| Berichte über den Klimawandel - Globale Berichte |
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IPCC-Bericht
zum Klimawandel - 4th Assessment Report |
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IPCC-Bericht
zum globalen Klimawandel |
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| Intergovernmental Panel on Climate Change - Fourth Assessment Report |
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| Climate
Change 2007: Climate Change Impacts, Adaptation and Vulnerability |
April
2007, Working Group II Contribution
Current
knowledge about observed impacts of climate change on the natural and human
environment
| Current knowledge about future impacts |
The
following is a selection of the key findings regarding projected impacts,
as well as some findings on vulnerability and adaptation, in each system,
sector and region for the range of (unmitigated) climate changes projected
by the IPCC over this century judged to be relevant for people and the
environment. The impacts frequently reflect projected changes in precipitation
and other climate variables in addition to temperature, sea level and concentrations
of atmospheric carbon dioxide. The magnitude and timing of impacts will
vary with the amount and timing of climate change and, in some cases, the
capacity to adapt. These issues are discussed further in later sections
of the Summary. More
specific information is now available across a wide range of systems and
sectors concerning the nature of future impacts, including for some fields
not covered in previous assessments.
top
| Fresh
water resources and their management |
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By
mid-century, annual average river runoff and water availability are projected
to increase by 10-40% at high latitudes and in some wet tropical areas,
and decrease by 10-30% over some dry regions at mid-latitudes and in the
dry tropics, some of which are presently water stressed areas. In some
places and in particular seasons, changes differ from these annual figures.
Drought-affected
areas will likely increase in extent. Heavy precipitation events, which
are very likely to increase in frequency, will augment flood risk. Adaptation
procedures and risk management practices for the water sector are being
developed in some countries and regions that have recognised projected
hydrological changes with related uncertainties.
In
the course of the century, water supplies stored in glaciers and snow cover
are projected to decline, reducing water availability in regions supplied
by meltwater from major mountain ranges, where more than one-sixth of the
world population currently lives.
Temperature
changes are expressed as the difference from the period 1980-1999. To express
the change relative to the period 1850- 1899, add 0.5°C.
Criteria
of choice: magnitude and timing of impact, confidence in the assessment,
representative coverage of the system, sector and region.
top
| Ecosystems |
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The
resilience of many ecosystems is likely to be exceeded this century by
an unprecedented combination of climate change, associated disturbances
(e.g., flooding, drought, wildfire, insects, ocean acidification), and
other global change drivers (e.g., land use change, pollution, over-exploitation
of resources).
Over
the course of this century net carbon uptake by terrestrial ecosystems
is likely to peak before midcentury and then weaken or even reverse, thus
amplifying climate change.
Approximately
20-30% of plant and animal species assessed so far are likely to be at
increased risk of extinction if increases in global average temperature
exceed 1.5-2.5°C.
For
increases in global average temperature exceeding 1.5-2.5°C and in
concomitant atmospheric carbon dioxide concentrations, there are projected
to be major changes in ecosystem structure and function, species - ecological
interactions, and species - geographic ranges, with predominantly negative
consequences for biodiversity, and ecosystem goods and services e.g., water
and food supply.
The
progressive acidification of oceans due to increasing atmospheric carbon
dioxide is expected to have negative impacts on marine shell forming organisms
(e.g., corals) and their dependent species.
top
| Food,
fibre and forest products |
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Crop
productivity is projected to increase slightly at mid to high latitudes
for local mean temperature increases of up to 1-3°C depending on the
crop, and then decrease beyond that in some regions.
At
lower latitudes, especially seasonally dry and tropical regions, crop productivity
is projected to decrease for even small local temperature increases (1-2°C),
which would increase risk of hunger.
Globally,
the potential for food production is projected to increase with increases
in local average temperature over a range of 1-3°C, but above this
it is projected to decrease.
Adaptations
such as altered cultivars and planting times allow low and mid- to high
latitude cereal yields to be maintained at or above baseline yields for
modest warming.
Increases
in the frequency of droughts and floods are projected to affect local production
negatively, especially in subsistence sectors at low latitudes.
Globally,
commercial timber productivity rises modestly with climate change in the
short- to medium-term, with large regional variability around the global
trend.
Regional
changes in the distribution and production of particular fish species are
expected due to continued warming, with adverse effects projected for aquaculture
and fisheries.
Assuming
continued greenhouse gas emissions at or above current rates and other
global changes including land use changes.
top
| Coastal
systems and low-lying areas |
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Coasts
are projected to be exposed to increasing risks, including coastal erosion,
due to climate change and sea-level rise and the effect will be exacerbated
by increasing human-induced pressures on coastal areas.
Corals
are vulnerable to thermal stress and have low adaptive capacity. Increases
in sea surface temperature of about 1 to 3°C are projected to result
in more frequent coral bleaching events and widespread mortality, unless
there is thermal adaptation or acclimatisation by corals.
Coastal
wetlands including salt marshes and mangroves are projected to be negatively
affected by sea-level rise especially where they are constrained on their
landward side, or starved of sediment.
Many
millions more people are projected to be flooded every year due to sea-level
rise by the 2080s. Those densely-populated and low-lying areas where adaptive
capacity is relatively low, and which already face other challenges such
as tropical storms or local coastal subsidence, are especially at risk.
The numbers affected will be largest in the mega-deltas of Asia and Africa
while small islands are especially vulnerable.
Adaptation
for coastal regions will be more challenging in developing countries than
developed countries due to constraints on adaptive capacity.
top
| Industry,
Settlement and Society |
|
Costs
and benefits of climate change for industry, settlement, and society will
vary widely by location and scale. In the aggregate, however, net effects
will tend to be more negative the larger the change in climate.
The
most vulnerable industries, settlements and societies are generally those
in coastal and river flood plains, those whose economies are closely linked
with climate-sensitive resources, and those in areas prone to extreme weather
events, especially where rapid urbanisation is occurring.
Poor
communities can be especially vulnerable, in particular those concentrated
in high-risk areas. They tend to have more limited adaptive capacities,
and are more dependent on climate-sensitive resources such as local water
and food supplies.
Where
extreme weather events become more intense and/or more frequent, the economic
and social costs of those events will increase, and these increases will
be substantial in the areas most directly affected. Climate change impacts
spread from directly impacted areas and sectors to other areas and sectors
through extensive and complex linkages.
top
| Health |
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Projected
climate change-related exposures are likely to affect the health status
of millions of people, particularly those with low adaptive capacity, through:
 increases in malnutrition and consequent disorders, with implications for
child growth and development;
increased deaths, disease and injury due to heat waves, floods, storms,
fires and droughts;
the
increased burden of diarrhoeal disease;
the increased frequency of cardio-respiratory diseases due to higher concentrations
of ground level ozone related to climate change; and, ...
the altered spatial distribution of some infectious disease vectors.
Climate change is expected to have some mixed effects, such as the decrease
or increase of the range and transmission potential of malaria in Africa.
Studies
in temperate areas have shown that climate change is projected to bring
some benefits, such as fewer deaths from cold exposure. Overall it is expected
that these benefits will be outweighed by the negative health effects of
rising temperatures world-wide, especially in developing countries.
The
balance of positive and negative health impacts will vary from one location
to another, and will alter over time as temperatures continue to rise.
Critically important will be factors that directly shape the health of
populations such as education, health care, public health prevention and
infrastructure and economic development.
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| Quelle:
Text IPCC; UNEP and WMO, 6 April 2007 |
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