The UN summit in the Danish capital is likely to end in a global deal to limit greenhouse gases in order to control global warming.But writing in the journal Nature, a group of leading academics, have warned that unless countries meet their most ambitious targets temperature rises will go above 3.6F (2C).
If there is a "weak agreement" temperatures may even rise by 7.2F (4C) by the 2060s.
This will mean melting of the glaciers, sea level rise, mass droughts and flooding.
Mark New of the University of Oxford and one of the authors of the paper, said even countries like Britain could suffer from problems like mass migration and food shortages.
"Even affluent communities would see substantial and unprecedented changes to how they live, while for the majority, fundamental transformations might be necessary for survival."
Dr New called for a rich countries to increase their targets, while also giving developing nations help to reduce emissions. He also said it will be necessary to help vulnerable countries like Bangladesh adapt to sea level rise and other impacts of warming.
"The challenges involved in reducting emissions soon and fast enough to have even a small chance of keeping temperatures below 2C are much larger than most people realise, requiring unprecedented collective will among the governments of both the developed and developing world. Ongoing climate negotiations offer little to suggest that sufficient collective will currently exists to meet this mitigation challenge. The risk of allowing the world to experience 4C of warming this century demands both accelerated efforts at effective mitigation and serious planning for adaptationto changes that may be larger than those usually considered."