Q.Write an explanatory note on "global warming".

Think of a car parked in the sun on a hot afternoon. The windows are rolled up, the seats are scorching, and the air inside is far hotter than the air outside. The sunlight gets in easily, but the heat that the seats and dashboard give off cannot escape back through the glass. So the inside just keeps warming up. That is the simplest picture of global warming: something lets energy in, but traps the outgoing heat.

Now scale that car up to the whole planet. The Earth gets its warmth from the Sun. Sunlight passes through the atmosphere and heats the ground and oceans. The Earth then radiates that heat back out into space. But certain gases in the atmosphere — carbon dioxide, methane, water vapour, nitrous oxide — act like the car's glass. They let sunlight in, but they absorb the outgoing heat and send some of it back down. This is the greenhouse effect, and it is natural. Without it, the Earth would be a frozen, lifeless ball. The problem is not that the effect exists; it is that we have been thickening that glass.

The thickening comes from human activity. Since the industrial revolution, we have been burning coal, oil, and natural gas for energy — to run factories, power vehicles, and light homes. Every time we burn these fossil fuels, carbon dioxide is released into the air. That is the single biggest cause. But it is not the only one. Cutting down forests matters too, because trees absorb carbon dioxide as they grow. When we clear land for farming or timber, we remove a natural sponge that was soaking up the gas. Agriculture adds its own share: livestock produce methane, and fertilised fields release nitrous oxide. Even the way we manage waste — landfills and burning rubbish — contributes.

So the precise meaning of "global warming" is this: the long-term rise in the Earth's average surface temperature, driven mainly by the extra greenhouse gases we have pumped into the atmosphere. It is not the same as weather. Weather is what you see outside today — a thunderstorm, a cold snap. Climate is the average of weather over decades. Global warming is a shift in that average, and a small shift in the average means far more extreme swings at the edges. …