What do we mean by a runaway greenhouse effect?

Venus may have experienced a runaway greenhouse effect involving carbon dioxide and water vapor. In this scenario, Venus may have had a global ocean in the past. As the sun's heat and brightness increased, the atmosphere's concentration of water vapor also rose, raising the temperature to the point where the oceans boiled and all of the water vapor entered the atmosphere.

Throughout Earth's history, the planet's climate has fluctuated between warm periods and ice ages. While some climate scientists argue that runaway greenhouse conditions are unlikely on Earth due to Earth's distance from the Sun, others contend that burning coal and extracting shale oil could lead to such a situation.

The majority of scientists, however, believe that as the Sun ages and gets bigger, there will eventually be a runaway greenhouse effect that could potentially result in the extinction of all life on Earth. The loss of oceans will make the Earth primarily a desert planet, with the only remaining water being large salt flats surrounding what was once the ocean floor and a few evaporating ponds scattered near the poles.

A runaway greenhouse effect occurs when a planet's atmosphere traps incoming solar radiation, leading to a rise in temperature. This intensified heat causes increased evaporation of substances like water, which, in turn, amplifies the greenhouse effect, creating a self-reinforcing cycle that further raises temperatures. This phenomenon can result in extreme and uninhabitable conditions on a planet.