Mumbai: On August 9, the Intergovernmental Panel on Climate Change (IPCC) released its latest Working Group I report that, for the first time, included a chapter on short-lived climate forcers such as methane and aerosols. Short-lived climate forcers, as the name suggests, are greenhouse gases that remain in the atmosphere for relatively shorter periods--compared to carbon dioxide.
Human emissions of carbon dioxide are the primary driver of climate change. Methane remains in the atmosphere for just about a decade, compared to centuries for carbon dioxide, but human emissions of methane are second only to carbon dioxide in contributing to global warming, according to the United Nations Environment Programme's (UNEP) Global Methane Assessment, 2021.
The latest IPCC report is the first of four expected ahead of the forthcoming United Nations Climate Change Conference (COP26) in Glasgow, Scotland, this October. It comes at a time when the world is experiencing extreme weather events more frequently than ever, be it flooding in western India or wildfires in southern Europe and the US. The IPCC report underlines the need for countries to take action to curb methane emissions as a step toward meeting the Paris Agreement's target of limiting global warming to 1.5 degrees Celsius of pre-industrial levels.
India is the third-largest source of methane emissions, a paper supported by the European Union's climate change project has found. Both the paper and the UNEP assessment point to existing low-cost technologies to reduce methane emissions, including better waste and livestock management practices. Methane released during fossil fuel production can also be captured for use as a valuable energy source.
Why we should worry about methane
Greenhouse gases (GHGs) such as carbon dioxide and methane trap heat in the atmosphere. They absorb energy that radiates upwards from the earth's surface and re-emit heat to the lower atmosphere, thus warming the earth. Human emissions of GHGs such as methane and carbon dioxide have increased their concentration in the atmosphere. This has caused an increased warming influence on climate since the year 1750. Some GHGs can remain in the atmosphere for decades, centuries or even longer, so the corresponding effects of human emissions on climate last for a long time.
Methane causes the second-most radiative forcing effect, i.e. warming, after carbon dioxide, in terms of the quantum of emissions of these GHGs. The warming effect of methane itself is 28 times that of carbon dioxide, according to the Global Methane Budget 2020.
Methane is naturally occurring, or biogenic, i.e. produced during decomposition of organic matter, including from vegetated wetlands and inland water systems (lakes, ponds, rivers), land geological sources (mud volcanoes, micro-seepage), wild animals, termites, thawing terrestrial and marine permafrost and oceanic sources. Less than half of global methane emissions, however, are biogenic; the rest comes from human-caused emissions.
The interaction of gases like methane with sunlight produces tropospheric ozone, a harmful GHG which damages human health, plants and ecosystems, according to the UNEP assessment. Thus, increased concentrations of methane in the atmosphere due to human-caused emissions are a precursor to tropospheric ozone pollution. Tropospheric ozone pollution attributable to human emissions of methane causes approximately half a million premature deaths globally, per UNEP. Reductions in methane emissions thus have direct and immediate benefits for public health via improved air and water quality.
Human-caused methane emissions largely stem from three sectors: fossil fuel production and consumption (35% of human-caused emissions), waste (20%) and agriculture (40%), per UNEP. Methane is emitted during the extraction and production of fossil fuels including oil, gas and coal. In agriculture, methane emissions can come from burning crop stubble after harvest and continuous flooding of paddy fields for rice production. Decomposing organic material in waste discarded by humans also produces methane. It is also a byproduct of digestion in cattle. India, with its huge cattle population, is the world's third-largest emitter of methane, according to a March 2019 paper by Veera Pekkarinen, supported by the European Union's ClimaSlow project.
The atmospheric concentration of methane has more than doubled since pre-industrial times, per the UNEP assessment, and is increasing faster now than at any time since the 1980s. The Paris Agreement's 1.5-degree-Celsius target cannot be achieved at a reasonable cost without reducing methane emissions by 40-45% by 2030, said UNEP.
Most countries address the issue of methane emissions in general terms, without a clear target to reduce emissions, said Pekkarinen's paper. While the Paris Agreement favours absolute economy-wide emission reduction targets, countries must also develop separate targets for all climate forcers, including methane, individually, the paper stated. Only nine of 174 signatories to the Paris Agreement, however, have set a separate target for reducing methane emissions.
How we can to reduce methane emissions--and harness a valuable energy source
"Methane can be captured from manure, waste and wastewater management systems and used to replace higher CO2-intensive energy sources such as wood, coal and oil," Pekkarinen's paper stated. Methane emissions can be effectively reduced by decreasing waste, especially food waste, as well as through increased composting of biodegradable waste. The paper also argued for substituting meat (especially beef) and dairy products with less GHG-intensive foods, to reduce agriculture's methane emissions. Reducing methane emissions through management of livestock manure and adjusting cattle feed, and through solid waste and waste-water management, were also highlighted by UNEP.
"Numerous cost-effective mitigation technologies and policies are readily available in the different methane-emitting sectors," said the paper. "In the United States, landfill [garbage dump] gas emissions declined by 40% from 1990 to 2016 through methane abatement strategies such as landfill gas collection and control systems. There is potential to spread these technologies to developing countries."
In the energy sector, switching from fossil fuels to renewable energy sources will be the most effective way to reduce methane emissions, the paper argued. While a full switch to renewables is a long way away, disseminating existing technologies and policies for methane emissions mitigation would effectively reduce the near-term heating effect of this sector.
During fossil fuel transportation, for instance, methane leaks can be reduced through routine maintenance of gas pipelines. Methane released from coal mines can also be captured and used as a valuable energy source, per the UNEP assessment. "However, any measures to reduce methane emissions from the fossil fuel sector should be undertaken as part of a clear plan to ultimately phase out oil, gas and coal production and consumption," the paper cautioned.