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how does the greenhouse effect cause global warming
Plot twist: the greenhouse effect keeps us alive. Without it, Earth would average minus 18 Celsius, frozen solid. With it, plus 15.
Earth runs on a budget. Sunlight brings in about 240 watts per square meter, so exactly 240 of heat must leave. A bare planet would do that at minus 18.
Sunlight is mostly visible light, and it sails through clear air to warm the ground. The air barely notices it.
The warm ground glows infrared. Carbon dioxide, water vapor and methane soak it up, then re-radiate in every direction, much of it back down.
Nitrogen and oxygen, ninety-nine percent of the air, let infrared straight through. The trace gases do the catching. The ground sends up 390 watts; only 240 escape.
Burning coal, oil and gas releases carbon buried for ages. Carbon dioxide has climbed from about 280 parts per million to over 420, up by half.
A thicker blanket sends more heat back down, so less escapes. Energy in beats energy out, and the planet warms until balance returns: more than one degree Celsius so far.
So, the whole picture: sunlight in, a gas blanket that sends heat back, heat out. Thicken the blanket and the planet settles warmer.
The greenhouse effect is Earth's warm blanket, and we are making it thicker.