UN body warns that 2070 is the deadline for ending CO2 emissions

The world must cut carbon dioxide emissions to zero by 2070 at the latest to keep global warming below dangerous levels and prevent a global catastrophe, the UN warns.

By 2100, all greenhouse gas emissions, including methane, nitrous oxide and ozone, as well as carbon dioxide (CO₂), must fall to zero, the United Nations Environment Programme (Unep) report says , or the world will face what Intergovernmental Panel on Climate Change scientists have described as "severe, widespread and irreversible" effects from climate change.

The Unep report published on Wednesday is based on the concept that the planet has a finite "carbon budget".

Since emissions surged in the late 19th century, 1,900 gigatonnes (Gt) of carbon dioxide and 1,000Gt of other greenhouse gases already have been emitted, leaving less than 1,000Gt of carbon dioxide left to emit before locking the planet into dangerous temperature rises of more than 2 degrees Celsius above pre-industrial levels.

Jacqueline McGlade, Unep's chief scientist, said that scientific uncertainties about the remaining carbon budget had diminished and the real uncertainty now was whether politicians had the will to act.

"The big uncertainty is whether you can put enough policies in place from 2020-2030, the critical window, to allow the least-cost pathways [to lower emissions and temperatures] to still stand a chance of being followed," she said. "The uncertainties have shifted from the science to the politics."