Global warming is nothing but the sudden increase in the temperature of the earth due to the excessive accumulation of greenhouse gases in the earth's atmosphere.
research indicated that the earth's average temperature has risen by 0.76 degrees Celsius over the past 100 years with most of it occurring in the past 20 years.
Although such a temperature change may seem oddly minimal for such a huge planet ,but has translated into a  heat expelling monster for the global climate system severely impacting not only human health and livelihood but the global ecosystems as-well,accelerating droughts,flood,heatwaves ,rising sea levels  and causing enormous amounts of economic and social damage.
The only solution to this lies in mitigation, mitigation not only  for a safer future but a cleaner and greener planet.
because as Woody Allen rightly quoted 'More than any other time in history, mankind faces a crossroads. One path leads to despair and utter hopelessness. The other, to total extinction. Let us pray we have the wisdom to choose correctly.'' 

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1) Global warming

Global Warming is the heating up of the Earth's Surface and the rise in the usual temperature of the Earth.
The main causes for the rise in temperature are :
The smoke from automobiles, 
The green house effect where the clouds hold the heat given by the sun and when Earth radiates it back the cloud cover reflect it back and so the excess heat cannot escape into the atmosphere and CFC's (Chlorofluorocarbon) given out by Air Conditioners,Fridges,coolers,etc.
The results of the Global Warming are that 
There is rise in temperature of the Earth's surface, 
The melting of glaciers at the poles causing in floods and depletion of the ozone layer with the effect of CFC and due to this a big hole in the ozone layer which protects us from sun's ultraviolet rays. The hole is over Antarctica whose extent is  as North America.
Ways to prevent Global Warming are:
1. To use CNG (Compressed Natural Gas) Buses.
2. Use of Buses with CNG because people can travel place to place with only the emission of gas from the bus, Suppose 30 people go in bus then it will produces less harm than if 30 people start their own cars.
3. Limited use of AC's.
4. Fridges must be left open for very less time.

2) On nature conservation(trees)

Since time immemorial, human beings have been depending heavily on forests for food, medicine, shelter, wood and fuel.With growing civilization the demands for raw materials like timber, pulp, minerals, fuel, etc., shoot up resulting in large scale mining, road building and clearing of forests. Our forests contribute substantially to our national economy.Excessive use of fuel wood and charcoal, expansion of urban, agricultural and industrial areas have together led to over exploitation of our forests leading to their rapid depletion.We should conserve forests as it is the place of many wildlife species and protect their natural habitat. It should be conserved to protect the loss of biodiversity and genetic diversity. It also regulates the hydrological cycle. Soil erosion can also be prevented if we conserve forests. Climatic changes and global warming can also be combated if we conserve forests.