Between 2020 and 2022, Earth experienced the largest rise in methane emissions since observations began nearly 40 years ago, and potentially the largest in 800,000 years when referring to ice core data.

Gordon Brailsford is a NIWA Atmospheric Principal Technician and co-author of the new research. He said that knowing where methane comes from is vital to mitigate further increases.

"Methane is a potent greenhouse gas; over a 100-year period, one molecule of methane traps 30 times more heat than one molecule of carbon dioxide and historic methane emissions have caused around a third of the planet’s additional warming since the Industrial Revolution. This makes it a key target for the fight against climate change," said Gordon.

Boulder’s Global Monitoring Laboratory (GML) analysed air samples from 22 sites around the world using a computer model to understand dominant drivers behind the increase.

This included data from NIWA, which has some of the world’s most precise and longest-running records of methane isotopes. Isotopes are atoms of the same element, such as carbon, but with different masses.

"Methane contains both heavier and lighter versions of carbon. Because methane produced by microbes contains more of the ‘light’ version than that produced by fossil fuels, we can measure the ratio of heavier vs lighter carbon in methane to determine the source of the additional methane," said Gordon.

Peter Sperlich is a NIWA atmospheric scientist and another co-author of the study. He said that from their analysis, they found that microbes were responsible for over 90% of the world’s increase in methane output since 2020.

"The microbes that produce this type of methane live in a variety of environments under quite unique conditions, including landfill sites, wetlands, permafrost, and the guts and manure of livestock," said Peter.

The time of extraordinarily high methane emissions coincided with a strong and long lasting La Niña event (2020-2023), which is associated with wetter climates in typical methane source regions.

"This could be a so-called positive climate feedback, where global warming leads to additional emissions that cause even more warming," said Peter.

However, this technique does not allow scientists to pinpoint the exact source of the microbial methane and whether it came from natural environments, such as wetlands, or human-driven ones, like cattle farms and waste, or even all the above.

Gordon says it’s clear that more research needs to be done but this is a huge discovery.

"Methane doesn’t stay in the atmosphere for too long, degrading within around 10 years, so tackling methane is one of the strongest levers we have in the short term for slowing climate change.

"It’s also important to stress that reducing our fossil fuel use is still crucial because it is the main source of carbon dioxide and therefore the biggest driver of climate change. It’s all connected - if the planet warms due to any source and causes permafrost to melt, for example, then this could release yet more methane into the atmosphere," said Gordon.