Science Alert: [2] Oceans are likely to rise as much as 1.3 metres by 2100 if Earth’s surface warms another 3.5 degrees Celsius, scientists warned Friday.
[3] By 2300, when ice sheets covering West Antarctica and Greenland will have shed trillions of tonnes in mass, sea levels could go up by more than five metres under that temperature scenario, redrawing the planet’s coastlines, they reported in a peer-reviewed survey of more than 100 leading experts. [4] About ten percent of the world’s population, or 770 million people, today live on land less than five metres above the high tide line.
[5] Even if the Paris climate treaty goal of capping global warming below 2 °C is met – a very big “if” – the ocean watermark could go up two metres by 2300, according to a study in the journal Climate Atmospheric Science.
[6] Earth’s average surface temperature has risen just over 1 °C since the pre-industrial era, a widely used benchmark for measuring global warming. [7] “It is clear now that previous sea-level rise estimates have been too low,” co-author Stefan Rahmstorf, head of Earth system analysis at the Potsdam Institute for Climate Impact Research (PIK), told AFP.

The new projections for both the 2100 and 2300 horizons are significantly higher than those from the UN Intergovernmental Panel on Climate Change (IPCC), including a special report on oceans it released in September.

“The IPCC tends to be very cautious and conservative, which is why it had to correct itself upwards already several times,” Rahmstorf said.