What is the Greenhouse Effect?
The Sun’s warmth heats the surface of the Earth, which in turn radiates energy back to space. Some of this radiation, which is nearly all in the infrared spectrum, is trapped in the atmosphere by greenhouse gases. For instance, water vapour strongly absorbs radiation with wavelengths between 4 and 7 micrometres, and carbon dioxide (CO2) absorbs radiation with wavelengths between 13 and 19 micrometres. The trapped radiation warms the lower atmosphere, or troposphere. Some heat then finds its way back down to the Earth’s surface, making it hotter than it would otherwise be. This is the greenhouse effect.
The greenhouse effect often gets a bad rap because of its association with global warming, but the truth is we couldn t live without it. What Causes the Greenhouse Effect? Life on earth depends on energy from the sun. About 30 percent of the sunlight that beams toward Earth is deflected by the outer atmosphere and scattered back into space. The rest reaches the planet s surface and is reflected upward again as a type of slow-moving energy called infrared radiation. As it rises, infrared radiation is absorbed by greenhouse gases such as water vapor, carbon dioxide, ozone and methane, which slows its escape from the atmosphere. Although greenhouse gases make up only about 1 percent of the Earth s atmosphere, they regulate our climate by trapping heat and holding it in a kind of warm-air blanket that surrounds the planet. This phenomenon is what scientists call the “greenhouse effect.” Without it, scientists estimate that the average temperature on Earth would be colder by approximately 3
To balance the incoming solar radiation, the earth emits energy that is, on average, equal to the amount of energy it absorbs. Because the earth is much colder than the sun, it radiates at much longer wavelengths, i.e., in the form of heat. This heat energy is absorbed by naturally occurring gases in the earth’s atmosphere, including water vapor and carbon dioxide. Like the earth, these gases radiate in the infrared, so energy is transmitted in all directions, including back to earth. Known as the greenhouse effect, heat is trapped by the atmosphere. Consequently our planet is roughly 33o Celsius warmer than it would be in the absence of an atmosphere, thus rendering it habitable.
The “greenhouse effect” refers to the role played by a layer of gases in the Earth’s atmosphere. These “greenhouse gases” effectively trap the heat from the Sun in the Earth’s atmosphere. This process is essential, as without it, the Earth would be too cold to be habitable. However, the concentration of these energy-absorbing gases is increasing, and this is consequently reducing the amount of heat energy escaping from the Earth’s atmosphere. This results in Global Warming and the associated climate change effects.
The Greenhouse Effect is related to global warming in that it’s the reason why excess heat from the surface of the Earth isn’t dispersed into space. The glass on a greenhouse allows one type of radiation in, but reduces the amount another type can escape; causing the interior of the greenhouse to remain warm. This is what we are experiencing on our planet – gases such as carbon dioxide and methane act as the glass; allowing solar radiation in, but preventing heat from escaping.
