Where the world is witnessing the record lows of Arctic Minimum Ice Extent, Global Methane Emissions strike the record high!
Global atmospheric concentrations of various greenhouse gases, i.e., carbon dioxide, methane, nitrous oxide, and other halogenated greenhouse gases, have constantly amplified over the past few hundred years. Each of these gases hangs around in the atmosphere long enough to ensure uniform mixing. It means that the amount of the gas measured in the atmosphere is roughly the same all over the world, regardless of the source of the emissions.
Methane is a colorless, odorless, short-lived greenhouse gas emitted from various outlets. It has calamitous effects on global climate systems, human health, crop, and vegetative productivity. The chemical composition of methane makes it adept at trapping solar radiation. The global warming potential of methane is much more than carbon dioxide. According to the IPCC Fifth Assessment Report, the impact of per unit mass of methane on climate change is 84 times stronger than carbon dioxide over 20 years. Methane has direct radiative forcing secondary to carbon dioxide. It also enables indirect radiative forcing when it is destroyed by chemical reactions involving free radicals, like OH, and produces CO2. This means that a carbon flux is constantly regenerated.
The interaction of methane with other organic environmental pollutants such as benzene or formaldehyde, can cause serious health issues, particularly for people who live near oil and gas extraction facilities. This climate pollutant gas, however, plays an important role in tropospheric ozone formation.
How does Methane affect Global Warming?
This potent climate pollutant gas can be produced biologically and be wafted away by atmospheric currents or it bubbles out of deep-sea mud volcanoes. Natural and human-released methane emissions are responsible for ¼ of the mean temperature rise. With the ever-growing emissions and planetary warming, scientists are afraid that vast methane reserves, unleashed from thawing permafrost and deep ocean volcanoes, will foster global warming.
Methane emissions were estimated as 10% of the total U.S Greenhouse Gas Emissions in 2018
When assessing the effects of any greenhouse gas emissions on the Global Mean Temperatures and on climate change, two factors are worthy of consideration; the residence time of the gas in the environment and its Global Warming Potential.
The residence time (the period for which a gas stays in the environment) is varied for each gas from as few as 1 year to thousands of years. This allows enough time for uniform mixing of the gases throughout the atmosphere. The resultant greenhouse gas blanket traps infrared radiations and blocks their escape, thus insulating the planet. Continuous anthropogenic emissions build up the concentration levels. Over time, these gases are also transferred to their natural sinks, like soil, vegetation and the ocean.
The residence time of methane gas is fleeting as compared to carbon dioxide and other GHGs. Once released, it can linger in the atmosphere for an average of 12 years before cycling out.
Global Warming Potential
By measuring the global warming potential, scientists estimate how much energy is absorbed by 1 ton of any gas as compared to carbon dioxide. It is usually measured over the time of 100 years. The GWP of methane is 28 as compared to 1 of carbon dioxide. Therefore, just a little methane leakage could substantially warm the environment.
Methane Emissions reach Record High
As per data recorded in Global Methane Budget 2020, the atmospheric methane concentrations have increased 2.6 timesthe pre-industrial levels; 1857 parts per billion in 2018 (Saunois et al., 2020). The burning of fossil fuels, deforestation, and other anthropogenic and natural activities has considerably played their role in the cause. This methane makes up about 23% of the radiative forcing accumulated since 1750. The methane radiative forcing is presently about 0.97Wm−2(Saunois et al., 2020).
These levels respond to the IPCC emission scenario between RCP 6.0 and RCP 8.0 (Saunois et al., 2020). These pathways correspond to the global mean temperature rise of up to 3 degrees Celsius, and by the end of the century that is an alarming situation.
Researchers agree that “This trajectory implies on massive emission cut down required to meet the 1.5-2℃ target of the Paris Agreement” (Saunois et al., 2020)
Top 3 Sources of Methane Emissions
There is a 40-60 split between natural and human-derived methane emissions, respectively. However, the recent surges in methane levels can be attributed solely to anthropogenic emissions.
If we were to list the various human-based sources of methane emissions, agriculture including livestock and flooded rice paddies would top the list. The low-oxygen waters i.e. rice paddies are home to methanogens. We consider these human-based sources because human beings get goods and services from agriculture and livestock. These agricultural endeavors significantly contribute to the methane budget.
Domestic livestock releases methane with every burp and gas. They host digestive microbes in their stomachs that produce methane as waste (enteric fermentation). Manure is another hotspot of microbes for methane emission. This potent source of methane in the U.S. accounted for about 25 MMT of methane in 2015.
2-Leakage from Natural Gas Systems:
The leakage from Natural gas systems is the second major source of methane emissions, as methane is its primary component. They release it to the environment in every step at drilling sites from production, storage to distribution, and refinement of natural gas and crude oil. Studies estimate that the oil wells in the U.S. alone are accountable for about 60% of methane emissions.
The list is followed by other sources too: oil and gas exploration incl. flaring, long-distance gas transmissions, transportation, coal mining, fossil fuel burning, wetlands, lagoons, wastewater treatment plants, and landfill sites.
