The greenhouse effect of solar radiation on the Earth's surface caused by emission of greenhouse gases. Radiative forcing (warming influence) of different contributors to climate change in 2011, as reported in the fifth IPCC assessment report.
A greenhouse gas (GHG or GhG) is a gas that absorbs and emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse gases in Earth's atmosphere are water vapor (H
2O), carbon dioxide (CO
2), methane (CH
4), nitrous oxide (N
2O), and ozone (O3). Without greenhouse gases, the average temperature of Earth's surface would be about −18:°C (0:°F), rather than the present average of 15:°C (59:°F). The atmospheres of Venus, Mars and Titan also contain greenhouse gases.
Human activities since the beginning of the Industrial Revolution (around 1750) have increased the atmospheric concentration of carbon dioxide by almost 50%, from 280 ppm in 1750 to 419 ppm in 2021. The last time the atmospheric concentration of carbon dioxide was this high was over 3:million years ago. This increase has occurred despite the absorption of more than half of the emissions by various natural carbon sinks in the carbon cycle.