Research on assignment 1

Global warming has become a hot topic since many countries are experiencing rise in temperature and the rise of the ocean level.

Here's some info i got from EPA usa...

The Earth's climate has changed many times during the planet's history, with events ranging from ice ages to long periods of warmth. Historically, natural factors such as volcanic eruptions, changes in the Earth's orbit, and the amount of energy released from the Sun have affected the Earth's climate. Beginning late in the 18th century, human activities associated with the Industrial Revolution have also changed the composition of the atmosphere and therefore very likely are influencing the Earth's climate.

Science

For over the past 200 years, the burning of fossil fuels, such as coal and oil, and deforestation have caused the concentrations of heat-trapping "greenhouse gases" to increase significantly in our atmosphere. These gases prevent heat from escaping to space, somewhat like the glass panels of a greenhouse.

Greenhouse gases are necessary to life as we know it, because they keep the planet's surface warmer than it otherwise would be. But, as the concentrations of these gases continue to increase in the atmosphere, the Earth's temperature is climbing above past levels. According to NOAA and NASA data, the Earth's average surface temperature has increased by about 1.2 to 1.4ºF in the last 100 years. The eight warmest years on record (since 1850) have all occurred since 1998, with the warmest year being 2005. Most of the warming in recent decades is very likely the result of human activities. Other aspects of the climate are also changing such as rainfall patterns, snow and ice cover, and sea level.

If greenhouse gases continue to increase, climate models predict that the average temperature at the Earth's surface could increase from 3.2 to 7.2ºF above 1990 levels by the end of this century. Scientists are certain that human activities are changing the composition of the atmosphere, and that increasing the concentration of greenhouse gases will change the planet's climate. But they are not sure by how much it will change, at what rate it will change, or what the exact effects will be.

Sources :
EPA USA

Chlorofluorocarbons (CFC) are compounds containing Chlorine , Florine and carbon only, that is they contain no hydrogen. They were formerly used widely in industry, for example as , refrigerant propellants, and cleaning solvents. Their use has been regularly prohibited by the Montreal Protocol, because of effects on the ozone layer(see ozone depletion). They are also powerful greenhouse gases, in terms of carbon dioxide equivalence (over a time period of one hundred years) between 5000 and 8100 per kg. CFCs have half-lives between 50-100 years, so their presence in the atmosphere and reactivity with ozone is long lived. One CFC molecule typically degrades around 10,000 ozone molecules before its removal, but this number can sometimes be in the millions.

Sources :
Wikipedia

Effects of CFCs on environment
CFCs, when released from the surface of the Earth, rise slowly into the stratosphere. Once there, they are bombarded by the incoming UV light from the Sun, releasing the chlorine atoms from the parent compound, which can then react with the ozone molecules (Figure 1). Eventually the chlorine atom is removed from the atmosphere by other reactions.

Figure 1: The destruction of stratospheric ozone (6)

Chlorofluorocarbons (which are used in aerosols, refrigerants, and other industrial products) are remarkably inert and nonreactive. Indeed, it is because of these characteristics---specifically because they are nontoxic and nonflammable---that they were invented. But when they eventually rise into the stratosphere, they are decomposed by solar ultraviolet radiations into free chlorine atoms:
Chlorofluorocarbon ---> Cl,
Cl + O3 ---> ClO + O2,
ClO + O ---> Cl + O2.
The chlorine atoms are recycled in these reactions, and are then free to attack other ozone molecules. A single chlorine atom, released by the action of UV radiation on chlorofluorocarbons, is capable of destroying catalytically tens of thousands of ozone molecules during its residence in the stratosphere.
The emission of chlorofluorocarbons (CFCs) from refrigerators, air conditioners, and aerosols attributes to an increasing “hole” in the ozone layer in the atmosphere above Antarctica, coupled with growing evidence of global ozone depletion. (7)

Source : Wei Zhong , Department of Chemistry University of Georgia