Scientists will warn this week that rising sea levels, triggered by
global warming, pose a far greater danger to the planet than previously
estimated. There is now a major risk that many coastal areas around the
world will be inundated by the end of the century because Antarctic and
Greenland ice sheets are melting faster than previously estimated.
Low-lying areas including Bangladesh, Florida, the Maldives and the Netherlands face catastrophic flooding,
while, in Britain, large areas of the Norfolk Broads and the Thames
estuary are likely to disappear by 2100. In addition, cities including
London, Hull and Portsmouth will need new flood defences.
now clear that there are going to be massive flooding disasters around
the globe," said Dr David Vaughan, of the British Antarctic Survey.
"Populations are shifting to the coast, which means that more and more
people are going to be threatened by sea-level rises."
The issue is set to dominate the opening sessions of the international climate change
conference in Copenhagen this week, when scientists will outline their
latest findings on a host of issues concerning global warming. The
meeting has been organised to set the agenda for this December's
international climate talks (also to be held in Copenhagen), which will
draw up a treaty to replace the current Kyoto protocol for limiting
carbon dioxide emissions.
And key to these deliberations will be
the issue of ice-sheet melting. The International Panel on Climate
Change (IPCC) - when it presented its most up-to-date report on the
likely impact of global warming in 2007 - concluded that sea-level
rises of between 20 and 60 centimetres would occur by 2100. These
figures were derived from estimates of how much the sea will increase
in volume as it heats up, a process called thermal expansion, and from
projected increases in run-off water from melting glaciers in the
Himalayas and other mountain ranges.
But the report contained an
important caveat: that its sea-level rise estimate contained very
little input from melting ice sheets in Antarctica and Greenland. The
IPCC forecast therefore tended to underestimate forthcoming changes.
IPCC felt the whole dynamics of polar ice-sheet melting were too poorly
understood," added Vaughan. "However, we are now getting a much better
idea of what is going on in Greenland and Antarctica and can make much
more accurate forecasts about ice-sheet melting and its contribution to
From studying satellite images, scientists have
watched the sea ice that hugs the Greenland and Antarctic shores
dwindle and disappear. Sea-ice melting on its own does not cause ocean
levels to rise, but its disappearance has a major impact on land ice
sheets. Without sea ice to prop them up, the land sheets tip into the
water and disintegrate at increasing rates, a phenomenon that is now
being studied in detail by researchers.
"It is becoming
increasingly apparent from our studies of Greenland and Antarctica that
changes to sea ice are being transmitted into the hearts of the
land-ice sheets in a remarkably short time," added Vaughan. As a
result, those land sheets are breaking up faster and far more melt
water is being added to the oceans than was previously expected.
revisions suggest sea-level rises could easily top a metre by 2100 - a
figure that is backed by the US Geological Survey, which this year
warned that they could reach as much as 1.5 metres.
addition, in September, a team led by Tad Pfeffer at the University of
Colorado at Boulder published calculations using conservative, medium
and extreme glaciological assumptions for sea-level rise expected from
Greenland, Antarctica and the world's smaller glaciers and ice caps.
They concluded that the most plausible scenario, when factoring in
thermal expansion due to warming waters, will lead to a total sea level
rise of one to two metres by 2100.
Similarly, a commission of 20
international experts, called on by the Dutch government to help plan
its coastal defences, recently gave a range of 55cm to 1.1 metres for
sea-level rises by 2100. "Equally important, this commission has
highlighted the fact that sea-level rise will not stop in the year
2100," said Professor Stefan Rahmstorf of Potsdam Institute for Climate
Impact Research. "By 2200, they estimate a rise of 1.5 to 3.5m unless
we stop the warming. This would spell the end of many of our coastal
This point was backed by Dr Jason Lowe of the Hadley
Centre, the UK's foremost climate change research centre. "It is still
not clear exactly how much the sea will rise by the end of this
century, but it is certain that rises will continue for hundreds of
years beyond that - even if we do manage to stabilise carbon dioxide
emissions and halt the rise in atmospheric temperature. The sea will
continue to heat up and expand. In addition, the Greenland ice sheets
will continue to melt," he said.
This latter effect could,
ultimately, have a particularly destructive impact. Scientists have
calculated that if industrial emissions of carbon dioxide and other
greenhouse gases eventually produce a global temperature increase of
around 4C, there is a risk that Greenland's ice covering could melt
completely. This could take several hundred years or it might require a
couple of thousand. The end result is not in doubt, however. It would
add around seven metres to the planet's sea levels. The consequence
would be utter devastation.
