8-2: Examples of regional impacts of climate change on water resources,
land degradation, and desertification.
|Reference Section in WGII TAR
||Changes in rainfall and intensified land use would exacerbate the
Desertification would be exacerbated by reduction in the average annual
rainfall, runoff, and soil moisture in countries of west African Sahel,
and northern and southern Africa (medium confidence).
Increases in droughts and other extreme events would add to stresses
on water resources, food security, and human health, and would constrain
development in the region (high confidence).
|TS 5.1.6, Chapter
10 ES, Sections 10.2.1
& 10.2.6, &
Table SPM 2
||Water shortage -- already a limiting factor for ecosystems, food
and fiber production, human settlements, and human health -- may
be exacerbated by climate change. Runoff and water availability may
decrease in arid and semi-arid Asia but increase in northern Asia
(medium confidence). Reduced soil moisture in summer would
exacerbate land degradation and desertification in arid and semi-arid
||TS 5.2.3 &
|Australia and New Zealand
||Interannual variability due to ENSO leads to major floods and droughts
in Australia and New Zealand. Such variations are expected to continue
under enhanced greenhouse gas conditions, but possibly with greater
Water is likely to be a key issue (high confidence) due to
projected drying trends over much of the region and change to a more
El Niño-like event state. Water quality would be affected,
and more intense rainfall events would increase fast runoff, soil
erosion, and sediment loading. Eutrophication is a major water quality
problem in Australia.
|TS 5.3 & Sections
||Summer runoff, water availability, and soil moisture are likely
to decrease in southern Europe, and would widen the gap between the
north and south (high confidence). Flood hazards will increase
across much of Europe (medium to high confidence); risk would
be substantial for coastal areas where flooding will increase erosion
and result in loss of wetlands. Half of alpine glaciers and large
permafrost areas could disappear by the end of the 21st century (medium
|TS 5.4.1, Chapter
13 ES, & Section
||Some studies based on model experiments suggest that under climate
change the hydrological cycle would be more intense, with changes
in the distribution of extreme rainfall, wet spells, and dry spells.
Frequent severe drought in Mexico during the last decade coincides
with some of these model findings. El Niño is related to dry
conditions in northeastern Brazil, northern Amazons, and the Peruvian-Bolivian
altiplano. Southern Brazil and northwestern Peru exhibit anomalous
wet conditions during these periods.
Loss and retreat of glaciers would adversely impact runoff and water
supply in areas where snowmelt is an important water resource (high
|TS 5.5.1, Chapter
14 ES, & Section
||Snowmelt-dominated watersheds in western North America will experience
earlier spring peak flows (high confidence) and reduction
in summer flow (medium confidence); adaptive responses may
offset some, but not all, of the impacts on water resources and aquatic
ecosystems (medium confidence).
||TS 5.6.2, Section
15.2.1, & Table
||Islands with very limited water supplies are highly vulnerable to
the impacts of climate change on the water balance (high confidence).
||TS 5.8.4, Section
17.2.6, & Table