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Categorized under: Super Pollutants

Minding Methane

Two major pieces of unfinished business on the global atmospheric pollution agenda could be addressed through a single strategy: cut methane emissions.  In an era where so many climate initiatives face fierce opposition, methane mitigation is low-hanging fruit.

The first issue is ground-level ozone. As a 2008 report by the UK Royal Society concluded,

In large areas of the industrialised and developing world, ground level O3 is one of the most pervasive of the global air pollutants, with impacts on human health, food production and the environment even at current ambient concentrations of 35-40 parts per billion.  . . . Existing emission controls are insufficient to reduce current background O3 concentrations to levels acceptable for human health and environmental protection  . . . [A new framework must] reduce both background and peak O3, at global, regional and national scales.

The other major piece of unfinished global atmospheric business is, of course, climate change. The failure to reach an international agreement in Copenhagen in 2009, or enact domestic legislation in 2009-10, only makes the issue more urgent.  Despite some skirmishes around the edges of the science, the evidence shows that climate change — especially in vulnerable regions such as the Arctic, the Amazon and the Himalayas — may be outpacing our collective ability to advance significant global CO2 reductions.

Significant, sustained reductions in CO2 emissions will have to be the foundation for any successful climate strategy—but that central fact should not distract policymakers from recognizing the powerful influence that other atmospheric pollutants such as methane have on both human health and the climate. Consider:

Human Health

  • Recent analysis shows that “global background ozone”—the kind that stays steady year round, as opposed to the summertime smog many urban residents experience—has increased in the last several decades; rising methane levels contribute to this problem. Methane controls will also have to become increasingly stringent as regulatory regimes shift from peak–ozone standards to ones based upon the total volume of exposure (see figure 1).
  • Another recent analysis suggests that a 20 percent reduction in global atmospheric methane emissions would reduce ozone enough to save up to 40,000 lives each year around the world.

Figure 1: A Clean Air Task Force analysis shows that the recently proposed federal 8-hour ozone standard will increase methane’s estimated contribution to violations significantly over the previous 1-hour and 8-hour standard.

Climate Change

  • Methane is the second most significant driver of climate warming after CO2. Although total methane emissions are small compared to CO2, it is a very potent greenhouse gas, and its warming effects occur through a variety of pathways; a recent analysis by Drew Shindell of NASA (figure 2) suggests that, a result, methane warms about two-thirds as much as CO2. By that measure, it has received far too little attention from climate policymakers to date.
  • Unlike CO2, which persists for centuries in the atmosphere, methane lasts only about a decade. So, to avoid  rapid warming in sensitive regions such as the Arctic, methane reductions may be a far more powerful tool, even though CO2 reductions are needed over the long run. Cutting CO2 will cool the planet in the twenty-second century—and, importantly, avoid accelerating the warming we are already committed to experiencing this century—but methane mitigation is truly a quick fix, a way of producing meaningful cooling on a decadal scale. That’s a rare quality among climate policies, and one that may become increasingly important if the effects of warming become more pronounced.

Figure 2: Relative climate forcing of various emissions (Source: Shindell et al., Science, 2009)

What Can Be Done?

Roughly half of human-caused methane emissions come from industrial and some agricultural sources: landfills, coal mines, oil production, natural gas processing, and manure. These sources can be controlled relatively easily using inexpensive “end-of-pipe” technologies that allow for methane re-use to displace dirtier energy sources, thus lowering their net cost. Reducing the other half of the methane inventory—mostly from cattle and other animals, as well as rice cultivation—is more challenging, but work is underway to develop options. While solutions to those sectors are developed, there’s plenty of work that can be done right now. The International Institute for Applied Systems Analysis estimates that 2020 global methane emissions could be reduced by about 40 percent at less than 40 Euros/ton of carbon equivalent.

Current and Future Initiatives

Methane has received some attention in recent years, but much more could be done. Several nations have begun to regulate methane emissions, especially from landfills and coal mines, as much for energy recovery as for environmental reasons. Some methane projects have been financed through the Clean Development Mechanism (CDM) of the Kyoto Protocol, but those projects have ground to a halt due to uncertainty about the post-Protocol climate architecture. Thirty countries have received technical assistance for project development through the global Methane to Markets Program, but only a fraction of the potential in this area has been tapped.

Activity is picking up, however.  A blue-ribbon panel of scientists, health and climate experts, advised by CATF and the International Cryosphere Climate Initiative, proposed in December 2009 a Global Methane Fund to jumpstart methane reduction projects by providing carbon-credit guarantees; several countries are discussing capitalizing the Fund. The Methane to Markets Program is also expanding, and the United Nations Environment Program is looking at methane’s potential to contribute to near-term cooling.

Has methane’s moment in policymakers’ spotlight finally arrived? If so, that would be a good thing for human health, agriculture, and the global climate. But only a fraction of the potential in this area has been tapped.