Walrus on ice floe; Greenpeace tour investigating climate change effects, Chukchi Sea, Alaska.
Imagine a world in which 17 million people are fleeing sea-rise
in Bangladesh. A world in which villages that rely on glacial melt
for their water supplies become ghost towns as the last of the ice
disappears. A world in which polar bears are extinct in the wild. A
world in which entire seaside economies and livelihoods are wiped
out by a rise in sea level that is measured in meters. Now imagine
that aspects of this world could be upon us within the lifetimes of
children being born today -- and in some scenarios, in our own
lifetimes.
It's a chilling vision of a warming world.
"Mass Balance of the Cryosphere" (Cambridge University Press)
has been written by a team of 23 scientists and edited by Dr
Jonathan Bamber and Dr Anthony Payne of Bristol University. It
focuses on two key components of this sensitive environment: land
ice, in the form of ice sheets, caps and glaciers, and sea ice.
These are important indicators of both short and long-term climate
change. The book warns that the cryosphere is far more sensitive to
climate change than has been generally accepted, and that we ignore
at our peril the dramatic and disturbing trends that have already
been observed globally.
Here are a few examples of the findings in the book:
- The Greenland ice sheet - the biggest ice mass in the Northern
Hemisphere - is melting around its margins. Some climate models
predict it could lose half its mass in the next 500-1000 years,
contributing 3 m to global sea level rise.
- The amount of Arctic summer sea ice has reduced dramatically in
the past 20 years and could disappear completely within an
estimated 100 years.
- Globally mountain and alpine glaciers everywhere are melting,
except for a few glaciers in Europe that are not retreating. The
rate of retreat is expected to accelerate over the next
century.
- Antarctica - the largest ice mass in the world - presents a
more complex picture, although parts of the West Antarctic Ice
Sheet and Peninsula ice shelves are in decline.
- Evidence indicates that some of the changes being seen in the
cryosphere are related to the underlying man-made component of
global warming.
Who needs ice?
The
implications of the decline of the cryosphere are far reaching and
go beyond merely losing snow and ice. Increased fresh water
influxes from the Arctic could trigger a slow down or diversion of
currents of the North Atlantic. What's commonly known as the Gulf
Stream is a part of a "conveyor belt" which brings warm water from
the Gulf of Mexico to the shores of Europe, circles up to the
Arctic, then plunges back into the deep ocean for another cycle.
Without its warming effect, North Western Europe would have a
climate similar to Greenland. Changes to the North Atlantic
currents could impact other sea currents and temperatures around
the globe, setting off chain-reaction climate impacts.
As icesheets retreat, snow which once reflected sunlight and
heat back into the atmosphere gives way to earth and rock which
absorb its heat. As a result, we may well see accelerated warming
in the Arctic, and with it accelerated melt. As the ice disappears,
habitats for Arctic animals such as polar bears, seals and other
large predators are lost.
Depending on how much of the cryosphere is lost, global sea
level rise could be measurable in metres. A sea level rise of only
1.5m would displace up to 17 million people in Bangladesh
alone.
And beyond the icesheets, glacial retreats in many parts of the
world will mean reduced water for human consumption, agriculture
and hydro-electricity, shifting economic and social patterns.
Sea Ice
There
are warning signs that during the latter half of the 20th Century
the Arctic has undergone substantial climate change. One of the key
indicators is sea ice extent and thickness, both of which have
shown a measurable and disturbing decrease during the last half of
the century.
If summer rates of ice decrease continue or accelerate there
could, potentially, be no summer sea ice in the Arctic within 100
years or less. This will have major impacts on energy and moisture
exchange and consequently on the climate of the Northern
Hemisphere, including the risk of altering or slowing down the Gulf
Stream.
The consequences of such dramatic changes in sea ice cover are
the subject of a number of climate modelling studies and it is,
currently, too early to say precisely what the implications of
these changes might be. However such changes are likely to include
impacts on wildlife and indigenous populations, as well as
increasing the positive feedback of higher temperatures as the ice
disappears.
There is general agreement that acceleration in melting globally
will take place over the next century if greenhouse gas emissions
continue to accelerate at the rate they have done for the past 50
to 100 years. Extrapolation of the present trend suggests a
reduction in area of the Arctic sea ice of 4.7 million square km by
2100, i.e. virtually complete elimination of the Arctic ice pack in
summer. If the predictions of warming in the Arctic over the same
time period are taken into account, the rate of melting could be
considerably faster as the Arctic is particularly sensitive to
temperature increase.
Greenland
In lower elevations in Greenland, ice sheet loss is
conservatively estimated to be 50 cubic km/year, which is
equivalent to 0.13 mm/year of sea level rise. As most ice sheet
data has been collected only over the past few decades or less, it
is difficult to know how long this negative imbalance has existed
but it has certainly been enhanced by the warming during the 1990s,
and the record melt extent observed in 2002.
The thinning rates cannot be explained by increased surface
melting alone, so the implication is that something else is causing
this. Extensive thinning in several separate areas suggests that
this may be climatically induced, for example, by increased surface
melt water reaching the bedrock on which the ice sits, causing the
ice to slide on its bed. If true, this is of profound significance
as it suggests that the dynamic response time of the ice sheet is,
potentially, much shorter than previously believed. Such a rapid
dynamic response to changing climate has not, to date, been
satisfactorily incorporated in modelling studies, nor have the
complex interactions between ice, the oceans, and the atmosphere.
All of which means that ice loss could in fact be much faster and
greater than currently predicted. This could mean that some of the
impacts previously predicted to occur hundreds of years in the
future could happen much faster, perhaps within a century.
