Presenting the most vivid evidence to date, the UN's IPCC report has warned that humans are responsible for changes to the earth's climate.
The UN IPPC report into climate change, due out tomorrow, will say scientists agree the world is getting warmer, and humans are to blame.
The government's top scientific advisor has warned of greater variability in UK weather as a result of climate change
The United Nations Environment Programme's executive director said today's IPCC report on climate change "is not about ideology".
Achim Steiner told a press conference the report is a "dramatic reminder of both the significance, the pace, and also our ability to increasingly understand what is happening to our planet".
Mr Steiner said, "This is not about ideology. This is not about self-interest. This is about the common interest of the international community, the planet, and ultimately our economies and society."
Questions have been raised about the slowdown in temperature rises in the past 15 years, with climate "sceptics" claiming it undermines the theory of climate change.
The Intergovernmental Panel on Climate Change's (IPCC) report acknowledges that there has been a reduction in the rate of warming between 1998 and 2012, and suggests it is the result of natural variation and the impacts of volcanoes and changes in the strength of the sun.
Over the long term, from 1951, climate models have matched what has happened to global temperatures, the report said.
One of the scientists leading the first section of the IPCC study said climate change "is the greatest challenge of our time."
Thomas Stocker said: "Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system.
"Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.
"Heatwaves are very likely to occur more frequently and last longer. As the Earth warms, we expect to see currently wet regions receiving more rainfall, and dry regions receiving less, although there will be exceptions."
The Intergovernmental Panel on Climate Change said carbon dioxide concentrations have increased by 40% since pre-industrial times, primarily from fossil fuels such as coal and petroleum.
The UN's Environment Programme wrote on Twitter:
The IPCC's report predicts that temperatures are set to rise by more than 1.5C above pre-industrial levels by the end of the century without ambitious action to tackle emissions, and could rise by over 4C if emissions continue to increase.
The UN panel of experts said ice sheets are losing mass, glaciers are shrinking, sea ice cover has reduced in the Arctic and the permafrost is thawing in the northern hemisphere as a result of global warming.
Storms will become more intense and frequent, sea levels will rise by between 26cm (10in) and 82cm (32in) by the end of the century and the oceans will become more acidic, their assessment projects.
Scientists are more certain than ever that humans are causing the majority of climate change, a key UN report has shown.
The first part of the Intergovernmental Panel on Climate Change's (IPCC) fifth assessment report shows that warming in the climate system is "unequivocal" and human influence on the climate is clear.
The report, which has been published after line-by-line scrutiny by scientists and policymakers, said they are 95% certain that the majority of the warming since the 1950s is down to human activity.
The likelihood is up from a 90% certainty in the last IPCC study in 2007.
A UN panel of climate scientists said 2001-2010 was the warmest decade on record.
Temperatures are expected to rise this century largely due to man-made global warming, a major UN report is to suggest.
UN scientists are expected to say they are 95% sure humans are responsible for climate change in key report to be published today. The findings are expected to show:
- Temperatures will rise by between 0.3C (0.5F) and 4.8C (8.6F) this century
- The lower end of the range will only be possible with emissions cuts deeper than anything that major economies have said they are prepared to tolerate
- Almost 200 governments have agreed in principle to limit global warming to a maximum rise of 2C (3.6F) above pre-industrial times
- The governments have promised to work out a UN deal to limit their emissions accordingly by the end of 2015.
Sceptics have said a slowing of the pace of warming this century after fast gains in the 1980s and 1990s, is a sign that global warming may not be as urgent a problem as previously believed, despite a major UN report on climate change due to be published today.
Some countries stressed that it was also "virtually certain", or at least 99 percent probable, that natural variations in the climate were not the sole cause.
The report will face extra scrutiny after the IPCC made errors in its 2007 report, including an exaggeration of the melt rate of Himalayan glaciers. An outside review of the IPCC found that the mistake did not affect its main conclusions.
Britain's climate could get cooler over the next 80 years, a major report by the UN on global warming is to suggest.
According to the Daily Telegraph, the UN Intergovernmental Panel on Climate Change (IPCC) will say that the circulation of warm and cold water in the Atlantic, which includes the Gulf Stream, will weaken by 20 to 44 per cent by the end of the century.
Scientists claim that such a slow-down in the Gulf Stream will have a big impact on Britain, causing cooling of about 1.8F (1C) and disrupting weather patterns.