Stop dumping biodegradable waste in landfills is a cheap measure to reduce methane emissions. Photo: / Jeni F CC BY-NC

Cut methane to reduce ozone

Global action to reduce methane emissions could by 2050 avoid 70,000 to 130,000 annual premature deaths due to ozone pollution globally, and 6,000 to 11,000 in the EU alone.

Ground-level, or tropospheric, ozone is produced by the interaction of sunlight with emissions of nitrogen oxides (NOx), carbon monoxide (CO), volatile organic compounds (VOC) and methane (CH4). Comparison of ozone observations at the end of the 20th century with earlier data shows that over the last century levels of ground-level ozone in Europe have more than doubled. While short-term peak levels of ozone in Europe and North America have declined over the last few decades as a result of lowered NOx and VOC emissions, no such trend can be found for average long-term levels.

Methane is not only a major source of ground-level ozone pollution, which damages human health and plants, it is also a significant contributor to global warming. Moreover, ozone is in itself a so-called short-lived greenhouse gas. Reducing methane emissions would therefore be beneficial for both air quality and climate change.

A new report by the EU’s Joint Research Council (JRC) analyses methane’s role in ozone formation, looks at emission trends, and estimates the impacts in Europe and globally of various future methane emission scenarios.
Since the pre-industrial era, methane concentrations have more than doubled. And after a period of stagnation, they are increasing again since the last decade.

“Worldwide, methane emissions increased by 17 per cent between 1990 and 2012, compared to a 53 per cent increase in CO2 emissions. The methane emissions of the EU28 and the contributions of methane to the overall EU GHG emissions declined substantially in the 1990s, but in the last 15 years the rate of decline has been much less,” explains JRC researcher Rita Van Dingenen.

Under business as usual, global man-made methane emissions could increase by 35–100 per cent by 2050, from the 2010 level of about 330 Tg. By contrast, more sustainable scenarios, such as those that target the 2° Paris Agreement goals, have projected methane emission reductions of up to 50 per cent by 2050.

If nothing is done about reducing methane emissions worldwide, they could cause between 40,000 and 90,000 more premature deaths globally by 2050, compared to the present situation. But if concerted action is taken to reduce emissions, the number of annual ozone mortalities could instead be cut by up to 40,000 (see Table).

Man-made methane emissions originate primarily from agriculture, landfills and wastewater, and fossil fuel production and distribution, so targeting these three sectors can bring a significant reduction in overall methane emissions and ozone concentrations globally.
The JRC points out that there are cheap and even profitable options for reducing methane emissions in a relatively short time frame. In particular, important emissions reductions can be obtained by:

  • Lowering energy consumption, substituting fossil fuels, upgrading old gas and oil production, and gas distribution infrastructure to reduce unintended leakage.
  • Enforcing maximum waste separation and treatment, and not using landfill for biodegradable waste. The global abatement potential in the solid waste landfill sector is estimated to be approximately 61 per cent of the baseline emissions by 2030, of which 12 per cent can be achieved at relatively low or zero costs.
  • Improving the sanitary standards in developing countries and implementing western standards for wastewater sanitation.
  • Following FAO recommendations to improve animal health and efficiency of milk and meat production. Ruminant enteric fermentation – an important source of methane – can also be reduced for instance through adjustment of animals’ diets and vaccination.
  • Changing dietary habits by reducing meat and dairy consumption, which would also bring additional health benefits.

In its 2016 “Declaration on the review of methane emissions”, the European Commission stated its intention to review methane emissions in the context of assessing options to further reduce ozone concentrations in the EU, and to promote methane reductions internationally.

According to the JRC, Europe’s contribution to global methane emissions is currently only about 6 per cent, so reducing emissions in Europe alone is not enough to make a difference. Global cooperation to reduce methane emissions is essential – not only for the climate but also to prevent air pollution.

Christer Ågren

The report “Global trends of methane emissions and their impacts on ozone concentrations”:
European Commission declaration on methane:

Table: Summary of global and European impacts of “high” and “low” methane emission scenarios. Figures show changes relative to base year 2010.

  High emission scenarios Low emission scenarios
  Change in global methane emissions relative to 2010 (Tg CH4/year)
2030 57 to 129 -132 to -87
2050 111 to 307 -183 to -102
  Change in CH4-related ozone mortalities relative to 2010 exposure levels
  Global Europe Global Europe
2030 15,000 to 30,000 1400 to 2800 -14,000 to -5000 -1200 to -400
2050 40,000 to 90,000 3600 to 8300 -40,000 to -30,000 -2800 to -2100
  Change in crop economic losses relative to 2010 (million USD)
  Global Europe Global Europe
2030 1050 to 2075 130 to 250 -920 to -290 -110 to -35
2050 2160 to 5000 265 to 600 -2000 to -1500 -250 to -180
  Change in global radiative forcing relative to 2010 (mW/m2)
2030 140 to 340 -280 to -190
2050 290 to 900 -370 to -220



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