A United Nations body is investigating controversial methods to avert runaway climate change by giving humans the go-ahead to re-engineer the Earth's oceans and atmosphere.

So-called geoengineering is seen as necessary to achieve the COP21 Paris agreement clinched in December, when 197 countries pledged to keep global temperatures rises below 2 degrees Celsius (3.6 degrees Fahrenheit), according to researchers who produced a report for the UN Convention on Biological Diversity.

"Within the Paris agreement there's an implicit assumption that there will need to be greenhouse gases removed," said Phil Williamson, a scientist at the U.K.'s University of East Anglia, who worked on the report. "Climate geoengineering is what countries have agreed to do, although they haven't really realized that they've agreed to do it."