A study by the Potsdam Institute published last month in the Proceedings of the National Academy of Sciences shows that greenhouse gases emitted today will cause sea levels to rise for centuries to come, an impact with potentially catastrophic implications for AOSIS members.
It found that each degree of global warming is likely to lead to sea level rise of more than 2 meters in the future.
Currently, thermal expansion and melting glaciers are the most important factors causing changes in sea level, but the loss from the Greenland and Antarctic ice sheets will be the dominant contributors within the next two millennia, according to the study. Half of that rise might come from ice-loss in Antarctica, which now contributes less than 10 percent. Other studies have made similar connections in the past, but this was the first of its kind to combine evidence from early climate history with extensive data from computer models of all four major contributors to long-term global sea-level rise.
The Potsdam study analyzed data from sea-bottom sediments and ancient raised shorelines around the world and combined them with models based on the fundamental laws of physics.
“The Antarctic computer simulations were able to simulate the past five million years of ice history, and the other two ice models were directly calibrated against observational data – which in combination makes the scientists confident that these models are correctly estimating the future evolution of long-term sea-level rise,” Peter Clark, a paleo-climatologist at Oregon State University and co-author on the study said in a press release.
Scientists say that while it remains difficult to simulate rapid ice-loss from Greenland and Antarctica, the models used were able to capture loss that occurs on longer time scales.
Under the scenario studied, if global mean temperature rises by 4 degrees compared to pre-industrial times, which is projected to happen within less than a century, if bold action to reduce emissions is not taken, the Antarctic ice sheet will contribute about 50 percent of sea-level rise over the next two millennia and Greenland will add another 25 percent to the total sea-level rise. Thermal expansion will contribute about 20 percent, and the contribution from mountain glaciers will decline to less than 5 percent as many of them will shrink to a minimum.
The study provides AOSIS with more evidence to argue for rapid emissions reductions, as well as support for the losses and damages from sea-level rise that can no longer be avoided.