Global trends of methane emissions and their impacts on ozone concentrations

Methane is the 2nd most important anthropogenic greenhouse gas after carbon dioxide. Since the pre-industrial era, methane concentrations have more than doubled, and at present sources related to human activities are about 50% larger than natural ones. After a period of stagnation, methane concentrations are increasing again since the last decade, and by 2020, may reach levels that match the most pessimistic projections used in the IPCC AR5 report. There are contrasting scientific hypotheses on the reasons for this uptick in methane, with a number of studies pointing to increasing emissions from agriculture, fossil fuel production and distribution, and in developing countries, solid waste in landfills and wastewater management.

It is often forgotten by policymakers that methane is also an important precursor of ozone in the troposphere. Ozone itself is a greenhouse gas and short-lived climate forcer, but it is also an atmospheric pollutant responsible for harmful impacts on human health and damage to crops and vegetation and for which air quality standards have been established. In various parts of the world environmental policies aim to reduce ground level ozone, but there is a risk that increasing methane emissions will counteract those regional efforts. Because methane stays about 10 years in the atmosphere, chemical mechanisms that lead to widespread ozone formation involve methane sources from everywhere in the world and mitigation efforts must become a global goal. Therefore, the UNECE Convention on Long Range Transport of Air Pollution and the European Commission commissioned studies to assess the role of methane in ozone air pollution and provide relevant and efficient options for control strategies.

This report shows how methane emission reductions can play a key-role in reducing ground level ozone in Europe and in the world. By 2050, between 70,000 to 130,000 annual premature deaths can be avoided globally, and 6,000 to 11,000 in the European Union alone, when the world consistently reduces CH4 emissions to reach climate, air pollution and other sustainability objectives (compared to doing nothing). Europe’s contribution to global methane emissions is too small to make the difference — a global collaborative approach to reduce methane emissions is essential not only for climate but also for air pollution. We know that there are low hanging fruits in several sectors where emission reductions may be cheap or even be profitable. This report presents methane emission reduction opportunities in the energy, waste and wastewater, and agricultural sectors, and provides additional reasons to reduce these emissions from a health and food-security perspective. It also highlights the risks for human health and environment that may come with inaction. Finally, it gives us all good reasons for expanding international cooperation to achieve better air quality for everyone in the world, reducing impacts of global climate change at the same time!