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Monday, May 28, 2012

Reduce methane to buy time on reducing CO2 argues climate scientist

Tackling reduction of carbon dioxide pollution is proving difficult to do, although much of this is political intransigence. Peter Cox Professor of Climate System Dynamics and leader of the inter-disciplinary "Climate Change and Sustainable Futures" activity at the University of Exeter, suggests we should come at the problem from a different angle - focusing at first in reducing methane emissions which would allow a greater CO2 budget to keep within. Buying us some time.

"It looks extremely unlikely that we can stop global warming at 2 °C just by reducing CO2 emissions," he told New Scientist in March 2012. "That probably requires peaking emissions by 2020. But drastic action on methane would make the task much more feasible."

Cox argues that a 40 per cent reduction in human-caused methane emissions, a greenhouse gas 21 times stronger than carbon dioxide, would permit the release of an extra 500 gigatonnes of CO2 - a third more than previously thought - before we exceeded 2 °C warming. "That is a 15-year breathing space at current CO2 emission rates," said Cox.

Human caused emissions of methane comes from a variety of controllable sources including:

  • Livestock. See CSIRO - Reducing livestock methane emissions
  • leaks from coal mines and gas pipelines, (See An assessment of mine methane mitigation and utilisation technologies 2005 (abstract)
  • landfills,
  • agriculture (See Mitigating Agricultural Emissions of Methane (1998) abstract).

Reducing methane would encourage land vegetation to absorb more CO2 and reduce troposheric ozone, which also damages plants according to Cox.

Human health and reduced mortality would also result from mitigating ozone pollution with methane emission controls. (See Global health benefits of mitigating ozone pollution with methane emission controls (2006) (abstract)) From the abstract of this paper:

we show that global decreases in surface ozone concentrations, due to methane mitigation, result in substantial and widespread decreases in premature human mortality. Reducing global anthropogenic methane emissions by 20% beginning in 2010 would decrease the average daily maximum 8-h surface ozone by ?1 part per billion by volume globally. By using epidemiologic ozone-mortality relationships, this ozone reduction is estimated to prevent ?30,000 premature all-cause mortalities globally in 2030, and ?370,000 between 2010 and 2030.....Methane mitigation offers a unique opportunity to improve air quality globally and can be a cost-effective component of international ozone management, bringing multiple benefits for air quality, public health, agriculture, climate, and energy.

So how do we reduce methane emissions? On a personal level we can cut down eating red meat from ruminants; recycle more and reduce landfill waste; use green energy to reduce our reliance on coal fired power (which produces a lot of methane as well as CO2). There are already technologies and industrial processes for tackling methane from coal mines, landfills, and processes for reducing methane from cows and sheep and agriculture. We just need to roll them out and apply them more stringently.

Methane emissions won't solve the problem of ocean acidification, but it might buy us time with regard to atmospheric temperature rise, and also devising ways to efficiently biosequester carbon through agriculture, forestation, and even through blue carbon projects such as restoration of seagrass meadows.

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