Gases that absorb and release infrared radiation are known as greenhouse gases. They absorb and re-radiate infrared radiation (heat energy) released by the earth's surface. Greenhouse gases trap heat in the atmosphere, contributing to global warming. Few examples of greenhouse gases include water vapour (H2O), carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). These gases further warm the surface of the earth and cause global warming, contributing to climate change. Globally, India is the third largest emitter of greenhouse gases after China and the United States, emitting approximately 2.6 billion tonnes CO2 equivalent per year. In this article, we will discuss Greenhouse Gases which will be helpful for UPSC exam preparation.

What is the Greenhouse Effect?

• The greenhouse effect is a naturally occurring phenomenon that blankets and warms the earth's lower atmosphere, keeping it at a temperature suitable for living things to survive.
• Water vapour and greenhouse gases warm the Earth in the same way that greenhouses keep the air warm inside their chambers.
• Greenhouse gases play an important role in the Earth's cooling and warming cycles.
• The greenhouse effect is a process (similar to the green house effect) caused by greenhouse gases that naturally occur in the atmosphere. This process is critical in warming the Earth's surface and making it habitable.
• Human-caused greenhouse gas emissions, on the other hand, disrupt the natural balance and lead to increased warmth.

Water Vapour as a Greenhouse Gas

• Water vapour is nothing but water in gaseous form.
• Water vapour is produced by the evaporation or boiling of liquid water, or by the sublimation of ice.
• Water vapour is the most significant overall contributor to the greenhouse effect, and humans are not directly responsible for emitting enough of this gas to change its concentration in the atmosphere.
• Under normal atmospheric conditions, water vapour is continuously produced by evaporation and removed by condensation.
• It is less dense and causes convection currents that can lead to clouds.
• Water vapour works as a blanket, keeping the earth from becoming too cold or too hot. Water vapour also adds to the stability and instability of the air.
• Water vapour is an effective greenhouse gas because it absorbs longwave radiation and radiates it back to the surface, contributing to warming as well as greenhouse effect.
• Water vapour is the most abundant greenhouse gas in the atmosphere, both in terms of weight and volume.
• Unlike CO2, water vapour moves quickly through the atmosphere, evaporating and condensing.
• Because evaporation rates increase with temperature, the amount of water vapour in the air at any given time (and the amount of warming it causes) is strongly related to the amount of other greenhouse gases in the air.

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Carbon Dioxide as a Greenhouse Gas

• Carbon dioxide (CO2) is a significant heat-trapping gas, often known as a greenhouse gas, that is produced by the extraction and combustion of fossil fuels, wildfires, and natural processes such as volcanic eruptions.
• Carbon dioxide is a very significant meteorological gas because it is transparent to incoming solar radiation but opaque to outgoing terrestrial radiation.
• Carbon dioxide and other pollutants together referred to as greenhouse gases, are emitted into the atmosphere as a result of both human and natural sources.
• Carbon dioxide absorbs some terrestrial radiation and reflects some of it back to the earth's surface. It is primarily responsible for the greenhouse effect.
• Because it is denser than air, its concentration is higher near the earth's surface.
• As a result of this process, the global temperature rises, resulting in a complex chain of events known as global climate change.
• Global climate change not only raises temperatures but also changes the earth's natural weather patterns and climate.

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Methane as a Greenhouse Gas

• Methane is a potent greenhouse gas, with a global warming potential of 28-34 times that of CO2.
• Human activity is responsible for roughly 60% of global methane emissions.
• The oil and gas industries, agriculture (including fermentation, manure management, and rice cultivation), landfills, wastewater treatment, and coal mine emissions are the primary sources of anthropogenic methane emissions.
• It is estimated that the production, distribution, and use of fossil fuels emit 110 million tonnes of methane per year.
• Methane is the main component of natural gas, and some of it is released into the atmosphere during its production, processing, storage, transmission, distribution, and use.
• It is estimated that approximately 3% of total global natural gas production is lost each year due to venting, leakage, and flaring, resulting in significant economic and environmental costs.

