1. Current Environmental Issues

2. Ozone Layer Depletion
The atmosphere of the Earth plays a crucial role in making it the only planet with life. Basically, the Earth's atmosphere is divided into several layers - stratosphere being one of them. Within the stratosphere, there lies a layer, made of a specialized form of oxygen, known as the ozone layer. The ozone layer is found between 10 to 20 miles above the surface of the Earth. This layer traps the harmful ultraviolet-B (UV-B) radiation emitted by the Sun, and hence plays a crucial role in supporting life on the Earth.

3. Causes of Ozone Depletion
The cause of ozone depletion is the increase in the level of free radicals such as hydroxyl radicals, nitric oxide radicals and atomic chlorine and bromine.
The most important compound, which accounts for almost 80% of the total depletion of ozone in the stratosphere are chlorofluorocarbons (CFC).
These compounds are very stable in the lower atmosphere of the Earth, but in the stratosphere, they break down to release a free chlorine atom due to ultraviolet radiation.
A free chlorine atom reacts with an ozone molecule (O3) and forms chlorine monoxide (ClO) and a molecule of oxygen. Now chlorine monoxide reacts with an ozone molecule to form a chlorine atom and two molecules of oxygen.
The free chlorine molecule again reacts with ozone to form chlorine monoxide. The process continues and the result is the reduction or depletion of ozone in the stratosphere.

4. Effects of ozone depletion
The ozone layer is responsible for absorbing the ultraviolet rays and thereby preventing them from passing through the atmosphere of Earth. Ultraviolet rays of the Sun are associated with a number of health related and environmental issues.
The most important of these is the association between ultraviolet rays and an increased risk of developing several types of skin cancers.
Ozone present in the lower atmosphere is mainly regarded as a pollutant and a green house gas that can contribute to global warming and climate change.
The effects of ozone depletion are not limited to humans only, as it can affect animals and plants as well.
The increasing concern for the causes and effects of ozone depletion led to the adoption of the Montreal Protocol.

5. Green house gas and green house effect
The term 'greenhouse gases' refers to various gases in the Earth's atmosphere, which are typically characterized by their ability to absorb infrared radiations of the Sun. The entire process wherein the Sun's infrared radiations are trapped within the atmosphere by these greenhouse gases is referred to as the 'greenhouse effect'. Greenhouse gases includes gases such as carbon dioxide, methane, ozone (troposphere), nitrous oxide, chlorofluorocarbons - some of which stay in the atmosphere for several years and contribute to the greenhouse effect on the planet. The atmospheric concentration of these gases is one of the main causes of the greenhouse effect.

6. Relative Contribution of Green House Gases to the Green House Effect :
CO2 (Carbon di oxide)
50-60
CFC
15-25
CH4 (Methane)
12-20
O3 (tropospheric Ozone) 8
N2O (Nitrous Oxide) 5

7. Green house gas and their sources
Carbon dioxide: burning fossil fuels, deforestation and burning wood
Methane: deforestation, decomposition of waste, rice and cattle farming generating methane from rotting vegetation
CFCs : used in aerosols , refrigeration
Nitrogen oxide: used in chemical fertilizers on farms, motor transport, burning fuels, deforestation and burning vegetation

8. Strategies to reduce green house gas emissions
Tree planting:
increases size of the CO2 store in the biosphere. It reduces soil erosion, improved habitats for species.
Alternative sources of energy:
replace fossil fuels with clean energy sources. This also help the conservation of non-renewable resources for future generations.
Energy conservation measures:
Reduce amount of fossil fuels burnt.
Ban use of CFCs in aerosols and fridges
Cuts emissions of CFCs and reduce health risks

9. Global warming
Global warming refers to an never-ending rise in global average temperature triggered by various natural and anthropogenic causes - greenhouse gases being one of them. Global warming is the process wherein the average temperature of the Earth's near surface air increases, owing largely to various anthropogenic activities. Though there are some natural causes for this rise in temperature, they stand to be insignificant when compared to the anthropogenic causes.

10. Causes of global warming
Natural Causes:
It includes the release of methane gas from arctic tundra and wetlands, volcanoes etc. Methane, a greenhouse gas which traps the heat within the earth's atmosphere, is let out in large quantities in the arctic tundra and wetlands. In case of volcanoes, when a volcano erupts, tons of ash is let out into the atmosphere. Even though nature contributes to global warming, this contribution is very insignificant when compared to human contribution for this hazard.

11. Causes of global warming
Anthropogenic causes
The most prominent cause being man-made pollution. A large part of this pollution can be attributed to the burning of fossil fuels. This includes burning coal to produce electricity as well as burning gasoline to power internal combustion engine vehicles. When these fossil fuels are burnt, they let out carbon dioxide, which is yet another greenhouse gas which traps heat within the atmosphere of the Earth and contributes to global warming.
Secondly when the Earth is dug to extract these fossil fuels in the process known as mining, the methane inside the Earth's crust escapes into the atmosphere and adds to other greenhouse gases such as carbon dioxide.
Even agriculture contributes to global warming, owing to the extensive use of fertilizers, and the dung produced by cattle which is another prominent source of methane.

12. World wide effects of Global warming
Change in global climate pattern
Melting of ice sheets in the arctic and Antarctica
Rising sea levels
Flooding of low-lying coastal areas-deltas, wetlands and coral islands
Previously populated areas no longer habitable
Widespread Extinction of Flora and Fauna
global warming will affect our food and water supplies as well as our health conditions.
Changes in precipitation will affect basic necessities such as agriculture, power production etc.
Increase in the temperature of ocean waters will hamper fisheries.

13. World wide effects of Global warming
The sudden change in climate patterns will have a hazardous effect on the human body which won't be able to tolerate the extreme conditions, a hint of which can be seen in form of frequent heat waves and cold waves.
Increase in natural calamities such as storms, will lead to heavy human causalities.
Infectious diseases will rise to a great extent as disease transmitting insects will adapt to wet, hot conditions.
Many people will die of malnutrition as food production will decrease due to frequent droughts and floods.

14. Sectors affecting by global warming
Regional climate: precipitation and temperature
Biodiversity and ecosystem
Global distribution of biomes
Ecosystem
Species lost
Agriculture: either positive or negative
Water resource and sea level rise (SLR)
Intense extreme event like flood and drought, rise in sea level
Health: hot, wet and humid environment: heat stroke, malaria, dengue

15. Sea level rise Green house gases make sea level rise due to :
Thermal expansion of sea water
Melting of polar and mountain ice
Estimated to be up to 1 meter by 2010
Why the concern?
The coastal zone (100 km from the sea) contains
1.5 billion people – that’s 1 in 4 people
17 out 20 of the largest cities
Effects
- Threat to coastal habitation and environment
Cause increased coastal erosion
Make buildings and other structures in the coastal zone more vulnerable to damage
Possible landward migration of estuaries and salt marshes
- Salt water intrusion into ground water supplies of coastal communities