The UN summit on climate change in Copenhagen may end in a global deal to cut greenhouse gases, but it can’t help prevent a ‘catastrophic climate change’, scientists have warned.

Writing in the journal Nature, a group of leading academics, have said that unless countries meet their most ambitious targets, temperature rises will go above 2 degrees Celsius.

If there is a “weak agreement” temperatures may even rise by 4 degrees Celsius by the 2060s. This will mean melting of the glaciers, sea level rise, mass droughts and flooding, they said.

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 was quoted as saying by The Telegraph.

He called for 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 reducing 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,” he said.

He regretted that 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 adaptation to changes that may be larger than those usually considered.”