Greenhouse Effect | Agriculture Optional Notes for UPSC PDF Download

What do you mean by the Greenhouse effect?

The greenhouse effect is a process that occurs within a greenhouse, which is a controlled environment designed for the cultivation of plants. Greenhouses are typically constructed with transparent materials, such as glass, for both their roofs and walls.

In a greenhouse what is the incident solar radiation?

Solar radiation entering the greenhouse consists of visible light as well as nearby infrared and ultraviolet wavelengths. This incoming radiation penetrates the glass walls and roof, where it is absorbed by the ground, the interior structure, and the items within the greenhouse. As these materials absorb the energy, they subsequently emit it as longer-wavelength infrared radiation, which is essentially heat radiation.

What is the reason infrared radiation cannot escape through radiative transfer?

The inability of infrared radiation to exit the greenhouse through radiative transfer is due to the fact that materials such as glass and other wall components employed in greenhouses do not allow the transmission of infrared energy. Since the greenhouse is enclosed and not open to the atmosphere, heat cannot escape via convection, resulting in a rise in the temperature within the greenhouse. This phenomenon is commonly referred to as the "greenhouse effect."

Natural Greenhouse Effect: Importance

The natural greenhouse effect is a long-standing natural process that has been ongoing on our planet for millions of years.

How natural greenhouse effect caused?

It is primarily brought about by the existence of water vapor and tiny water droplets in the atmosphere, and it plays a vital role in enabling life on Earth. Together, these elements are responsible for over 95 percent of the overall greenhouse warming.

• This natural greenhouse effect helps sustain average global temperatures at approximately 15°C. 
• Without this mechanism, the Earth's average temperature might have plummeted to as low as -17°C, which would have made it inhospitable for life to thrive.

Greenhouse Gases (GHGs)

What gases contribute to the greenhouse effect?

The greenhouse effect is a consequence of certain atmospheric gases, including carbon dioxide, methane, nitrous oxide (N₂O), water vapor, and chlorofluorocarbons, having the ability to trap the outgoing infrared radiation emitted from the Earth's surface. These gases are commonly referred to as greenhouse gases, and the warming effect they produce is known as the greenhouse effect.

Are all nitrogen oxides greenhouse gases?

Not all nitrogen oxides are greenhouse gases. Nitrogen oxides with the general formula NOx, including NO (nitric oxide) and NO₂ (nitrogen dioxide), actually function as global cooling agents. In contrast, nitrous oxide (N₂O) qualifies as a greenhouse gas.

Consequences of Unchecked Greenhouse Gases

Failure to regulate greenhouse gases could result in a temperature increase of up to 5°C by the turn of the century. According to scientific assessments, such a temperature rise would have detrimental effects on the environment, leading to unusual climate patterns, such as more frequent El Niño events, which, in turn, would accelerate the melting of polar ice caps as well as ice caps in regions like the Himalayas.

Impact on the Cryosphere

The cryosphere refers to the frozen water component of Earth's water system and encompasses polar regions and snow caps in high mountain ranges. The consequences of rising temperatures would include a gradual increase in sea levels, submerging numerous coastal regions and causing the loss of critical coastal ecosystems, including marshes and swamps.

Greenhouse Gases (GHGs) and Their Sources

• Carbon Dioxide (CO₂)
  • Source: Emitted from the burning of fossil fuels and deforestation.
  • Significance: CO₂ is a crucial greenhouse gas that plays a major role in the greenhouse effect by absorbing outgoing radiation from Earth's surface.
• Chlorofluorocarbons (CFCs):
  • Source: Found in refrigeration, solvents, insulation foams, aero propellants, and various industrial and commercial uses.
  • Significance: CFCs contribute to the greenhouse effect and were phased out due to their role in ozone depletion.
• Methane (CH₄):
  • Sources: Emitted from various sources such as paddy cultivation, cattle and livestock excreta, termites, burning of fossil fuels and wood, landfills, wetlands, and fertilizer factories.
  • Significance: Methane is a potent greenhouse gas and a major contributor to the greenhouse effect.
• Nitrogen Oxides (N₂O):
  • Sources: Emitted from activities like burning fossil fuels, the use of fertilizers, burning wood, and crop residue.
  • Significance: N₂O contributes to the greenhouse effect, and the emissions of NO and NO₂ lead to the formation of (OH) radicals, which counteract the effects of other greenhouse gases.
• Carbon Monoxide (CO):
  • Sources: Released from iron ore smelting, burning of fossil fuels, and e-waste combustion.
  • Significance: While CO is a short-lived greenhouse gas, it indirectly affects other greenhouse gases like methane and tropospheric ozone through chemical reactions.
• Carbon Dioxide (CO₂):
  • CO₂ plays a significant role in meteorology, as it allows incoming solar radiation but prevents the escape of outgoing radiation. 
  • It contributes significantly to the greenhouse effect, keeping the Earth's temperature stable.
• Ozone:
  • Ozone, although present in small amounts at the Earth's surface, is crucial. Most ozone resides in the stratosphere, where it absorbs harmful UV radiation. 
  • Ground-level ozone is formed through chemical reactions between NO₂ and volatile organic compounds in the presence of sunlight.
• Water Vapor:
  • Water vapor is a unique greenhouse gas because it absorbs both incoming and outgoing solar radiation. 
  • Its concentration varies with regions, with high levels in warm, humid areas and lower levels in dry, cold regions.
• Methane:
  • Methane is the second most important greenhouse gas after CO₂ and is produced from the decomposition of organic matter, including animal waste. 
  • Controlling methane emissions can be achieved by utilizing animal waste for biogas production.
• Nitrous Oxide (N₂O):
  • N₂O is a greenhouse gas generated from various sources, and it also influences methane concentrations. 
  • Emissions of NO and NO₂ play a role in the creation of (OH) radicals that counteract the effects of other greenhouse gases.
• Carbon Monoxide:
  • Carbon monoxide is a short-lived greenhouse gas that indirectly affects other gases by increasing methane and tropospheric ozone concentrations. 
  • Natural atmospheric processes eventually oxidize it to CO₂.
• Fluorinated Gases:
  • Fluorinated gases, including chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride, are potent greenhouse gases used in various applications, including refrigeration, semiconductors, and electrical transmission.
• Black Carbon:
  • Black carbon, also known as soot, is a solid particle that contributes to global warming. 
  • It results from incomplete combustion and affects climate by absorbing heat, darkening snowpacks, and reducing albedo. 
  • Its effects are regional and short-lived.
• Brown Carbon:
  • Brown carbon is another particle produced from combustion sources, particularly biomass burning. 
  • It is often considered a greenhouse gas, distinguishing it from black carbon.
• GHG Protocol:
  • The Greenhouse Gas Protocol (GHG Protocol) develops standards and tools for tracking and managing greenhouse gas emissions from various sources, including private and public sector operations. 
  • It offers a framework for corporate GHG accounting and reporting and aims to support climate goals. 
  • The protocol was established in collaboration between the World Resources Institute (WRI) and the World Business Council for Sustainable Development (WBCSD) in response to the need for a global standard for GHG measurement and reporting.