Sea-level rise ‘could last twice as long as human history’ | Environment | Damian Carrington, The Guardian

Research warns of the long timescale of climate change impacts unless urgent action is taken to cut emissions drastically Plastic waste near Dakar, Senegal. Around two-thirds of the national population lives in the Dakar coastal area, which is threatened by sea-level rise.

Huge sea-level rises caused by climate change will last far longer than the entire history of human civilisation to date, according to new research, unless the brief window of opportunity of the next few decades is used to cut carbon emissions drastically. Even if global warming is capped at governments’ target of 2C – which is already seen as difficult – 20% of the world’s population will eventually have to migrate away from coasts swamped by rising oceans. Cities including New York, London, Rio de Janeiro, Cairo, Calcutta, Jakarta and Shanghai would all be submerged. “Much of the carbon we are putting in the air from burning fossil fuels will stay there for thousands of years,” said Prof Peter Clark, at Oregon State University in the US and who led the new work. “People need to understand that the effects of climate change won’t go away, at least not for thousands of generations.” “The long-term view sends the chilling message of what the real risks and consequences are of the fossil fuel era,” said Prof Thomas Stocker, at the University of Bern, Switzerland and also part of the research team. “It will commit us to massive adaptation efforts so that for many, dislocation and migration becomes the only option.” The report, published in the journal Nature Climate Change, notes most research looks at the impacts of global warming by 2100 and so misses one of the biggest consequences for civilisation – the long-term melting of polar ice caps and sea-level rise. This is because the great ice sheets take thousand of years to react fully to higher temperatures. The researchers say this long-term view raises moral questions about the kind of environment being passed down to future generations. The research shows that even with climate change limited to 2C by tough emissions cuts, sea level would rise by 25 metres over the next 2,000 years or so and remain there for at least 10,000 years – twice as long as human history. If today’s burning of coal, oil and gas is not curbed, the sea would rise by 50m, completely changing the map of the world. “We can’t keep building seawalls that are 25m high,” said Clark. “Entire populations of cities will eventually have to move.” Advertisement By far the greatest contributor to the sea level rise – about 80% – would be the melting of the Antarctic ice sheet. Another new study in Nature Climate Change published on Monday reveals that some large Antarctic ice sheets are dangerously close to losing the sea ice shelves that hold back their flow into the ocean.

Read more: Sea-level rise ‘could last twice as long as human history’ | Environment | The Guardian

Uncorking East Antarctica yields unstoppable sea-level rise — PIK Research Portal

Uncorking East Antarctica yields unstoppable sea-level rise05/05/2014 – The melting of a rather small ice volume on East Antarctica’s shore could trigger a persistent ice discharge into the ocean, resulting in unstoppable sea-level rise for thousands of years to come. This is shown in a study now published in Nature Climate Change by scientists from the Potsdam Institute for Climate Impact Research (PIK). The findings are based on computer simulations of the Antarctic ice flow using improved data of the ground profile underneath the ice sheet. Photo: M. Martin/PIK“East Antarctica’s Wilkes Basin is like a bottle on a slant,” says lead-author Matthias Mengel, “once uncorked, it empties out.” The basin is the largest region of marine ice on rocky ground in East Antarctica. Currently a rim of ice at the coast holds the ice behind in place: like a cork holding back the content of a bottle. While the air over Antarctica remains cold, warming oceans can cause ice loss on the coast. Ice melting could make this relatively small cork disappear – once lost, this would trigger a long term sea-level rise of 300-400 centimeters. “The full sea-level rise would ultimately be up to 80 times bigger than the initial melting of the ice cork,” says co-author Anders Levermann. “Until recently, only West Antarctica was considered unstable, but now we know that its ten times bigger counterpart in the East might also be at risk,” says Levermann, who is head of PIK’s research area Global Adaptation Strategies and a lead-author of the sea-level change chapter of the most recent scientific assessment report by the Intergovernmental Panel on Climate Change, IPCC. This report, published in late September, projects Antarctica’s total sea level contribution to be up to 16 centimeters within this century. “If half of that ice loss occurred in the ice-cork region, then the discharge would begin. We have probably overestimated the stability of East Antarctica so far,” says Levermann.Emitting greenhouse-gases could start uncontrollable ice-melt

Source: Uncorking East Antarctica yields unstoppable sea-level rise — PIK Research Portal