Energy from the Sun arrives as shortwave radiation. Earth’s surface absorbs some of that energy and re-radiates heat as longer-wave infrared radiation.
Greenhouse gases in the atmosphere — water vapour, carbon dioxide, methane, nitrous oxide, and others — absorb and re-emit some of that outgoing heat. Without any greenhouse effect, Earth would be far too cold for the life we know.
The problem today is not the existence of the greenhouse effect. It is the strengthening of it. Burning fossil fuels and other human activities have raised atmospheric CO₂ from about 280 parts per million in pre-industrial times to over 420 ppm.
More greenhouse gases mean more of the outgoing heat is kept in the system. Oceans absorb a large share of that extra heat, which is why marine heatwaves and sea-level rise matter as much as hotter summers on land.
This is established physics, not a contested opinion. Debates about policy and pace of action are real; the basic mechanism of warming is not.
Quick check — 3 questions
Check your understanding — pick an answer, or reveal the correct ones when ready.
1. What does the natural greenhouse effect do for Earth?
2. What has happened to atmospheric CO₂ since pre-industrial times?
3. Why is more greenhouse gas a problem today?