During the last interglacial period ~ 125,000 years ago, sea level was roughly 6 m higher than today.  Evidence of this can be seen throughout the Caribbean, where 125,000 year old fossil coral reefs form much of the shoreline (see this image below).  This was presumably because temp. was higher during that period.  When they were alive, these reefs were under 3-5 m of water (at least).  You can still easily identify the coral species of the fossils and thus estimate the depth that section of reef must have been at based on the coral assemblages current depth profile.

A new study just published in Nature puts this into a probabilistic context with some smarty-smart stats and geo-chrono techniques.

PRINCETON—The planet’s polar ice sheets are vulnerable to large-scale melting even under moderate global warming scenarios. Such melting would lead to a large and relatively rapid rise in global sea level, submerging many coastal areas.

That finding is based on new analysis of the geological record of the Earth’s sea level, carried out by scientists at Princeton and Harvard universities and published in the Dec. 16 issue of Nature.

The researchers employed a novel statistical approach that reveals an additional 2 degrees of global warming could commit the planet to 6 to 9 meters (20 to 30 feet) of long-term sea level rise.

This rise would inundate low-lying coastal areas where hundreds of millions of people now reside. It would permanently submerge New Orleans and other parts of southern Louisiana, much of southern Florida and other parts of the U.S. East Coast, much of Bangladesh, and most of the Netherlands, unless unprecedented and expensive coastal protection were undertaken.

And while the researchers’ findings indicate that such a rise would likely take centuries to complete, if emissions of greenhouse gases are not abated, the planet could be committed during this century to a level of warming sufficient to trigger this outcome.

read the full article on Futurity here

read the press release here

see the paper in Nature here

From Nature: With polar temperatures ~3–5 °C warmer than today, the last interglacial stage (~125 kyr ago) serves as a partial analogue for 1–2 °C global warming scenarios. Geological records from several sites indicate that local sea levels during the last interglacial were higher than today, but because local sea levels differ from global sea level, accurately reconstructing past global sea level requires an integrated analysis of globally distributed data sets. Here we present an extensive compilation of local sea level indicators and a statistical approach for estimating global sea level, local sea levels, ice sheet volumes and their associated uncertainties. We find a 95% probability that global sea level peaked at least 6.6 m higher than today during the last interglacial; it is likely (67% probability) to have exceeded 8.0 m but is unlikely (33% probability) to have exceeded 9.4 m. When global sea level was close to its current level (≥-10 m), the millennial average rate of global sea level rise is very likely to have exceeded 5.6 m kyr^-1 but is unlikely to have exceeded 9.2 m kyr^-1. Our analysis extends previous last interglacial sea level studies by integrating literature observations within a probabilistic framework that accounts for the physics of sea level change. The results highlight the long-term vulnerability of ice sheets to even relatively low levels of sustained global warming.