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.
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.
The warming effect produced when radiation is trapped in
a closed area , e.g. a greenhouse. The objects inside absorb
the sun's radiation and re emit lower energy radiation
which cannot pass back through the glass . carbon dioxide
in the atmosphere forms a similar barrier , and its level
is increasing , hence the earth is getting slowly warmer.
A greenhouse is designed to facilitate the cultivation,
propagation and protection of young seedlings and delicate
plants. The greenhouse has glass paned roof and walls which
is perfect for regulating temperature, humidity, soil
moisture and light.
The inside of a green house is always warm, the reason
is that glass or polythene transmits only the short wavelength
infrared radiations. It is opaque to the infra red radiations
of long wavelengths. The visible light and thermal radiations
of short wavelength from the sun therefore pass through
the walls of the green house and they are absorbed by the
plants inside it .
The air inside thus becomes warm. The warm objects inside
emit radiations which Are of comparatively longer wavelengths.
Glass / polythene being opaque to them does not allow them
to pass out. Thus the heat remains inside the green house
keeping it warm.
Earth's atmosphere acts like a greenhouse, warming our
planet in much the same way that an ordinary greenhouse
warms the air inside its glass walls. Like glass, the gases
in the atmosphere let in light yet prevent heat from escaping.
This natural warming of the planet is called the greenhouse
effect.
Greenhouse gases -- carbon dioxide, methane, nitrous
oxide, and others -- are transparent to certain wavelengths
of the Sun's radiant energy, allowing them to penetrate
deep into the atmosphere or all the way to Earth's surface.
Clouds, ice caps, and particles in the air reflect about
30 percent of this radiation, but oceans and land masses
absorb the rest, then release it back toward space as infrared
radiation.
The greenhouse gases and clouds effectively prevent some
of the infrared radiation from escaping; they trap the
heat near Earth's surface where it warms the lower atmosphere.
If this natural barrier of atmospheric gases were not present,
the heat would escape into space, and Earth's mean global
temperatures could be as much as 33 degrees Celsius cooler
[about -18 degrees Celsius as opposed to 15 degrees Celsius
.
The greenhouse effect is important to life on Earth, without
it the Earth would be far too cold for us. But some scientists
are concerned that humans are producing too many greenhouse
gases, and that we may be warming the Earth too much.
The first step to a safe future is to be aware of the possible
problems. Next we must study climate and atmospheric trends,
which will take many years of observation.
NASA is very involved in these studies, measuring greenhouse
gases in the atmosphere from satellites in space. As we
develop a deeper understanding of climate trends, we can
better predict what affects we have on our environment,
and how to ensure a healthy future.
The natural greenhouse effect is a phenomenon created by
the heat energy radiated by the sun and greenhouse gases
normally present in the atmosphere. In simple terms, sunlight
passes through the atmosphere, warming the Earth.
In turn, the Earth radiates this energy back towards space.
As it passes through the atmosphere, greenhouse gases (water
vapour, carbon dioxide, methane and nitrous oxide) absorb
part of the energy, while the remainder escapes into space.
This means that some of the sun's energy becomes trapped
- thus making the lower part of the atmosphere, and Earth,
warmer
The greenhouse effect keeps the Earth's average surface
temperature at about 60°F (15°C). If there
were no greenhouse gases in the atmosphere, the planet's
temperature would be 0°F (-18°C), too cold for most
life. Most of the heat radiated from the Earth's surface
would be lost directly to outer space.
Mars has a very thin atmosphere with a weak greenhouse
effect. Its surface is much colder than Earth's. In fact,
it is frozen.
Venus has an intense greenhouse effect. Its atmosphere
is thick with carbon dioxide and other gases that trap heat.
The surface of Venus is much hotter than Earth's--hot enough
to melt lead.
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