| |
Small Islands and Low-Lying Coasts
|
|
| 3.23 |
Populations that inhabit small islands
and/or low-lying coastal areas are at particular risk of severe social
and economic effects from sea-level rise and storm surges. Many
human settlements will face increased risk of coastal flooding and erosion,
and tens of millions of people living in deltas, low-lying coastal areas,
and on small islands will face the risk of displacement of populations
and loss of infrastructure and/or substantial efforts and costs to protect
vulnerable coastal areas. Resources critical to island and coastal populations
such as freshwater, fisheries, coral reefs and atolls, beaches, and wildlife
habitat would also be at risk.
|
WGII TAR Sections 7.2.2, 17.2,
& 19.3.4 |
| 3.24 |
Projected sea-level rise will increase
the average annual number of people flooded in coastal storm surges (high
confidence). The areas of greatest absolute increase in populations
at risk are southern Asia and southeast Asia, with lesser but significant
increases in eastern Africa, western Africa, and the Mediterranean from
Turkey to Algeria. Significant portions of many highly populated coastal
cities are also vulnerable to permanent land submergence and especially
to more frequent coastal flooding superimposed on surge heights, due to
sea-level rise. These estimates assume no change in the frequency or intensity
of storms, which could exacerbate the effects of sea-level rise on flooding
risks in some areas.
|
WGII TAR Sections 6.5.1,
7.2.2, & 17.2.2 |
| |
Market Effects
|
|
| 3.25 |
The aggregated market sector effects,
measured as changes in gross domestic product (GDP), are estimated to be
negative for many developing countries for all magnitudes of global mean
temperature increases studied (low confidence), and are estimated
to be mixed for developed countries for up to a few °C warming (low
confidence) and negative for warming beyond a few °C (medium
to low confidence). The effects of climate change will have
market sector effects by changing the abundance, quality, and prices of
food, fiber, water, and other goods and services (see Table 3-5). In addition,
climate change can have market effects through changes in energy demand,
hydropower supply, transportation, tourism and construction, damages to
property and insurance losses from extreme climate events, loss of coastal
land from sea-level rise, location and relocation decisions for development
and populations, and the resource needs and costs of adapting to climate
change. Estimates of net market effects from a few published studies, aggregated
across sectors and to national or regional scales, indicate losses for most
developing countries and regions studied. Both gains and losses are estimated
for developed countries and regions for increases in global mean temperature
of up to a few °C. Economic losses are estimated for developed countries
at larger temperature increases. When aggregated to a global scale, world
GDP would change by plus or minus a few percent for global mean temperature
increases of up to a few °C, with increasing net losses for larger increases
in temperature. The estimates generally exclude the effects of changes in
climate variability and extremes, do not account for the effects of different
rates of climate change, only partially account for impacts on goods and
services that are not traded in markets, and treat gains for some as canceling
out losses for others. Therefore, confidence in estimates of market effects
for individual countries is generally low, and the various omissions
are likely to result in underestimates of economic losses and overestimates
of economic gains.
|
WGII TAR Sections 6.5, 7.2-3,
8.3, 18.3.4,
18.4.3, 19.4.1-3,
& 19.5 |
| |
| Table
3-5: Other market sector effects of climate change if no climate
policy interventions are made.* |
| |
2025 |
2050 |
2100 |
| CO2 concentrationa |
405-460 ppm |
445-640 ppm |
540-970 ppm
|
| Global mean temperature change from the year 1990b |
0.4-1.1°C |
0.8-2.6°C |
1.4-5.8°C |
| Global mean sea-level rise from the year 1990b |
3-14 cm |
5-32 cm |
9-88 cm |
| Other Market Sector Effectsc |
| Energy [WGII
TAR Section 7.3] |
Decreased energy demand for heating buildings (high
confidenced).
Increased energy demand for cooling buildings (high
confidenced). |
Energy demand effects
amplified (high confidenced). |
Energy demand effects
amplified (high confidenced). |
Financial sector [WGII
TAR Section 8.3]
|
|
Effects on financial sector amplified. |
Increased insurance prices and reduced insurance availability
(high confidenced). |
| Aggregate market effectse [WGII
TAR Sections 19.4-5] |
Net market sector losses in many developing countries
(low confidenced).
Mixture of market gains and losses in developed countries (low
confidenced). |
Losses in developing countries amplified (medium
confidenced).
Gains diminished and losses amplified in developed countries (medium
confidenced). |
Losses in developing countries amplified (medium
confidenced).
Net market sector losses in developed countries from warming of more
than a few °C (medium confidenced). |
| * Refer to footnotes
a-d accompanying Table 3-1. |
|
|
| |
Figure 3-5: Projected
changes in average annual water runoff by the year 2050, relative to average
runoff for the period 1961-1990, largely follow projected changes in
precipitation. Changes in runoff are calculated with a hydrologic
model using as inputs climate projections from two versions of the Hadley
Centre AOGCM for a scenario of 1% per year increase in effective CO2
concentration in the atmosphere: (a) HadCM2 ensemble mean and (b) HadCM3.
Projected increases in runoff in high latitudes and southeast Asia, and
decreases in central Asia, the area around the Mediterranean, southern Africa,
and Australia are broadly consistent across the Hadley Centre experiments,
and with the precipitation projections of other AOGCM experiments. For other
areas of the world, changes in precipitation and runoff are scenario- and
model-dependent. |
WGII TAR Section 4.3.6 |
