Greenhouse Gases-Carbon dioxide and Methane: Potential Effects, Mitigation

The atmospheric gases that possess the ability to retain heat are commonly referred to as greenhouse gases. The Earth’s atmosphere contains trace amounts of water vapor (H₂O), carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O), which contribute to the natural greenhouse effect. These gases facilitate the transmission of solar radiation to the Earth’s surface, while concurrently impeding the emission of infrared radiation from the Earth. This results in the elevation of the planet’s surface temperature.

It is imperative to differentiate between the inherent greenhouse effect and the amplified greenhouse effect. The natural greenhouse effect is a phenomenon that arises from the presence of greenhouse gases in the atmosphere, which is considered to be crucial for the sustenance of life on Earth. If the natural greenhouse effect were not present, the Earth’s surface would experience a decrease in temperature of approximately 33°C. The term “enhanced greenhouse effect” pertains to the supplementary radiative forcing that arises from the amplified levels of greenhouse gases caused by anthropogenic activities. The concentrations of several primary greenhouse gases, including carbon dioxide, methane, nitrous oxide, hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), and ozone in the lower atmosphere, are observed to be increasing.

5 Main Greenhouse Gases

Greenhouse gases, such as carbon dioxide, methane, and nitrous oxide, are known to accumulate in the atmosphere and form a heat-reflective layer that plays a crucial role in maintaining the Earth’s habitable temperature. These gaseous substances constitute the insulating layer that maintains the planet’s temperature at a level conducive to the sustenance of life.

Several of the most prevalent and concerning greenhouse gases include:

Carbon dioxide (CO₂)

Carbon dioxide (CO₂) is introduced into the atmosphere via various sources, including the combustion of fossil fuels such as coal, natural gas, and oil, as well as the incineration of solid waste and biological materials such as trees. Additionally, certain chemical reactions, such as those involved in cement production, can also contribute to the release of carbon dioxide into the atmosphere. The process of sequestration involves the removal of carbon dioxide from the atmosphere, which occurs when plants absorb it as part of the biological carbon cycle.

Methane (CH₄)

This is a greenhouse gas that is released into the atmosphere during the processes of coal, natural gas, and oil production and transportation. Methane emissions are also generated through agricultural practices, including livestock production and land use, as well as the decomposition of organic waste in landfills for municipal solid waste.

Nitrous oxide (N₂O)

Nitrous oxide (N₂O) is a greenhouse gas that is released into the atmosphere through a variety of anthropogenic sources, including agricultural, land use, and industrial activities. Additionally, it is produced during the combustion of fossil fuels and solid waste, as well as during the treatment of wastewater.

Fluorinated gases

Fluorinated gases, namely hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride, are anthropogenic greenhouse gases with potent radiative forcing properties. These gases are released into the atmosphere through a range of domestic, commercial, and industrial activities and applications. Hydrofluorocarbons, among other fluorinated gases, are occasionally employed as replacements for stratospheric ozone-depleting agents such as chlorofluorocarbons, hydrochlorofluorocarbons, and halons. Fluorinated gases are known to possess high global warming potential despite being emitted in relatively lower quantities compared to other greenhouse gases. High-GWP gases are characterized by global warming potentials (GWPs) that usually range from thousands to tens of thousands. This is due to their ability to trap significantly more heat than CO₂ for a given amount of mass.

Water vapor

Water vapor is the most prevalent greenhouse gas, and it differs from other greenhouse gases in that alterations in its atmospheric levels are not directly associated with human activities. Instead, they are connected to the warming that arises from the other greenhouse gases that we discharge. The capacity of air to hold water increases with an increase in temperature. As water vapor is a constituent of greenhouse gases, the absorption of more water leads to an increase in heat absorption, thereby exacerbating the warming effect and sustaining a positive feedback mechanism.

It is noteworthy that the overall effect of this feedback loop remains uncertain, given that the augmentation of water vapor also amplifies cloud cover, which can deflect solar radiation from the earth during the day but retain heat during the night.

Consequences of the greenhouse effect

Presently, the levels of anthropogenic greenhouse gases in the atmosphere have reached unprecedented heights, leading to a rise in global temperatures. The average temperature of the earth has risen by nearly 2 degrees Fahrenheit (1.1 degree Celsius) since preindustrial times, with the majority of this increase taking place in recent decades.

