As we face rising sea levels, famine, disease and the loss of the most precious treasures of our planet, UN warns it is our last chance

THE Earth faces "abrupt and irreversible changes" that will make the planet unrecognisable unless urgent action is taken, the most definitive report on climate change so far has revealed.

The UN's Nobel-winning Intergovernmental Panel on Climate Change (IPCC) also warned of inevitable human suffering and the threat of species extinction.

However, the landmark report also offered blueprints to avert the worst catastrophes. UN Secretary-General Ban Ki-moon said climate change imperils "the most precious treasures of our planet".

The potential impact of global warming is "so severe and so sweeping that only urgent, global action will do," Ban told the IPCC yesterday, after it issued its fourth and final report this year.

The IPCC adopted the report, along with a summary, after five days of sometimes tense negotiations. It lays out blueprints for avoiding the worst catastrophes - and various possible outcomes, depending on how quickly and decisively action is taken.

The document says recent research has heightened concern that the poor and the elderly will suffer most from climate change; that hunger and disease will be more common; that droughts, floods and heatwaves will afflict the world's poorest regions; and that more animal and plant species will vanish.

The Summary for Policymakers, and the longer version, called the Synthesis Report, distil thousands of pages of data and computer models from six years of research compiled by the IPCC.

The information is expected to guide policy makers meeting in Bali, Indonesia, next month to discuss an agreement to succeed the Kyoto Protocol, which expires in 2012.

The panel was awarded the Nobel Peace Prize this year along with former US Vice President Al Gore for their efforts to raise awareness about the effects of climate change.

The report is important because it is adopted by consensus, meaning countries accept the underlying science and cannot disavow its conclusions. While it does not commit governments to a specific course of action, it provides a common scientific baseline for the political talks.

The UN says a new global plan must be in place by 2009 to ensure a smooth transition after the expiration of the Kyoto terms, which require 36 industrial countries to radically reduce their carbon emissions by 2012.

"There are real and affordable ways to deal with climate change," Ban said, adding that a new agreement should provide funding to help poor countries adopt clean energy and to adapt to changing climates.

The report says carbon emissions, which come primarily from fossil fuels, must stabilise by 2015 and go down after that. Otherwise, the consequences could be "disastrous," IPCC chairman Rajendra Pachauri said.

In the best-case scenario, temperatures will continue to rise from carbon already in the atmosphere, the report said. Even if factories were shut down today and cars taken off the roads, the average sea level will reach as much as 1.4 metres (4.6 feet) higher than the preindustrial period, or about 1850.

"We have already committed the world to sea level rise," said Pachauri. If the Greenland ice sheet melts, the scientists could not even predict by how many feet the seas will rise, drowning coastal cities.

As early as 2020, between 75 million and 250 million people in Africa will suffer water shortages, residents of Asia's megacities will be at great risk of river and coastal flooding, Europeans can expect extensive species loss, and North Americans will experience longer and hotter heat waves and greater competition for water, the report says.

"What's new is the clarity of the signal, how clear the scientific message is," said Yvo de Boer, the UN's top climate change official. "The politicians have no excuse not to act."

Opening with a sweeping statement directed at climate change sceptics, the summary declares that climate systems have already begun to change.

Environment campaigners hailed the report as indispensable for the 10,000 delegates who were expected at Bali.

"We expect to see their personal copies of the Synthesis Report return from Bali, battered and worn from frequent use, with paragraphs underlined and notes in the margin," said Stephanie Tunmore of Greenpeace.

Yet differences remain stark on how to control carbon emissions. While the European Union has taken the lead in enforcing the carbon emission targets outlined in Kyoto, the United States opted out of the 1997 accord.

US President George W Bush described it as flawed because major developing countries such as India and China, which are large carbon emitters, were excluded from any obligations.

Sharon Hays, a White House science official and head of the US delegation, said the certainty of climate change was clearer now than when Bush rejected Kyoto.