Antarctic Ice Sheet
While
the East Antarctic Ice Sheet appears to be close to balance; it is
a different story on the West Antarctic Ice Sheet. There has been a
significant warming on the peninsula of about 4 degrees Celsius in
the last 50 years, associated with a regional decline in sea ice.
While this is a strong signal, it's quite localised. Ice shelves
along the Peninsula are only a few hundred metres thick and float
on the surface of the ocean and are quite sensitive to changes in
the ocean temperature and ocean circulation. Two major ice shelf
collapses have been observed over the last decade along the
Peninsula.
Glaciers and ice caps
Water stored in glaciers and icecaps around the world would
contribute 0.5m sea level rise if they all melted. This is small
compared to the 68.3m sea level rise that total melting of the
Greenland and Antarctica ice sheets would cause (6m and 62m,
respectively). However, glaciers respond much more rapidly than ice
sheets. Glacier and ice cap response times are typically below 100
years, which means that the bulk of the cryosphere's contribution
to human-induced sea-level rise over the coming century is likely
to come from these types of ice mass. There are more than 160,000
glaciers worldwide, making measurement of glacier mass balance very
difficult, but existing research indicates that glacial loss is
responsible for between 0.22mm to 0.25mm a year sea level rise.
More complex analysis is needed to understand how glaciers react
once melting begins, and what a partial loss of glacier ice would
mean for its water flow system. The assessment of historical and
predicted future contributions to sea level from glaciers is still
in its infancy. Changes in ice amounts have clearly been large and
are likely to continue to be important over the coming century,
however many challenges still remain in their accurate
measurement.
Sea ice loss - one example of how this might affect the environment
According
to the Third Assessment Report of Intergovernmental Panel on
Climate Change (IPCC), a reduction in sea ice will reduce ice
edges, which are prime habitat for marine organisms. Habitat loss
for some species of seal, walrus, and polar bear results from ice
melt, and animals at the top of the food chain - with their
low-reproductive rates - are vulnerable to changes in the polar
marine food chains. Some animals may be threatened (e.g., walrus,
polar bear, and some species of seal), whereas others may flourish
(e.g., some species of fish and penguins).
According to Dr Andrew DeRocher of the University of Alberta,
who is a world authority on polar bears, if the sea ice habitat
continues to deteriorate at current rates, polar bears and their
prey, such as ringed and bearded seals, would be unlikely to retain
their current population sizes and distribution. At some point, if
the loss of sea ice became so severe that all the Arctic sea ice
was lost for a substantial part of the year, we may lose polar
bears as a wild species.
The whole Arctic marine ecosystem is tied to the presence and
dynamics of the sea ice. The main productivity bloom that occurs
each spring is exploited by both resident species and migrants,
which is tied to the melting of the annual sea ice. Some arctic
species travel halfway around the world to exploit the food sources
that flourish along the edge of the melting ice. Life along the
edge of the melting sea ice is the basis of Arctic marine
ecosystems. Removing this dynamic would have profound consequences
for all marine life. If the sea ice is drastically reduced or the
timing changed, we can expect the loss of many species that are
reliant upon this special habitat. It is likely that we will see
species expand from southern latitudes to occupy some of these
environments but it is impossible to say which ones. It is hard to
understand the dynamics of Arctic ecosystems and even harder to
predict with any certainty what may happen if the climate changes
substantially.
What causes climate change
Climate
change is directly linked to our fossil energy consumption. Global
warming of the earth is the result of increasing greenhouse gas
emissions. The principal cause is carbon dioxide (CO2), which is
released when fossil fuels such as coal, oil and gas are
burned.
In 2001 the IPCC issued its Third Assessment Report, which found
new and stronger evidence that most of the observed warming of the
past 50 years is attributable to human activities. It found that
about three-quarters of the anthropogenic (human created) emissions
of CO2 during the past 20 years are due to fossil fuel burning.
The IPCC also reported that the average global temperature was
projected to rise between 1.4 and 5.8 degrees Celsius in the next
100 years. This is a large increase over projections in the Second
Assessment Report (1995), which estimated the increase in
temperature to be between 1 and 3.5 degrees. In addition,
predictions suggest that this warming will be larger in the polar
regions, exacerbating the worrying trends already observed. A
2-degree increase would produce substantial damage to or loss of
many natural ecosystems, lead to spread of diseases such as malaria
and cause substantial damage to agriculture in developing
countries.
Conclusion
Scientific understanding of the Earth's climate and how humans
are affecting it is constantly improving, but there is still much
to learn about what climate change will mean to natural systems
such as the cryosphere. For most people polar regions are remote
places that are out of sight and perhaps out of mind. They are,
however, highly sensitive to climate change with strong feedbacks
at play. Dramatic and disturbing trends have already been observed
in the Arctic, Greenland, the Antarctic Peninsula and in glaciers
globally.
Risk of sea level rise that could displace millions of people;
radical alterations of ocean currents that in turn affect regional
climate; loss of glaciers that provide water people need to live;
changes to the food chain and even possible dramatic and rapid
irreversible changes to the global climate - these are some of the
possible impacts of climate change.
The Kyoto Protocol is the one global mechanism to address
climate change. As the latest round of Kyoto talks get underway in
Milan in December 2003, evidence about the serious impact of
climate change is mounting. Governments and industry must take
action to protect the climate now and stop trying to weaken the
Protocol. It is not only the cryosphere at risk, but also
potentially the global climate system.
More Information
Visit our document library of in-depth information on
what's at stake at this month's meeting of the UN Framework
Convention on Climate Change in Milan.
Kyoto Protocol Thermometer from United Nations
Framework Convention on Climate Change
Greenpeace Climate Change pages
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