A little bit of physics ?
The atmosphere is made up of gaseous particles that each react differently towards solar radiation. Its composition is: 78% nitrogen, 21% oxygen, as well as traces of several other gases. Among the latter, some are "opaque" to infrared radiations emitted by the Earth (when reflecting solar radiation), and of limiting the re-emission of these infrareds to space. As a result, the average ground temperature on Earth is kept around 14,5°Celsius, whereas it would not exceed -18°C if these "greenhouse gases" did not have that effect.
Consequently, any increase in quantity of these gases in the Earth's atmosphere raises the ground temperature.
Since humans have begun to exploit the fossil energy resources (the hydrocarbons: coal, petroleum, natural gas), their combustion has induced a constantly increasing atmospheric emission of carbon dioxide (CO2), a greenhouse gas, causing a faster and faster rise of its concentration. This creates a phenomenon of global warming.
Although it is recognized that other natural elements such as solar cycles have an influence on the average ground level temperature of the Earth,
ALL RECENT SCIENTIFIC DATA SHOW NOW VERY CLEARLY THAT HUMAN ACTIVITY IS RESPONSIBLE FOR THE REINFORCEMENT OF THE PHENOMENON.
The Intergovernmental Panel on Climate Change is an organization put up on demand of the G7 that is under the aegis of the World Meteorological Organization and of the United Nations Environment Program. It gathers the 189 member states of the United Nations and has the function of assessing scientific, technical and socio-economical information related to human-induced climate change. It is an organization made up of experts who analyse and assess existing scientific data, but it does not undertake research itself. The IPCC elaborates a synthesis on up-to-date results of international research, in order to illuminate the issue for all policymakers and politicians, and to help the decision-making process during international negotiations.
The IPCC has so far published 4 reports: in 1990, 1995, 2001, and lately in 2007, that eliminate all doubts on the climate modification initiated. The climate system is transforming in a worrying way.It is not the purpose of this website to prove right these facts to a doubtful audience, for science has already made them certain. Nonetheless, it is evident that the perception of the energy/climate issue by society is a major concern if we want to reach emission abatement targets. Under any circumstances it is of great importance that everyone gets correct information from reliable sources, here IPCC naturally stands as the best one.