How the Greenhouse Effect Works
2
7/27/2019 How the Greenhouse Effect Works http://slidepdf.com/reader/full/how-the-greenhouse-effect-works 1/2 PART B : HOW THE GREENHOUSE EFFECT WORKS The greenhouse effect results from the interaction between sunlight and the layer of greenhouse gases in the Earth's atmosphere that extends up to 100 km (60 mi) above Earth's surface. Sunlight is composed of a range of radiant energies known as the solar spectrum, which includes visible light, infrared light, gamma rays, X rays, and ultraviolet light. When the Sun’s radiation reaches the Earth’s atmosphere, some 25 percent of the energy is reflected back into space by clouds and other atmospheric particles. About 20 percent is absorbed in the atmosphere. For instance, gas molecules in the uppermost layers of the atmosphere absorb the Sun’s gamma rays and X rays. The Sun’s ultraviolet radiation is absorbed b y the ozone layer, located 19 to 48 km (12 to 30 mi) above the Earth’s surface. About 50 percent of the Sun’s energy, largely in the form of visible light, passes through the atmosphere to reach the Earth’s surface. Soils, plants, and oceans on the Earth’s surface absorb about 85 percent of this heat energy, while the rest is reflected back into the atmosphere — most effectively by reflective surfaces such as snow, ice, and sandy deserts. In addition, some of the Sun’s radiation that is absorbed by the Earth’s surface becomes heat energy in the form of long-wave infrared radiation, and this energy is released back into the atmosphere. Certain gases in the atmosphere, including water vapor, carbon dioxide, methane, and nitrous oxide, absorb this infrared radiant heat, temporarily preventing it from dispersing into space. As these atmospheric gases warm, they in turn emit infrared radiation in all directions. Some of this heat returns back to Earth to further warm the surface in what is known as the greenhouse effect, and some of this heat is eventually released to space. This heat transfer creates equilibrium between the total amount of heat that reaches the Earth from the Sun and the amount of heat that the Earth radiates out into space. This equilibrium or energy balance —the exchange of energy between the Earth’s surface, atmosphere, and space— is important to maintain a climate that can support a wide variety of life.
Transcript of How the Greenhouse Effect Works
7/27/2019 How the Greenhouse Effect Works
http://slidepdf.com/reader/full/how-the-greenhouse-effect-works 1/2
PART B :
HOW THE GREENHOUSE EFFECT WORKS
The greenhouse effect results from the interaction between sunlight and the layer of
greenhouse gases in the Earth's atmosphere that extends up to 100 km (60 mi) above
Earth's surface. Sunlight is composed of a range of radiant energies known as the solar
spectrum, which includes visible light, infrared light, gamma rays, X rays, and
ultraviolet light. When the Sun’s radiation reaches the Earth’s atmosphere, some 25
percent of the energy is reflected back into space by clouds and other atmospheric
particles. About 20 percent is absorbed in the atmosphere. For instance, gas molecules
in the uppermost layers of the atmosphere absorb the Sun’s gamma rays and X rays.
The Sun’s ultraviolet radiation is absorbed by the ozone layer, located 19 to 48 km (12
to 30 mi) above the Earth’s surface.
About 50 percent of the Sun’s energy, largely in the form of visible light, passes
through the atmosphere to reach the Earth’s surface. Soils, plants, and oceans on the
Earth’s surface absorb about 85 percent of this heat energy, while the rest is reflectedback into the atmosphere — most effectively by reflective surfaces such as snow, ice, and
sandy deserts. In addition, some of the Sun’s radiation that is absorbed by the Earth’s
surface becomes heat energy in the form of long-wave infrared radiation, and this
energy is released back into the atmosphere.
Certain gases in the atmosphere, including water vapor, carbon dioxide, methane, and
nitrous oxide, absorb this infrared radiant heat, temporarily preventing it from dispersing into
space. As these atmospheric gases warm, they in turn emit infrared radiation in all directions.
Some of this heat returns back to Earth to further warm the surface in what is known as the
greenhouse effect, and some of this heat is eventually released to space. This heat transfer
creates equilibrium between the total amount of heat that reaches the Earth from the Sun and
the amount of heat that the Earth radiates out into space. This equilibrium or energy
balance —the exchange of energy between the Earth’s surface, atmosphere, and space— is
important to maintain a climate that can support a wide variety of life.
7/27/2019 How the Greenhouse Effect Works
http://slidepdf.com/reader/full/how-the-greenhouse-effect-works 2/2
The heat-trapping gases in the atmosphere behave like the glass of a greenhouse. They let
much of the Sun’s rays in, but keep most of that heat from directly escaping. Because of this,
they are called greenhouse gases. Without these gases, heat energy absorbed and reflected
from the Earth’s surface would easily radiate back out to space, leaving the planet with an
inhospitable temperature close to – 19°C (2°F), instead of the present average surface
temperature of 15°C (59°F).
