Andreas Späth

Said the one polar bear to the other...

2016-04-04 09:41

Andreas Wilson-Späth

... as their patch of sea ice dissolved into the Arctic Ocean in the anomalous winter heat: “There goes the neighbourhood!”

It’s not a joke – regardless of the myriad of internet memes featuring stricken white bears on miniscule floats – it’s actually happening. And not only at the North Pole, but on the southern end of the planet, too. Said the one emperor penguin to the other as the West Antarctic Ice Sheet started to disintegrate all around them...

Last week, the US National Snow & Ice Data Center (NSIDC) released the latest data on this northern winter’s maximum extent of sea ice cover in the Arctic, which turned out to be 14.52 million square kilometres. That may sound like a lot, but it represents the lowest cold season maximum since records were started way back in 1979.

“I’ve never seen such a warm, crazy winter in the Arctic,” said NSIDC director Mark Serreze.

Simply put, the amount of sea ice in the Arctic is shrinking. The latest measurements form part of a multi-year trend of decreasing winter sea ice and experts now believe that the Arctic will experience completely ice-free summers within the next 20 to 25 years.

Disappearing sea ice in the northern polar regions adds to rising sea level and has significant consequences for climate patterns elsewhere. A recent study shows that it also contributes to increased surface ice melting in Greenland. According to the authors, “reduced summer sea ice favors stronger and more frequent occurrences of blocking-high pressure events over Greenland. Blocking highs enhance the transport of warm, moist air over Greenland, which increases downwelling infrared radiation, contributes to increased extreme heat events, and accounts for the majority of the observed warming trends”. The result: even more sea level rise.

On the other end of the planet, researchers are becoming increasingly aware of the fragility of Antarctica’s massive ice sheets. A new paper published by a group of scientists lead by outspoken climatologist James Hansen, formerly of NASA and now at New York City’s Colombia University, evaluates the effects of melting ice in Greenland and the southern continent. They forecast, among other things, drastic changes in oceanic circulation, increasingly powerful storm events and “growing sea level rise, reaching several meters over a timescale of 50–150 years”.

The work is controversial, not least because until now, many researchers have assumed that Antarctica will gain rather than lose ice in the future and the UN’s Intergovernmental Panel on Climate Change has previously pegged potential sea level rise at a maximum of one metre by the end of the century.

Now, however, Hansen & Co's predictions have found support from independent research published in the influential journal Nature last week. Authors Robert DeConto and David Pollard emphasise the importance of the melting Antarctic ice sheets and take into account various factors that have previously been neglected or underestimated.

Their models suggest that even if the world meets the emission reduction targets proposed at last year’s climate summit in Paris, sea level may rise by a metre by 2100. If they are not, we may be looking at two metres in the same timeframe and at more than 15 metres by 2500.

At the moment, sea level rise is measured in mere millimetres per annum, but that may increase to several centimetres a year, which “could spell disaster for many low-lying cities,” says DeConto. “At that point it becomes about retreat, not engineering of defences”.

Numerous large and growing urban centres around the globe will be under potential threat if the predictions are accurate. Think New York, Nagoya, Guangzhou, Mumbai, Miami, several cities along the African coast, etc.

Opinions among scientists active in this field remain divided. Some, like the British Antarctic Survey’s Richard Hindmarsh believe that sea level will not rise by more than a metre by the end of the century, while others, like Pennsylvania State University glaciologist Richard Alley think that the new predictions “should not be considered to be a ‘worst case’ scenario”.

On one point, however, there is consensus: to halt the ocean from rising altogether would require that we reduce carbon emissions to zero, and quickly.

- Andreas is a freelance writer with a PhD in geochemistry. Follow him on Twitter: @Andreas_Spath

Send your comments to Andreas

Disclaimer: News24 encourages freedom of speech and the expression of diverse views. The views of columnists published on News24 are therefore their own and do not necessarily represent the views of News24.

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