Scientists are calling on world leaders to sign up to an eight-point plan of action at landmark talks in Paris.
The key element is the goal to limit global warming to below 2C by moving to zero carbon emissions by 2050.
The UN meeting in December is "the last chance" to avert dangerous climate change, according to the Earth League.
Scientific evidence shows this can be achieved, but only with bold action now, says an alliance of climate researchers from 17 institutions.
The statement involves eight calls for action:
- Limiting global warming to below 2 degrees Celsius
- Keeping future CO2 emissions below 1,000 gigatonnes (billion tonnes)
- Creating a zero-carbon society by 2050
- Equity of approach - with richer countries helping poorer ones
- Technological research and innovation
- A global strategy to address loss and damage from climate change
- Safeguarding ecosystems such as forests and oceans that absorb CO2
- Providing climate finance for developing countries.
Chair of the Earth League, Johan Rockstrom, of the Stockholm Resilience Centre in Sweden, said the statement set out the scientific stance on what needed to happen at the Paris talks.
"Six years after the failure at Copenhagen, the world now has a second chance to agree upon a safe pathway towards a future that does not undermine human well-being in the world."
He said the statement summarised what the group of scientists believe has to happen at the Paris talks to avoid the risk of severe climate change linked with sea-level rise, heat waves, droughts and floods.
"The window is still open but just barely," he said. "There is still an opportunity to transition into a safe, reasonably stable climate future."
He added: "The statement says very clearly that 2 degrees is the absolute upper limit that the world should aim for."
'In this together'
The Earth League includes 17 scientific research institutions around the world, including two in the UK.
Professor Sir Brian Hoskins of the Grantham Institute - Climate Change and the Environment, Imperial College, London, said to achieve the goal, global carbon emissions would need to peak around 2020 and fall very rapidly to near zero by around 2050.
He said rich countries would have to take the lead on this and help the less developed world.
"We're all in this together - we share one planet, we share one atmosphere, we share one climate system."
The statement was released to coincide with Earth Day, an annual event to demonstrate support for environmental protection.
WWF-UK said governments around the world must agree a fair deal at Paris, but should take action beyond this.
Head of climate and energy policy, Emma Pinchbeck, said: "The next UK Government must reaffirm our leadership on this key international issue, and commit to decarbonising policy in line with the science.
"When it comes to government action on climate change, we will benefit from ambition and will regret inaction."