GREENHOUSE GASES(GHGs)
Greenhouse gases are gases that trap heat in the Earth's atmosphere, leading to the greenhouse effect and contributing to global warming. These gases include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3), and fluorinated gases (such as hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride).
These gases allow sunlight to enter the Earth's atmosphere freely. Once absorbed, the Earth's surface emits infrared radiation, but instead of allowing this radiation to escape back into space, greenhouse gases trap and re-radiate some of it back towards the Earth's surface. This process warms the Earth's surface and lower atmosphere, leading to the greenhouse effect.
Human activities, such as the burning of fossil fuels, deforestation, and industrial processes, have significantly increased the concentration of greenhouse gases in the atmosphere, amplifying the greenhouse effect and contributing to global climate change
Here are the major greenhouse gases:
- Carbon dioxide (CO2): The most abundant greenhouse gas emitted through human activities. It is released when fossil fuels like coal, oil and natural gas are burned
- Methane (CH4): Methane is emitted from agriculture, waste decomposition, and fossil fuel production. It is a more potent greenhouse gas than CO2, but it breaks down in the atmosphere more quickly
- Nitrous oxide (N2O): Nitrous oxide is emitted from agriculture, industrial processes, and burning fossil fuels. It is a long-lived greenhouse gas that can stay in the atmosphere for centuries
- Fluorinated gases These are man-made chemicals used in refrigerants, air conditioners, and fire extinguishers. They are very potent greenhouse gases, but they are emitted in much smaller quantities than other greenhouse gases
- Water vapor (H2O): The most abundant greenhouse gas in the atmosphere. Water vapor plays an important role in the natural greenhouse effect, but human activities do not significantly affect the amount of water vapor in the atmosphere
3. What is the Greenhouse gas effect?
The greenhouse effect is a natural process that occurs when certain gases in the Earth's atmosphere trap heat from the sun. This process is essential for maintaining the Earth's temperature within a range suitable for life. Without the greenhouse effect, the Earth would be much colder, and life as we know it would not exist.
Here's how the greenhouse effect works:
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Solar radiation: Sunlight reaches the Earth's atmosphere and passes through it, warming the Earth's surface.
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Absorption and re-radiation: The Earth's surface absorbs some of this solar energy and then emits it as infrared radiation (heat). Greenhouse gases in the atmosphere, such as carbon dioxide (CO2), methane (CH4), water vapor (H2O), and others, absorb some of this infrared radiation.
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Re-emission: The absorbed energy is re-radiated in all directions, including back toward the Earth's surface. This trapped heat warms the lower atmosphere and the Earth's surface, similar to how a greenhouse traps heat.
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Balance: The greenhouse effect helps maintain the Earth's temperature in a range suitable for life. However, human activities, such as burning fossil fuels and deforestation, have significantly increased the concentration of greenhouse gases in the atmosphere, leading to enhanced greenhouse effect or global warming
- Hydrofluorocarbons (HFCs) are a class of synthetic greenhouse gases commonly used in refrigeration, air conditioning, foam blowing agents, aerosol propellants, and other industrial applications. They are composed of hydrogen, fluorine, and carbon atoms.
- HFCs were developed as alternatives to chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), which were phased out due to their significant ozone-depleting potential. Unlike CFCs and HCFCs, HFCs do not contain chlorine atoms, so they do not contribute to ozone depletion.
- However, they are potent greenhouse gases, with high global warming potentials (GWPs), meaning they trap heat in the atmosphere at a much higher rate than carbon dioxide (CO2).
- Due to their role in contributing to climate change, efforts have been made internationally to regulate and phase out the use of HFCs. The Kigali Amendment to the Montreal Protocol, adopted in 2016, aims to gradually reduce the production and consumption of HFCs globally.
