Researchers say two-metre sea level rise is possible if global temperatures warm by five degrees Celsius by 2100.

Global sea levels could rise by two metres and displace tens of millions of people by the end of the century if greenhouse emissions remain unchecked, according to a new study.

The authors of the report, released on Monday in the Proceedings of the National Academy of Sciences journal, said this outcome is the worst-case scenario, in which global temperatures would warm more than five degrees Celsius by 2100.

The new projections, which double benchmark estimates by the United Nations, suggest the melting of the vast ice sheets of Greenland and Antarctica will contribute to accelerating the rise of seas levels, adding that they contain enough frozen water to lift the world’s oceans dozens of metres.

The UN’s Intergovernmental Panel on Climate Change (IPCC) said its 2013 Fifth Assessment Report suggested that in a “business-as-usual” scenario, sea levels would likely to rise by up to one metre by 2100.

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That prediction has since been viewed as conservative, as the levels of planet-warming greenhouse gas emissions continue to rise year on year, and satellites show accelerated rates of melt-off from massive ice sheets atop Antarctica and Greenland.

In October, the IPCC released a landmark climate report that called for a drastic and immediate reduction in coal, oil and gas consumption in order to arrest the rapid rise in the levels of greenhouse gases in the atmosphere. That report, however, did not include revised estimates of sea-level rise.

‘P rofound consequences’

Researchers on the study say a sea-level rise of the suggested magnitude would have profound consequences for humanity.

“The two-metre sea level rise that we project is not the most likely scenario but it is a plausible scenario. So it is one we should consider if we want to plan and adapt to future sea level rises,” Jonathan Bamber, a professor at the University of Bristol and the lead researcher of the study, told Al Jazeera.

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“It was based on the assumption that we carry on increasing our emissions of greenhouse gasses into the future and sadly carbon emissions have carried on increasing even after the Paris Agreement of 2015,” he added.

The Paris climate deal, struck between nations in 2015, aims to limit global temperature rises to well below two degrees Celsius and encourages countries to work towards a 1.5-degree cap.

The authors said the area of land lost to the ocean could be equivalent to that of France, Germany, Spain and Britain combined, and would displace more than 180 million people.

Earth has already heated one degree Celcius since pre-industrial times, contributing roughly 3 millimetres to sea levels each year.