Global warming could drive a much more dramatic increase in sea levels than current projections suggest, scientists say, citing a rise of 10 metres (33 feet) during Earth’s last warming interlude more than 100,000 years ago.
Such a change far outstrips current projections and could be catastrophic for vast swathes of humanity, a team at Australian National University concluded in a study.
During the last interglacial period, “sea levels rose at up to three metres per century, far exceeding the roughly 0.3-metre rise observed over the past 150 years,” they said in a blog about their findings, published Wednesday in the journal Nature Communications.
Over the last million years, Earth has alternated between roughly 100,000-year-long cold periods -- ice ages -- and shorter, temperate spells such as the last 11,500 years, known as the Holocene.
The scientists reported that during Earth’s last interglacial period 125,000 to 118,000 years ago, when temperatures were only 1.0 degrees Celsius higher than today, the sea rose 10 metres.
The findings do not necessarily foretell our short-term future but they do provide a plausible analogue for the consequences of manmade climate change.
“Greenhouse gas emissions over the past 200 years have caused climate changes that are faster and more extreme than experienced during the last interglacial,” the scientists noted.
“This means past rates of sea level rise provide only low-end predictions of what might happen in the future.”
Far from being a “sleeping giant”, Antarctica is a key variable in rising sea levels, with ice sheets that “can change quickly”.
In the last interglacial period it was ice loss in Antarctica -- as is happening today -- that changed “the way the Earth’s oceans circulated,” they said.
“This caused warming in the northern polar region and triggered ice melt in Greenland,” they added.