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GREEN HOUSE EFFECT

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.

Incoming UV radiation easily passes through the glass walls of a greenhouse and is absorbed by the plants and hard surfaces inside. Weaker IR radiation, however, has difficulty passing through the glass walls and is trapped inside, thus warming the greenhouse. This effect lets tropical plants thrive inside a greenhouse, even during a cold winter.

A similar phenomenon takes place in a car parked outside on a cold, sunny day. Incoming solar radiation warms the car's interior, but outgoing thermal radiation is trapped inside the car's closed windows.

Global warming

Greenhouse gas levels have been increasing since the start of the Industrial Revolution, but over the last few decades growth has been particularly fast. Total greenhouse gas emissions have increased by about 80% since 1970,2creating a radiative forcing of 2838 mW/m^2 equivalent to an atmospheric concentration of 473 ppm CO2e.3

With increasing levels of greenhouse gases being added daily, the greenhouse effect is now enhanced to the point where too much heat is being kept in the Earth's atmosphere. The heat trapped by carbon dioxide and other greenhouse gases has increased surface temperatures by 0.75°C (1.4°F) over the last 100 years.4

Global warming is harming the environment in several ways including:

• Desertification
• Increased melting of snow and ice
• Sea level rise
• Stronger storms and extreme events

CFCs (Chlorofluorocarbons)

What is it?

Chlorofluorocarbons (CFCs) are a group of compounds which contain the elements chlorine, fluorine and carbon. At room temperatures, they are usually colourless gases or liquids which evaporate easily. They are generally unreactive and stable, non-toxic and non-flammable. CFCs are also a part of the group of chemicals known as the volatile organic compounds (VOCs). What is it used for? The properties of CFCs make them useful for a variety of commercial and industrial purposes: as a propellant in aerosol sprays (now banned in the US and Europe), in refrigeration and air conditioning systems, in foams, in cleaning solvents and in electrical components. Where does it come from? Most CFCs have been released to the atmosphere through the use of aerosols containing them and as leakages from refrigeration equipment. Other releases may occur from industry producing and using them and other products containing them. There are not thought to be any natural sources of CFCs to the environment. How might it affect the environment? CFCs are unlikely to have any direct impact on the environment in the immediate vicinity of their release. As VOCs, they may be slightly involved in reactions to produce ground level ozone, which can cause damage to plants and materials on a local scale. At a global level however, releases of CFCs have serious environmental consequences. Their long lifetimes in the atmosphere mean that some end up in the higher atmopshere (stratosphere) where they can destroy the ozone layer, thus reducing the protection it offers the earth from the sun's harmful UV rays. CFCs also contribute to Global Warming (through "the Greenhouse Effect"). Although the amounts emitted are relatively small, they have a powerful warming effect (a very high "Global Warming Potential"). How might exposure to it affect human health? Chlorofluorocarbons enter the body primarily by inhalation of air containing chlorofluorocabons, but can also enter by ingestion of contaminated water, or by dermal contact with chlorofluorocarbons. Inhalation of high levels of chlorofluorocarbons can affect the lungs, central nervous system, heart, liver and kidneys. Symptoms of exposure to chlorofluorocarbons can include drowsiness, slurred speech, disorientation, tingling sensations and weakness in the limbs. Exposure to extremely high levels of chlorofluorocarbons can result in death. Ingestion of chlorofluorocarbons can lead to nausea, irritation of the digestive tract and diarrhoea. Dermal contact with chlorofluorocarbons can cause skin irritation and dermatitis. Chlorofluorocarbons are involved in the destruction of the stratospheric ozone layer resulting in increased exposure to UV radiation which is known to cause skin cancer. The International Agency for Research on Cancer has not designated chlorofluorocarbons as a group in terms of their carcinogenicity. The International Agency for Research on Cancer has designated chlorofluoromethane and chlorodifluoromethane as being not classifiable as to their carcinogenicity to humans. However, exposure to chlorofluorocarbons at normal background levels is unlikely to have any adverse effect on human health.

PHOTOSYNTHESIS

Six facts about photosynthesis

-The process mostly takes place in the chloroplasts of plant leaf mesophyll cells.
-The energy for photosynthesis comes from light.
-Light energy is converted to chemical energy by chlorophyll.
-There are two sets of reactions, light dependent and light independent.
-Photosynthesis is affected by temperature, light intensity, light wavelength and carbon dioxide level. 

 -All living things depend on the organic molecules synthesised by plants as a result of photosynthesis.

Plants use photosynthesis to produce carbohydrates from inorganic substrates.

http://commons.wikimedia.org/wiki/File:Photosynthesis_equation.svg

All organisms need energy to grow and reproduce. Many organisms (including all plants) use cellular respiration to produce ATP, which is used for cellular energy. The respiration reaction uses carbohydrates like glucose as a substrate. Whereas humans eat food to provide the fuel for respiration, plants make their own through photosynthesis.

Without photosynthesis, plants would not have carbohydrates for respiration.

In addition, the carbohydrates produced in photosynthesis are also used to build plant cell structures, like the cellulose cell wall.