Earth's energy budget and albedo

Earth's climate depends on its energy budget, the balance between energy arriving from the Sun and energy leaving to space. Sunlight arrives mostly as visible light. About 30 percent of it is reflected straight back to space by clouds, ice, snow, and other bright surfaces, a fraction called Earth's albedo, and the rest is absorbed by the land, oceans, and atmosphere and warms them. Earth then gives off energy as infrared radiation. Greenhouse gases such as water vapor, carbon dioxide, and methane let visible sunlight through but absorb much of the outgoing infrared radiation and send part of it back down, keeping Earth's average surface temperature near 15 °C instead of about -18 °C without them. When incoming and outgoing energy are equal, the average temperature stays steady; when more energy comes in than goes out, Earth warms until a new balance is reached. Climate can therefore change when the Sun's output changes, when albedo changes, for example as ice melts or as a large volcanic eruption spreads reflective particles in the stratosphere (Mount Pinatubo's 1991 eruption cooled Earth by about 0.5 °C for a year or two), or when greenhouse gas levels change. Today, rising greenhouse gases mean Earth absorbs more energy than it gives off, an imbalance measured by satellites and by the steady warming of the oceans, which have taken up about 90 percent of the extra heat.

This explanation is AI-generated and can occasionally be wrong. 🚩 Report