Sea levels have always been influenced by climatic shifts, changes to coastlines, volcanic eruptions and other factors. But a new study that has reconstructed a history of sea levels over the past 3,000 years suggests that we've never seen anything like the rate of change that we're witnessing today.

As reported over at The Washington Post, the study shows that we experienced more than twice the sea level rise than would have been expected under the highest estimates had there been no human influence, and the rate of change has accelerated in recent decades to a current rate of 3.4 millimeters per year. (Compare that to an average of 1.4 millimeters per year between 1900 and 2000.)

The results are devastating, from threatened island nations to world treasures and even cities. that may eventually disappear. Of course, many people have been worrying about sea level rise for some time — and using it as a major motivator for shifting to a low emissions economy as soon as possible. But even on this point, the study brings troubling news: Even if we ceased polluting tomorrow, the seas would continue to rise for decades and centuries to come. (Another recent study has suggested that human-induced sea level rise could last twice as long as human history so far!)

That's not to say we should throw up our hands and give up. We just need to acknowledge that acting on climate now might mean the difference of limiting the consequences to "very, very bad" instead of "totally catastrophic." There's no longer a get-out-jail-free card for humanity. Indeed the latest study, which was published in the Proceedings of the National Academy of Sciences, suggests that we can still influence just how much our sea levels continue to rise. Researchers say the difference between a low emissions development path or the opposite could mean the difference between 24-61 centimeters of sea level rise this century (on the low end), or 52-131 centimeters if we proceed with business as usual.

Bob Kopp, a climate scientist at Rutgers University who led the research, issued one important caveat: If the huge ice sheets that cover Greenland and Antarctica start to melt at a higher level than expected, then all bets are off.