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How would Earth’s average temperature differ without the natural greenhouse effect?

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World map shaded to show annual carbon dioxide emissions by country in 2022, with China, the United States, and India highlighted as top emitters in dark red. A bar chart below lists the top ten emitting countries by million metric tons. — Greenhouse gas Map of annual carbon dioxide emissions by country in 2014.

Without the natural greenhouse effect, Earth’s average surface temperature would be approximately 33 °C (59 °F) colder than it is today.12

At this significantly lower temperature, the planet would be frozen and likely uninhabitable. The natural greenhouse effect is driven by atmospheric constituents such as water vapour, carbon dioxide, and methane, which absorb infrared radiation emitted from the surface and reradiate it back toward Earth, maintaining a warmer climate than would otherwise exist.123