Methane gas second most abundant greenhouse gas after carbon dioxide.




The second most abundant greenhouse gas after carbon dioxide.


Dr Graham Phillips Introduction: Carbon dioxide is synonymous with climate change but what about the other greenhouses gases that we hear little about. Dr Paul Willis reports on a gas that is 20 times more potent than carbon dioxide, and unleashed could have devastating consequences.

Narration: We know that global warming is complex.

Dr Evelyn Krull: We are not looking at the whole picture.

Narration: Perhaps we’re missing something important.

Dr Andrew Smith: Increased in concentration by something like two hundred and fifty percent.

Narration: A climate player with a murky past

Dr David Etheridge: warming the globe for very long periods.

Dr Paul Willis: When it comes to climate change, carbon dioxide gets all the attention, but these cows here are producing a greenhouse gas that is more potent than carbon dioxide. It’s a gas that’s been implicated in the greatest mass extinction of all time, and we’re pumping it out at an ever increasing rate.

Dr Etheridge: It has some fairly complex roles in our climate and in the chemistry of the atmosphere.

Dr Smith: It is an important player.

Narration: It’s methane, the forgotten greenhouse gas. And it’s a gas that’s surrounded in myths. Contrary to popular opinion, it doesn’t smell, and no, it’s not a major component of farts. More methane is actually pumped out from the other end… In fact one cow can belch out an astounding 700 litres of methane in a day! But there are many other sources of methane…

Dr Smith: The sources of methane can be broadly categorized as biogenic, of biological origin, pyrogenic, which is basically combusted biomass, and fossil sources.

Narration: Some of the methane in the atmosphere today has natural origins. But more than half of it was put there by us… And of that landfill, agriculture and mining account for about a third each. The atmospheric methane concentration today is just under 2 parts per million compared to carbon dioxide which is currently 384 parts per million. But atom for atom methane is far more potent than CO2 and it accounts for a whopping 20% of the green house warming effect. Working out where atmospheric methane has come from is a tricky business but it is a vital part of developing strategies to control it.

Dr Etheridge: So one way we do it, is we take air off the roof there, down a line, into a pump, and then take it over here where we analyse it for Methane.

Narration: Dr David Etheridge measures air samples from the roof of his CSIRO lab in Melbourne.

Dr David Etheridge: This is the methane concentration right now from above our roof top.

Narration: And with new technology they are now able to analyse bottled atmosphere from this library of air archive. Some of these canisters were stored 30 years ago.

Paul: This is the oldest specimen it comes from Cape Grim and it was collected in 1978.

Dr Etheridge: These are remote stations which have been placed to capture air coming off oceans, which is pretty much what we call background or baseline air.

Narration: So what’s the picture so far?

Dr Etheridge: From 1978 onwards (the earliest measurements) there was a rapid increase in methane concentration.

Narration: And this was mainly because of an increase in agriculture and industry. But then something unexpected happened –

Dr Etheridge: Methane has stabilized in concentration ah beginning in about 1999. And it wasn’t too clear what that was…

Narration: We’ll deal with the future of methane later, but how do we investigate what happened prior to 1978? The answer is trapped in ice.

Dr Smith: That’s a nice sample.

Narration: CSIRO scientist, Dr Andrew Smith and his colleagues have been drilling ice cores in Antarctica as well as recovering samples from Greenland. And the challenge is enormous …

Dr Andrew Smith: Aiming to produce a five microgram carbon sample after having liberating the air from a hundred kilograms of ice – this is tough.

Paul: This is a cut section of the ice core, and you can actually see the tiny bubbles of ancient atmosphere that these guys are interested in.

Narration: After painstakingly extracting the methane gas from the ice core, it’s converted into carbon, and then, it’s ready for analysis.

Paul: This is ANTARES the Australian National Tandem for Applied Research. It’s an extremely accurate atom counter and it’s just the tool you need to work out the history of methane in the atmosphere.

Narration: Samples are mounted on a sample wheel, ionised, accelerated, have their polarity reversed, stripped of their electrons all in a trillionth of a blink of an eye and they end up here.

Paul: So how sensitive is this? How many atoms can you count?

Dr Smith: Well this equipment, it gives us the ability to detect just one carbon fourteen atom in amongst ten to the sixteen stable carbon atoms. That’s a very big number. Ah it’s equivalent for example to finding one yellow grain of sand in amongst twenty tons of orange sand.

Paul: One in a gazillion.

Narration: Thanks to the work of scientists around the world, we can now track the history of atmospheric methane back some 800,000 years. Generally levels go down when there’s an ice age and they come up again in the interglacial periods. But something alarming has happened to methane levels since the beginning of the industrial revolution.

