World 'needs radical cuts' on CO2
That is the conclusion of a report by the Worldwatch Institute which urges bigger cuts in greenhouse emissions.
The authors say that even a rise in temperatures of 2 degrees C poses unacceptable risks to natural systems.
But they add that it is still possible to arrest and manage climate change with renewable technologies and more efficient ways of living.
"Sealing the deal to save the global climate will require mass public support and worldwide political will to shift to renewable energy, new ways of living, and a human scale that matches the atmosphere's limits," said Robert Engelman, vice president for programmes at the Worldwatch Institute.
Commenting on the report, Ian Lowe, president of the Australian Conservation Foundation, said: "It is a persuasive call to action. Unless we take early concerted action, the impacts of climate change will overwhelm our capacity to adapt."
Global greenhouse gas emissions need to peak before 2020 and decrease drastically until 2050, the report says.
More CO2 will have to be absorbed than emitted in the second half of this century.
The report, The State of the World 2009, outlines 10 key challenges that must be adopted to avoid catastrophic climate change.
These include long-term planning, global co-operation and innovative solutions such as improved building design incorporating a variety of efficiency measures.
"The report is particularly timely. It addresses climate change concerns and provides a wide range of options for tackling this multi-faceted problem," said Stephen Lincoln at the University of Adelaide in Australia.
In December 2009, government representatives from 170 countries will meet to create a global climate agreement.
The president of the Worldwatch Institute, Christopher Flavin, said: "The outcome of this meeting will be written in the history books - and in the lasting composition of the world's atmosphere."