|photo by IAN JOUGHIN
One heck of a big ice-cube: There are at least 22 million cubic kilometres of land ice on Antarctica, about 2.5 million cubic kilometres on Greenland and another 2.5 million cubic kilometres on the Arctic polar margins of Siberia, Northern Canada, Alaska and Asia. This is a total of about 27 million cubic kilometres of land based polar ice. A cubic metre of ice weighs about 900 million tons /tonnes. So, the land based polar ice is at least 27 million cubic kilometres that weigh 24,300,000,000,000,000 tons /tonnes. In English that is 24.3 million, billion tons.
The latest technical reports in Science, analysed by journalists at Time, National Geographic, ScienceMag, The Irish Times and most major news media say that is now accepted that the polar ice is now, 1951 to 2011, melting twice as fast as it did from 1900 to 1950, due to global warming. This has two impacts on the sea-level:
First – The higher global temperatures in the oceans expand the water because warm water is less dense than cold water (and rises to the surface). In the 111 years from 1900 to 2011, this expansion has increased sea-level by about 0.23mm per year – 25mm, about 1 inch in 111 years.
Second – The land based ice reduction through melting in the past 20 years is estimated to be 255 cubic kilometres weighing 230 billion tons. This has added a meagre 12mm, about ½ inch to the sea-level.
So, not much to worry about, then? “…Well not exactly Mr President.” National Geographic quote reports saying that by year 2100, sea-level will rise by the lowest estimate of 2 metres (6.5 feet) or by the higher estimates of 7 metres (23 feet). The news and analyses of New York’s devastating Hurricane Sandy woke us all up to the fact that storm-surges grow far larger as sea-level rises. The next batch of storms will do more damage.
The oceans have a surface area of 335 million square kilometres. Antarctica has an area of 13.8 million square kilometres which is 98% covered in ice, with a depth of up to 5 kilometres. Greenland, in the Arctic, has an area of 2.2 million square kilometres, with an ice cap of up to 2.6 kilometres. Should both the Antarctic and Arctic land based ice caps melt, the sea-level would rise 113 metres, or 370 feet. Eighty percent of all the people in the world live below 300 feet, on the coastal margins. Greater London is all below 300 feet. Florida’s east coast urban areas are below 30 feet. Manhattan Island rises just 36 feet above the ocean. The infamous settlement of Monmouth Junction in New Jersey is built at 135 feet above sea-level. The centre of Oxford, England is 200 feet above sea-level. SW2000 Telework Studies 1994.
While I don’t want to worry readers unduly, I think all the current published calculations are too conservative and too slow on time scale – by at least ten times. In 1994, long before my interests included polar-meltdown, I was asked to look at polar ice statistics for an environmental transport conference in New Zealand – near’ish to Antarctica. The data showed that if all the polar ice melted, sea-level would rise 113 metres (370 feet). It hasn’t all melted in millions of years, so it is unlikely to all melt now. How fast it is melting is a question with answers that have changed by a factor of 1,000 times in 20 years. I think, from reading scientific reports that the meltdown is happening far, far faster than responsible scientists are publicly reporting.
To set out possible scenarios we have to shift from scientific fact to fiction. The possible futures are scary for all except young, tough, rugged survivalists. The best advice at present for less gymnastic and non-military people is:
MOVE TO HIGHER GROUND.