*[Enwl-eng] Why methane is so scary
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No images? Click here  Rising levels of methane in the atmosphere may be a sign that a great transition in Earth’s climate has begun. That’s the scary conclusion of new research that applies a geological perspective to this aspect of the climate crisis. You’re reading the Imagine newsletter – a weekly synthesis of academic insight on solutions to climate change, brought to you by The Conversation. I’m Will de Freitas, energy and environment editor, covering for my colleague Jack Marley, who is on holiday but probably still worrying about geological perspectives on the climate crisis. This week, we’ll focus not on carbon dioxide but on the other main greenhouse gas: methane. There’s less methane in the atmosphere than CO₂ and it doesn’t last as long, but it is much more potent as a greenhouse gas. After CO₂, methane is the second biggest driver of global warming and no other gas comes close. But over the past decade or two, methane has been rising fast. Here’s Euan Nisbet, an earth scientist at Royal Holloway University of London and author of the new study: “Imagine accelerating a car with your foot flat down. The car speeds up but eventually air resistance equals engine power and the car hits maximum speed. In 1999, it looked like methane had reached a similar equilibrium between its sources and sinks. Then in late 2006, the amount of methane in the air climbed fast. Even more unexpectedly five years later, the rate of growth sped up again. During the 2020s the growth rate has become yet faster, faster even than during the peak of gas industry leaks in the 1980s.” Nisbet says this growth is likely down to livestock, landfills and, most significantly, wetlands. In fact, a group of researchers, led by Judith Rosentreter of Yale, published research showing aquatic ecosystems are responsible for half of global methane emissions. This includes natural, human-created and human-impacted aquatic ecosystems. As they put it, everything “from flooded rice paddies and aquaculture ponds to wetlands, lakes and salt marshes.” Here’s how it works: “Most of the methane emitted from aquatic ecosystems is produced by micro-organisms living in deep, oxygen-free sediments. These tiny organisms break down organic matter such as dead algae in a process called "methanogenesis”. This releases methane to the water, where some is consumed by other types of micro-organisms. Some of it also reaches the atmosphere.“ Nisbet says an increase in these emissions is one impact of climate change: "increasing rainfall has made wetlands wetter and bigger while rising temperatures have boosted plant growth, providing more decomposing matter and so more methane.” Rosentreter and colleagues also point out that human-impacted aquatic ecosystems – rivers polluted with fertiliser, aquaculture farms, rice farms and so on – “increase the amount of organic matter available to produce methane, which causes emissions to rise”. They say that “globally, rice cultivation releases more methane per year than all coastal wetlands, the continental shelf and open ocean together.” There are solutions. Rosentreter and co suggest restoring salt marshes and mangroves, reducing the amount of fertiliser washing into rivers and wetlands (which leads to algal blooms and more methane when that algae is broken down), and “managing aquaculture farms and rice paddies so they alternate between wet and dry conditions”. Nisbet also cites “plugging leaks in the oil and gas industry, covering landfills with soil, reducing crop-waste burning”. There should be some relatively easy wins, as just 13% of human-made emissions from agriculture, energy and waste are properly regulated, according to a study published earlier this year by Maria Olczak at Queen Mary University of London. “Within almost every sector there are major methane sources that have been largely overlooked”, she writes. “These include the digestive gases of cows and other livestock, methane from the ventilation shafts of coal mines, high-emitting sources in the oil and gas sector (so called super-emitters), and from abandoned mines and oil and gas wells.” Fixing those leaks from the oil and gas industry could actually pay for itself, says Jim Kane of Rice University in the US. He cites a report that suggests “a one-time investment of $11 billion would eliminate roughly 75% of methane leaks worldwide.” Investments in infrastructure and repairs would “not only reduce warming”, he writes, “but they would also generate profits for producers”. There are more leftfield solutions too, such as feeding seaweed to cows. “The native Australian red seaweed Asparagopsis has been shown to markedly reduce methane production in cattle, when added to their diet”, says Catriona McLeod from the University of Tasmania’s Fisheries and Aquaculture Centre. But back to the really scary part. In Nisbet’s new study, he looked at periods over the past few million years when Earth’s climate has flipped from ice age to warmer interglacial periods. He notes that: “With each flip from a glacial to an interglacial climate there have been sudden, sharp rises in atmospheric methane, likely from expanding tropical wetlands.” His worry is that something similar is happening now. The rapid growth of methane since 2006 is “comparable with records of methane from the early years of abrupt phases of past [shifts to interglacial conditions], like the one that warmed Greenland so dramatically less than 12,000 years ago.” “In the past, this took Earth out of stable ice age climates and into warm inter-glacials. But we are already in a warm interglacial. What comes next is hard to imagine”. When you spend your days editing the latest academic research on climate change it can be tempting to zone out a bit, to not let individual bits of bad news affect you too much. But this piece really shook me. My colleague Jack, who worked on the story, described it as the scariest he had ever edited. Nisbet’s article is our most read of 2023. If you’re one of the many people who have already read it, perhaps you could share it with someone else? - Will de Freitas, Energy and environment editor Was this email forwarded to you? Join the 20,000 people who get one email every week about the most important issue of our time. Subscribe to Imagine.  The last time methane in the air rose so fast, Greenland warmed by 10°C within decades.  Half
of global methane emissions come from aquatic ecosystems – much of this
is human-made  Methane must fall to slow global heating – but only 13% of emissions are actually regulated Major sources, like oil and gas 'super-emitters', are almost entirely neglected by regulations.  130 countries have signed a pledge to cut methane emissions by 30%. Success could have a swift impact on global warming.  Can seaweed save the world? Well it can certainly help in many ways Seaweed is in the spotlight for so many reasons. It all sounds too good to be true. So can this wonder weed live up to expectations and fulfill its promise to save us from ourselves? Latest from The Conversation on climate change
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