The causes are many of which the main culprit is the increase in the greenhouse gases that is produced by burning fossil fuel and deforestation, thus intensifying the greenhouse effect leading to global warming. The four main contributors of the greenhouse effect are, water vapor, carbon dioxide, methane and ozone.
Mining for coal and oil releases methane in the atmosphere. More ever the leakage from natural gas fields and landfills are additional source of methane. Excessive cutting down of the trees is another factor causing global warming. When deforestation happens the efficiency by which carbon dioxide is stored and oxygen released by the green plants are decreased to a huge rate in turn causing increased concentration of carbon dioxide that leads to increased greenhouse effect.
The nitrous oxide from fertilizers, gases used for refrigeration and industrial processes are other factors that cannot be forgotten as the cause of Global Warming.
Another source of methane is methane clathrate, a compound containing large amounts of methane trapped in the crystal structure of ice. As methane escapes from the Arctic seabed, the rate of global warming will increase significantly.