Monday, April 23, 2007

What is the Greenhouse Effect?

Many people are talking about the Greenhouse Effect and Global Warming, yet not everyone understands the dynamics of the cycle of changes. Over several posts and with some help from our friends at NOAA and the University Corporation for Atmospheric Research we will try to explain some of the foundations and concerns regarding Global Warming.

The following is excerpted from “Our Changing Climate

The Greenhouse Effect
Carbon dioxide gas constitutes a tiny fraction of
the atmosphere. Only about one air molecule in
three thousand is CO2. Yet despite their small
numbers, CO2 molecules can have a big effect on
the climate. To understand why they are so
important, we need to know about the greenhouse
effect of the atmosphere. Earth’s atmosphere
lets in rays of sunshine and they warm the
surface. The planet keeps cool by emitting heat
back into space in the form of infrared radiation—
the same radiation that warms us when we
sit near a campfire or stove. But while the
atmosphere is fairly transparent to sunshine, it is
almost opaque to infrared radiation. Much like a
garden greenhouse, it traps the heat inside.

About half of the solar energy that reaches
Earth passes through the atmosphere and is
absorbed at the surface. In contrast, about 90%
of the infrared radiation emitted by the surface
is absorbed by the atmosphere before it can
escape to space. In addition, greenhouse gases
like CO2 as well as clouds can re-emit this radiation,
sending it back toward the ground. The fact
is, Earth’s surface receives almost twice as much
energy from infrared radiation coming down
from the atmosphere as it receives from sunshine.
If all greenhouse gases were removed
from the atmosphere, the average surface temperature
of Earth would drop from its current
value of 59°F (15°C) to about 0°F (-18°C). Without
the atmosphere’s greenhouse effect, Earth
would be a frozen and nearly lifeless planet.

As you can see the greenhouse effect is a necessary element of our planet’s survival. It is our effect on the greenhouse effect that is the cause for concern.

More in our next post…


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