The average surface temperature is about 150 C. This is about 330C higher than it would be in the absence of the greenhouse effect. Without such gases, most of the Earth`s surface would be frozen with a mean air temperature of –180C.
Human activities during the last few decades of industrialization and population growth have polluted the atmosphere to the extent that it has begun to seriously affect the climate. The carbon dioxide in the atmosphere has increased by 31% since pre-industrial times, causing more heat to be trapped in the lower atmosphere. There is evidence to show that carbon dioxide levels are still increasing. Many countries have signed a convention to reduce Green House Gases under the United Nations Framework Convention on Climate Change (UNFCC). However, the current international agreements are not still effective enough to prevent the significant changes in climate and a rise in sea levels.
Global Warming is accelerating faster than what climatologists had calculated a few years ago. In 1995, the Intergovernmental Panel on Climate Change(IPCC) predicted that global warming would raise temperatures by 3.50-100C during the 21st century, If the present trends continue. It is now believed that it could be much greater. This would lead to not only to changes in temperature but also in the amount of rainfall. we may see great annual fluctuations in rainfall leading to floods and droughts.