Britannica Sources used in this answer

How do a planet’s atmosphere and reflectivity affect its surface temperature?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Habitable zone The habitable zones (green) for stars that are like the Sun (middle), hotter than the Sun (top), and cooler than the Sun (bottom). The red areas are those in which liquid surface water would be lost as a result of a runaway greenhouse effect, and the blue areas are those in which liquid surface water would be completely frozen.

A planet’s surface temperature is fundamentally shaped by the interplay between its atmosphere and its reflectivity, or albedo. These factors determine how much solar energy is absorbed versus how much is lost to space, directly influencing a planet's potential to maintain liquid water.1

The Role of Reflectivity (Albedo)

A planet’s albedo is the fraction of incident solar radiation reflected back into space. Surfaces with high reflectivity, such as ice or thick clouds, absorb less energy, which tends to cool the surface. Conversely, low-albedo surfaces absorb more solar energy, contributing to higher temperatures. Changes in albedo can trigger feedback loops; for example, melting ice reduces reflectivity, leading to increased heat absorption and further warming.423

The Role of the Atmosphere

The atmosphere acts as a radiative blanket through the greenhouse effect. While the atmosphere can scatter incoming sunlight, its primary impact on temperature comes from greenhouse gases like carbon dioxide, methane, and water vapor. These gases absorb infrared radiation emitted by the planet's surface and re-emit it in all directions, trapping heat that would otherwise escape to space. Without this natural warming, many planets, including Earth, would be frozen and uninhabitable.23