Such a scenario is distant, but real,
scientists insist. However, at present, the most important issue, they
argue, is that of short-term sea-level rises: probably around one metre
by 2100. When that occurs, the Maldives will be submerged, along with
islands like the Sunderbans in the Bay of Bengal, and Kiribati and
Tuvalu in the Pacific. The US - which has roughly 12,400 miles of
coastline and more than 19,900 square miles of coastal wetlands - would
face a bill of around $156bn to protect this land. Cities such as
London would require massive investments to provide defences against
the rising waters. Others, such as Alexandria, in Egypt, would simply
Rising oceans will also contaminate both surface
and underground fresh water supplies, worsening the world's existing
fresh-water shortage. Underground water sources in Thailand, Israel,
China and Vietnam are already experiencing salt-water contamination.
farmland will be wiped out, triggering massive displacements of men,
women and children. It is estimated that a one-metre sea-level rise
could flood 17% of Bangladesh, one of the world's poorest countries,
reducing its rice-farming land by 50% and leaving tens of millions
Such destruction would not be caused merely by
rising sea levels, however. Other effects of global warming will also
worsen the mayhem that lies ahead: in particular, the increase in major
storms. "When we talk about the dangers of future sea-level rises, we
are not talking about a problem akin to pouring water into a bath,"
added Dr Colin Brown, director of engineering at the Institution of
Mechanical Engineering. "Climate-change research shows there will be
significant increases in storms as global temperatures rise. These will
produce more intense gales and hurricanes and these, in turn, will
produce massive storm surges as they pass over the sea."
result will be the appearance of the super-surge, a climatic double
whammy that will savage low-lying regions that include Britain's
south-eastern coastline, in particular East Anglia and the Thames
Estuary, along with cities such as London, Portsmouth and Hull, which
are rated as being particularly vulnerable to sea-level rise.
addition to these hotspots, the country will also face massive
disruption to its transport and energy systems unless it acts swiftly,
according to a report - Climate Change, Adapting to the Inevitable -
published last month by the Institution of Mechanical Engineers. Many
rail lines run along river valleys that will be flooded with increased
regularity while bridges carrying trains and lorries often cross
shipping lanes and may have to be redesigned to accommodate rising
"Power supplies will also be affected," added
Brown. "The Sizewell B nuclear plant has been built on the Suffolk
coast, a site that has been earmarked for the construction of several
more nuclear plants. However, Sizewell will certainly be affected by
rising sea levels. Engineers say they can build concrete walls that
will keep out the water throughout the working lives of these new
plants. But that is not enough. Nuclear plants may operate for 50
years, but it could take hundreds of years to decommission them. By
that time, who knows what sea-level rises and what kinds of inundations
the country will be experiencing?"
Most scientists believe
Britain remains relatively well placed to combat sea-level rises. "The
government has been fairly far-sighted over this issue, with projects
such as Thames Estuary 2100 being set up to prepare flooding defence
projects," said Professor Robert Nicholls, of Southampton University.
does not stop the controversy, however. In its report, the Institution
of Mechanical Engineers warned that many areas would have to be
abandoned because they are simply too expensive to protect. In
particular, large areas of the Norfolk coastline would be left to be
inundated, a massive loss of human habitat.
But this approach
represents an abrogation of national duty to many people - particularly
those whose homes will be destroyed, individuals such as Martin George,
former chairman of the Broads Society. "A country that has the
technological know-how to extract oil and coal from below the North Sea
should surely be capable of finding a way to protect a concrete sea
wall against the effects of climate change. We should do our damnedest
to safeguard our heritage," he said.
- Additional research by Lisa Kjellsson
Why the sea is rising
Thermal expansion. All bodies expand when they are heated, and that is
true for the water that covers 70 per cent of the planet. The oceans
are expanding - upwards. It is estimated this increase in volume will
raise levels by 10-40 cms.
- Melting glaciers and mountain ice
caps - outside Greenland and Antarctica - are also adding water to
rivers that flow to the oceans. However, these remain a modest source
of sea-level rise. Possibly around 10 cms.
- The Greenland and
Antarctic ice sheets represent vast reserves of frozen fresh water. The
former would add 7m to sea levels if melted completely; the latter
would bring a further 60m rise to the levels of the world's oceans.