Revision: Atmospheric Pollution Chemistry (English Medium) ICSE Class 9 CISCE

The heating-up of the earth’s atmosphere due to trapped infrared rays reflected from the earth's surface by atmospheric gases is called the greenhouse effect.

The gradual increase in Earth’s average surface temperature due to rising concentrations of greenhouse gases in the atmosphere is called global warming.

The warming up of the atmosphere due to trapping of the solar radiation reflected by the earth by gases like carbon dioxide is called Greenhouse effect.

The gradual increase in the average surface temperature of the Earth due to rising concentrations of greenhouse gases in the atmosphere is called global warming.

1. Acid rain forms when rainwater absorbs industrial gases like CO₂, SO₂, and nitrogen oxides, making it more acidic.
2. It harms soil and vegetation, corrodes buildings, damages monuments by reacting with calcium, and reduces visibility.
3. It also acidifies water bodies, endangering fish and aquatic life.
4. Soil pollution reduces soil fertility and nutrients.
5. Waste control is essential to protect soil health.

• The greenhouse effect is a naturally occurring phenomenon that heats Earth's surface. Without it, Earth's temperature would be -18°C instead of 15°C.
• Greenhouse gases are transparent to solar radiation but retain and reflect back long-wave heat radiation. Main gases — CO₂ (60%), CH₄ (20%), CFCs (14%), N₂O (6%).
• Earth's surface re-emits heat as infrared radiation. Greenhouse gases like CO₂ and CH₄ absorb this and return heat to Earth's surface — causing the greenhouse effect.
• Rising CO₂ due to the burning of fossil fuels and deforestation intensifies the greenhouse effect, causing global warming.
• Global warming leads to melting of polar ice, rising sea levels, changes in rainfall patterns and loss of biodiversity.

• Global warming — rise in Earth's temperature due to increased greenhouse gases. Earth's temperature rose by 0.6°C in the past century, mostly in the last three decades.
• Causes odd climatic changes like the El Niño effect, melting of polar ice caps and Himalayan snow caps, and submergence of coastal areas.
• Chewang Norphel ("Ice Man of India"), a civil engineer from Ladakh, built 13 artificial glaciers to combat global warming, increasing groundwater recharge and providing irrigation water.
• Artificial glaciers are built at lower elevations so they melt earlier, expanding the growing season.
• Control measures — reduce fossil fuel use, improve energy efficiency, reduce deforestation, plant trees and control population growth.

• Ozone layer — present in the stratosphere (12–15 km above Earth). Absorbs harmful UV radiation. Thickness measured in Dobson Units (DU).
• CFCs rise to the stratosphere → UV rays release Cl atoms → Cl acts as a catalyst → continuously degrades O₃ → forms ozone hole, particularly over the Antarctic region.
• Other ozone-depleting substances — SO₂, nitrogen oxides and methyl chloroform.
• UV-B (280–322 nm) — damages DNA, causes mutations, skin cancer, ageing and snow blindness/cataract. It can permanently damage the cornea.
• The Montreal Protocol was signed at Montreal, Canada, in 1987 (effective 1989) to control the emission of ozone-depleting substances.