Well-pronounced sources of methane seepage are the abandoned old coal mines. Coal-mine methane emissions, bound to grow in this fossil-fuel-based industrialized era, have been highly underestimated. International Energy Agency (IEA) quantified global methane emissions in World Energy Outlook (WEO) 2019 to be 40 metric tons each year from operational coal mines.
About one-third of the methane is released by microorganisms in the oxygen-deprived environments, like wetlands and bogs, by digestion of organic content.
Landfill sites are the third major methane hotspot in the U.S. The microbes at these sites chomp waste and pump out methane. Other micro sources of methane emission include oceans, permafrost thawing, volcanoes, and wildfires.
Global Methane Budget
Global Methane Budget is a worthy initiative of the Global Carbon Project (GCP) that tracks the sources, sinks, and the resident methane gas around the globe. The organization publishes a report every three years. It employs two approaches, the bottom-up approach and the top-down approach.
The first approach focuses on the data which individual countries provide in National Greenhouse Gas Inventories to the United Nations. This data, combined with model simulations and satellite data of micro sources, helps in real-time estimation of the methane emissions.
The second approach works backward. Starting off with observations of global methane abundance using model simulations, it levels down to the point of origin. Global Methane Budget of 2017 was provided using the top-down approach. The top-down approach is more reliable than the former one that helps identify the emissions in specific regions. The budget represents an annual growth rate of 16.8 (Tg Ch4/year). According to which the average global methane emissions equaled approximately 600 metric tons in 2017.
Source: Global Methane Budget
Tera-grams of methane emissions, Sources and Sinks, per year (TgCH4 yr−1). Biomass and bio-fuel burning emissions are depicted here as natural as well as anthropogenic emissions. Agriculture is included in Anthropogenic Sources because it is Human-based gas outlet. (Saunois et al., 2020).
Increased fossil fuel emissions in China, North America, Africa, and Asia whereas Agricultural and Waste emissions in Africa, Southern America, and Southern Asia are accountable for this increment (Saunois et al., 2020). This is about 10% greater than the average recorded over 2000-2006.
Humans Release More Methane
In an article published in Nature, Hmeil and colleagues suggest that human-released methane is vastly underestimated. The human-released source of this climate-altering methane makes the bigger slice of global greenhouse emissions. The observations are 20-40% higher than previously estimated.
The icy methane gas hydrates are hawked as time machines for studying the origin and composition of the emitted methane. Hmiel and Dyonisius along with fellow collaborators conducted a study of Greenland’s ice-core from 1750 through 2013, using radioactive isotope carbon-14, to determine the origin of ancient methane. Based on the levels of signatory carbon-14, atmospheric methane can be categorized as fossil methane and biological methane.
The methane trapped in the ice cores came from either the biological methane (agricultural and livestock sources; contains C-14) or fossil methane (geological extraction operations, old fossil fuels do not contain carbon-14). They drilled about 11 tons of the Antarctic ice sheets; melted the cores, siphoned off the gas, and measured the levels of carbon-14.
Biological sources dominated until the 1870s, after which fossil fuels were in full swing. This led to an increase in the carbon-14 depleted concentrations up to the 1940s (data from later years is skewed as nuclear bombings during the World Wars boosted carbon-14 levels). This methane came from man-made sources. It is released during harvesting, mining, and transportation of gas, oil, and coal.
The data has far-reaching implications for climate research and modeling. Methane shares a larger portion of the total greenhouse gas emissions and is more potent than CO2 when it comes to warming potential. Thus, controlling the amount that winds up in the atmosphere would be a big bang for a buck.
"Stringent emission regulations on the fuel industry would help significantly reduce the planetary warming," Hmiel says.
Even if we curb our carbon emissions completely, it will persist in the environment for a hundred years. Changes in methane emissions would be manifested more quickly. There’s hope in methane for climate change mitigation. Hence slashing its emissions from human activities can have an outsized effect on global temperature.
How to Reduce Methane Emissions
Methane capture from landfill sites and waste treatment plants could help in eliminating problems arising from leachate seepage into local water bodies. The captured methane can be used as fuel source in power sector. Methane controlling technologies also mitigate the associated VOCs and other local air pollutants. This improves the air and water quality indexes, and overall environmental health and integrity.
You have heard of the 3Rs. It is high time to work on them. There are many ways you can reduce your methane, or generally your carbon-footprint in your daily life.
Without immediate actions, methane concentrations are bound to increase until 2030. Curbing methane emissions can potentially save us from crossing the tipping points in climate change. The short lifetime of methane makes it much more desirable for climate change mitigation approaches. It stabilizes and neutralizes within decades. Various low-emission pathways can reduce planetary warming due to methane emissions as well as improve ecosystem health and overall trophic productivity
Nida Riaz is a freelance blogger based in Pakistan. She started writing about her passion for the environment when the world came to a stop in early 2020.