Dr Smith: The methane concentration has increased by two hundred and fifty percent over the agro-industrial period.

Narration: While that rise is alarming and its consequences unknown, there is an upside to the methane story. We can do something about it – by harnessing its energy.

Paul: Most of the methane in the atmosphere today has been put there by humans through landfill, coal mining, agriculture and other activities; But unlike CO2 it’s relatively easy to capture methane before it gets loose… and it pays to do so.

Narration: As the rubbish decomposes methane is released and captured in these pipes. It’s then pumped to this power station. The energy generated here has the potential to provide electricity to 16,000 homes… and even though CO2 is being produced in the process, the original methane is 20 times more harmful as a green house gas. While it looks like we can control the release of methane from some sources we shouldn’t be too complacent. There could be a spectre of doom lurking, a vast hidden source of methane… They’re called clathrates. It’s methane that’s been locked inside the crystal structure of water ice. They are found around the continental margins of oceans and polar regions, in very cold, high pressure conditions. They’re also locked up in the frozen tundra…

Dr Smith: There’s an enormous amount of this stuff. Something like five thousand gigatonnes of carbon locked up as methane clathrate. That’s about the same as all the carbon that’s locked up in oil, gas and coal reserves.

Narration: But if temperatures rise or if the tundra melts they could be destabilised, releasing massive amounts of methane.

Dr David Etheridge: So you’d only need to release one percent of them and you have multiplied your atmosphere by about ten times concentration of methane.

Narration: And the consequences could be catastrophic. Sound far fetched? It may have happened before…

Paul: This is Scarborough to the north of Wollongong and the rocks here were laid down at a very important time in the history of the earth. To the north of here towards Sydney the rocks get progressively younger they’re going into the age of the dinosaurs. Going that way to the south they get older they go into the Palaeozoic or time of ancient life but right here is known as the Permian extinction it was a time when life on the planet was almost snuffed out and it looks like the culprit was methane.

Narration: Dr Evelyn Krull has been researching the Permian extinction

Dr Krull: We were collected samples across the Permian Triassic boundary and analysing those on our mass spectrometers.

Narration: The ratio of carbon isotopes in the rocks indicates that 250 million years ago there was a very rapid and extremely large release of methane into the atmosphere. And the fossils from before and after the extinction describe two completely different worlds.

Dr Krull: You see that these beautiful big trees were replaced by these ferns. They don’t have as much organic matter in them. So these ferns grew in a completely different environment.

Paul: So these are from a colder environment and this is a, a warmer world?

Dr Krull: That’s correct, yes. So it radically changed and these plants were not able to grow there anymore. It was essentially a chain of events that that was happening.

Narration: Just before the extinction there was a huge amount of volcanic activity in what is now Siberia. It pumped a massive amount of CO2 into the atmosphere causing significant global warming. This may have triggered what has been called The Clathrate Gun. Clathrates melt releasing vast quantities of methane into the air, feeding the global warming loop and releasing more methane….

Dr Krull: The calculations at the Permian Triassic boundary are that about two thousand four hundred gigatons of carbon were released from methane clathrates.

Narration: This resulted in massive global warming, perhaps 10 degrees or more in a couple of decades. So is it possible that the clathrate gun could fire again?

Dr Evelyn Krull: The chances are actually pretty high that this will occur again just simply because we are warming the atmosphere and we are causing shifts right now in these high latitude environments.

Narration: While it could happen again, it’s unlikely to be on the same scale as the Permian extinction. But remember earlier we said that methane levels in the atmosphere have been stable for most of the last decade? Well the latest data is of grave concern.

Dr Etheridge: In the last year and a half, methane is now increasing again in the atmosphere.

Narration: And given its history, methane is certainly a potent player in global warming…

Dr Krull: It might just come up and make everything ten times warmer than before.

Narration: We need to watch this gas very carefully. Although the chance of a methane meltdown is remote, if it happens, this hospitable planet as we know it would cease to exist…

Topics: Environment

  • Reporter: Dr Paul Willis
  • Producer: Ingrid Arnott
  • Researcher: Holly Trueman
  • Camera: Kevin May
    Tom Gelai
    Greg Ashman
  • Sound: Steve Ravich
    Graeme Cornish
    Phil Jinks
  • Editor: Sasha Madon


Dr Andrew Smith
Senior Principal Research Scientist

Dr David Etheridge
CSIRO Marine and Atmospheric Research

Dr Evelyn Krull
Research Scientist and Group Leader
Carbon and Nutrient Cycling
CSIRO Land & Water



Australian Nuclear Science and Technology Organisation

CSIRO Marine and Atmospheric Research

CSIRO Land and Water – Dr Evelyn Krull

Methane Time Bomb

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