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If greenhouse gas concentrations keep rising, climatic
changes are likely to result. Those changes will potentially
have wide-ranging effects on the environment and socio-economic
sectors.
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The projection of future climate change depends partly
on the assumptions made about future emissions of greenhouse
gases and aerosol precursors and the proportion of emissions
remaining in the atmosphere.
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Projected anthropogenic CO2
emissions from fossil fuel use, deforestation and cement
production for the six IPCC emission scenarios.
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Climate models calculate that the global mean surface
temperature could rise by about 1 to 4.5 centigrade by
2100.
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Models project an increase in global mean sea level of
between 13 and 94 cm by the year 2100.
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The potential impacts of climate change on the environment
and socio-economic systems can be understood in terms
of sensitivity, adaptability and vulnerability of the
system.
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Some reports suggest that increase in climate variability
or extremes has taken place in recent decades.
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Forests
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The figure shows a comparison of current vegetation zones
at a hypothetical dry temperate mountain site with simulated
vegetation zones under a climate-warming scenario.
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Cryosphere
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Ice draft in the 1990s is more than a meter thinner than it was 20 to 40 years earlier.
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Winter ice on the Tornio River in Finland has broken
up earlier and earlier since records began in 1693.
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Widespread loss of discontinous permafrost will trigger
erosion or subsidence of ice-rich landscapes, change
hydrologic processes, and release CO2
and methane to the atmosphere.
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Oceans and coastal areas
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The global conveyor belt thermohaline circulation is
driven primarily by the formation and sinking of deep
water (from around 1500m to the Antarctic bottom water
overlying the bottom of the ocean) in the Norwegian
Sea.
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Bangladesh, one of the world's poorest nations is also
the country most vulnerable to sea-level rise.
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The Nile Delta is one of the oldest intensely cultivated
areas on earth. It is very heavily populated, with population
densities up to 1600 inhabitants per square kilometer.
The low lying, fertile floodplains are surrounded by
deserts. Only 2,5% of Egypt's land area, the Nile delta
and the Nile valley, is suitable for intensive agriculture.
Most of a 50 km wide land strip along the coast is less
than 2 m above sea-level and is protected from flooding
by a 1 to 10 km wide coastal sand belt only, shaped
by discharge of the Rosetta and Damietta branches of
the Nile. Erosion of the protective sand belt is a serious
problem and has accelerated since the construction of
the Aswan dam.
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Rising sea level would destroy weak parts of the sand
belt, which is essential for the protection of lagoons
and the low-lying reclaimed lands. The impacts would
be very serious: One third of Egypt's fish catches are
made in the lagoons. Sea level rise would change the
water quality and affect most fresh water fish. Valuable
agricultural land would be innundated.
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Agriculture
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The figure shows change in cereals production under
three different GCM equilibrium scenarios (percent from
base estimated in 2060).
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In Uganda, the total area suitable for growing Robusta
coffee would be dramatically reduced with a temperature
increase of 2 centigrades.
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Freshwater resources
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Even if the world maintained the pace of the 1990s in
water supply development, it would not be enough to
ensure that everyone had access to safe drinkning water
by 2025.
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One study suggests that although global water conditions
may worsen by 2025 due to population pressure, climate
change could have a net positive impact on global water
resources.
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Human health
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Climate change and altered weather patters would affect
the range (both altitude and latitude), intensity, and
seasonality of many vector-borne and other infectioius
diseases.
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A warmer climate increases occasions of vector borne
tropical diseases. The figure depicts weeks of potential
dengue transmission under current temperature and 2°C
and 4 °C warming.
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Plasmodium vivax, with the Anopheles mosquito as a vector,
is an organism causing malaria. The main climate factors
that have bearing on the malarial transmission potential
of the mosquito population are temperature and precipitation.
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