As per the Intergovernmental Panel on Climate Change (IPCC), in order to maintain a minimum probability of 50 percent to remain below the crucial limit of 1.5 degrees Celsius (2.7 degrees Fahrenheit) of warming, the global carbon dioxide emissions must not exceed a cumulative amount of 400 billion tonnes from the commencement of the year 2020. Based on our current rate of carbon emissions, it is projected that the world will exhaust its entire carbon budget by approximately 2030.

• The combustion of fossil fuels is causing global warming, which is inducing alterations in the earth’s climate systems, including:
• The exacerbation of extreme weather phenomena, such as heat waves, hurricanes, droughts, and floods, is being observed with greater frequency and/or intensity.
• The phenomenon of precipitation extremes exacerbation is characterized by an increase in the intensity of rainfall in already wet regions and a decrease in rainfall in already dry regions.
• The elevation of sea levels is attributed to the melting of ice sheets and glaciers, as well as a rise in ocean temperatures. The expansion of warmer water is a contributing factor to the increase in sea level.
• The modification of ecosystems and natural habitats has resulted in changes to the geographic ranges, seasonal activities, and migration patterns of various animal species.
• The phenomenon of climate change has significant implications on the geographical locations suitable for human habitation, occupational opportunities, and agricultural practices, particularly for individuals residing or employed in frontline communities. Elevated temperatures have been observed to result in an increase in the population of disease-carrying insects such as those responsible for the transmission of dengue fever. Additionally, heat waves have been noted to intensify in severity, posing a greater threat to human life.
• The agricultural sector is significantly threatened by the occurrence of droughts and floods that are driven by climate change. According to research findings, an increase of one degree Celsius in global temperature would lead to a reduction in crop yields by a range of 3 to 7 percent.

Increased Level of Carbon dioxide

The elevated level of carbon dioxide is resulting in an intensified greenhouse effect, surpassing the level that would occur through natural means. A correlation has been observed between the rise in atmospheric carbon dioxide concentration and temperature fluctuations. Specifically, as the concentration of carbon dioxide has increased, there has been a corresponding general increase in the global average temperature.

How does carbon dioxide trap heat?

• It is a widely known fact that carbon dioxide and other greenhouse gases function as a thermal insulators, impeding the dissipation of heat that would have otherwise been released into the atmosphere.
• Upon reaching the Earth’s surface, sunlight is partially absorbed and subsequently re-emitted as infrared radiation, commonly perceived as heat.
• The infrared waves propagate upwards through the atmosphere and will dissipate into outer space in the absence of any obstruction.
• In the atmosphere, infrared waves are not impeded by the presence of oxygen and nitrogen. Oxygen and nitrogen have the capacity to absorb energy with tightly packed wavelengths of approximately 200 nanometers or less, while infrared energy propagates at wider and more relaxed wavelengths ranging from 700 to 1,000,000 nanometers.
• The non-overlapping nature of those ranges results in the infrared waves being imperceptible to oxygen and nitrogen, thereby allowing the waves and associated heat to permeate the atmosphere without hindrance.
• Carbon dioxide has the capacity to absorb energy across a range of wavelengths spanning from 2,000 to 15,000 nanometers. This range is inclusive of infrared energy wavelengths. When carbon dioxide absorbs infrared radiation, it undergoes vibrational excitation and subsequently emits the absorbed energy in all directions. Approximately 50% of the energy is emitted into the outer space, while the remaining 50% is absorbed by the Earth’s atmosphere and subsequently released as heat, thereby augmenting the phenomenon of the greenhouse effect.
• Visible light is the form in which energy enters the Earth’s atmosphere, while the energy attempts to exit in the form of infrared radiation. The energy that reaches our planet from the Sun is received in one form and is emitted in a different form.
• Carbon dioxide molecules do not significantly interact with the wavelengths of sunlight. The absorption of energy by CO₂ and other greenhouse gases occurs subsequent to the Earth’s absorption of sunlight and subsequent remission of energy in the form of infrared waves. Hence, CO₂ traps heat in but not out.

