BIOLOGY PRESENTATION

GREEN HOUSE EFFECT

What Is the Greenhouse Effect?

• The exchange of incoming and outgoing radiation that warms the Earth is often referred to as the greenhouse effect because a greenhouse works in much the same way.

MECHANISM OF GREEN HOUSE EFFECT

• If it were not for greenhouse gases trapping heat in the atmosphere, the Earth would be a very cold place. Greenhouse gases keep the Earth warm through a process called the greenhouse effect.

• The Earth gets energy from the sun in the form of sunlight. The Earth's surface absorbs some of this energy and heats up. That's why the surface of a road can feel hot even after the sun has gone down—because it has absorbed a lot of energy from the sun. The Earth cools down by giving off a different form of energy, called infrared radiation. But before all this radiation can escape to outer space, greenhouse gases in the atmosphere absorb some of it, which makes the atmosphere warmer. As the atmosphere gets warmer, it makes the Earth's surface warmer, too.

GREENHOUSE GASES• Greenhouse gases trap heat in the atmosphere, which

makes the Earth warmer. People are adding several types of greenhouse gases to the atmosphere, and each gas's effect on climate change .

• Greenhouse gas are efficient in absorbing IR light…The most important greenhouse gases are:– H2O – Water vapor.– CO2 – Carbon Dioxide– CH4 – methaneThe most abundant greenhouse gas in Earth’s

atmosphere is water vapor. Most of the greenhouse heating of Earth’s atmosphere is due to Water vapor absorption of IR radiation emitted by Earth, and then transferring the energy to the surrounding air molecule

MAJOR GREENHOUSE GASES

What causes the man-made greenhouse effect?

• The man-made (or anthropogenic) component of the greenhouse effect is caused by man’s activities that emit greenhouse gases to the atmosphere.

• The most important of these is the burning of fossil fuels. Fossil fuels contain carbon, and when they are burnt this carbon combines with oxygen in the atmosphere to form carbon dioxide.

• Changes in land use are also important sources of greenhouse gas emissions. For example deforestation results in the emission of carbon dioxide to the atmosphere that was previously stored on the Earth’s surface in the form of trees and other vegetation, or locked up in soils.

• We emit carbon dioxide to the atmosphere in enormous quantities because we burn so much fossil fuel and the changes in land use that we have implement are so widespread.

• This is why carbon dioxide is the most important gas in the man-made component of the greenhouse effect.

• Coal burned in power stations contains carbon which combines with oxygen in the atmosphere to form carbon dioxide.

What evidence is there that the Earth’s climate is changing?

• Eleven of the twelve warmest years since 1850 occurred between 1996 and 2006. Average global temperatures have risen by about 0.74°C between 1906 and 2005. The temperature increase is widespread over the globe but is greater at higher northern latitudes.

• Sea levels have also increased in this period. Since 1961 the average rate has been 1.8 mm per year but since 1993 this has increased to 3.1 mm per year. The total rise for the 20th century is estimated to be about 0.17 m.

• The average amount of water vapour in the atmosphere has increased since the 1980s over land and the ocean and this is consistent with the fact that warmer air can hold more water than colder air.

• Mountain glaciers and snow cover have declined on average in both the northern and southern hemispheres. Widespread decreases in glaciers and ice caps have contributed to sea level rise. Satellite data since 1978 show that annual average arctic sea extent has shrunk by 2.7% per decade although larger decreases in the summer have occurred (average of 7.4 per cent).

• There are many other observed changes.

• Widespread decreases in glaciers and ice caps have contributed to sea level rise.

• The greenhouse effect, combined with increasing levels of greenhouse gases and the resulting global warming, is expected to have profound implications, according to the near-universal consensus of scientists.

HOW TO REDUCE GREENHOUSE EFFECT ?

• Reduce, Reuse, Recycle• Use Less Heat and Air Conditioning• Replace Your Light Bulbs• Drive Less and Drive Smart• Buy Energy-Efficient Products• Use Less Hot Water• Use the "Off" Switch• Plant a Tree    • Get a Report Card from Your Utility Company• Encourage Others to Conserve

•MADE BY :

•SANAA SIAL