The impacts of global warming are likely to be "severe, pervasive and irreversible", a major report by the UN has warned.

Scientists and officials meeting in Japan say the document is the most comprehensive assessment to date of the impacts of climate change on the world.

Members of the UN's climate panel say it provides overwhelming evidence of the scale of these effects.

Natural systems now bear the brunt, but a growing impact on humans is feared.

Our health, homes, food and safety are all likely to be threatened by rising temperatures, the summary says.

The report was agreed after almost a week of intense discussions here in Yokohama.

This is the second of a series from the Intergovernmental Panel on Climate Change (IPCC) due out this year that outlines the causes, effects and solutions to global warming.

This latest Summary for Policymakers document highlights the fact that the amount of scientific evidence on the impacts of warming has almost doubled since the last report in 2007.              

 The impact of climate change

Be it the melting of glaciers or warming of permafrost, the summary highlights the fact that on all continents and across the oceans, changes in the climate have caused impacts on natural and human systems in recent decades.

In the words of the report, "increasing magnitudes of warming increase the likelihood of severe, pervasive and irreversible impacts".

IPCC Chairman Rajendra Pachauri said the findings in the report were "profound"

"Nobody on this planet is going to be untouched by the impacts of climate change,'' IPCC chairman Rajendra Pachauri told journalists at a news conference in Yokohama.

Dr Saleemul Huq, a convening lead author on one of the chapters, commented: "Before this we thought we knew this was happening, but now we have overwhelming evidence that it is happening and it is real."

Michel Jarraud, secretary-general of the World Meteorological Organization, said that, previously, people could have damaged the Earth's climate out of "ignorance".

"Now, ignorance is no longer a good excuse," he said.

Mr Jarraud said the report was based on more than 12,000 peer-reviewed scientific studies. He said this document was "the most solid evidence you can get in any scientific discipline".

The report details significant short-term impacts on natural systems in the next 20 to 30 years. It details five reasons for concern that would likely increase as a result of the warming the world is already committed to.

These include threats to unique systems such as Arctic sea ice and coral reefs, where risks are said to increase to "very high" with a 2C rise in temperatures.

The summary document outlines impacts on the seas and on freshwater systems as well. The oceans will become more acidic, threatening coral and the many species that they harbour.

On land, animals, plants and other species will begin to move towards higher ground or towards the poles as the mercury rises.

Humans, though, are also increasingly affected as the century goes on.

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