Tags Current Affairs

Issue

Oceans are likely to rise as much as 1.3 metres by 2100 if Earth's surface warms another 3.5 degrees Celsius, scientists have warned.

 

Background

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. Rise in sea levels will directly affect their livelihood.

 

Details

• 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.

• Even if the Paris climate treaty goal of capping global warming below 2C is met, the ocean watermark could go up two metres by 2300.

• Earth's average surface temperature has risen just over one degree Celsius since the pre-industrial era, a widely used benchmark for measuring global warming.

• 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.

• While less visible than climate-enhanced hurricanes or persistent drought, sea level rise may ultimately prove the most devastating of global warming impacts.

• Across the 20th century, sea level rise was caused mainly by melting glaciers and the expansion of ocean water as it warms. But over the last two decades the main driver has become the melting and disintegrating of Earth's two ice sheets.

• Over the last decade, the sea level has gone up about four millimetres per year. Moving into the 22nd century, however, the waterline could rise ten times faster, even under an optimistic greenhouse gas emissions scenario.

• The Greenland and West Antarctic ice sheets hold enough frozen water to lift oceans about 13 metres. East Antarctica, which is more stable, holds another 50 metres' worth.