We’re set on the path of rising sea levels, even if the pledges made for the Paris climate agreement are met and global temperatures stabilize, a new paper reports.

The Paris agreement on climate change mitigation was adopted in December 2015 and aims to limit the rise of global average temperatures to a maximum of 2°C compared to pre-industrial levels. The ideal scenario under the agreement would be to limit this figure to 1.5°C, and the countries that signed into the agreement are expected to make efforts towards this goal.

While a successful Paris agreement would do wonders for our efforts against climate heating and environmental degradation, we’re already set for rising sea levels around the world by 2300, a new study reports.

We’re already there

“Even if we were to meet these initial goals of the Paris agreement, the sea level commitment from global warming will be significant,” said Peter Clark, an Oregon State University climate scientist and a co-author of the study.

“When we pump more carbon into the atmosphere, the increase in temperature is almost immediate. But sea level rise takes a lot longer to respond to that warming. If you take an ice cube out of the freezer and put it on the sidewalk, it takes some time to melt. The bigger the ice cube, the longer it takes to melt.”

The authors say this is the first effort to quantify how sea levels will rise from carbon emissions (both past and future) released since the agreement was signed. In the first 15 years following the agreement, they report, will cause a rise of roughly 20 centimeters (7.9 in) by 2300. The estimate does not take into account the effect of irreversible melting in parts of the Antarctic ice sheet, the team adds, which is already underway.

A one-meter rise is expected by 2300, caused by emissions dating back to the year 1750. Around 20% of that rise can be traced back to emissions released since after the Paris agreement was signed. Around half of it (so 10% of the total projected rise) is attributable to the world’s top five polluters, the team found: the United States, China, India, Russia, and the European Union

Sea level rise is a huge threat to coastal ecosystems and human communities, with the potential to affect and/or displace hundreds of millions around the world (coastal areas are the most heavily-inhabited regions on Earth). Sea level rise is mostly driven by melt from glaciers and ice sheets draining into the ocean. But these are massive structures strewn all over the world, and they each respond to climate heating in their own time, ranging from decades to millennia.

“Much of the carbon dioxide we’ve emitted into the atmosphere will stay up there for thousands of years,” said Clark, who is on the faculty of OSU’s College of Earth, Ocean, and Atmospheric Sciences.

“So our carbon emissions this century are not only committing our planet to a warmer climate, but also to higher sea levels that will also persist for thousands of years.”

The paper “Attributing long-term sea-level rise to Paris Agreement emission pledges” has been published in the journal Proceedings of the National Academy of Sciences.