Effects of Increased level of carbon dioxide

The concentration of carbon dioxide in the atmosphere has experienced an increase from approximately 270 parts per million (ppm) prior to the year 1700 to approximately 355 ppm at present.  The impact of elevated carbon dioxide concentrations and alterations in climate are mentioned below:

• Elevations in CO₂ levels have the potential to contribute to the phenomenon of global warming. This, in turn, may lead to several consequences, including

• Under conditions of elevated CO₂, the majority of plant species exhibit augmented rates of photosynthesis, enhanced growth, reduced water usage, and decreased concentrations of nitrogen and protein in their tissues. It is probable that the increase in carbon dioxide levels during the upcoming century will have an impact on agricultural productivity and the nutritional value of food. Consequently, it is probable that the growth and composition of natural plant communities will be impacted in intricate ways by the increase in CO₂ levels.
• The elevation of photosynthesis due to elevated carbon dioxide concentration leads to a modification in the carbon and nitrogen metabolism of the plant, as a consequence of increased carbohydrate production. In addition to its direct impact on photosynthesis, numerous physiological processes are modulated indirectly, primarily through sugar sensing and signaling pathways.

Increased Level of Methane Gas Emission

Over the course of the past 250 years, there has been an increase of over 100% in the concentration of methane present in the Earth’s atmosphere. It has been attributed to approximately 20% of the observed increase in the Earth’s average surface temperature, commonly referred to as global warming.

However, its recent history is convoluted and perplexing. The upward trajectory of emissions came to a halt during the 1990s. The emissions remained constant for a period of approximately ten years until the year 2007, after which they experienced a sudden resurgence in their upward trajectory.

How does Increased level of Methane contribute to Climate change?

• Methane is among the various gases that function as an insulating layer between the Earth’s surface and the stratosphere. Through the process of harnessing solar radiation, these entities are able to preserve thermal energy and elevate the temperature of the surrounding atmosphere. The phenomenon not only leads to an increase in worldwide temperatures, but also plays a role in climate change occurrences such as the thawing of polar ice caps and the escalation of ocean levels. Additionally, it results in more conspicuous indications such as the occurrence of extreme weather events that are more frequent and severe.
• For example, methane possesses the potential to undergo explosive reactions when combined with other atmospheric constituents. Methane is estimated to have a warming potential that is up to 80 times greater than that of carbon dioxide within a span of two decades. Hence, the long-term impact of methane on global warming is more concerning compared to that of greenhouse gas or carbon dioxide emissions, since the consequences of methane emissions may not manifest until several years later.
• Methane is involved in the production of ground-level ozone, a gas that poses a threat to human health, despite the absence of direct emission of these compounds into the atmosphere. Ground-level ozone is generated through the chemical reaction of diverse compounds and chemicals, frequently stemming from the emissions of gasoline-fueled automobiles or the operations of nuclear facilities.
• When methane is combined with solar radiation, it can stimulate the production of ground-level ozone, which can have negative impacts on vulnerable ecosystems, forests, and crops due to their tendency to remain close to the surface.

Sources of Methane gas Emission

The rate at which methane emissions are being generated by human activities exceeds the capacity of the Earth to effectively eliminate them. The escalation of methane levels on a global scale has been observed. Throughout the past 800,000 years, there has been a consistent fluctuation in methane concentrations within the range of 350-800 ppb. Following the onset of the Industrial Revolution, there has been a notable increase in methane concentrations. To a significant extent, their size has increased by a factor of 2.5.

Anthropogenic Methane Emissions

The anthropogenic emission of methane has been on the rise since the onset of the Industrial Revolution. The present escalation in methane levels can be attributed to the production of fossil fuels and the practice of intensive livestock farming. The combined contribution of these two sources accounts for 60% of the total methane emissions attributed to human activities. Additional sources of emissions comprise of landfills and waste (16%), biomass combustion (11%), rice cultivation (9%), and biofuels (4%).

Production, distribution, and utilization of fossil fuels

The primary anthropogenic contributor to atmospheric emissions is derived from the extraction, transportation, and utilization of fossil fuels. This accounts for 33% of anthropogenic methane emissions. Methane emissions are generated in locations where fossil fuels are present. The release of this substance occurs concomitantly with the extraction of fossil fuels from subterranean deposits. Methane is generated as a byproduct of fossil fuel combustion.

