AYDEV JANA
Ahead of the 28th Climate Summit (CoP-28) at Dubai, the UN Environment Programme (UNEP) released a report entitled ~ the Emissions Gap Report 2023: Broken Record ~ Temperatures hit new highs, yet world fails to cut emissions (again). The report states that the planet is heading for a temperature rise far above the Paris Agreement goal unless countries deliver more than they promised.
What is worrisome is that at present only four countries ~ India, Indonesia, the UK and Switzerland ~ out of as many as 196 signatories to the pact are on track to meet the existing targets. As a result, instead of being cut by 8 per cent annually, GHG emissions have grown by 1.2 per cent from 2021 to 2022 globally. It is confirmed that the global temperature rise is within striking distance of shattering the 1.5°C mark compared to preindustrialized era (1850 to 1900), a target set by the UN in the Paris climate agreement in 2015 to prevent devastating consequences.
There were at least 86 instances just this year of temperature breaching the dreaded 1.5°C threshold. 2023 is going to be the ‘warmest year’ in a 174- year observational record, surpassing the previous joint warmest years, 2018 at 1.29°C above pre-industrial era and 2020 at about 1.22°C. The world will heat up by nearly 3°C by the end of the century. In simplest terms, ‘greenhouse gases (GHGs)’ let sunlight through to the earth’s surface while trapping ‘outbound’ radiation.
This alters the radiative balance ~ the relationship between the amount of energy reaching an object (or a portion of it) and the amount leaving it ~ of the earth and results in a warming of the earth’s surface. The most abundant GHGs in the Earth’s atmosphere in decreasing order of average global mole fraction are water vapour, carbon dioxide, methane, nitrous oxide, ozone, chlorofluorocarbons, hydrofluorocarbons and perfluorocarbons.
Though water vapour is a potent GHG, it is not one that humans are directly adding to. It is therefore not one of the drivers of climate change that the Intergovernmental Panel on Climate Change (IPCC) is concerned with and is therefore not included in the IPCC list of GHGs. Moreover, change in water vapour is a feedback that impacts climate sensitivity in complicated ways.
All GHGs are infrared active and hence they are able to absorb infrared radiation. Gases whose molecules have two different atoms (such as carbon monoxide, CO), and all gasses with three or more atoms (including water vapor (H2O) and carbon dioxide (CO2) are infrared active and act as GHGs. Technically, this is because an asymmetric in the molecule’s electric charge distribution allows molecular vibrations to interact with electromagnetic radiation. But gases with one atom (such as Argon, (Ar) do not have vibrational modes.
And molecules containing two atoms of the same element such as Nitrogen (N2) and Oxygen (O2), major atmospheric constituents, have no asymmetry in the distribution of their electric charges when they vibrate. Hence they seem transparent to and totally unaffected by infrared thermal radiation. N2 and O2 are able to absorb and emit small amounts of infrared thermal radiation as a result of collision-induced absorption. However, even taking relative abundances into account, the effect is smaller compared to the influences of Earth’s major GHGs. According to IPCC, methane (CH4), the second most important GHG after CO2, is a powerful and short-lived GHG, with a lifetime of about a decade before breaking down, unlike CO2 which lasts for over 100 years. According to scientists, reduction of CH4 emissions results in lowering of its atmospheric concentration as well as its warming impacts simultaneously.
But even if CO2 emissions reach zero or net zero, the accumulated CO2 in the atmosphere will continue to warm the planet over the course of its lifetime. Due to the chemical bonds within its molecule, CH4 is much more efficient at absorbing heat than CO2.
In the first 20 years of its release into the atmosphere, its warming impact has been found to be 81.2 times stronger than CO2. It is responsible for approximately a third of the warming we are experiencing today. Moreover, it also harms human and ecosystem health.
Its emissions lead to ground-level ozone pollution which causes approximately a million premature deaths per year globally and reduces crop productivity. In 2019, the global level of methane emission was 9.8 gigatonnes of CO2 equivalent (GtCO2e), which was 25 per cent higher than it was in 1990 (7.8 GtCO2e). If no action is taken to cut its emissions, global anthropogenic methane emissions are projected to rise by up to 13 per cent between 2020 and 2030.
