If we want to see the future of our planet, we might as well peer into the past. The state of affairs during the last interglacial 125,000 years ago, to be more precise. So say the authors of a new study published in the journal Nature Communications.

Between the last interglacial, which lasted from 125,000 to 118,000 years ago, global temperatures were up to 1℃ higher than they are today. That may seem like a minor difference, yet planetary warming caused massive ice melt. First, the ice melted in Antarctica, then a few thousand years later it did so in Greenland too. As a result, the global sea level rose by about 10 meters above the current level, inundating large swathes of coastal areas for millennia.

“Sea levels rose at up to 3 metres per century, far exceeding the roughly 0.3-metre rise observed over the past 150 years,” write the three authors of the study in an article published in The Conversation. “The early ice loss in Antarctica occurred when the Southern Ocean warmed at the start of the interglacial. This meltwater changed the way Earth’s oceans circulated, which caused warming in the northern polar region and triggered ice melt in Greenland.”

That is bad news as the planet’s surface temperature is expected to rise by 1℃ on average in the next few decades as a result of manmade climate change. “What is striking about the last interglacial record is how high and quickly sea level rose above present levels,” the authors note. “Temperatures during the last interglacial were similar to those projected for the near future, which means melting polar ice sheets will likely affect future sea levels far more dramatically than anticipated to date.”

The experts caution against drawing exact parallels between the last interglacial and today because, they explain, incoming solar radiation was higher back then than it is today because of differences in Earth’s position relative to the sun. Meanwhile, carbon dioxide levels in the atmosphere were only 280 parts per million, as opposed to upwards of 410 parts per million today.

“Crucially, warming between the two poles in the last interglacial did not happen simultaneously,” the point out. “But under today’s greenhouse-gas-driven climate change, warming and ice loss are happening in both regions at the same time. This means that if climate change continues unabated, Earth’s past dramatic sea level rise could be a small taste of what’s to come.”

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