Man-made climate change poses an "immediate threat" to Australia's way of life, a major UN report has warned.
The Intergovernmental Panel on Climate Change (IPCC) released its latest major update in Japan on Monday, with claims the effects of a changing global climate are being felt across the globe.
- UN panel's reasons to worry about warming
- UN climate committee 'optimistic' on chances of managing climate change risks
The UN-led IPCC report, Climate Change 2014: Impacts, Adaptation and Vulnerability was produced by 309 authors and editors from 70 countries and backed by many governments around the world.
"In many cases, we are not prepared for the climate-related risks that we already face," said Vincente Barros, co-chairman of the IPCC's Working Group II that produced the report.
The report paints an alarming portrait of the impact of climate change for Australia.
It cites rising sea levels, loss of animal habitat, increasing heatwaves and droughts as a "very real and immediate threat to Australia's society and economy".
The report said the Great Barrier Reef faces "irreparable damage" within 25 years.
"Even a one degree Celsius temperature change will bring devastating impacts," said Professor Ove Hoegh-Guldberg, a Brisbane-based marine biologist and a lead author of the IPCC report.
"Over half of the Great Barrier Reef has already disappeared in the last 27 years from ocean acidification due to carbon emissions, causing mass bleaching and death to many of its ecosystems."
UN document warning of grave climate future completed
Leading scientists and officials completed a fresh climate report Sunday expected to lay bare the grim impact of climate change, with warnings that global food shortages could spark violence in vulnerable areas.
Part of a massive overview by the United Nations' Intergovernmental Panel on Climate Change (IPCC) set for release on Monday, the report is likely to shape international policy on climate for years to come, and will announce that the impact of global warming is already being felt.
Some 500 scientists and government officials have been gathered since Tuesday in Yokohama, south of Tokyo, to hammer out its wording.
It will serve as the second of three volumes into climate change's causes, consequences and possible solutions by the expert panel.
Leading Australian health academic, Helen Berry, said that while the Earth has been warmer and colder throughout it's history, the rate of change has never been as fast as it is today.
"What is remarkable, and alarming, is the speed of the change since the 1970s, when we started burning a lot of fossil fuels in a massive way," the associate dean in the faculty of health at the University of Canberra told Fairfax.
"We can't possibly evolve to match this rate [of warming] and, unless we get control of it, it will mean our extinction eventually."
Professor Berry contributed on the health chapter of the IPCC report, which outlined the health risks of rapid global warming.
"Human-driven climate change poses a great threat, unprecedented in type and scale, to wellbeing, health and perhaps even to human survival," the report said.
The work comes six months after the first volume in the long-awaited Fifth Assessment Report declared scientists were more certain than ever that humans caused global warming.
A leaked draft seen by AFP warned that rising greenhouse gas emissions will "significantly" boost the risk of floods while droughts will suck away sustainable water supplies.
A "large fraction" of land and freshwater species may risk extinction, and a warming climate is projected to reduce wheat, rice and corn yields, even as food demand rises sharply as the world's population grows.
Meanwhile hundreds of millions of coastal dwellers around the world will be displaced by the year 2100, the draft said, while the competition for dwindling resources could even spark violent conflicts.
However, the world can avoid many of the worst-case scenarios with swift and decisive policy steps to cut emissions now, the scientists urged.
The delegates were originally expected to finish drafting the official summary text late Saturday evening, but needed extra time to update definitions and digest new approaches.
"I felt the meeting was very constructive, and governments appreciated why the authors did things the way they did them," said Maarten van Aalst, director of Red Cross/Red Crescent Climate Centre.
"While it may seem as if a long meeting could signal we had problems to solve, it was actually a sign of a very productive and collaborative process," said Van Aalst, who is one of the IPCC lead authors.
The panel has issued four previous "assessment reports" in its quarter-century history.
The IPCC's last big report in 2007 helped unleash political momentum leading to the 2009 UN climate summit in Copenhagen.
UN author says draft climate report alarmist, pulls out of team
One of the 70 authors of a draft U.N. report on climate change said he had pulled out of the writing team because it was "alarmist" about the threat.
Richard Tol told Reuters he disagreed with some findings of the summary to be issued in Japan on March 31.
"The drafts became too alarmist," the Dutch professor of economics at Sussex University in England said by telephone from Yokohama, Japan, where governments and scientists are meeting to edit and approve the report.
But he acknowledged some other authors "strongly disagree with me".
The final draft says warming will disrupt food supplies, slow economic growth, and may already be causing irreversible damage to coral reefs and the Arctic.
"The report is a product of the scientific community and not of any individual author," the U.N.'s Intergovernmental Panel on Climate Change (IPCC) said in a statement. "The report does not comprehensively represent the views of any individual."
It said Tol notified it in September that he was withdrawing from the team writing the summary. He had been invited to Japan to help the drafting and is also the coordinating lead author of a sub-chapter about economics.
Tol, who has sometimes been at odds with other scientists in the past by pointing to possible benefits from global warming, had not made his pullout widely known until now.