However, methane has been the focus of climate mitigation policy ever since it was discovered that its emissions have higher warming impacts on the planet than CO2. Methane is emitted from a variety of anthropogenic (human-influenced) and natural sources. Anthropogenic emission sources include landfills, oil and natural gas systems, agricultural activities, coal mining, stationary and mobile combustion, waste-water treatment, and certain industrial processes.
Methane is the second most abundant anthropogenic GHG after CO2, accounting for about 16 per cent of global emissions. China, the United States, Russia, India, Brazil, Indonesia, Nigeria and Mexico are estimated to be responsible for nearly half of all anthropogenic methane emissions. Agriculture is the predominate source. Methane emissions from agriculture come from livestock production ~ enteric fermentation in ruminant animals and manure management ~ and rice cultivation.
Livestock production contributes onethird of the total global anthropogenic methane emissions, making it the largest single source. Flooding of paddy fields for rice production cuts off oxygen to the soil allowing methaneproducing microbes to thrive. This leads to about 8 per cent of global anthropogenic methane emissions, concentrated heavily in Asia ~ mainly India and China. Methane emissions also take place from landfills and waste water handling and constitute about 12 per cent of global anthropogenic methane emissions. According to the IPCC’s Sixth Assessment Report (2019), global methane emissions from energy supply, primarily fugitive emissions from the production and transport of fossil fuels, accounted for about 32 per cent of global methane emissions.
Moreover, methane is also emitted from coal mines and throughout the process of natural gas extraction and use. Agriculture is the largest human-driven source of excess methane, but its association with livelihood and nutrition makes it a tricky sector to tackle. According to IPCC, mitigation of methane in the sector is ‘still constrained by cost, the diversity and complexity of agriculture systems, and by increasing demand to raise agricultural yields, and increasing demand for livestock products.’
Population growth, economic development and urban migration have stimulated unprecedented demand for animal protein and with the global population approaching 10 billion, the hunger for animal protein is expected to increase by up to 70 per cent by 2050.
Indeed, enteric fermentation is a natural part of the digestive process in ruminant animals such as cattle, sheep, goats and buffalo, etc.
Microbes in their digestive tract, or rumen, decompose and ferment food, producing CH4 as a byproduct. It is the largest single source of CH4 emissions from agriculture. In response to a query in the Lok Sabha in December, 2021, Ashiwini Kumar Choubey, the Minister of State for Consumer Affairs, Food and PDS and Environment, Forest and Climate Change, in the context of food security, replied that India’s methane emissions were “survival” emissions as opposed to luxury emissions.
Since India is one of the largest producers and exporters of rice, attempts to control agricultural methane emissions could impact Indian farmers’ incomes, the country’s agricultural production and trade and economic prospects. UNEP Food Systems and Agriculture Adviser James Lomax aptly said that the world needs to begin by ‘rethinking our approaches to agricultural cultivation and livestock production.’
That includes leveraging new technology, shifting towards plant-rich diets and embracing alternative sources of protein. Indeed, scientists are experimenting with alternative types of feed to reduce the methane produced by cows and looking at ways to manage manure more efficiently by converting it, composing it, or using it to produce biogas. In case of rice paddy, experts recommend alternate wetting and drying approaches that could halve emissions. Rather than allowing the continuous flooding of fields, paddy could be irrigated and drained two to three times throughout the growing season, limiting methane production without impacting yield. That process would also require one-third less water, making it more economical. However, the biggest opportunities to cut methane lie in the fossil fuel sector.
Oil and gas are the only sectors for which most emissions can be reduced in a cost-effective manner with viable technologies that are presently available.
On fossil fuel methane emissions, the IPCC’s Sixth Assessment Report asserts, “about 50-80 per cent of methane emissions from these fossil fuels could be avoided.” The International Energy Agency suggests it is technically possible to avoid three-quarters of current CH4 emission from global oil and gas operations.
The cost effective technologies include leak detection, installing emission control devices and replacing components and devices that emit methane in their normal operations. Cutting methane emissions is the fastest opportunity we have to immediately slow the rate of global warming, even as we decarbonize our energy systems.
(The writer is a retired IAS officer)