The utilization of fossil fuels is associated with a significant contribution to the primary source of methane emissions. The annual production, distribution, and utilization of fossil fuels results in the emission of approximately 110 million tonnes of methane. A significant proportion of methane emissions are attributed to the production and consumption of natural gas. Natural gas primarily consists of methane. The release of methane directly into the atmosphere occurs as a result of leakage within this particular industry. The aforementioned activities encompass the retrieval, refinement, and conveyance of methane gas.

Combustion of fossil fuels

Coal constitutes a significant contributor to the emission of methane. During the process of coal formation, methane pockets become ensnared in and around the rock. Methane, which is trapped in coal deposits, is released into the atmosphere through various coal mining activities such as extraction, crushing, and distribution. Methane is emitted from both active underground and surface mines, as well as from abandoned ones.

Methane deposits may also be present in oil wells and can be released during the processes of drilling and extraction. The process of oil refinement, transportation, and storage has been identified as a significant contributor to methane emissions.

Methane emissions are also generated as a result of incomplete combustion of fossil fuels. The efficiency of any combustion process is not absolute and can never reach one hundred percent. The utilization of fossil fuels for the generation of electricity, heat, or transportation results in the emission of methane.

Livestock farming

Livestock farming is the practice of raising animals for various purposes, such as food, fiber, and labor. It is a significant component of agriculture and plays a crucial role in meeting the nutritional needs of humans. The practice involves the management of various animal species, including cattle, pigs, sheep, and poultry, among others. Livestock farming has been practiced for centuries and has undergone significant changes over time, driven by technological advancements and changing consumer preferences.
Enteric fermentation in farm animals is a significant contributor to methane emissions. This accounts for 27% of anthropogenic methane emissions. Ruminant animals, such as cows, sheep, and goats, are exemplars of this particular classification. They produce significant quantities of methane during their regular digestive process. The phenomenon of enteric fermentation is attributed to the presence of microorganisms in the gastrointestinal tract of said animals. The process generates methane as a secondary product, which is either exhaled by the organism or discharged through flatulence.

The emissions from these animals are anthropogenic in nature, as they are reared by humans for the purpose of consumption. The consumption of meat on a daily basis has a significant influence on the overall methane emissions. The practice of livestock farming is responsible for the production of approximately 90 million tonnes of methane on an annual basis.

Landfills and waste

Landfills and waste represent a significant anthropogenic source of methane emissions. The process of solid waste decomposition in landfills results in the production of methane. This phenomenon is also observed in waste streams generated by animals and humans. This constitutes 16% of the total methane emissions produced by humans. The annual production of methane from landfills and waste amounts to 55 million tonnes.1

Organic matter is abundantly present in landfills and open garbage dumps. The waste materials commonly found in our garbage include organic matter such as food scraps, paper products like newspapers, as well as yard waste like cut grass and leaves. With each new addition of refuse, it is layered atop the preexisting waste. The organic material present in our waste is subjected to anaerobic conditions, leading to its entrapment.

The prevailing conditions are conducive to the proliferation of microorganisms that produce methane. The waste will undergo decomposition, resulting in significant quantities of methane emissions. Following the closure of a landfill, the process of waste decomposition by bacteria persists. This will result in the emission of methane over an extended period of time.

Methane emissions can also be generated by wastewater originating from domestic, municipal, and industrial sources. Wastewater has the potential to be discharged, retained, or subjected to remediation processes aimed at eliminating impurities. Similar to the case of landfills, anaerobic degradation of organic matter in wastewater can result in the production of methane.

Biomass

The combustion of organic matter, commonly referred to as biomass burning, is a process that involves the release of energy through the oxidation of carbon-based materials.
The combustion of biomass is responsible for a significant quantity of methane emissions. Biomass refers to the substance derived from organic matter, whether living or deceased. The incomplete combustion of biomass has been found to result in the emission of methane. Significant quantities can be generated through extensive combustion processes on a large scale. This accounts for 11% of methane emissions attributed to human activities.

