Q.The gas which traps heat 20 times more than Carbon-dioxide is:

Greenhouse Effect and Global Warming

The greenhouse effect is the natural warming of the Earth caused by certain atmospheric gases. Sunlight reaches the Earth's surface, which absorbs it and re-emits heat as infrared (long-wave) radiation. Greenhouse gases — chiefly carbon dioxide (CO₂) and methane (CH₄), along with water vapour, nitrous oxide (N₂O) and chlorofluorocarbons (CFCs) — absorb and trap this outgoing infrared radiation, preventing its escape to space and reheating the atmosphere.

Without this effect the Earth would be too cold for life; however, rising anthropogenic emissions intensify it, causing global warming — an increase in average global temperature.

Relative contribution to global warming (approximate): CO₂ ≈ 60%, methane ≈ 20%, CFCs ≈ 14%, and N₂O ≈ 6% (values vary between sources). Methane, though present in smaller amounts, is a far more potent greenhouse gas per molecule than CO₂.

Consequences include melting of polar ice, rising sea levels, and shifts in rainfall and agriculture. Mitigation involves cutting fossil-fuel use, reforestation and reducing emissions of these gases. …