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Nitrous Oxide as a Greenhouse Gas

• Nitrous oxide is naturally present in the atmosphere as part of the Earth's nitrogen cycle, and it comes from a variety of sources.
• Nitrous oxide molecules spend an average of 114 years in the atmosphere before being removed by a sink or destroyed by chemical reactions.
• As a greenhouse gas, nitrous oxide has significant global warming potential.
• Nitrous oxide has 298 times the atmospheric heat-trapping ability of carbon dioxide (CO2) per molecule over a 100-year period.
  • However, due to its low concentration (less than 1/1,000 of that of CO2), its contribution to the greenhouse effect is less than one-third that of CO2, and also less than water vapour and methane.
• Nitrous oxide is primarily produced by humans through the combustion of fossil fuels, biomass burning, the industrial production of nitric acid, and the application of fertilisers to agricultural crops.
• Nitrous oxide, like carbon dioxide, contributes to the greenhouse effect by absorbing reradiated infrared radiation from the Earth's surface and warming the troposphere (lower atmosphere).
• It is chemically inert in the troposphere and remains there for about 120 years before moving into the stratosphere, where it eventually destroys stratospheric ozone.
• Human activity has increased the concentration of nitrous oxide in the atmosphere.

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Fluorinated Gases as a Greenhouse Gas

• Fluorinated gases, unlike many other greenhouse gases, have no significant natural sources and are almost entirely produced by human activity.
• They are emitted as a result of their use as ozone-depleting substitutes and a variety of industrial processes such as aluminium and semiconductor manufacturing.
• Because many fluorinated gases have extremely high global warming potentials (GWPs) in comparison to other greenhouse gases, even low atmospheric concentrations can have disproportionately large effects on global temperatures.
• They can also have long atmospheric lifetimes, lasting thousands of years in some cases.
• Most fluorinated gases, like other long-lived greenhouse gases, are well-mixed in the atmosphere and spread globally after they are emitted.
• Many fluorinated gases are only removed from the atmosphere when they are destroyed by sunlight in the uppermost layers of the atmosphere.
• Fluorinated gases, in general, are the most potent and long-lasting type of greenhouse gas emitted by human activity.

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Black Carbon

• Black carbon (BC) is a form of particulate air pollutant produced by incomplete combustion of fossil fuels, biofuel, and biomass.
• It is a type of aerosol released by gas and diesel engines, coal-fired power plants, and other fossil-fuel-burning sources.
• Black carbon particles are made up of nearly pure elemental carbon with a small amount of oxygen and hydrogen bonded together.
• Among aerosols (including brown carbon and sulphates), black carbon (BC) has been identified as the second most important anthropogenic agent for climate change and the major indicator for understanding the negative effects of air pollution.
• Black carbon warms the Earth by absorbing heat in the atmosphere and decreasing albedo (the ability to reflect sunlight) when deposited on snow and ice.
• It darkens snow packs and glaciers through deposition and causes ice and snow to melt.
• Regionally, Black Carbon disturbs cloudiness and monsoon rainfall, as well as accelerates the melting of mountain glaciers like the Hindu Kush-Himalayan glaciers.
• BC is a short-lived pollutant that is the second-largest contributor to global warming after carbon dioxide (CO2).

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Brown Carbon

• Brown carbon is brown smoke produced by the burning of organic matter. When discharged into the atmosphere, it coexists with black carbon.
• It is a significant warming factor because it disturbs the temperature pattern of the atmosphere and the process of cloud formation.
• It also alters the pattern of solar absorption and the nature of clouds.
• Brown carbon is characterised by its light brownish colour and absorbs significantly in ultraviolet wavelengths but less in visible wavelengths.

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Global Initiatives to Reduce Greenhouse Gas Emissions

• Intergovernmental panel on climate change (IPCC): The World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) established IPCC in 1988 to provide policymakers with periodical assessments of the scientific basis of climate change, its impacts and future risks, as well as alternatives for adaptation and mitigation.
• United Nations Framework Convention on Climate Change: It was signed in 1992 and entered into force in 1994 to achieve "stabilisation of atmospheric greenhouse gas concentrations at a level that would prevent dangerous anthropogenic intervention with the climate system."
• The Kyoto Protocol (KP): It is an international agreement that was adopted at the 3rd COP in 1997. Its primary goal was to cut global greenhouse gas emissions by at least 5% compared to 1990 levels by 2012.
• CO2, CH4, N2O, Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs), and Sulfur Hexafluoride (SF6) were among the greenhouse gases to be reduced.
• The Paris Agreement: The Paris Agreement, which was adopted by consensus in December 2015, is a UNFCCC agreement that deals with GHG emissions mitigation, adaptation, and finance.
• It intends to address the threat of global climate change by keeping global temperature rises well below 2 degrees Celsius above pre-industrial levels, and to pursue measures to restrict temperature rises even further to 1.5 degrees Celsius.
• International Carbon Action Partnership (ICAP): ICAP was founded in 2007 as a multilateral forum of governments and public agencies focusing solely on cap and trade systems for GHG mitigation, with the goal of sharing best practices and discussing emission trading scheme design elements. It intends to contribute to the worldwide effort to establish a global carbon market.

