5.17—Anthropogenic climate change and greenhouse gases

Earth’s surface absorbs solar energy and emits infrared radiation. Greenhouse gases absorb some of that outgoing radiation and re-radiate it, reducing heat loss to space; higher concentrations increase the warming influence.

The natural greenhouse effect makes Earth habitable. Anthropogenic climate change refers to additional warming linked to human-driven increases in gases such as carbon dioxide and methane from fossil-fuel use, land-use change and agriculture.

Deforestation removes a carbon sink while fossil-fuel combustion adds carbon dioxide. Landfill and ruminants add methane; each pathway changes atmospheric composition through a different mechanism.

The greenhouse effect is not the same as ozone depletion, and correlation alone does not prove causation. Separate the physical mechanism from evidence about human sources.