The 1.5˚C to 6˚C global average
temperature rise projected by IPCC for the current century may seem
modest, but as noted, it could imply quite serious impacts. What,
really, might be the consequences? The most sophisticated climate
models speak to a wide variety of possible impacts from global
warming. Recall that a 6˚C drop
in global average temperature is all that separates Earth’s present
climate from an ice age. Fortunately, it does not appear that a
comparable rise will have consequences as devastating as two-mile-thick
ice sheets over populated areas of the Northern Hemisphere (a common
characteristic of an ice age), but that doesn’t mean the consequences
of a few degrees or more of global warming will not be substantial and
disruptive with potential dangerous outcomes (see Mastrandrea and Schneider, 2004; also see
their supplement).
Global warming obviously means
higher temperatures. But just how will the temperature rise be
distributed in time and in space? We’ve been looking mostly at
the global average temperature rise, but in fact, global warming will
vary substantially from one geographical region to another, and it will
have different effects on night and day, winter and summer, land and
sea, temperature and precipitation.
Climate models have reached rough
consensus on many temperature-related projections. In general,
temperature rises are projected to be greatest in the subpolar regions,
and to affect the polar winter more dramatically than the summer.
Similarly, nighttime temperatures are projected to rise more than
daytime temperatures. Land temperatures are projected to rise
more than oceans, for the most part, influencing the patterns of
monsoons and the life-giving rains (and deadly floods) they
engender.
The broadest impacts of climate
change on human society are likely to occur in coastal areas, in
agriculture and water supplies, although research has shown that even
areas considered untouched, like pristine sections of the Amazon rain
forest, are being affected by climate change (see Laurance et al., 2004). Health effects,
including heat stress (see Hayhoe
et al., 2004) and the spread of lowland tropical diseases into
currently unaffected regions, may also be significant, depending on the
effectiveness of adaptive measures to reduce the threat (e.g.,
development of a malaria vaccine). Many projections have been
made regarding the extent and dollar value of potential climate-related
damages, as discussed in Climate
Policy.
One point that needs clarifying is
that of human carrying capacity. A 2004 Pentagon report on abrupt
climate change (see Contrarian
Science for a full account) states that carrying capacity
"is the ability for the Earth and its natural ecosystems including
social, economic, and cultural systems to support the finite number of
people on the planet" (page 15). It goes on to say that "Abrupt climate
change is likely to stretch carrying capacity well beyond its already
precarious limits.. As abrupt climate change lowers the world's
carrying capacity aggressive wars are likely to be fought over food,
water, and energy. Deaths from war as well as starvation and disease
will decrease population size, which over time, will re-balance with
carrying capacity" (page 15). While I agree that climate change does
pose a real threat of lowering our population support systems, I also
think that the concept of carrying capacity is not well-developed in
the Pentagon report. While the carrying capacity of a rat species is a
function of available resources, the same situation is not true for
humans. Human carrying capacity is not some limit governed by
resources, but rather is a function of a given standard of living,
which can be traded off against damage to nature. Humans are
distinguished from animals by their technological and organizational
adaptive capacities, and human carrying capacity depends not only on
resources but on choices of standards of living, the side-effects of
those choices, and humans' capacity to substitute alternate resources
for those that have been depleted.
Natural ecosystems are likely to respond adversely
to global warming; in fact, it is widely thought that natural systems will
be less resilient than social systems. With temperatures changing
much more rapidly than in most natural sustained global climatic shifts,
temperature-sensitive plant species may find themselves unable to migrate
fast enough to keep up with the changing climate. Even though their
suitable habitats may shift by only a few hundred miles, a few hundred miles
is a long way for a plant, and if species cannot reestablish themselves
quickly enough, then they — and many of the animal species that depend
on them — will go extinct, at least locally. Scientists have also
identified various "geoboundaries", locations such as coastlines and mountaintops
that are more prone than other areas to irreversible losses. If these areas
become unsuitable for their present occupants or disappear altogether, extinction
will be even more probable. A report by Still et
al., 1999 and "Cloud forest agenda", a report commissioned by the
United Nations Environment Programme (UNEP), for example, both lay out the
problems associated with climate change, geoboundaries, and cloud forests.
The worry is that cloud forests -- often situated at the peaks of mountains
-- will be at risk of extinction as the climate warms because there will
be nowhere for them to relocate (as they cannot move farther up the mountain
to cooler climates if they're already at the top). This will affect not
only the trees of the cloud forest, but all the plant and animal species
within the cloud forest community (see Pounds and Puschendorf, 2004).
