Keep coal, gas & oil in ground to save Antarctic ice sheet, study warns #ClimateChange

There are enough fossil fuels buried in the ground to melt the whole of the Antarctic ice sheet – should we choose to burn them, according to new research.
Though it may take thousands of years, that future would see sea level rise by more than 50 metres – inundating cities from London to Barcelona and Tokyo to Washington D.C.

This “mind boggling” finding shows that our actions now have the power to change the face of the planet for tens of thousands of years to come, lead author Dr Ricarda Winkelmann, from the Potsdam Institute for Climate Impact Research, tells Carbon Brief. She says:
“To put it bluntly: if we burn it all, we melt it all.”

58 Metres

The Antarctic ice sheet is the largest mass of ice on our planet, a white blanket spreading out over 14m square kilometers of the continent.

Global temperature rise, driven by global greenhouse gas emissions, is causing parts of the ice sheet to melt and become unstable. According to NASA, Antarctica has lost an average of 118bn tonnes of ice per year since 2004.
As the majority of the ice sheet sits on land, melting ice adds to global sea levels. At the moment, melting of Antarctic ice contributes 0.4mm to global sea levels each year, but such is the size of Antarctica, there’s enough ice on it to raise sea levels by 58 metres.
The new study, published in Science Advances, warns that burning all our remaining fossil fuel resources now could commit us to enough warming to melt the entire ice sheet.
This is a stark illustration that what happens thousands of years from now is intimately tied to the actions we take now, the authors explain.

12,000 billion tonnes

The researchers use an ice sheet model to test how Antarctica responds to increases in the total amount of carbon dioxide in the atmosphere.
They looked at what happened if different amounts of carbon get added to the atmosphere compared to 2010 levels, from an extra 100bn tonnes right up to 12,000bn tonnes.
The lower bound is a very optimistic situation where only a very small fraction of known resources are exploited. The upper bound is scientists’ estimate of the total amount of coal, oil and gas exists across the world and can potentially be extracted.

These high temperatures speed up ice loss on Antarctica, mainly as warmer water melts the ice shelves that extend out from the continent over the ocean from the bottom up. This, in turn, sets off a process that further accelerates melting, the paper explains:
“Once a critical temperature is reached, a second self-reinforcing feedback kicks in and destabilizes the remaining ice.”
Over thousands of years, large parts of the ice sheet melt or drain into the ocean, raising global sea level by several tens of metres, the paper says.
The most vulnerable region to ice loss is the West Antarctic ice sheet, which becomes unstable with 600-800bn extra tonnes of carbon in the atmosphere. Recent research shows glaciers there may have already tipped into unstoppable ice loss, the paper explains.
If total emissions reached 10,000bn tonnes above 2010 levels, Antarctica would become almost ice-free, raising sea levels by three metres per century over the first 1,000 years.
With unrestrained emissions, sea-level rise from Antarctica could exceed 50 meters over the next 1,000 years and could ultimately lead to the loss of the entire ice sheet. The changes won’t be quick, but they will be serious, Winkelmann tells Carbon Brief:
“The changes we are looking at in our study do not happen overnight, but – as we’re saying in the press release – the mind boggling point is that our actions today – within just a few decades – are changing the face of planet Earth as we know it and will continue to do so for tens of thousands of years to come.”
Prof Ted Scambos, senior scientist at the US National Snow and Ice Data Center, who wasn’t involved in the study, tells Carbon Brief why policymakers should sit up and take notice of the study:
“It shows that in the next two centuries or so, we could commit ourselves to truly disastrous sea level rise, as well as many other climate impacts, if we continue on our present course.”

Press link for more: 11 Sep 2015, 19:00Robert McSweeney and Roz Pidcock | carbon


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