"What's changed since 2001 is the scientific certainty that this is happening," she said in a conference call to reporters late Friday.

"Back in 2001 the IPCC report said it is likely that humans were having an impact on the climate," but confidence in human responsibility had increased since then.

Prime Minister Gordon Brown said he was seeking to introduce greater long-term cuts in carbon emissions than previously planned. Brown will set out in the next few days various ways in which he believes emissions can be cut.

He also said the UN climate change conference in Bali next month "is the opportunity to provide political answers to these scientific findings".

And he warned: "Climate change will affect developing countries the most. Those who are most vulnerable are also the most at risk from this threat."

Brown added: "The IPCC's measured assessment shows that the world needs to face up to the challenge of climate change, and to do so now. It is clear that climate change poses an urgent challenge, not only a challenge that threatens the environment but also international peace and security, prosperity and development."

Brown said developed countries "must show leadership and take the first and largest responsibility".

He added: "That is why I am asking the UK's independent climate change committee to report on whether our target of a 60% reduction in emissions by 2050, already greater than most other countries, should be even stronger still.

"I will be setting out in the next few days some of the further action we will be taking in Britain to reduce carbon emissions, and climate change will be one of the key issues discussed at next week's meeting of Commonwealth leaders."

The Government is facing pressure after it emerged that up to £270m of cuts are being planned at the Department for Environment, Food and Rural Affairs (Defra),

which could hit a wide range of Defra responsibilities, such as recycling, nature protection and reducing energy use.

International development agency Christian Aid called on world leaders to agree an emergency programme of carbon emission cuts in the light of the report.

Andrew Pendleton, the charity's senior climate change policy analyst, said: "It is difficult to welcome a document that contains so much bad news, but it is a timely, and very stark warning, that urgent action is needed.

"Countries rich and poor need to agree an emergency programme where the industrialised world, which has grown rich through carbon emissions, puts its own house in order while helping emerging economies cut emissions.

"There has been a lot of talk about climate change this year but what little action there currently is to cut emissions amounts to corrections in the margin when the whole story needs rewriting."

Kit Vaughan, climate change adaptation adviser with WWF-UK, said: "We think it's a cracking report. It sends a really strong signal that climate change is happening here and now, it's an urgent global priority.

"We are seeing impacts already, and they are only going to get worse. We are pleased that Ban Ki-moon gave a personal account of climate change.

"By coming out with such a strong message on top of the report, he's signalling that there must be progress at Bali. It's a global emergency, and politicians must respond."

The Liberal Democrat's environment spokesman Chris Huhne commented: "This report highlights the urgency with which the meetings in Bali must now address the global crisis of climate change. We are stealing the future from our children and grandchildren, and it is imperative we put our own behaviour on a sustainable footing.

"The industrial countries have to take the lead because they are responsible for 70% of the carbon that has been emitted, and every extra ounce of carbon has a life of 100 years in the atmosphere."

Meanwhile, Opec has said it is concerned about climate change and is willing to help develop ways to cut emissions.

The group's Secretary General, Abdullah al-Badri, said Opec would be willing to play its part to develop the technology alongside developed countries.

"This needs a lot of money, this needs a lot of research," al-Badri said ahead of an Opec heads of state summit this weekend.

Key warnings that give major cause for concern

Climate systems have already begun to change, with rising air and sea temperatures melting ice caps.

• The poor and the elderly will suffer most from climate change.

• Hunger and disease will be more common.

• Droughts, floods and heatwaves will afflict the world's poorest regions.

• More animal and plant species will vanish.

• Emissions of carbon, which comes primarily from fossil fuels, must stabilise by 2015 and then go down, otherwise the consequences could be "disastrous".

• As early as 2020, between 75 million and 250 million people in Africa will suffer water shortages.

• Residents of Asia's large cities will be at greatest risk of river and coastal flooding.

• North Americans will experience longer heatwaves and greater competition for water.