For example, the natural flows of carbon could change in a way that
allows feedbacks to come into play. ‘Some of the feedbacks are potentially
large and could significantly influence future carbon dioxide levels,’ says
the first chapter of a report by the science working party of the Intergovernmental
Panel on Climate Change.

In the longer term, the possibility of ‘unexpected large changes’ in
the mechanisms of the carbon cycle as a result of human-induced climate
change cannot be ruled out, says the report. And it also repeats earlier
warnings that the climate change expected as the planet warms could come
in abrupt shifts, rather than as gradual change.

The working party’s report, which is currently in a second draft, is
being finalised at a meeting being held in Windsor this week. It will form
one of three background reports which have been prepared over the past 18
months for discussions at the World Climate Conference in Geneva in November,
covering the scientific, economic and political aspects of climate change.

The scientific working party is made up of leading international authorities
on the science of climate change, and is chaired by John Houghton, the head
of Britain’s Meteorological Office. In its report, the chapter on the science
of greenhouse gases points out that the amount of carbon dioxide in the
atmosphere today is already rising faster than during earlier sudden increases.

Studies of ice cores from Greenland suggesting past shifts of about
50 parts per million of volume (ppmv) in less than 100 years have been associated
with ‘abrupt, drastic climate events’. And concentrations have risen from
315 ppmv to 354 ppmv in the past 30 years alone.

Even disregarding the expected assistance of feedback mechanisms, computer
models predict that atmospheric levels of carbon dioxide will reach 600
ppmv by 2050 if emissions continue to grow at their present rate, and 450
ppmv if emissions are kept at 1990 levels.

These predictions, however, are conservative, as the models do not take
into account those feedback mechanisms which, although understood in general
terms, cannot be quantified specifically enough for inclusion in complex
computer programmes.

Alarmingly, however, almost all the feedbacks listed by the report seem
likely to enhance rather than diminish the greenhouse warming and accelerate
the pace of climate change. For example, the oceans will not conveniently
absorb increasing amounts of atmospheric carbon dioxide at the same pace
as the increases.

Climate change is also expected to alter the distribution and composition
of species in marine ecosystems, affecting the amount of carbon dioxide
these species absorb. The report adds that as the oceans heat up, warmer
sea temperatures are likely to speed up the decomposition of dissolved organic
carbon, converting it into carbon dioxide and leading to a greater increase
in atmospheric concentrations of the gas.

On land, plants will respire at a faster rate as air temperatures rise,
with a corresponding increase in the amounts of carbon they release into
the atmosphere. According to the report, estimates suggest the additional
flux could be significant, perhaps ‘one or a few’ billion tonnes of carbon
a year.

It also corroborates the fears of large-scale forest dieback raised
in the 1987 Bellagio report. If the rate of climate change is fast, the
report says, large areas of forest may be unable to adapt rapidly enough
and could die off, releasing more carbon dioxide.

The scientists also expect ‘numerous potentially important’ feedbacks
between climate change, tropospheric ozone and hydroxyl radicals, highly
reactive chemical agents. While it is not yet possible to quantify these
feedbacks, the report says, changes in cloud cover, precipitation and circulation
patterns – as well as changes in the biospheric production of methane, carbon
monoxide, non-methane hydrocarbons and nitrogen oxides – will modify reactions
controlling amounts of ozone and hydroxyls.

The draft report has been compiled by the United Nations Environment
Programme’s International Committee on the Effects of Ozone Depletion. It
shows that the ozone layer is now becoming depleted. While additional research
is still needed, the report says it is clear that ozone loss poses significant
threats to human health and to the world’s ecosystems.

Phytoplankton fix more than half the carbon dioxide produced globally
each year. They are highly sensitive to increased levels of ultraviolet
radiation because they lack the protective outer layers enjoyed by higher
plant and animal species.

The report warns that the adverse effects on phytoplankton populations
will have long-term consequences for global climate and will make sea levels
rise even more than predicted.

‘A 10 per cent decrease in carbon dioxide uptake by the oceans would
leave about the same amount of carbon dioxide in the atmosphere as is produced
by fossil fuel burning,’ the report says. The marine food web will be thrown
into disorder as plankton populations diminish and juvenile fish, crabs
and shrimp are damaged or killed by the extra ultraviolet radiation.

On land, many plant species will not grow as well as they should; germination
and flowering rates will be inhibited, and crop yields will drop.

The report also warns of possible drastic nitrogen deficiencies for
plant ecosystems like rice paddies. Organisms like the cyanobacteria which
fix nitrogen in tropical rice paddies are extremely sensitive, even to current
levels of ultraviolet radiation.

‘The annual nitrogen assimilation by this group of (prokaryotic) organisms
alone has been assumed to amount to 35 million tons, which exceeds the 30
million tons of artificial nitrogen fertiliser produced annually. The amounts
of artificial nitrogen fertiliser necessary to compensate for a substantial
loss will stress the capabilities of less developed countries.’