The same fate could await many
animal species (for early signs of this, see, for example, "North Sea faces collapse of its ecosystem").
In a recent study, Thomas
et al. (2004) assessed extinction risks for regions covering
about 20% of the Earth's surface and found that, based on their
projections, anywhere from 15%-37% of the species in those regions
would be "committed to extinction" by 2050. This is alarming given
that, as discussed by Daily
(1997), the goods and services that nature provides us could be
valued in the trillions of dollars, and many systems would be
devastated without them. About one third of our food, for example,
comes from plants that must be pollinated by creatures such as birds,
bees, flies, and bats. Without the service they provide, many plants
would face extinction and crops would become economically impractical,
yet many pollinator species are threatened by combinations of land use
changes, introduced “exotic” species, pesticides, and climate change.
Many are already beginning to relocate themselves to less hostile
environments. These impacts could well lower resources available to
humans, meaning that maintaining any given population level would
likely reduce per capita standards of living, cause more disruption to
nature, or both. However, there are still methodological debates over
the Thomas et al. work (see Buckley and Roughgarden, 2004; Harte
et al., 2004; and Thuiller et al., 2004; and a reply by Thomas et al.), though I believe
the synergy of habitat fragmentation and rapid climate change is a
threat to biodiversity.
This movement of plants and animals
is not just theory, as recent analyses have shown that birds are laying
eggs a few weeks earlier, butterflies are moving up mountains, and that
trees are blooming earlier in the spring and dropping their leaves
later in the fall, among other impacts (see Root et al., 2003; Parmesan and Yohe, 2003; The Birdwatcher's Guide to Global Warming).
Root et al. conclude that the most consistent explanation for these
observed changes in environmental systems over the past few decades is
global warming. This opinion was first assessed, and then echoed, by
Working Group II in the Third Assessment Report of the IPCC (2001b).
Whether the regional climatic changes that seem to be driving these
impacts are themselves anthropogenically-induced is more controversial.
However, given that the responses observed are, in about 80 percent of
the cases, in the direction that would be expected with global warming,
Root and Schneider argue that global warming is the most consistent
explanation (see Chapter 1 of Wildlife
Responses to Climate Change). Further research on this issue is
underway in the hopes that climatologists and ecologists can detect
whether the regional warmings that caused the biological responses
reported are human-induced. Recent work in progress by Terry Root,
myself, and others strongly suggests anthropogenic climate change is
indeed detectable in the plant and animal changes. More on this soon.
Other weather-related projections of
the effects of global warming include increased frequency of intense
precipitation events, more and longer heat waves, more summer droughts,
and fewer cold spells. The intensity of tropical cyclones
(hurricanes and typhoons) is likely to increase, although it is less
clear whether the frequencies or locations of these storms will
change. Hail and lightning are also likely to occur more
often. The large-scale Pacific Ocean fluctuation known as the El
Niño/Southern Oscillation could become more persistent, which
would have a substantial climatic impact on the Americas. All
these projected changes will impact agriculture and may increase
flooding and erosion, with reverberating effects on health and on the
insurance industry (see Walker, 2003 and Coleman, 2003). It appears that these
projections are already becoming reality. As discussed in the IPCC
Synthesis Report (2001), after accounting for inflation,
weather-related economic losses have increased tenfold since the 1950s.
While part is likely due to growth in wealth and population, part is
likely climate-related. For more on climate change financial damage
estimates, see Climate
Policy.
As shown in Projected Effects of Global Warming,
the confidence level in these projections ranges from medium
(likelihood between one-third and two-thirds) to high (chances greater
than two-thirds). Keep in mind, however, that the probabilities
given in Projected Effects of Global Warming are not
based on conventional statistical analysis because they refer to future
events that are not expected to follow past patterns, and the future
hasn’t occurred yet! Rather, these are subjective odds
based on scientific judgment that is as expert as current understanding
permits. Not surprisingly, that subjective element encourages
some participants in the political process to attempt to discount these
probability estimates (see Schneider and Kuntz-Duriseti, 2002 for more
discussion on uncertainties and methods to deal with them).