Agricultural activities

Rice agriculture constitutes a significant anthropogenic contributor to methane emissions. The cultivation of rice in paddy fields involves the creation of artificial wetlands. These entities exhibit a significant level of moisture, experience a reduction in oxygen levels, and possess a substantial amount of organic matter. The conducive conditions fostered by this phenomenon facilitate the proliferation of microorganisms that generate methane through the process of organic matter decomposition.

A portion of the methane generated undergoes absorption by microorganisms that consume methane. However, the overwhelming majority is discharged into the atmosphere. The rice cultivation process, owing to its marshy nature, contributes to approximately 9% of the total methane emissions produced by human activities. The process of rice cultivation is responsible for the production of approximately 31 million tonnes of methane on an annual basis.

Biofuels

Biofuels are a notable source of methane, generating approximately 12 million tonnes of this gas annually. Any organic matter utilized for generating energy for household or industrial applications is classified as a biofuel. The incomplete combustion of biofuels results in the generation of methane. This accounts for 4% of the total methane emissions produced by humans.1

Approximately 80% of biofuels are utilized for household purposes such as cooking, heating, and lighting. Frequently, open cooking fires utilize combustible materials such as wood, agricultural residue, or animal excrement. This factor represents the most significant source of biofuel-related greenhouse gas emissions on a global scale. Approximately 2.7 billion individuals, comprising nearly 50% of the global populace, utilize solid biofuels for the purposes of cooking and residential heating on a daily basis. The majority of individuals are of low socioeconomic status and reside in nations that are in the process of economic growth and advancement.

Mitigation of Increased Carbon dioxide and Methane gas

The process of mitigating climate change entails the reduction of heat-trapping greenhouse gases that are released into the atmosphere. This can be achieved by either decreasing the sources of these gases, such as the combustion of fossil fuels for transportation, heat, or electricity, or by improving the “sinks” that accumulate and store these gases, including the oceans, forests, and soil.

The objective of mitigation is to prevent substantial anthropogenic impact on the Earth’s climate. This includes stabilizing greenhouse gas concentrations within a timeframe that permits ecosystems to adapt to climate change autonomously, safeguarding food production, and promoting sustainable economic development.

• The energy and petrochemical sectors are significant contributors to methane emissions. Therefore, transitioning away from fossil fuels would be a substantial measure in mitigating the accumulation of methane in the Earth’s atmosphere.
• The aforementioned entails a shift towards utilizing cleaner and sustainable energy sources, alongside a decrease in the utilization of plastic commodities.
• The agricultural sector is a significant contributor to methane emissions. Therefore, transitioning towards a predominantly plant-based dietary pattern could potentially mitigate this issue.
• Enhancing waste disposal techniques and elevating recycling rates are alternative approaches to mitigate methane emissions.
• .Deforestation is a notable contributor to carbon emissions. The process of carbon sequestration is facilitated by trees, which are capable of absorbing and retaining carbon dioxide from the atmosphere. However, the capacity of trees to sequester carbon is rendered ineffective upon their deforestation. The act of planting trees is considered to be a cost-effective and environmentally-friendly approach towards mitigating climate change and minimizing our adverse ecological footprint.
• The implementation of clean energy sources presents a viable approach towards mitigating carbon emissions. Renewable energy sources such as solar panels, wind turbines, and geothermal energy exhibit greater sustainability, generate minimal carbon emissions, and reduce our reliance on natural gas and resource extraction.
• In states where energy supplier choice is available, it is advisable to prioritize seeking out suppliers that utilize renewable energy sources.
• Finally, endeavor to decrease energy consumption in your daily routine. It is recommended to purchase appliances that adhere to the energy efficiency standards set.
• Additionally, regulating temperatures through the use of a thermostat and minimizing the usage of air conditioning can be effective in reducing energy consumption. Turning off all lights and appliances when not in use is also advised. Furthermore, replacing outdated light bulbs with LED alternatives that consume less energy can be a viable solution.

References

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• Ainsworth, E. A. Rice production in a changing climate: a meta-analysis of responses to elevated carbon dioxide and elevated ozone concentration. Global Change Biology 14, 1642-1650 (2008).
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