According to the United Nations Framework Convention on Climate Change (UNFCCC) the term “climate change” refers to "a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods."
Among human activities responsible for climate change, adding up of billions of tones of carbon dioxide and other man- made gases like methane and chlorofluorocarbons to the atmosphere is of serious concern. Billions of tones of carbon dioxide, the principal heat trapping gas is released every year into the atmosphere through the activity of burning fossil fuels like coal, oil, and natural gas. Large scale uses of the chemical compounds known as chlorofluorocarbons (CFCs) and their release into atmosphere are other reasons behind the climate change. Lots of methane gas is generated in rain-fed paddy cultivation in many areas of the world. All these gases accumulate around the earth to form a thick belt that allows the heat of the sun to pass through and to reach to the earth but does not allow the heat of the earth to go out. Thus the temperature around the earth is bound to increase which results into changes in the global pattern of environment and thus, the climate change.