Between 2000 and 2017, levels of the potent greenhouse gas methane barrelled up toward amounts that could lead to 3-4°C of warming before the end of this century, researchers at Stanford University have found.
Increases are being driven primarily by the growth of emissions from coal mining, oil and natural gas production, cattle and sheep ranching, and landfills, contributing to climate change, and could lead to an increase in natural disasters, including wildfires, droughts and floods they say.
Methane is a colourless, odourless gas that is 28 times more powerful than carbon dioxide at trapping heat over a 100-year period. In 2017, the Earth’s atmosphere absorbed nearly 600 million tons of methane, a nine per cent rise since the early 2000s, with more than half of all emissions coming from human activities such as the burning of fossil fuels and agriculture.
In terms of warming potential, adding this much extra methane to the atmosphere since 2000 is akin to putting 350 million more cars on the world’s roads, the researchers say.
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“We still haven’t turned the corner on methane,” said Rob Jackson, a professor of Earth system science in Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth).
“Emissions from cattle and other ruminants are almost as large as those from the fossil fuel industry for methane. People joke about burping cows without realising how big the source really is.”
Curbing methane emissions will require reducing fossil fuel use and controlling errant emissions such as leaks from pipelines and wells, as well as changes to the way we feed cattle, grow rice and eat, the researchers say.
“We’ll need to eat less meat and reduce emissions associated with cattle and rice farming, and replace oil and natural gas in our cars and homes,” Prof Jackson said.
Do we really know what climate change will do to our planet?
Asked by: Jennifer Cowsill, via email
There is no doubt that greenhouse gas emissions caused by humans are changing our climate, resulting in a progressive rise in global average temperatures. The scientific consensus on this is comparable to the scientific consensus that smoking causes lung cancer.
Our climate is a hugely intricate system of interlinking processes, so forecasting exactly how this temperature increase will play out across the globe is a complex task. Scientists base their predictions on powerful computer models that combine our understanding of climatic processes with past climate data.
Many large-scale trends can now be calculated with a high degree of certainty: for instance, warmer temperatures will cause seawater to expand and glaciers to melt, resulting in higher sea levels and flooding. More localised predictions are often subject to greater uncertainty.