One final note on the issue of
climatic impacts: Like abatement, adaptation also varies across regions
and brings up complex issues of justice and fairness. The socioeconomic
conditions driving emissions also help to form the adaptive and
mitigative capacities of various countries, meaning that the countries
that have contributed the most to global emissions (see a graphic from
the Hadley Centre on the Guardian website, "Carbon dioxide emissions"; a graphic
about U.S. CO2 emissions; and a
Guardian article titled "Road
to Ruin: How America is Ravaging the Planet") will have higher
adaptive capacities. Less developed countries and disadvantaged groups
within countries, on the other hand, will tend to have lower adaptive
capacities, as they are oftentimes limited by financial, technological,
and governmental constraints. Suffering in Bangladesh due to rises in
sea level or more intense storms is made worse by the nation's lack of
adaptive capacity, given its geographic, economic and social conditions
relative to, say, Holland, a country for which adaptation to sea level
rise is much more feasible and likely. The International Red Cross/ Red
Crescent estimates that people caught in natural disasters in
low-income countries are four times more likely to die than people
confronted by natural disasters in high-income countries. The problem
with this inequality is that climate change promises to bring an uneven
distribution of consequences; the hotter, poorer nations (the same
countries that have less adaptive capacity) will be more vulnerable to
climate change damages and more in need of successful adaptation. This
will be especially true if and when thresholds are exceeded and
surprise events are triggered.
The Ecological Footprint Accounts, published
in a report titled "Ecological Footprint of Nations" by Redefining Progress,
provide us with a good way of considering adaptive capacity. A country's
ecological footprint is basically the land area required to support it.
Unsurprisingly, the US has the world's largest footprint -- 9.57 hectares
per capita -- whereas developing nations like Bangladesh and Mozambique
have per capita footprints of 0.53 hectares. 1.88 hectares is considered
sustainable in that study. While this assessment is not based solely on
CO2 emissions. Redefining Progress
says that much of the industrialized nations' ecological impacts are due
to fossil fuel usage, and shifting to renewables can significantly reduce
footprint size. Like emissions levels, footprint size appears to correlate
highly with adaptive capacity, but ironically, reducing the footprint size
can now help developed countries to experience many benefits, including
environmental health, economic vitality, and social equity.
Abatement also brings up equity issues in terms
of the trade-off between adaptation and abatement. It is often assumed,
particularly in a cost-benefit analysis (CBA) framework, that mitigation
and adaptation can be viewed as competitive strategies to deal with climate
change, but we must first consider the potential implications of the oft-stated
trade-off. Suppose it were cheaper for an industrialized, high-emitting
nation in the political North to adapt than to mitigate. If that nation
chose only to adapt, it would likely be detrimental to a poorer, less adaptable
country in the South. Simply comparing mitigation and adaptation costs and
aggregating the values across all nations is a "one dollar, one vote" aggregate
prescription, and it clearly has serious equity implications. The low-cost
option for one country is most like not synonymous with the low-cost option
for its neighbors or the world at large.
In addition, technically speaking, in a cost-benefit
framework, the mitigation/adaptation trade-off consideration would not be
meaningful over time, since mitigation costs in a CBA are weighed against
the benefits of avoided climate damages and not against adaptation costs.
Adaptation can subtract from climate damages, which constitute much of the
"trade-off", but at low levels of climate change, adaptation costs are likely
to be low, whereas first steps in abatement may be higher (presuming perfect
markets and no "no regrets" options). However, as greenhouse gas concentrations
increase and climate change intensifies, adaptation costs will likely rise,
and adaptation may not even be feasible for large or irreversible climate
changes. As Grubb,
2004 states, "There are also impacts that can hardly be mitigated
by adaptation. Some coastal deltas and swamp habitats may be impossible
to protect against rising sea levels. Nothing [within the realm of adaptation]
can stop the melting of mountain glaciers, the loss of mountain ecosystems,
or the bleaching of coral reefs due to warmer waters. Probably not much
can be done to prevent some other ecosystems and species dying out as climatic
zones shift." In this light, it is clear that adaptation is an important
measure, but it is not a substitute for abatement. An adapt-only strategy
will likely just postpone trouble for the future.
In the Regional adaptive capacity table
below, the IPCC authors summarize a comprehensive list of potential
climate change impacts for most of the world's regions and economic
sectors. As depicted in the table, damages may be asymmetrically felt
across the developed/developing country divide as climate change
becomes more of a problem in the future, eliciting questions of
inter-country and intergenerational equity. If mitigation measures are
postponed, as the income gaps between populations and countries grow
larger, climate change is likely to increase world- and country-scale
inequity, both within the present generation and between present and
future generations, particularly in the developing countries. While
this may not move some traditional advocates of aggregate cost-benefit
methods, it drives the realpolitik of international climate
policy negotiations (see a chapter by Baer, and a chapter by Agarwal, in Climate Change Policy: a Survey, 2002).