As far as humans are concerned, ozone depletion seems likely to increase
the number of outbreaks of infectious diseases. The report says normal immune
systems become less effective when they have been exposed to increased amounts
of ultraviolet ‘B’ radiation (UV-B). The amount of this harmful light that
reaches Earth is expected to increase as stratospheric ozone diminishes.
Outbreaks of infectious diseases like measles, herpes, tuberculosis and
leprosy can be expected to occur on a broader scale and with greater severity,
says the report.

Compounding these problems will be a reduction in the effectiveness
of vaccinations. When antigens (substances foreign to the body which stimulate
its defences) are injected through human skin that has been exposed to UV-B,
they induce tolerance to a disease, rather than immunity.

Increases in UV-B are also expected to spark a significant increase
in the development of cataracts. Unlike the skin, the eye does not develop
any tolerance to UV-B. Instead, it becomes more sensitive with repeated
exposures. For every 1 per cent depletion of ozone, an extra 100,000 people
will go blind, predicts the report.

Pollution will also become more of a problem as ozone depletion continues.
The extra ultraviolet radiation getting through to the lower layers of the
atmosphere will increase amounts of reactive radical molecules like hydroxyls
in the troposphere (the lowest layer of the atmosphere). These chemicals
could cause significant increases in levels of tropospheric ozone and other
potentially harmful pollutants like hydrogen peroxide and acids.

In addition, a range of materials will degrade faster under the increased
ultraviolet radiation. Plastics, rubber, wood, textiles and paints are all
expected to be affected. In a summary of its main concerns, the UN committee
says that additional research is needed to gain a deeper understanding of
the primary effects of ozone loss, especially in tropical and subtropical
areas where they are likely to be most marked. The summary calls for ‘global
action to prevent or mitigate the damage’.

A RISE in the sea level of 1 metre before the end of the next century would affect up to 300 million people, according to the chairman of the coastal impacts working group of the Intergovernmental Panel on Climate Change (IPCC).

Pier Vellinga, who also coordinates the Netherlands Climate Programme, says that the global cost of protecting human life and investment against a rise of this magnitude is likely to reach Pounds sterling 13.3 billion per year. Moreover, a Dutch study which assesses the most economic ways of dealing with rising sea levels shows that at least half the world will not be able to afford to build the dykes and barriers that would keep rising seas at bay.

The IPCC’s report estimates that in the US, it will cost $160 million (Pounds sterling 266 million) to protect vulnerable industries and investments against a rise in sea level of 1 metre. But the benefits of protection are far higher, at $2.1 billion (Pounds sterling 3.5 billion).

For a nation such as Bangladesh, however, where studies suggest that between 40 million and 80 million people are vulnerable to the effects of flooding and storms, the Dutch research shows that coastal protection would cost around Pounds sterling 332 million, five to 10 times as much as the economic benefits that would accrue. The same picture applies to nations such as the Gambia, Brazil, Vietnam and Mozambique.

The report recommends that in these circumstances, adaptation of land use, such as building mounds for use as sanctuaries, is more beneficial than the construction of costly protective works. It urges these nations to strengthen their political and planning procedures for dealing with sea level rises, rather than initiating the construction of protective defences.

Governments need to begin identifying regions at risk, it says. They should consider the type of protection they can afford to provide, assess the cost of protection compared with their GNP (see map), and establish what expertise they have available.

‘It is important to begin planning for drainage, early warning systems, emergency repairs and procedures for dealing with temporary refugees,’ says Vellinga. ‘Nations also need to establish what tax systems will be needed for relocation and planning, how infrastructures need to be adapted and what legal and institutional changes will be needed to permit land use adaptation.’

The report says that individual nations should devise equitable systems through which the population as a whole can share the cost of protecting people in a coastal zone at risk. It also discusses possible funding mechanisms by which the richer nations could offer assistance, for example if people need to be resettled in other countries should their own disappear completely beneath the ocean.

The report discusses the most cost-effective means to adapt land to deal with emergencies. It recommends the construction of mounds where people could take refuge from floods. Early warning systems will be crucial, it says, to allow people to reach the mounds, or higher land, in time. Efficient drainage systems are also essential to allow flood water to drain away rapidly.

‘It will probably be necessary to extend considerably the Southeast Asian practice of building houses on poles,’ says Vellinga, who is based at the Dutch Ministry of Housing, Physical Planning and the Environment in The Hague. He adds that even with measures such as this, rising waters are likely to displace tens of millions of people permanently.

Early warnings of what is to come are already evident. Around Jakarta, the seas are rising at the rate of 1.2 millimetresa year, and saltwater penetrates 15 kilometres inland. In China, Shanghai has already acted to protect its buildings against intruding sea water, which breaches sea walls in high seas. Mukan Han of the University of Beijing said in December at a conference in Cairo on climate change that a rise in sea levels of 50 centimetres would inundate the whole of Canton.

Education and information for people likely to be affected will be crucial to any response to flooding, says Vellinga.

The IPCC’s report, however, follows an announcement by American scientists who believe that rises in sea level may have been overestimated (This Week, 16 December). The rate of the rise depends on predictions of the time it takes to double the amount of carbon dioxide in the air.