The tale we’re told on climate change – by the media, politicians, NGOs and scientists – is about fossil fuels. We hear that by burning coal, oil and gas, and producing carbon dioxide, we cause global warming. If the villains in this story are fossil fuels, the hero is renewable energy.

If you’re reading this worried about what kind of crank has hacked into The Fifth Estate, exhale now. I don’t disagree with anything in the first paragraph, but I don’t think it tells the full story. Carbon dioxide has actually caused only 64 per cent of warming since the pre-industrial era. The rest has been caused by other emissions, principally methane.

We need to recognise methane’s role as carbon dioxide’s chief accomplice. Methane’s global warming potential is 28 times greater than carbon dioxide, and it has caused 17 per cent of warming to date (for some reason the GWP of methane is habitually under-reported, even by science correspondents). In fact, both these figures are probably underestimates. Methane has complex, and still partly unresolved, effects on climate through its role in the formation of ozone and other gases. The IPCC says taking these effects into account increases methane’s GWP to 34, meaning its real contribution to historical warming may be more than 30 per cent.

The case against methane gets worse if we look at its medium-term impact. The GWPs cited above are based on the effect of greenhouse gases over a 100 year period. This 100-year accounting has become such a convention it’s rarely noted that it’s actually a choice based on policy rather than science. Methane only persists in the atmosphere for about 12 years, and if we look at its impacts over a 20-year period it is 86 times more potent than carbon dioxide (according to the IPCC).

These dry statistics about methane matter deeply if we want any chance of preventing catastrophic climate change. To avoid the dangerous 2°C threshold, humans must reduce carbon dioxide emissions to zero in the next few decades. This is a massive task, but tackling methane buys us time by slowing the rate of warming.

One study showed that temperature rises could be delayed by 15 years with 40 per cent cuts in methane. Fifteen years gets you a lot of solar and wind farms. For a 2050 target, decreasing methane emissions by 46 per cent would have the same effect as stopping CO2 emissions entirely. On the other hand, if we overlook methane’s role in climate change and fail to reduce its emissions, we’ll exceed the two degree threshold whatever action we take on carbon dioxide.

Paying attention to methane means taking a hard look at the sectors that produce it. Humans produce methane in several ways, but the sectors that account for the majority of it are fossil fuels and agriculture. The extraction of all types of fossil fuels and the handling and transport of natural gas (which is predominantly methane) lead to large amounts of methane leaking every year (shale gas and oil installations seem particularly leaky, casting serious doubt over the shale industry’s claims to be part of the transition to a low carbon economy). This is concerning, but most governments are at least making some plans to decarbonise energy systems, and this would bring fossil fuel-related methane under control.

However, the principal source of anthropogenic methane has nothing to do with energy – it is agriculture, particularly the farming of ruminant livestock such as cattle and sheep. Measures to combat this are barely discussed, and most governments ignore the whole agricultural sector in their emissions reduction targets. And yet, according to the UN’s Food and Agriculture Organization, the livestock sector accounts for 37 per cent of our methane emissions – the burped output of three billion ruminant stomachs. If we also take into account its contribution to CO2 and nitrous oxide, the livestock sector causes more climate disruption than transport – the world’s entire fleet of ships, planes, trains, cars and trucks. These figures use 100-year horizons. On 20-year accounting they would look even worse for livestock.

There is some potential to reduce methane emissions from livestock through technical approaches such as cattle feed additives. But any gains are likely to be marginal – swamped by future growth in livestock numbers. By 2050, consumption of both meat and dairy is expected to have risen by about 70 per cent. If we allow this growth to occur the world could smash through the 2°C limit, however quickly we install solar panels.

It’s not as if animal husbandry has a great environmental upside. Livestock production is also the single largest driver of deforestation and biodiversity loss, and a leading cause of soil erosion and water pollution. As a way of feeding ourselves it is outrageously inefficient. Per unit of protein, beef requires 32 times more land than soybeans. Growing food for animal consumption uses three quarters of the world’s agricultural land, including more than half of the entire Australian landmass. These facts are even more shocking when we remember that eating meat is not a necessity, simply a habit and a preference. We certainly don’t need to eat more than our body weight every year as we do in Australia.

The good news is that agriculture can be part of the solution to climate change. Instead of clearing more land for grazing we could revegetate the most inefficient pastures, turning them into areas of carbon sequestration. But this can only happen if we reassess our diets – otherwise climate breakdown seems inevitable.

Michael Lord is senior manager – environment & sustainability at RPS Australia Asia Pacific.

NOTE 5 February 2016 : This article blames livestock and their methane production for a big part of global warming. However, an alternative view from rural specialist Asa Wahlquist,  now come to light, points out that animals and livestock have blended harmoniously with the eco system for thousands of years without causing global warming.  “Within 9 to 15 years, the carbon in that methane will be sequestered again in a plant, perhaps in grass, to go again through the same cycle. Cattle are part of a natural biological cycle,” the article says.  Fossil fuels, however, take carbon stored hundreds if not thousands of years ago and it remains in the atmosphere for about 100 years. Our global warming problem arrived with the advent of fossil fuels, not animals that have existed and blended more harmoniously with an eco system for thousands of years. Ross Garnaut’s Climate Change Review reported livestock greenhouse gas emissions accounted for about 10 per cent of Australia’s total, Wahlquist says.

See Wahlquist’s full article here . It also explains why soy beans and other vegetable based products are not as good for the environment and land use as we may think.

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  1. Cow-fart is the worst possible example of methane production, since it’s carbon they have ingested as grass, recently photosynthesised from the air: so it is a very small short-term carbon cycle, not a net atmospheric gain. Time to let the cattle off the methane hook, guys. Just saying.

    1. Thank you for pointing this out Elizabeth.
      Just did a search on this topic now and found specialist rural and agriculture writer Asa Wahlquist agrees with you in a detailed report in Shaping Tomorrow’s World.

      “Cattle emissions have been roped into the climate change debate,” she says. “The increase in greenhouse gases in our atmosphere is overwhelmingly the result of burning fossil fuels. If that wasn’t happening we would not be having this discussion.

      “Fossil fuels consist of carbon, sequestered using the energy of the sun, hundreds of millions of years ago. Just four litres of petrol uses what was 90 tonnes of ancient life. In the space of one year, the world is using over 400 years of stored ancient energy and carbon. The carbon dioxide produced will remain in the atmosphere for a century. It is a one way street.”

      On the other hand “carbon released by cattle in methane was sequestered just last week, last month, maybe even last year. And within nine to 15 years, the carbon in that methane will be sequestered again in a plant, perhaps in grass, to go again through the same cycle.”

      Walquist’s article well worth the read. See