Scientists know that recent climate change is caused by human activities.
The speed of the current climate change is faster than most past warming events, making it more difficult for human societies and the natural world to adapt.
The key ideas are explained in a publication called -
Climate Change: Evidence and Causes
It was put together by the Royal Society and the National Academy of Sciences, their equivalent in the USA.
The Royal Society is a self-governing Fellowship of many of the world’s most distinguished scientists.
The Society’s fundamental purpose, reflected in its founding Charters of the 1660s, is to recognise, promote, and support excellence in science and to encourage the development and use of science for the benefit of humanity.
Professor Tim Palmer FRS, Royal Society Research Professor in Climate Physics, University of Oxford
“The threat of dangerous man-made changes to global climate is quite unequivocal.
It follows that if we want to reduce this threat, we must cut our emissions of greenhouse gases."
Professor John Shepherd FRS, Ocean & Earth Science, University of Southampton:
“The evidence is very clear that the world is warming, and that human activities are the main cause.
Natural changes and fluctuations do occur but they are relatively small."
Professor Joanna Haigh CBE FRS, Professor of Atmospheric Physics, Imperial College London
“The concentration of carbon dioxide in the Earth’s atmosphere now exceeds anything it has experienced in the past 3 million years and its continuing upward trend is almost certain to result in further global warming."
Professor Sir Brian Hoskins FRS, Director of the Grantham Institute for Climate Change at Imperial College London:
“The evidence of changes in many different aspects of the climate system, from the ice sheets to the deep ocean, shows that climate change is happening.
To reduce the serious risks posed by increasing changes in the climate, we need to redouble our efforts globally to limit carbon dioxide and other greenhouse gas emissions.”
The Royal Society has also published a "Short Guide to Climate Change"
Another organisation offering an important document is the Geological Society of London.
The Geological Society of London say -
This rate of increase of CO2 is unprecedented.....
even in comparison with the massive injection of carbon into the atmosphere 55 million years ago that led to the major PETM warming event....
and is likely to lead to a similar rise in both temperature and sea level.
Climate Change: Evidence from the Geological Record
Another expert who is good at explaining climate change is
Dr Marshall Shepherd.