I . WHAT' S HAPPENIN G TO GLOBA L CLIMAT E
Soaring Temperatures at the Poles Antarctica appears to be warming faster than anywhere else on the planet and grass is now beginning to push up from what was frozen wasteland just a few years ago. Penguins, in particular, are suffering from the heat and a number of their breeding colonies are now threatened with extinction. Meanwhile, in the Alaskan Arctic, Eskimo communities are becoming increasingly worried at the signs of warming all around them. The ice is melting, the tundra is drying, summer rainfall is significantly less and the winters markedly warmer. Melting permafrost is threatening communities with unprecedented landslides and storms at sea are getting wilder. All such signs have been predicted in the IPCC models, but not for now - for fifty years hence.6
might have to spend up to $300 billion just for coastal protection.7
The Met Office estimates that with coastal protection remain ing as it is but the sea rising, in the mid-21st century as many as 78 million people worldwide, but especially in south Asia and the small island states, could be at risk from wild storm conditions. That evaluation takes population growth into account and espe cially the demographic factors which lead to more people settling in low-lying coastal areas. The claim is that with 'evolving pro tection' the numbers of people at risk would be reduced by 28 mil lion to 50 million overall: but all that is without taking any Antarctic ice-melting into account. The number at risk would rise tenfold or more were the sea to rise at double the rate indicated from today's climate models.8
Storm surge and salt-wate r intrusio n The problem is not just sea-level rise on its own. Other factors, such as spring tides, heavy rain inland, deep depressions at sea and storm-force winds can turn what appears to be a minimal sea-level rise into a catastrophe. In Britain we saw a foretaste of what can happen 45 years ago, on January 31st 1953, when a deep depres sion swung around Scotland and headed south towards the Nether lands. At the centre of the depression, the pressure had fallen by 56 millibars, an incredible amount, and that alone was sufficient to raise the level of the sea by half a metre. To add to that, the stormforce winds generated by the depression drew up waves as high as six metres. Meanwhile heavy rains inland had caused floods over low-lying land towards the coast. As a final stroke, it happened to be the time of a strong spring tide when the Sun and the Moon were aligned. Quite apart from the waves, the average height of the sea was two metres higher than normal in Lincolnshire, 2.5 metres up in the Thames estuary and over three metres up in the Netherlands. By the end of that ferocious night the North Sea had breached the line of dykes protecting the land in Holland and one-sixth of all Holland was under sea-water. The death toll was 264 people drowned in south-east England and 1,835 in the Netherlands.9
The Chinese coast is particularly subject to high sea-levels because of strong depressions and storm-force winds. During typhoons, surges of up to five or more metres are not unusual. A sea-level that started a metre or so higher combined with such storms would wreak havoc. Some parts of the world are sinking, for instance around the Black Sea and parts of Indonesia. Gener ally such subsidence is at a rate of around 30 centimetres a centu ry, although much higher rates of several metres are also known. Indonesia has 15 per cent of all the world's coastlines and as much as 40 per cent of its land surface is vulnerable to rising sea-levels. As elsewhere in the Tropics, one of the most important natural defences against the incursion of the sea - the mangroves - have been decimated to make way for shrimp. In Thailand, around the Bight of Bangkok, the destruction of the mangroves has led to seawater intruding inland far enough to make rice-growing impossi ble over a wide area.10
Salt-water intrusion is already a serious problem in the mouth of the River Rhine, penetrating as much as 50 kilometres upstream. In the Netherlands, according to Gerrit Hekstra in the Ministry of the Environment, it might become necessary to flood reclaimed land with fresh water from the Rhine, just to keep seawater at bay. In the UK too, the government has decided to aban don the age-long struggle to protect vulnerable coastlines, such as along the Norfolk coast: instead, the idea is to allow salt marshes to re-establish themselves as the primary barrier against sea rise and sea surges.
Flooding nuclear power station s Meanwhile, several of the UK's nuclear power plants, such as at Hinkley Point and Sizewell, are vulnerable to sea-level rise and storm-force sea surges. The Magnox station, Sizewell A, for instance, is sited just a few metres above sea-level in an area where sea-levels are rising at twice the national level. And the reactor at Bradwell is even lower.
The threats to safety from storms and flooding are not idle. In the late 1980s storm-force winds and incoming sea spray knocked out the incoming electricity supply to the Hinkley Point site. The operators, the Central Electricity Generating Board, had difficulty getting auxiliary power back-up switched on and the site was without power for as long as 20 minutes. It was potentially an extremely dangerous situation, with the twin AGR reactors heat ing up because of the failure of the gas coolant pumps to take away the residual heat produced by fission products in the fuel. As the nuclear physicist Richard Webb has shown, had the reactors not shut down at the moment of the power cut, they could have overheated and exploded." Worldwide, many other nuclear power stations are sited on the coast, some in areas that would be threat ened by sea-level rise. Nuclear power stations, particularly in the United States, now keep all their nuclear waste in cooling ponds on site, within the containment structure of the reactor. Those ponds need active cooling 24 hours a day every day. Any threat to the reactor from sea-level rise is therefore magnified because of the presence of such waste. Chemical waste dumps in low-lying areas close to coastlines, such as Pitsea in Essex, could also be swamped because of a rising sea combined with sea surges. Such flooding would spell catastrophe for groundwater supplies as a result of toxic chemical contamination.
