Emissions of the greenhouse gas methane caused by the fossil fuel industry is up to 40 per cent higher than previously assumed, a damning study reveals.
Researchers from the University of Rochester in New York found the bulk of methane in the atmosphere comes from the burning of fossil fuels.
Lead author Benjamin Hmiel says while this is bad news for the environment, it does have a bright side – ‘being man made means we have control over it’, he said.
Placing stricter controls on methane emissions from the fossil fuel industry could reduce future global warming more than previously thought, the authors claim.
This shows the cross section of fossil and biological methane sources. Both can come from natural or man made sources including fossil fuel burning and livestocks as well as natural oil seeps and wetlands
The study, published in Nature, involved examining ice core samples from Greenland dating from 1750 to 2013 as they act a ‘time capsule’ for environmental conditions.
His team found that the amount of naturally generated methane in the atmosphere was a factor of 10 lower than they expected before the study.
An analysis of its ‘chemical fingerprint’ found emissions from gas, oil and coal production were 25 to 40 per cent greater than existing calculations.
‘Stricter methane emission regulations on the fossil fuel industry could reduce future global warming to a larger extent than previously thought.’ Hmiel said.
Fossil fuel extraction and use are among the largest sources of methane emissions.
The burning of fossil fuel by humans accounts for a significant proportion of methane put into the atmosphere, researchers discovered
The research team discovered natural sources were responsible for up to 190 billion ounces of methane emissions per year.
That figure is down from the previously assumed maximum of 2.1 trillion ounces coming from the likes of geological seeps and, plants and wildlife.
They calculated the difference by looking at the amount of methane present in ice core samples from before the industrial revolution to today.
In contrast human activity – specifically from burning fossil fuels – account for up to 6.7 trillion ounces of methane emissions annually, researchers discovered.
That is up to 40 per cent higher than previously thought – or about 2.4 trillion ounces more methane coming from the likes of burning fossil fuels.
Methane makes up just 16 per cent of global greenhouse gases and is shorter-lived than the CO2 which accounts for three-quarters.
However, it is an important greenhouse gas to monitor as it has a much more powerful warming effect on the atmosphere than CO2.
It can be sorted into two categories based on its signature of carbon-14, a rare radioactive isotope.
Fossil methane has been sequestered – hidden away – for millions of years in ancient hydrocarbon deposits and no longer contains carbon-14.
Biological methane is in contact with plants and wildlife on the planet’s surface and does contain carbon-14.
Another source of human derived methane is livestock and landfill. In the background of this picture is a bio gas installation that processes cow dung to produce a fuel source
Wetlands are also a natural source of methane, in this image you can see a blue damselfly sitting on a methane gas bubble produced in the moor
It can be released naturally from sources such as wetlands or via anthropogenic – human made – sources such as landfills, rice fields, and livestock.
Fossil methane can be emitted via natural geologic seeps or as a result of humans extracting and using fossil fuels.
Hmiel said: ‘If we stopped emitting all carbon dioxide today, high carbon dioxide levels in the atmosphere would still persist for a long time.
‘Methane is important to study because if we make changes to our current methane emissions, it is going to reflect more quickly.’
Previously it has been difficult for researchers to determine exactly where methane emissions originate – whether biological or from Fossil fuel activity.
Biological methane can be released from sources such as wetlands or landfills, rice fields and livestock.
Fossil methane can be emitted through natural geological seeps or as a result of humans extracting and using fossil fuels including oil, gas and coal.
Both include emissions from human activity as well as natural activity.
There are natural oil seeps across the world that produce methane emissions, including this one in the reservoir rock outcrop in Bojonegoro, Indonesia – they only account for a fraction of the overall total
The two types of methane can be distinguished, because biological methane contains measurable amounts of radiocarbon, the team found.
In fossil methane, all the radiocarbon has decayed away while the gas was stored in underground reservoirs but modern air cannot separate fossil methan that is emitted naturally from industrial sources.
‘As a scientific community we’ve been struggling to understand exactly how much methane we as humans are emitting into the atmosphere,’ says Dr Vasilii Petrenko.
‘We know that the fossil fuel component is one of our biggest component emissions, but it has been challenging to pin that down because in today’s atmosphere, the natural and anthropogenic components of the fossil emissions look the same.’
Trapped methane bubbles frozen into the water, like these under the thick cracked and folded ice on Abraham Lake can be used to study past atmospheres
The ice core samples are like time capsules – containing bubbles with small quantities of ancient air trapped inside.
The researchers use a melting chamber to extract it and then study its chemical composition – in this case to look for methane levels.
Humans did not begin using fossil fuels in significant amounts until the mid-19th Century and so by measuring carbon-14 isotopes in 200 year old air they found almost all of the methane emitted was biological in nature until 1870.
That’s when the fossil component began to rise rapidly. The timing coincides with a sharp increase in the use of fossil fuels.
The data has important implications for climate research, said Dr Hmiel.
It suggests reducing emissions from human activities like fossil fuel extraction and use will have a greater impact on curbing future global warming than hoped.