The United Nations agreement on climate change set two goals in regard to global warming. The main goal calls for nations to ensure global temperatures increase no more than 2 degrees Celsius above the pre-indsturial average. But the Paris agreement also put forward an aspirational target of limiting warming to 1.5 degrees Celsius by the end of the century.

Whether either target is sufficient or possible remains a matter of debate, but most scientists believe the 1.5 degree target is more likely to avoid global warming's worst case scenarios.

Now, new research has confirmed that the half-degree separating the two targets is far from inconsequential. According to climate scientists at Princeton University, an extra half degree of warming would trigger additional sea level rise, flooding coastal regions and islands currently inhabited by some 5 million people.

Researchers used the most up-to-date sea level and storm surge prediction models to gauge the impact of three different global warming scenarios -- warming of 1.5, 2 and 2.5 degrees Celsius. The published the results of their analysis in the journal Environmental Research Letters.

"People think the Paris Agreement is going to save us from harm from climate change, but we show that even under the best-case climate policy being considered today, many places will still have to deal with rising seas and more frequent coastal floods," lead study author D.J. Rasmussen, an environmental policy grad student at Princeton's Woodrow Wilson School of Public and International Affairs, said in a news release.

Using tidal records to inform the latest models of sea level rise and storm models, scientists showed that extreme sea-level events will become more frequent under all three warming scenarios. A 1.5-degree increase in global temperature is likely to raise sea levels by an average of 1.6 feet, while a 2.0-degree increase lead to a 1.8 foot rise in sea level.

The new models also showed what previous studies have -- that even if global warming is halted within the next few decades, seas are likely to continue rising well into the next century.