Monday, March 26, 2007

What's wrong with the Earth ?

Some of the global environmental problems you should know.

Global environmental problems are much spoken nowadays. The ecology of the Earth is becoming worse and worse each year. Scientist are making predictions about the future of the Earth that are closely linked with such global problems as global warming, greenhouse effect and gases, ice melting. I want to inform you and to give you an idea of them.

So, here we go:

Greenhouse effect is the process in which the emission of infrared radiation by an atmosphere warms a planet's surface.The main problem is a raise of carbonic dioxide (CO2) in the atmosphere. In a common usage, "greenhouse effect" may refer either to the natural greenhouse effect due to naturally occurring greenhouse gases, or to the enhanced (anthropogenic) greenhouse effect which results from gases emitted as a result of human activities.On Earth, the major natural greenhouse gases are water vapor, which causes about 36-70% of the greenhouse effect (not including clouds); carbon dioxide, which causes 9-26%; methane, which causes 4-9%, and ozone, which causes 3-7%.

The increased CO2 in the atmosphere warms the Earth's surface and leads to melting of ice near the poles. As the ice melts, land or open water takes its place. Both land and open water are on average less reflective than ice, and thus absorb more solar radiation. This causes more warming, which in turn causes more melting, and this cycle continues.

Look the process of the Greenhouse effect

The green house gases are components of the atmosphere that contribute to the Greenhouse effect. Some greenhouse gases occur naturally in the atmosphere, while others result from human activities. Naturally occurring greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Certain human activities add to the levels of most of these naturally occurring gases.

The Antarctic ozone hole is an area of the Antarctic stratosphere in which the recent ozone levels have dropped to as low as 33% of their pre-1975 values. The overall cause of ozone depletion is the presence of chlorine-containing source gases.

In the presence of UV light, these gases dissociate, releasing chlorine atoms, which then go on to catalyze ozone destruction. The Cl-catalyzed ozone depletion can take place in the gas phase, but it is dramatically enhanced in the presence of polar stratospheric clouds (PSCs).

The role of sunlight in ozone depletion is the reason why the Antarctic ozone depletion is greatest during spring. During winter, even though polar stratospheric clouds are at their most abundant, there is no light over the pole to drive the chemical reactions. During the spring, however, the sun comes out, providing energy to drive photochemical reactions, and melt the polar stratospheric clouds, releasing the trapped compounds.

The Antarctic ozone hole

1 comment:

Anonymous said...

speaking of the climate changes, the temperatures are moving to a more extreme to each level. hotter in summer colder in winter. what would cause the temperature to drop this much?