Global Warming
The mechanism, the evidence, and the feedbacks.
Global warming is the long-term rise in Earth's average surface temperature. The mechanism is the greenhouse effect, which is itself entirely natural and necessary — without it the planet would average about −18 °C. The issue is its intensification.
The mechanism
Solar radiation arrives mostly as short-wave visible light, passes through the atmosphere and warms the surface. The surface re-radiates that energy as longer-wave infrared. Greenhouse gas molecules absorb infrared and re-emit it in all directions, including downward. Adding more of those molecules slows the escape of heat.
| Gas | Main sources | Note |
|---|---|---|
| Carbon dioxide | Fossil fuels, cement, land clearance | Long atmospheric lifetime |
| Methane | Livestock, rice, landfill, gas leaks | Far stronger per molecule, shorter-lived |
| Nitrous oxide | Fertiliser, industry | Very long-lived |
| Water vapour | Evaporation | A feedback, not a driver — warmer air holds more |
Feedbacks
Ice-albedo: ice reflects sunlight, open water absorbs it, so melting ice accelerates warming. Permafrost: thawing releases stored carbon. Water vapour: warmer air holds more, and water vapour is itself a greenhouse gas. These are positive feedbacks — they amplify rather than stabilise.
Weather is not climate
A cold winter does not contradict a warming trend, any more than one tall pupil contradicts an average height. Climate is the distribution; weather is a single draw from it. Warming shifts the distribution, which changes how often extremes occur.