been described in recent years and need to be better understood.”

Cattle and flooded areas of the Amazon and Pantanal are the main sources of methane emissions in Brazil. Waterlogged land accumulates decomposing organic matter, leading to lower levels of oxygen and the buildup of methane.

Herds of cattle emit methane during digestion. Changes in land use also affect the proportions of methane that are released into the atmosphere and consumed.

Microorganisms in the environment play a major role in global methane emissions. Although recent advances have given rise to new knowledge, there are still more questions than answers about the global volume of methane, its biogeochemical cycle, and the microbiology of methanogenesis (production) and methanotrophy (consumption).

Scientists are looking for organisms that produce and consume methane in manmade environments as well as some of the most extreme natural environments on Earth. The School also discussed methodologies that could be used to detect the presence of methane elsewhere in space besides Earth, such as Jupiter’s moons. Methane is considered a possible sign of extraterrestrial life.

“Methane is a key element for astrobiology and to enable us to know more about the origin of life,” said Ken Takai, a researcher at the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) and a speaker at the event.

Another topic discussed was the recent application of knowledge about methane to bioenergy production, waste management, and agronomy. “The methane that forms in the soil isn’t released into the atmosphere if there are biological activities that consume enough of it. It is released if methane production and consumption are unbalanced. This was one of the main discussions at the event relating to agriculture and soil management,” said Fernando Dini Andreote, a professor at ESALQ-USP.

Ice that burns

Natural clathrate or gas hydrates are networks of water crystals that house gas molecules, typically methane. They burn easily and are considered possible future sources of fuel by the energy industry. This gas remains stable when these crystals are trapped under the seabed at low temperatures or in ice.

“However, we have evidence that sea levels have changed significantly throughout our history. The reduction in pressure from the oceans due to this change, in addition to the rise in sea temperature, is one source of gas hydrate release. We know sea temperature has risen, so we’re probably reaching an age or period in which more gas hydrate is exposed than ever before in human history,” Boetius said.

The situation in the Arctic is particularly alarming, he warned, as there are many gas hydrate deposits in shallow waters, only a few meters below the ice. “The Arctic has many kilometers of shallow sea, which many contain large deposits of gas hydrate. Most of the Arctic is frozen at this time, but we don’t know if it will remain so until the end of the century,” he said.

Investment in research

In addition to these large deposits of gas hydrate, global methane emissions from the oceans can only be estimated. There are well-known methods of measuring these emissions, but many more data points are required in addition to the few existing ones to produce a reliable estimate.

“For this kind of survey, we need ships, robots and engineers. It’s a very high-tech endeavor, so few countries are in a position to do it, although all countries should at least measure emissions in their own exclusive economic zone. In sum, for these reasons, we don’t have enough data right now,” Boetius said.

Methane emissions may therefore be underestimated, as stressed in the latest reports from the Intergovernmental Panel on Climate Change (IPCC). “We only have estimates based on scant scientific data,” he noted.

Changing the status quo requires heavy investment in research. However, the United States has reduced its investment in research in the last two years despite being the second-largest emitter of greenhouse gases in the world, behind China.

“The US has a disproportionate impact on the climate because of our lifestyle and the way we manage our industry. We contribute a great deal to the amount of methane in the world. As a result, we have the responsibility to do something about it,” said Brendan Bohannan, a professor at the University of Oregon and one of the organizers of the School.

“At the same time, funding for science in the US has been flat or actually fallen. Not to mention the overall decline in the importance of science to policymaking at the federal level. This is a major concern. Unfortunately, when the US makes a national decision, it has a global impact. I hope Brazil takes the US as a bad example and avoids doing the same.”

In addition to attending lectures, presenting research findings and engaging in group activities, the participants made technical visits to ESALQ-USP and the same university’s Center for Nuclear Energy in Agriculture (CENA-USP), which is also located in Piracicaba.

For more information on the São Paulo School of Advanced Methane Science: spsasmethane.com.