Climate change over the next 20 years could result in a global  catastrophe costing millions of lives in wars and natural disasters.. 
A  secret report, suppressed by US defence chiefs and obtained by The  Observer, warns that major European cities will be sunk beneath rising  seas as Britain is plunged into a 'Siberian' climate by 2020. Nuclear  conflict, mega-droughts, famine and widespread rioting will erupt across  the world.  
The document predicts that abrupt climate change  could bring the planet to the edge of anarchy as countries develop a  nuclear threat to defend and secure dwindling food, water and energy  supplies. The threat to global stability vastly eclipses that of  terrorism, say the few experts privy to its contents.  
'Disruption  and conflict will be endemic features of life,' concludes the Pentagon  analysis. 'Once again, warfare would define human life.'  
The  findings will prove humiliating to the Bush administration, which has  repeatedly denied that climate change even exists. Experts said that  they will also make unsettling reading for a President who has insisted  national defence is a priority.  
The report was commissioned by  influential Pentagon defence adviser Andrew Marshall, who has held  considerable sway on US military thinking over the past three decades.  He was the man behind a sweeping recent review aimed at transforming the  American military under Defence Secretary Donald Rumsfeld.  
Climate  change 'should be elevated beyond a scientific debate to a US national  security concern', say the authors, Peter Schwartz, CIA consultant and  former head of planning at Royal Dutch/Shell Group, and Doug Randall of  the California-based Global Business Network.  
An imminent  scenario of catastrophic climate change is 'plausible and would  challenge United States national security in ways that should be  considered immediately', they conclude. As early as next year widespread  flooding by a rise in sea levels will create major upheaval for  millions.  
Last week the Bush administration came under heavy  fire from a large body of respected scientists who claimed that it  cherry-picked science to suit its policy agenda and suppressed studies  that it did not like. Jeremy Symons, a former whistleblower at the  Environmental Protection Agency (EPA), said that suppression of the  report for four months was a further example of the White House trying  to bury the threat of climate change.  
Senior climatologists,  however, believe that their verdicts could prove the catalyst in forcing  Bush to accept climate change as a real and happening phenomenon. They  also hope it will convince the United States to sign up to global  treaties to reduce the rate of climatic change.  
A group of  eminent UK scientists recently visited the White House to voice their  fears over global warming, part of an intensifying drive to get the US  to treat the issue seriously. Sources have told The Observer that  American officials appeared extremely sensitive about the issue when  faced with complaints that America's public stance appeared increasingly  out of touch.  
One even alleged that the White House had written  to complain about some of the comments attributed to Professor Sir  David King, Tony Blair's chief scientific adviser, after he branded the  President's position on the issue as indefensible.  
Among those  scientists present at the White House talks were Professor John  Schellnhuber, former chief environmental adviser to the German  government and head of the UK's leading group of climate scientists at  the Tyndall Centre for Climate Change Research. He said that the  Pentagon's internal fears should prove the 'tipping point' in persuading  Bush to accept climatic change.  
Sir John Houghton, former chief  executive of the Meteorological Office - and the first senior figure to  liken the threat of climate change to that of terrorism - said: 'If the  Pentagon is sending out that sort of message, then this is an important  document indeed.'  
Bob Watson, chief scientist for the World  Bank and former chair of the Intergovernmental Panel on Climate Change,  added that the Pentagon's dire warnings could no longer be ignored.  
'Can  Bush ignore the Pentagon? It's going be hard to blow off this sort of  document. Its hugely embarrassing. After all, Bush's single highest  priority is national defence. The Pentagon is no   wacko, liberal group,  generally speaking it is conservative. If climate change is a threat to  national security and the economy, then he has to act. There are two  groups the Bush Administration tend to listen to, the oil lobby and the  Pentagon,' added Watson.  
'You've got a President who says global  warming is a hoax, and across the Potomac river you've got a Pentagon  preparing for climate wars. It's pretty scary when Bush starts to ignore  his own government on this issue,' said Rob Gueterbock of Greenpeace.  
Already,  according to Randall and Schwartz, the planet is carrying a higher  population than it can sustain. By 2020 'catastrophic' shortages of  water and energy supply will become increasingly harder to overcome,  plunging the planet into war. They warn that 8,200 years ago climatic  conditions brought widespread crop failure, famine, disease and mass  migration of populations that could soon be repeated.  
Randall  told The Observer that the potential ramifications of rapid climate  change would create global chaos. 'This is depressing stuff,' he said.  'It is a national security threat that is unique because there is no  enemy to point your guns at and we have no control over the threat.'  
Randall  added that it was already possibly too late to prevent a disaster  happening. 'We don't know exactly where we are in the process. It could  start tomorrow and we would not know for another five years,' he said.  
'The  consequences for some nations of the climate change are unbelievable.  It seems obvious that cutting the use of fossil fuels would be  worthwhile.'  
So dramatic are the report's scenarios, Watson  said, that they may prove vital in the US elections. Democratic  frontrunner John Kerry is known to accept climate change as a real  problem. Scientists disillusioned with Bush's stance are threatening to  make sure Kerry uses the Pentagon report in his campaign.  
The  fact that Marshall is behind its scathing findings will aid Kerry's  cause. Marshall, 82, is a Pentagon legend who heads a secretive  think-tank dedicated to weighing risks to national security called the  Office of Net Assessment. Dubbed 'Yoda' by Pentagon insiders who respect  his vast experience, he is credited with being behind the Department of  Defence's push on ballistic-missile defence.  
Symons, who left  the EPA in protest at political interference, said that the suppression  of the report was a further instance of the White House trying to bury  evidence of climate change. 'It is yet another example of why this  government should stop burying its head in the sand on this issue.'  
Symons  said the Bush administration's close links to high-powered energy and  oil companies was vital in understanding why climate change was received  sceptically in the Oval Office. 'This administration is ignoring the  evidence in order to placate a handful of large energy and oil  companies,' he added.