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.
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 30 degrees Celsius (54 degrees Fahrenheit), far too cold to
sustain our current ecosystem.
While the greenhouse effect is an essential environmental prerequisite for life
on Earth, there really can be too much of a good thing.
The problems begin when human activities distort and accelerate the natural
process by creating more greenhouse gases in the atmosphere than are necessary
to warm the planet to an ideal temperature.
Burning natural gas, coal and oil —including gasoline for automobile
engines—raises the level of carbon dioxide in the atmosphere.
Some farming practices and land-use changes increase the levels of methane and
Nitrous oxide.
Many factories produce long-lasting industrial gases that do not occur
naturally, yet contribute significantly to the enhanced greenhouse effect and
“global warming” that is currently under way.
Deforestation alsocontributes to global warming. Trees use carbon dioxide and
give off oxygen in its place, which helps to create the optimal balance of
gases in the atmosphere. As more forests are logged for timber or cut down to
make way for farming, however, there are fewer trees to perform this critical
function.
Population growth is another factor in global warming, because as more people
use fossil fuels for heat, transportation and manufacturing the level of
greenhouse gases continues to increase. As more farming occurs to feed
millions of new people, more greenhouse gases enter the atmosphere.
Ultimately, more greenhouse gases means more infrared radiation trapped and
held, which gradually increases the temperature of the Earth’s surface and the
air in the lower atmosphere.
The Average Global Temperature is Increasing Quickly
Today, the increase in the Earth’s temperature is increasing with unprecedented
speed. To understand just how quickly global warming is accelerating, consider
this:
During the entire 20th century, the average global temperature increased by
about 0.6 degrees Celsius (slightly more than 1 degree Fahrenheit).
Using computer climate models, scientists estimate that by the year 2100 the
average global temperature will increase by 1.4 degrees to 5.8 degrees Celsius
(approximately 2.5 degrees to 10.5 degrees Fahrenheit).
Not All Scientists Agree
While the majority of mainstream scientists agree that global warming is a
serious problem that is growing steadily worse, there are some who disagree.
John Christy, a professor and director of the Earth System Science Center at the
University of Alabama in Huntsville is a respected climatologist who argues that
global warming isn’t worth worrying about.
Christy reached that opinion after analyzing millions of measurements from
weather satellites in an effort to find a global temperature trend. He found no
sign of global warming in the satellite data, and now believes that predictions
of global warming by as much as 10 degrees Fahrenheit by the end of the 21st
century are incorrect.
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