Global warming is a phenomenon of increase in the average temperature of the oceans and the Earth’s atmosphere, measured globally over several decades, reflecting an increase in the amount of heat at the Earth’s surface. In its common meaning, the term is applied to a global warming trend observed since the early twentieth century.
In 1988, the UN created the Intergovernmental Panel on Climate Change (IPCC) charged with making a synthesis of scientific studies on this issue. In his latest and fourth report, which involved more than 2500 scientists from 130 countries1, the IPCC says that global warming since 1950 is very probably due to the increase in anthropogenic greenhouse gas. The IPCC’s findings were approved by more than forty scientific societies and academies of science, including all of the national academies of science of the major industrialized country. In a study published late 2012, which compiled and compared twenty different simulations from computer models and information from satellite observations, a team of climate scientists from Lawrence Livermore National Laboratory of the Department of Energy of the United States (DoE) and 16 other organizations found that temperature changes in the troposphere and stratosphere are real and they are clearly linked to human activities.
The projections of climate models presented in the latest IPCC report indicate that the global surface temperature is likely to increase by 1.1 to 6.4° C over the extra twenty-first century. The differences between the projections comes from the use of models with differing sensitivity to concentrations of greenhouse gases and using different estimates for future emissions. Most studies focus on the period up to 2100. However, warming is expected to continue beyond that date, even if emissions stop, because of the great heat capacity of the oceans and the life of the carbon dioxide and other greenhouse gas into the atmosphere.
Uncertainties in global average temperature rise remain because of the precision of the models used, and the present and future state and individual behavior. The economic, political, social, environmental or moral issues, being major, they arouse much international debates, as well as controversies. Nevertheless the economic, sociological, environmental or geopolitical impacts of these projections is overall negative medium and long term.
The first stated objective of the United Nations Climate Change Conference, in December 2015, is also to maintain global warming to below 2° C by 2100 compared to pre-industrial times.
Translated from Wikipedia