Serious disagreement has broken out among scientists over a United Nations climate report's contention that the world's greatest wilderness - Antarctica - will be largely unaffected by rising world temperatures.

The report, to be published on Friday, will be one of the most comprehensive on climate change to date, and will paint a grim picture of future changes to the planet's weather patterns. Details of the report were first revealed by The Observer last weekend.

However, many researchers believe it does not go far enough. In particular, they say it fails to stress that climate change is already having a severe impact on the continent and will continue to do so for the rest of century. At least a quarter of the sea ice around Antarctica will disappear in that time, say the critics, though this forecast is not mentioned in the study.

One expert denounced the report - by the UN's Intergovernmental Panel on Climate Change, or IPCC - as 'misleading'. Another accused the panel of 'failing to give the right impression' about the impact that rising levels of carbon dioxide will have on Antarctica.

Antarctica possesses the Earth's greatest mass of ice and acts as an engine that drives the globe's weather systems. Disturbances to Antarctica could have wide repercussions. If all its ice were to melt, sea levels round the world would rise by 70 metres. The fate of that continent crucially affects the fate of the planet, and according to scientists at the British Antarctic Survey it is already being affected by global warming.

'The greatest temperature rise on Earth over the past five decades has been found on the Antarctic peninsula, which stretches north from the continent towards South America,' said Dr John Turner. 'Temperatures have risen 5C on the peninsula.' That figure is 10 times the average global temperature rise for the same period.

In addition, researchers reported last October that in just over a month, an entire Antarctic ice shelf, bigger than Gloucestershire, had disintegrated and disappeared, with its loss directly linked to man-made global warming.

Yet there is no mention of these events in the draft version of the panel's report obtained by this newspaper. It paints a broad picture of how carbon emissions will alter global temperatures, which will rise by between 3C to 5C by the end of the century, triggering storms of increasing severity, the acidification of seas and the spreading of deserts.

But when it comes to certain types of climate change, especially those concerned with Antarctica, the report is fairly coy. 'Current global studies project the Antarctic ice sheet will remain too cold for widespread surface melting and is expected to gain in mass due to increased snowfall,' states the draft version of the report.

But this vision is disputed. Last year, Dr Turner and colleagues, using records returned by Russian research balloons that were flown over the whole of Antarctica between 1971 and 2003, discovered that temperatures in the lowest level of the atmosphere over the continent have already risen by about 0.7C. Their paper, in Science, was published in March, too late for inclusion in the IPCC's deliberation.

Other factors - including the expected disappearance of the Antarctic ozone hole, which has had a cooling effect on the continent - will lead to a further rise of 5C-6C over parts of the continent over the rest of the century.

Critics point out that the IPCC is a conservative body whose documents are a co-operative effort, with contributions from hundreds of scientists. Only points that are considered indisputable by all of them are included. This consensus deflects potential accusations that the body might be exaggerating the threat to the planet. But the critics say it also means its documents tend to err too much on the side of caution.

'From what I hear of the report, it seems misleading to suggest nothing much is going to happen to the Antarctic over the coming decades,' said Dr Chris Rapley, director of the British Antarctic Survey.

'Some parts of the continents are already losing substantial amounts of ice and others will in future - and that will have direct consequences for the rest of the planet.'

David Astor memorial lecture

David Astor was this newspaper's editor for 27 years from 1948 to 1975. Ever a campaigner, he fought for an end to apartheid, the abolition of the death penalty - and for a greater awareness of our environment. With this in mind, The Observer has joined forces with his daughter, Lucy, to stage the first in an annual David Astor Memorial Lecture series.

Klaus Toepfer, the outgoing under-secretary general and executive director of the United Nations Environmental Programme (UNEP), will ask, 'How can democracy and liberal values survive in a world of finite and diminishing resources?'

The lecture will be held at the Royal Society of Arts, John Adam Street, London WC1, at 7pm (doors open 6.30pm) on 6 February, followed by a drinks reception. We have a limited number of places available for readers. To secure yours, email rsvp@theguardian.com with 'David Astor' in the subject area and state the number of tickets you require, or write to Carla Dowling, 119 Farringdon Road, London EC1R 3ER. Please give your name and address.