Global Warming: is the increase in average temperature of the atmosphere, oceans, and landmasses of Earth. The planet has
warmed during 4.65 billions of years. Right now Earth appears to be facing a rapid warming. The cause is : the burning of
fossil fuels , such as coal, oil and natural gas which releases into the atmosphere carbon dioxide and other substances known
as greenhouse gases. As the atmosphere becomes richer in these gases it becomes a better insulator, retaining more of the
heat provided by the Sun. The average surface temperature of the Earth is about 15 C and over the last century this average
has risen by about .6 CV. This temperature rise is expected to melt polar ice caps and glaciers as well as warm the oceans,
which will expand ocean volume and raise sea level by 9 to 100 cm. This will for sure flood some islands and some coastal
regions. Some areas in warmer climates will recieve more rainfall and soils will dry out faster between storms. This may damage
food crops, disrupt food supplies in some parts of the world. Plant and animal species will relocate towards the north and
to higher elevations to seek cooler temperatures. Some species may become extinct because of this shift.
Greenhouse Effect:
The energy that lights and warms Earth comes from the Sun. Most of the energy that floods onto our planet is short-wave
radiation, including visible light. When this energy hits Earth it becomes heat and warms the Earth. Earth's surface releases
some of this heat as long-wave infrared radiation. Much of this long-wave infrared radiation makes it all the way back out
to space, but some of it remains trapped in Earth's atmosphere. Some gases in the atmosphere including water vapor, carbon
dioxide and methane provide the trap. These gases conserve heat as the glass in a greenhouse does and are then known as greenhouse
gases. As these greenhouse gases in the atmosphere increase, more heat energy remains trapped below. All life on Earth depends
on this effect, and the planet would be much colder without it. But, a growing excess of greenhouse gases in Earth's atmosphere
threatens to tip the balance in the other direction, toward continual warming.
|
