Greenhouse Gases - Environment

Greenhouse Gases - Environment

Atmosphere as a Protective Layer

The atmosphere surrounding the Earth acts like a windowpane. The Earth's atmosphere is made up of major gases, namely nitrogen and oxygen, and minor constituents such as carbon dioxide and water vapour.

Role of Gases in Moderating Earth’s Temperature

• These gases play a crucial role in moderating the Earth's atmosphere.

• This is because these gases are relatively transparent to incoming visible light from the sun, but absorb the heat radiation given off by the ground and objects exposed to the Sun.

The Greenhouse Effect Explained

• As a result, they produce a heating of the atmosphere by what is known as the greenhouse effect.

• The name is derived from the fact that inside a glass-enclosed greenhouse, the temperature is warmer than outside.

• Such greenhouses are used for growing plants, especially in the interseason, that require higher temperatures for growth.

How a Greenhouse Works

• The green greenhouse looks like a small glasshouse.

• In a greenhouse, the glass panel lets the light in, but does not allow heat to escape.

• Therefore, the greenhouse warms up, very much like inside a car that has been parked in the sun for a few hours.

Greenhouse Effect

Impact Without Greenhouse Gases

• Without the greenhouse gases in the atmosphere and the resulting greenhouse effect, the Earth's average surface temperature would have been a chilly 18°C to 20°C rather than the present average of 15°C.

Modern Concerns Over Greenhouse Gases

• But what is of concern today is the ever-increasing level of carbon dioxide and other greenhouse gases (methane, CFCs, nitrous oxide) in the atmosphere during the past several decades (increased by 0.6°C).

• Estimates suggest that by the middle of the 21st century, the Earth may be 2° to 9°C warmer.

• This global warming will result in many climatic changes, such as sea level rise, severe weather, etc.

Increase in Concentrations of Greenhouse Gases

The trends in the increase in concentrations of greenhouse gases since pre-industrial times are briefly described below—

a. Carbon dioxide (C02)

• Carbon dioxide is the most abundant greenhouse gas in the atmosphere.

• The level of carbon dioxide in the atmosphere has increased from the pre-industrial level of 280 ppm (parts per million) to about 368 ppm in 2000.

• This has been largely the result of fossil fuel burning, deforestation, and changes in land use​​. The carbon dioxide persists for 5 to 200 years in the atmosphere.

b. Methane (CH4)

• Methane concentration in the atmosphere has more than doubled [from 700 ppb (parts per billion) to 1750 ppb].

• Methane is largely a product of incomplete decomposition and is produced by a group of bacteria called methanogens under anaerobic conditions.

• The major sources of methane include freshwater wetlands, enteric fermentation in cattle, and flooded rice fields. Biomass burning also produces methane.

• Methane persists for 12 years in the atmosphere.

c. Chloroflurocarbons (CFCs)

• Chlorofluorocarbons are non-toxic and non-flammable, highly stable, and synthetic gaseous compounds of carbon and halogens.

• Although these compounds were synthesised during the 20th century, their concentration in the atmosphere has increased.

  • For example, the concentration of CFC-11 and HFC-23 in the air was approximately 282 ppt (parts per trillion) in 2000, which means that 0 ppt means absent before industrialisation (before 1750).

• The major sources of chloroflurocarbons are leaking air conditioners, refrigeration units, evaporation of industrial solvents, and production of plastic foams and propellants in aerosol spray cans.

• The chloroflurocarbons persist for 45 to 260 years or more in the atmosphere.

d. Nitrous oxide (N20)

• The concentration of nitrous oxide in the atmosphere has increased from approximately 270 ppb in pre-industrial times to approximately 316 ppb in recent times.

• The main sources of nitrous oxide are agriculture, biomass burning, and industrial processes.

• Nitrous oxide is produced during nylon production, the burning of nitrogen-rich fuels, livestock waste, the breakdown of nitrogen-rich fertilisers in soil, and nitrate-contaminated groundwater.

Sharing of Greenhouse Gases to Global Warming

Sharing of greenhouse Gases to Global warming

The relative sharing of different greenhouse gases to global warming is shown in the above figure.

• It is estimated that Carbon dioxide (C02) contributes about 60% of the total global warming. 

• The combustion of fossil fuel (i.e., combustion of coal) vehicles' emissions is the major source (about 74%) of CO_2, and deforestation & combustion of biomass are the subsidiary sources (about 25%) of CO_2.

• The share of Methane (CH4), Chloroflurocarbons (CFCs), and Nitrous oxide (N20) is 20%, 14% and 6% respectively.

Final Thoughts

The Earth’s atmosphere acts as a vital protective shield, regulating temperature and sustaining life. Greenhouse gases, such as carbon dioxide, methane, CFCs, and nitrous oxide, play a key role in maintaining this balance, but their excessive increase in recent decades has disrupted the natural climate system.

Human activities like fossil fuel burning, deforestation, and industrial emissions are the main drivers of this rise, leading to global warming and severe environmental consequences. Without immediate action, global temperatures could rise by 2° to 9°C by the mid-21st century, causing sea level rise, extreme weather, and biodiversity loss.

The fact that CO₂ alone contributes about 60% of total warming underscores the urgency for change. To safeguard the planet’s future, it is essential to adopt sustainable practices, reduce emissions, and protect natural ecosystems.

The fight against climate change begins with awareness and action from every individual, community, and nation.