A: Scientists with relevant expertise agree that the world is unequivocally warming. They also agree that human activity is the primary cause of the warming experienced over the past 50 years. This conclusion is based on multiple lines of evidence, from basic physics to the patterns of climate change through the layers of the atmosphere. The warming of global climate and its causes are not matters of opinion, they are matters of scientific evidence, and that evidence is clear.
These two basic conclusions, that the world is warming and that humanity is the primary cause, are well documented in the reports of the Nobel prize-winning Intergovernmental Panel on Climate Change. Further, these major conclusions have been endorsed by the National Academies of Sciences of all major countries including the U.S., and all relevant scientific organizations such as the American Geophysical Union, American Meteorological Society, American Association for the Advancement of Science, and the Royal Society of the United Kingdom.
A study published in the journal Science surveying all papers on the subject of global climate change published between 1993 and 2003 found that not a single paper published in the peer-reviewed scientific literature refuted these basic conclusions.