Greenhouse Effect?

Question

Can anyone do a better job than Wikipedia of explaining how the greenhouse effect "really works"? I.e. everything about the radiation-emitting band of the atmosphere moving upwards, etc. etc..

Answer 1

Very good question and here is the scientific answer you have been looking for. Solar radiation which peaks in the shortwave visible band of the electro-magnetic EM spectrum is transmitted (to an extent) through the atmosphere and is absorbed at the Earth's surface. It is not absorbed in the atmosphere. After being absorbed at the surface, the surface warms and retransmits longwave infrared EM radiation upwards toward space. The predominant Greenhouse gas is water vapor which absorbs this radiation, some of which is then retransmitted back down to earth. In other words the constituents in the atmosphere act as a partial block to outgoing radiation, keeps it in and uses it to heat the Earth. It is a similar process as what goes on in a real greenhouse where shortwave radiation penetrates the glass, warms what is in the greenhouse, and does not permit the longwave radiation from escaping. In the Earth's atmosphere there are also other "Greenhouse" gases besides the predominant one. They are carbon dioxide from fossil fuels and methane from decomposition to name but two. I hope you have a little better understanding of this phenomena now. If not, let me know. It's a lot easier to describe on a blackboard.

Answer 2

Water vapour is a powerful absorber of heat radiation that is emitted by the earth's surface.It is because of this property of water vapour that the atmosphere near the surface of the Earth does not cool rapidly when layers of low or medium cloud cover are present in the atmosphere.The heat radiation from the Earth's surface is readily absorbed by the cloud layer and re-radiated back to the Earth's surface with the result that there is less colling of the surface and the atmosphere near the surface becomes warm and sultry.This effect of water vapour and the cloud cover is called Greenhouse Effect.

Answer 3

In simple terms, the greenhouse effect "THEORY" is that increased levels of C02 in the atmosphere causes warming of the Earth. However, it is not known if C02 levels increase the temperature of the Earth or if C02 levels increase when the Earth warms up. There is not a good explanation as to why C02 warms the Earth. So you might have difficulty finding this information. A primary reason for the Earth heating up is due to increased solar activity. In other words, the premise behind the greenhouse effect causing warming could be a false notion.

Answer 4

Have you already watched _An Inconvenient Truth_?

Answer 5

...i think to get a good answer here you will have to educate yourself by reading lots of different boooks so you dont get a biased opinion.

Answer 6

This section provides an overview of the earth's atmospheric "greenhouse effect" by briefly exploring the atmospheres of nearby planets and discussing our atmosphere's greenhouse gases. The general concepts found in this section include the following:

The earth's "greenhouse effect" is what makes this planet suitable for life as we know it.


The earth's atmosphere contains trace gases, some of which absorb heat. These gases (water vapor, carbon dioxide, methane, ozone, and nitrous oxide) are referred to as "greenhouse gases."


Albedo has an important influence on the earth's temperature.


Greenhouses are structures designed to retain heat.


The heat-trapping ability of a greenhouse is influenced by a number of factors including the transparency of the greenhouse cover, color of the surfaces inside the greenhouse, and type of surfaces inside.
This section includes two classroom activities.


Introduction

The Goldilocks Principle can be summed up neatly as "Venus is too hot, Mars is too cold, and Earth is just right." The fact that Earth has an average surface temperature comfortably between the boiling point and freezing point of water, and thus is suitable for our sort of life, cannot be explained by simply suggesting that our planet orbits at just the right distance from the sun to absorb just the right amount of solar radiation. Our moderate temperatures are also the result of having just the right kind of atmosphere. A Venus-type atmosphere would produce hellish, Venus-like conditions on our planet; a Mars atmosphere would leave us shivering in a Martian-type deep freeze.



Instead, parts of our atmosphere act as an insulating blanket of just the right thickness, trapping sufficient solar energy to keep the global average temperature in a pleasant range. The Martian blanket is too thin, and the Venusian blanket is way too thick! The 'blanket' here is a collection of atmospheric gases called 'greenhouse gases' based on the idea that the gases also 'trap' heat like the glass walls of a greenhouse do.



These gases, mainly water vapor ( ), carbon dioxide (), methane (), and nitrous oxide (), all act as effective global insulators. To understand why, it's important to understand a few basic facts about solar radiation and the structure of atmospheric gases.

Solar Radiation

The sun radiates vast quantities of energy into space, across a wide spectrum of wavelengths.



Most of the radiant energy from the sun is concentrated in the visible and near-visible parts of the spectrum. The narrow band of visible light, between 400 and 700 nm, represents 43% of the total radiant energy emitted. Wavelengths shorter than the visible account for 7 to 8% of the total, but are extremely important because of their high energy per photon. The shorter the wavelength of light, the more energy it contains. Thus, ultraviolet light is very energetic (capable of breaking apart stable biological molecules and causing sunburn and skin cancers). The remaining 49 - 50% of the radiant energy is spread over the wavelengths longer than those of visible light. These lie in the near infrared range from 700 to 1000 nm; the thermal infrared, between 5 and 20 microns; and the far infrared regions. Various components of earth's atmosphere absorb ultraviolet and infrared solar radiation before it penetrates to the surface, but the atmosphere is quite transparent to visible light.



