The UN Intergovernmental Panel on Climate Change is due to publish the predictions in its fifth major assessment of global warming on Friday.
Compiled by more than 2,000 scientists over three years, it is intended to be the most comprehensive analysis of climate change and its underlying causes.
The report will say that the warming of the oceans will interfere with the currents in the Atlantic, also known as the Atlantic Meridional Overturning Circulation.
It will say: "It is very likely that the Atlantic Meridional Overturning Circulation will weaken over the 21st century.
"It is likely that there will be some decline in the AMOC by 2050, but there will be some decades when the AMOC increases."
The IPCC report provides a basis for governments around the world to draw up policies aimed at tackling climate change and reducing emissions of carbon dioxide.
However, tense discussions all this week between government officials from around the world over the final wording of the report have fallen a long way behind schedule.
Professor Corinne Le Quere, director of the Tyndall Centre for Climate Change Research at the University of East Anglia and one of the authors of the IPCC report, said: "The policy makers see the information from quite a different angle as they have to make a relationship with policy.
"They go through it line by line, paragraph by paragraph and suggest changes which the scientists then respond to."
Delegates stayed up until 3am on Wednesday night as they deliberated over controversial points such as sea level rise and the current "pause" in global temperature rise.
Negotiations were expected to drag into the early hours of Friday morning as officials attempt to finalise the report.
Delegates have already finalised the wording of the report's summary on topics including temperature, sea level rise and the melting of glaciers but debate on some sections including "attribution" – the extent that humans are responsible for global warming – only began on Thursday.
One of the major sticking points came when political officials from Britain, the USA, Brazil and other leading powers stepped in to alter the wording of a section which addresses the comparatively slow increase in global temperatures over the past 15 years – the so called warming "pause".
The officials demanded the wording be changed to explain the slow down temperature rise and wanted to insert clauses that emphasised that global warming has not stopped.
A source at the meeting said: "What has been interesting is you definitely have some governments really trying to get the scientists to explain the [temperature] record.
"They spent hours trying to make the language as clear as possible."
Sceptics have pointed at the pause in global temperature increase as a sign that predictions of catastrophic global warming fail to reflect the reality.
Instead they argue the way the climate responds to increasing carbon dioxide levels in the atmosphere is still not fully understood and so major policy decisions by governments should be delayed to avoid unnecessary costs.
Dr Benny Peiser, director of the Global Warming Policy Foundation, said: "The biggest problem facing the IPCC is that none of the models predicted the warming pause that has occurred in the past 16 years.
"The IPCC is a highly political process and it often fails to reflect that the models do not accurately reflect what is going on and that we don't fully understand the highly complex climate system."
However, many scientists and campaigners warn that the risk of failing to take action to tackle climate change outweighs the costs.
Lord Stern, who conducted a review into the economics of climate change for the Labour government, said: "The kind of temperatures we risk are way outside human experience and would probably involve a recasting of where many people could live.
"Those that would have us delay taking action have to be able to argue that they are confident that the risks are small, which would be an astonishing statement to make."
via Science - Google News http://news.google.com/news/url?sa=t&fd=R&usg=AFQjCNFXbZXwmgHzHQ6LtU9_9KXIHXqIfg&url=http://www.telegraph.co.uk/earth/environment/climatechange/10337064/IPCC-report-Britain-could-cool-if-Gulf-Stream-slows.html
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