Conclusion

For the past 150 years, the use of fossil fuels and the destruction of forests, which naturally remove carbon dioxide from the atmosphere, has led greenhouse gas levels to rise. To prevent climate change, we must reduce the number of greenhouse gases, such as carbon dioxide. Planting trees, bamboo, and other plants; protecting existing carbon sinks through conserving forests, grasslands, peatlands, and wetlands; farming practises such as cover crop planting and crop rotation, carbon dioxide removal technologies; use of renewable energy as they do not burn fossil fuels, have the potential to remove substantial volumes of greenhouse gases from the environment.

FAQs

MCQs

1. Which of the following is the primary greenhouse gas responsible for global warming?

A) Methane
B) Nitrous oxide
C) Carbon dioxide
D) Ozone

2. What human activity is the largest contributor to greenhouse gas emissions?

A) Deforestation
B) Industrial processes
C) Burning fossil fuels
D) Agriculture

3. Which of the following gases has the highest global warming potential (GWP)?

A) Carbon dioxide
B) Nitrous oxide
C) Methane
D) Water vapor

4. Which international agreement aims to limit global warming and reduce greenhouse gas emissions?

A) Kyoto Protocol
B) Paris Agreement
C) Montreal Protocol
D) UN Framework Convention on Climate Change (UNFCCC)

5. Which of the following is a natural source of greenhouse gases?

A) Fossil fuel combustion
B) Deforestation
C) Volcanic eruptions
D) Agriculture

GS Mains Questions and Model Answers

Q1: How does the increase in greenhouse gas emissions impact global climate patterns?

Answer: The increase in greenhouse gas emissions leads to an enhanced greenhouse effect, causing a rise in global temperatures. This warming alters global climate patterns, leading to more frequent and severe weather events such as hurricanes, floods, droughts, and heatwaves. These changes affect ecosystems, agriculture, and human societies, leading to disruptions in food and water security, biodiversity loss, and increased risks to human health. The rising temperatures also contribute to melting ice caps, rising sea levels, and changes in ecosystems, putting additional pressure on both natural and socio-economic systems.

Q2: Discuss the role of renewable energy in reducing greenhouse gas emissions in India.

Answer: Renewable energy plays a crucial role in reducing greenhouse gas emissions in India by replacing fossil fuel-based energy sources with cleaner alternatives. Solar, wind, and hydroelectric power provide low-carbon energy that can significantly reduce India’s carbon footprint. India has set ambitious targets for renewable energy capacity, aiming for 500 GW of non-fossil fuel-based capacity by 2030. This transition to renewable energy is essential for meeting India's climate commitments under the Paris Agreement and mitigating the impacts of climate change. Moreover, renewable energy also reduces dependency on imported fuels, supports job creation, and promotes sustainable development.

Q3: How can international cooperation enhance efforts to reduce greenhouse gas emissions?

Answer: International cooperation is essential for addressing the global challenge of reducing greenhouse gas emissions, as climate change is a global issue that requires coordinated action. Agreements like the Paris Agreement encourage countries to set emission reduction targets and share technology, financing, and expertise to help achieve these goals. Developed nations, which have historically contributed more to emissions, have a responsibility to support developing countries through climate finance and capacity-building initiatives. International cooperation also promotes the development of global standards for emissions reduction, carbon pricing, and clean technology innovations, ensuring that all nations can contribute to the fight against climate change.

Previous Year Questions on Greenhouse Gases

1. UPSC CSE Prelims 2020:

Question: Which of the following gases contributes the most to the greenhouse effect?

A) Nitrous oxide
B) Methane
C) Water vapor
D) Carbon dioxide

Answer: (D)

Explanation: Carbon dioxide (CO2) is the most significant greenhouse gas contributing to global warming due to its higher concentration and long-term persistence in the atmosphere.

2. UPSC CSE Mains 2019 (GS Paper 3):

Question: Evaluate the impact of increased greenhouse gas emissions on the Indian subcontinent.

Answer: Increased greenhouse gas emissions have exacerbated climate change in the Indian subcontinent, resulting in unpredictable weather patterns, intense heatwaves, floods, and droughts. These changes affect agricultural productivity, water resources, and public health. India faces significant challenges in managing these impacts, especially with its large population and dependence on agriculture. Policy responses must focus on emission reduction, adaptation strategies, and sustainable development to mitigate these risks.