The consequences of sea-level rise are unthinkable, particularly i f the ice-sheets begin melting and slip into the sea. Major capital cities, such as Bangkok may have to be abandoned, or protected at great expense through a system of massive dykes and barriers. The Netherlands is a past master at coastal protection, but with every metre rise in sea-level the cost of protection increases dispropor tionately. There is already great cause for concern, not only because of the threat to cities, but also because a large proportion of the world's best agricultural land will fall victim to the waves.
Dr Grover Foley works as a writer in Sydney, Australia and in the Philippines. He was formerly an editor for the Gaia Foundation.
References: 1. G. P. Hekstra, Global Warming and Rising Sea Levels: The Policy Implications, The
Ecologist, Vol.19, No.l , 1989. 2. Climate Change and its impacts: a Global Perspective, The Met Office, 1997, pi4 . 3. Rick Frolich, New Scientist, Vol. 124, Nov. 4, 1989. 4. W. Krabill, Rapid Thinning of Parts of the Southern Greenland Ice Sheet, Science, Vol. 283. No.5407, Issue 5 March 1999. pp 1522-1524. 5. Op.cit.l. 6. US EPA Office of Policy, Planning and Evaluation: Policy Options for stabilizing
Global Change, December 1990. 7. R. Scherer, Science, Vol. 281, p.82, 1998. 8. H. H. Lamb, Climate History and the Modern World, Methuen, 1982 9. Op.cit.l. 10. R. E. Webb, Hinkley Point: Nuclear Accident Hazards, available from the author,
June 16th, 1989. 11. Kieran Mulvaney, Arctic Voices, New Scientist, Nov. 14, 1998.
The Ecologist, Vol. 29, No 2, March/April 1999 1. What's happening to global climate?
How Global Warming
Could Cause Northern Europe to Freeze
- B Y PETER BUNYARD
Warmer temperatures over Greenland and the Arctic because of global warming could cause the Gulf Stream - on which northen Europeans depend for
their mild climate - to slow down and even cease. Were that to occur, Northern
Europe would be plunged into winters that resemble those of the frozen
wastelands of Labrador and Siberia.
Every year 3,300 cubic kilometres of fresh water run off into the Arctic Ocean, adding some thirty centimetres of fresh water to the surface and reducing its salinity. That input of fresh water is a critical component of the process that drives the major ocean currents, first by making the sea less salty so that the freezing point rises and second, as a consequence of ice forming more easily, leaving saltier, denser, waters behind that tend to sink. In effect, the freshwater flow impinges on the rate and timing of the sinking of the surface waters of the upper north Atlantic. Once the waters have sunk, they flow back along the sea-floor all the way down to Antarctica where they join the circumpolar current before moving back to the Tropics and up north. The complete journey - oceanographers call it the conveyor belt circulation may take up to one thousand years.
That 'thermohaline' sinking of the surface waters in the north Atlantic has a major consequence for the countries of northern Europe, in particular Ireland, Britain and Scandinavia as well as the countries such as the Netherlands. It draws the Gulf Stream along behind it, together with all the heat that the ocean has
absorbed when down in the Tropics.
In its full glory the Gulf Stream carries warm water to a depth of up to 100 metres at rates of up to 8 kilometres an hour and pen etrates right up into the Arctic Circle, to the north of Scandinavia, bearing with it a climate that makes life just about tolerable, even in the thick of the winter. The energy it carries in the form of heat is equivalent to 100 times the entire use of energy in human soci eties across the world or put another way, more than 27,000 times the UK's electricity-generating capacity. In terms of temperature the Gulf Stream heats the surface over a wide area by at least 5°C. Were the Gulf Stream to fail, temperatures over northern Europe would plummet by more than 10°C during the winter months. North Europe would have a climate comparable to Labrador or conceivably Siberia: just how it would support its current popula tion is difficult to imagine. Both Labrador and Siberia are 'waste lands' with very small populations relative to their size.
I f the Gulf Stream were like 'ole man river that just keeps on rolling' we would have little to worry about, at least on that score. But, as we have recently discovered from looking at fossilised life
When the Gulf Stream Runs Cold Compute r simulatio n show s globa l warmin g coul d eventuall y shu t dow n th e Gul f Strea m plungin g Britai n int o a min i ic e a
As the pumps weaken, the currents slow down and may suddenly switch off
I The pumps are powered
I by high salt concentrations | near the waters surface. | Melting ice dilutes the salt and weakens the pump
m The Gulf Stream
brings warm water from the tropics as part of a worldwide network of ocean currents
The system depends on so-called "natural pumps" around Greenland which draw warm water up towards northwest Europe and send cold water back southwards
Were the Gulf Stream to fail, temperatures over northern Europe would plummet by more than 10°C during the winter months. North Europe would have a climate comparable to Labrador or conceivably Siberia: just how it would support its current population is difficult to imagine.
on the ocean floor and from geological evi dence, the Gulf Stream has had a history of stalling or having its circulation greatly cur tailed, leaving northern waters deprived of its vital heat and climate-moderating influence. Paradoxically that 'stalling' appears to have occurred following somewhat warmer periods during ice-ages when vast chunks of ice have slid from the interior of the North American continent through Hudson Bay and into the northern ocean. In essence, the injection of vast quantities of fresh water into the sea prevented the sinking of cold salty waters. Climatologists are now concerned that the flush of fresh water
The Ecologist, Vol. 29, No 2, March/April 1999