- Many countries are transitioning to alternative refrigerants with lower global warming potentials, such as hydrofluoroolefins (HFOs) and natural refrigerants like ammonia and carbon dioxide. These efforts are essential for mitigating climate change by reducing the emissions of potent greenhouse gases like HFC
- The primary consequence of intensified greenhouse gas effect is global warming. Increased concentrations of greenhouse gases in the atmosphere trap more heat, leading to a rise in average global temperatures
- Global warming alters weather patterns and climatic conditions worldwide, leading to changes such as more frequent and intense heatwaves, storms, droughts, and floods. These changes can disrupt ecosystems, agriculture, and water supplies, leading to ecological imbalances and economic losses
- Warmer temperatures cause polar ice caps and glaciers to melt, contributing to rising sea levels. This phenomenon threatens coastal communities, low-lying islands, and habitats, increasing the risk of flooding and erosion
- Increased atmospheric CO2 levels lead to higher levels of carbon dioxide dissolving into oceans, resulting in ocean acidification. This harms marine life, particularly organisms with calcium carbonate shells or skeletons, such as corals, mollusks, and certain plankton species
- Climate change disrupts ecosystems and habitats, forcing species to migrate, adapt, or face extinction. The rapid pace of climate change often outpaces the ability of many species to adapt, leading to biodiversity loss and ecosystem degradation
- Climate change exacerbates health risks, including heat-related illnesses, respiratory problems from poor air quality, increased prevalence of infectious diseases, and food and water insecurity due to changing agricultural conditions
- Climate change can lead to displacement of populations due to extreme weather events, loss of livelihoods in sectors such as agriculture and fishing, and increased conflicts over resources like water and arable land. These disruptions can strain social systems and economies, particularly in vulnerable regions
The Montreal Protocol is an international environmental agreement aimed at protecting the Earth's ozone layer by phasing out the production and consumption of ozone-depleting substances (ODS). It was negotiated in 1987 and entered into force in 1989. The protocol is regarded as one of the most successful international environmental treaties.
Key points about the Montreal Protocol include:
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Objective: The primary goal of the Montreal Protocol is to phase out the production and consumption of ODS, which are substances that contain chlorine and bromine atoms and are responsible for ozone depletion in the stratosphere.
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Ozone Layer: The ozone layer is a region of the Earth's stratosphere that contains a high concentration of ozone molecules (O3). This layer plays a crucial role in absorbing and filtering out harmful ultraviolet (UV) radiation from the sun, protecting life on Earth from its harmful effects.
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Ozone-Depleting Substances: The Montreal Protocol targets several categories of ODS, including chlorofluorocarbons (CFCs), halons, carbon tetrachloride, and methyl chloroform, among others. These substances were commonly used in refrigeration, air conditioning, foam blowing agents, fire extinguishers, and other industrial applications.
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Phasing Out: The protocol established a timetable for phasing out the production and consumption of ODS, with developed countries committing to earlier phase-out schedules and developing countries given more time to comply. Amendments to the protocol tightened regulations and accelerated the phase-out schedules over time.
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Success: The Montreal Protocol is widely regarded as successful in achieving its objectives. By reducing the production and consumption of ODS, the protocol has led to a gradual recovery of the ozone layer. Scientific assessments have confirmed a decrease in the atmospheric concentrations of ODS and a healing of the ozone layer.
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International Cooperation: The Montreal Protocol exemplifies successful international cooperation in addressing global environmental challenges. It has been ratified by almost every country in the world, demonstrating a shared commitment to protecting the ozone layer and mitigating climate change (as many ODS are also potent greenhouse gases)
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For Prelims: General issues on Environmental ecology, Bio-diversity and Climate Change – that do not require subject specialization
For Mains: General Studies III: Conservation, environmental pollution and degradation, environmental impact assessment
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Previous Year Questions
1.Global warming is attributed to the presence of the following gases in the atmosphere : (UGC NET 2022)
(A) Methane
(B) Sulphur dioxide
(C) Surface Ozone
(D) Nitrogen dioxide
(E) Carbon dioxide
Choose the correct answer from the options given below :
1.(A), (B), (C), (E) only
2.(A), (C), (E) only
3.(A), (C), (D), (E) only
4.(A), (B), (D), (E) only
Answer (2)
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