Absorbed by land, oceans, and vegetation at the surface, the visible light is transformed into heat and re-radiates in the form of invisible infrared radiation. If that was all there was to the story, then during the day earth would heat up, but at night, all the accumulated energy would radiate back into space and the planet's surface temperature would fall far below zero very rapidly. The reason this doesn't happen is that earth's atmosphere contains molecules that absorb the heat and re-radiate the heat in all directions. This reduces the heat radiated out to space. Called 'greenhouse gases' because they serve to hold heat in like the glass walls of a greenhouse, these molecules are responsible for the fact that the earth enjoys temperatures suitable for our active and complex biosphere.

Greenhouse Gases

Carbon dioxide () is one of the greenhouse gases. It consists of one carbon atom with an oxygen atom bonded to each side. When its atoms are bonded tightly together, the carbon dioxide molecule can absorb infrared radiation and the molecule starts to vibrate. Eventually, the vibrating molecule will emit the radiation again, and it will likely be absorbed by yet another greenhouse gas molecule. This absorption-emission-absorption cycle serves to keep the heat near the surface, effectively insulating the surface from the cold of space.




Carbon dioxide, water vapor (), methane (), nitorus oxide (), and a few other gases are greenhouse gases. They all are molecules composed of more than two component atoms, bound loosely enough together to be able to vibrate with the absorption of heat. The major components of the atmosphere ( and ) are two-atom molecules too tightly bound together to vibrate and thus they do not absorb heat and contribute to the greenhouse effect.

Greenhouse Effect

Atmospheric scientists first used the term 'greenhouse effect' in the early 1800s. At that time, it was used to describe the naturally occurring functions of trace gases in the atmosphere and did not have any negative connotations. It was not until the mid-1950s that the term greenhouse effect was coupled with concern over climate change. And in recent decades, we often hear about the greenhouse effect in somewhat negative terms. The negative concerns are related to the possible impacts of an enhanced greenhouse effect. This is covered in more detail in the Global Climate Change section of this Web site. It is important to remember that without the greenhouse effect, life on earth as we know it would not be possible.

While the earth's temperature is dependent upon the greenhouse-like action of the atmosphere, the amount of heating and cooling are strongly influenced by several factors just as greenhouses are affected by various factors.

In the atmospheric greenhouse effect, the type of surface that sunlight first encounters is the most important factor. Forests, grasslands, ocean surfaces, ice caps, deserts, and cities all absorb, reflect, and radiate radiation differently. Sunlight falling on a white glacier surface strongly reflects back into space, resulting in minimal heating of the surface and lower atmosphere. Sunlight falling on a dark desert soil is strongly absorbed, on the other hand, and contributes to significant heating of the surface and lower atmosphere. Cloud cover also affects greenhouse warming by both reducing the amount of solar radiation reaching the earth's surface and by reducing the amount of radiation energy emitted into space.

Scientists use the term albedo to define the percentage of solar energy reflected back by a surface. Understanding local, regional, and global albedo effects is critical to predicting global climate change.

Concluding Thoughts

The ability of certain trace gases to be relatively transparent to incoming visible light from the sun, yet opaque to the energy radiated from the earth is one of the best understood processes in the atmospheric sciences. This phenomenon, the greenhouse effect, is what makes the earth habitable for life. For students to truly understand the nature and importance of the greenhouse effect, they should understand the answers to these questions:


The greenhouse effect is the rise in temperature that the Earth experiences because certain gases in the atmosphere (water vapor, carbon dioxide, nitrous oxide, and methane, for example) trap energy from the sun. Without these gases, heat would escape back into space and Earth’s average temperature would be about 60ºF colder. Because of how they warm our world, these gases are referred to as greenhouse gases.
Have you ever seen a greenhouse? Most greenhouses look like a small glass house. Greenhouses are used to grow plants, especially in the winter. Greenhouses work by trapping heat from the sun. The glass panels of the greenhouse let in light but keep heat from escaping. This causes the greenhouse to heat up, much like the inside of a car parked in sunlight, and keeps the plants warm enough to live in the winter.
The Earth’s atmosphere is all around us. It is the air that we breathe. Greenhouse gases in the atmosphere behave much like the glass panes in a greenhouse. Sunlight enters the Earth's atmosphere, passing through the blanket of greenhouse gases. As it reaches the Earth's surface, land, water, and biosphere absorb the sunlight’s energy. Once absorbed, this energy is sent back into the atmosphere. Some of the energy passes back into space, but much of it remains trapped in the atmosphere by the greenhouse gases, causing our world to heat up.



(D)
The greenhouse effect is important. Without the greenhouse effect, the Earth would not be warm enough for humans to live. But if the greenhouse effect becomes stronger, it could make the Earth warmer than usual. Even a little extra warming may cause problems for humans, plants, and animals.

Answer 7

just check this http://en.wikipedia.org/wiki/Greenhouse_effect