Predicting the effects of climate change is tricky business, and nowhere is that more evident that in the oceans. In 2011, sea levels actually declined sharply, before going up again in 2012. Despite the year-to-year wonkiness, there is scientific consensus that we are in the early stages of what is likely to be a substantial rise in sea level. But how fast it will happen--and how high they will rise--is up for debate.
A study published in Nature Geoscience offers some intriguing clues on the question. The research, headed by Michael O'Leary of Australia's Curtin University, focuses on the warm period in earth history that preceded the last ice age (the Eamian epoch), a time with planetary temperatures much like the ones expected in the coming decades. At NYT, Justin Gillis explains:
Dr. O’Leary’s group found what they consider to be compelling evidence that near the end of the Eemian, sea level jumped by another 17 feet or so, to settle at close to 30 feet above the modern level, before beginning to fall as the ice age set in.
Dr. O'Leary believes that the 17-foot leap happened over less than a thousand years--a mere instant in geologic times. The only possible explanation is a sudden polar ice sheet collapse.
Another recent paper by Anders Levermann and a team of international scientists found that for every degree Fahrenheit of global warming due to carbon pollution, global average sea level will rise by about 4.2 feet in the long run. When multiplied by the current rate of carbon emissions, this translates to a long-term sea level rise commitment that is now growing at about one foot per decade.
This interactive map published on Climate Central visualizes Levermann's findings. According to Climate Central's calculations, continuing on our current emissions trend would mean locking in a long-term sea level rise of 23 feet. With aggressive emission cuts, however, we could limit that to seven feet.
None of this is very comforting to leaders of coastal cities looking ahead to the future. If indeed sea level is capable of going up several feet per century, as Dr. O’Leary’s paper suggests, then we may not be waiting long before a global catastrophe.
Photo: Sheldon Glacier, a rapidly melting ice cap in Antarctica. (NASA)