A woman passes by a #COP29 sign during the United Nations climate change conference COP29 in Baku, Azerbaijan November 11, 2024. REUTERS/Maxim Shemetov
BAKU (Reuters) - Fast-rising methane emissions could undermine efforts to limit global warming by mid-century, prompting scientists and policymakers to urge aggressive action to curb output of the potent greenhouse gas.
Nearly 160 countries have pledged a 30% cut from 2020 methane emissions levels by the end of this decade.
Over the last five years atmospheric methane levels have risen at their fastest rate since record-keeping began in the 1970s, driven in part by natural sources, according to the 2024 Global Methane Budget report.
Here is why controlling methane emissions is so important.
HEAT-TRAPPING POWER
Methane molecules are more powerful than carbon dioxide (CO2) in trapping heat, meaning it takes fewer of them to cause the same amount of warming and reducing them can have a more immediate effect than reducing CO2.
Tackling methane also makes financial sense. United Nations analyses have found cutting methane emissions is likely cheaper than CO2 cuts for a comparable climate benefit.
While CO2 remains in the atmosphere for centuries, methane breaks down after about a decade - meaning it has less of a long-term impact on temperatures.
Scientists normally compare the overall warming effects of methane versus CO2 over a century, calculating that methane emissions are about 28 times worse than CO2 for global warming.
Over a shorter timespan of 20 years, however, methane is 80 times worse.
Methane has led to around 0.5 degrees Celsius of warming so far, or about one-third of the roughly 1.3 C of warming experienced to date since pre-industrial times.
SURGING EMISSIONS
Methane concentrations are rising faster than any other major greenhouse gas, with human activities driving at least two-thirds of global emissions, according to the 2024 Global Methane Budget.
That includes the agriculture sector, including rice farming and livestock, fossil fuel activities, and landfills and other waste.
The report, published every five years, found methane emissions from these human activities have risen overall by 20% over the last two decades.
Most of the methane mitigation efforts under way, including EU legislation, are focused on the oil and gas sector, where the emissions are easier to tackle than in agriculture, according to the food-focused investor initiative called FAIRR.
NATURAL SOURCES A CONCERN
The remaining third of the world's methane emissions comes from natural sources such as thawing permafrost, peat bogs and wetlands - and emissions could rapidly increase as temperatures rise.
Animals, including humans, are also a source of methane.
While it is easy to measure atmospheric methane, understanding where it comes from is crucial for tackling the problem.
By analyzing distinct isotope signatures in methane detected, scientists can investigate whether the the gas comes from biological sources or industry.
(Reporting by Gloria Dickie; Editing by Katy Daigle and Barbara Lewis)
