Rising methane emissions threaten to push climate change goals out of reach

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The Earth’s climate crisis is starting to look even worse than scientists feared – partly because of the amount of meat we eat and our movements.

Global emissions of methane, a potent greenhouse gas, have skyrocketed over the past decade, according to two new studies that have tracked the growing sources of odorless and colorless gas. The increase in methane, combined with carbon dioxide and other greenhouse gases, could warm the Earth’s atmosphere by 3 to 4 degrees Celsius before the end of this century – well above levels that , scientists say could be catastrophic for millions of people around the world.

“It completely exceeds our budget to stay below 1.5 to 2 degrees of warming,” said Benjamin Poulter, researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Poulter is the author of two studies published Tuesday, one in the journal Earth System Science Data and the other in the journal Environmental Research Letters.

Poulter and his colleagues found that since 2000, the largest increases in methane emissions have come from agricultural activities – particularly livestock, such as cattle and sheep – and the fossil fuel industry, which includes the extraction of coal as well as oil and gas production.

Human activities account for around 60% of global methane emissions, the researchers said. Agriculture accounts for about two-thirds, with the production and use of fossil fuels accounting for most of the rest.

In the new studies, researchers analyzed methane emissions from 2000 to 2017 – the last year for which complete methane figures are available – and found that the Earth’s atmosphere absorbed a record 600 million tonnes of methane in 2017. Annual methane emissions have also increased at a rate of 9% per year since the early 2000s, a rate that could contribute to more than 2 degrees Celsius of global warming by 2100.

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A report published by the Intergovernmental Panel on Climate Change in October 2018 noted that the planet has already warmed by 1 degree Celsius since the 19th century; he used 1.5 degrees of warming above pre-industrial levels as a threshold beyond which the effects of climate change, including extreme heat and sea level rise, became fatal for tens of millions of people around the world.

Another author of the two studies, Rob Jackson, professor of earth system science at Stanford University, said that the amount of methane released into the atmosphere since 2000 is roughly equivalent to the addition of 350 million cars. additional on the road.

In 2017, methane emissions from agriculture increased by almost 11% compared to the 2000-2006 average, while methane from fossil fuels jumped by almost 15% compared to the early 2000s .

Methane is released to the atmosphere when coal, oil and natural gas are extracted and transported, but microbes also emit it in oxygen-poor environments.

“Any place with little or no oxygen – wetlands, paddy fields, landfills, a cow’s gut – are all sources of methane,” said Jackson.

Overall, methane accounts for a much lower percentage of global greenhouse gas emissions than carbon dioxide, but it is of particular concern to scientists because the molecular structure of methane makes it more capable of absorbing thermal radiation.

“Methane doesn’t last as long in the atmosphere as carbon dioxide, but it is much more effective at trapping heat than carbon dioxide,” said Poulter, making gas a key contributor to global warming. .

To limit methane emissions, countries must reduce their dependence on fossil fuels, in addition to reducing the number of harmful leaks from pipelines and wells, Jackson said.

Scientists are also studying how to minimize methane emissions from farming practices, such as changing water levels in rice fields and experimenting with changes in the diet of cattle and sheep to reduce the amount of methane eroded from their digestive systems. Burger King recently announced that it was adding lemongrass to their cows’ feed to reduce methane emissions with a low-carb diet.

But slowing greenhouse gas emissions will also require greater changes in human behavior, said Jackson.

“Diet matters,” said Jackson. “Here in the United States, we have one of the highest red meat consumption rates in the world. We don’t necessarily have to stop eating red meat, but eating less meat or eating more fish and chicken instead of beef will reduce emissions, too. “

And although the coronavirus pandemic is expected to cause a significant drop in carbon dioxide emissions in 2020 – mainly due to economic downturns and closings that have greatly reduced air travel and other transportation – similar declines are not planned with methane.

“Our farmers are still producing food, oil and gas production has not yet declined much, and methane plays only a minimal role in the transportation sector,” said Jackson. “So, although we may see a small decrease this year due to the coronavirus, methane emissions over the past decade are increasing. And at this rate, we will not see a spike in methane emissions anytime soon. “

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