How does Greenhouse Effect work?
The greenhouse effect is the process by which certain gases in the Earth’s atmosphere trap and radiate heat, keeping the planet warm enough to sustain life. It works like this: sunlight consists of various wavelengths including visible light, which easily passes through the Earth’s atmosphere. When sunlight reaches the Earth’s surface, it is absorbed and reemitted as infrared radiation. Some of this infrared radiation escapes back into space, but a significant portion is absorbed by greenhouse gases in the atmosphere. These gases then re-radiate some of this energy back towards Earth, effectively trapping heat within the lower atmosphere and causing global warming.
Long answer
The greenhouse effect is a natural phenomenon that allows heat from the sun to be retained within the Earth’s atmosphere, making our planet habitable. Incoming solar radiation consists of various wavelengths, including visible light. When sunlight reaches the Earth, it warms its surface. As a result, the warmed surface emits thermal (infrared) radiation.
Certain gases present in the Earth’s atmosphere - known as greenhouse gases - play a crucial role in absorbing and re-radiating some of this outgoing thermal radiation. The main greenhouse gases are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and water vapor (H2O). These gases are transparent to incoming solar radiation but absorb thermal radiation emitted by the Earth.
When thermal radiation emitted by the warm surface encounters greenhouse gases in the lower layers of the atmosphere, it continues to heat them. The energized molecules then re-radiate some of that energy back towards both upper atmospheric layers and Earth’s surface – essentially trapping some of the heat within our planet’s lower atmosphere.
This process acts similarly to a greenhouse hence its name: it allows sunlight to pass freely through while trapping heat inside, just as glass walls do in a garden greenhouse. Over higher time frames, such as centuries or millennia, an equilibrium is reached, where the amount of incoming and outgoing energy is roughly balanced.
However, human activities, particularly the burning of fossil fuels (like coal, oil, and gas) and deforestation, have increased the concentration of greenhouse gases in the atmosphere. This increase in greenhouse gases enhances their ability to trap thermal radiation, leading to an intensification of the greenhouse effect. Consequently, more heat is retained within Earth’s system than is radiated back into space, resulting in global warming and climate change.