Table — Regional adaptive capacity,
vulnerability, and key concerns (relevant sections of IPCC 2001b for each example are given in
square brackets). a,
b (source: IPCC 2001b, table SPM-2).
Region
|
Adaptive Capacity, Vulnerability, and Key
Concerns |
Africa |
- Adaptive capacity of human systems in Africa is low due to
lack of economic resources and technology, and vulnerability high as a
result of heavy reliance on rain-fed agriculture, frequent droughts and
floods, and poverty. [5.1.7]
- Grain yields are projected to decrease for many scenarios,
diminishing food security, particularly in small food-importing
countries (medium to high confidence). [5.1.2]
- Major rivers of Africa are highly sensitive to climate
variation; average runoff and water availability would decrease in
Mediterranean and southern countries of Africa (medium confidence).
[5.1.1] [Lakes are expected to become warmer and shrink in size,
threatening species and the people who depend on them, as described in “Global Warming is Choking the Life Out of Lake
Tanganyika.” - SHS ]
- Extension of ranges of infectious disease vectors would
adversely affect human health in Africa (medium confidence).
[5.1.4]
- Desertification would be exacerbated by reductions in
average annual rainfall, runoff, and soil moisture, especially in
southern, North, and West Africa (medium confidence). [5.1.6]
- Increases in droughts, floods, and other extreme events
would add to stresses on water resources, food security, human health,
and infrastructures, and would constrain development in Africa (high
confidence). [5.1]
- Significant extinctions of plant and animal species are
projected and would impact rural livelihoods, tourism, and genetic
resources (medium confidence). [5.1.3]
- Coastal settlements in, for example, the Gulf of Guinea,
Senegal, Gambia, Egypt, and along the East–Southern African coast would
be adversely impacted by sea-level rise through inundation and coastal
erosion (high confidence). [5.1.5]
|
Asia |
- Adaptive capacity of human systems is low and
vulnerability is high in the developing countries of Asia; the
developed countries of Asia are more able to adapt and less vulnerable.
[5.2.7]
- Extreme events have increased in temperate and tropical
Asia, including floods, droughts, forest fires, and tropical cyclones (high
confidence). [5.2.4]
- Decreases in agricultural productivity and aquaculture due
to thermal and water stress, sea-level rise, floods and droughts, and
tropical cyclones would diminish food security in many countries of
arid, tropical, and temperate Asia; agriculture would expand and
increase in productivity in northern areas (medium confidence).
[5.2.1]
- Runoff and water availability may decrease in arid and
semiarid Asia but increase in northern Asia (medium confidence).
[5.2.3] For information on already-perceived changes in river ice
thickness and stream flow in the Lena River in Siberia, see Yang
et al., 2002.
- Human health would be threatened by possible increased
exposure to vector-borne infectious diseases and heat stress in parts
of Asia (medium confidence). [5.2.6]
- Sea-level rise and an increase in the intensity of
tropical cyclones would displace tens of millions of people in
low-lying coastal areas of temperate and tropical Asia; increased
intensity of rainfall would increase flood risks in temperate and
tropical Asia (high confidence). [5.2.5 and Table TS-8]
- Climate change would increase energy demand, decrease
tourism attraction, and influence transportation in some regions of
Asia (medium confidence). [5.2.4 and 5.2.7]
- Climate change would exacerbate threats to biodiversity
due to land-use and land-cover change and population pressure in Asia (medium
confidence). Sea-level rise would put ecological security at risk,
including mangroves and coral reefs (high confidence). [5.2.2]
- Poleward movement of the southern boundary of the
permafrost zones of Asia would result in a change of thermokarst and
thermal erosion with negative impacts on social infrastructure and
industries (medium confidence) . [5.2.2]
|
Australia and New Zealand |
- Adaptive capacity of human systems is generally high, but
there are groups in Australia and New Zealand, such as indigenous
peoples in some regions, with low capacity to adapt and consequently
high vulnerability. [5.3 and 5.3.5]
- The net impact on some temperate crops of climate and CO2
changes may initially be beneficial, but this balance is expected to
become negative for some areas and crops with further climate change (medium
confidence). [5.3.3]
- 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 average state. [5.3 and 5.3.1]
- Increases in the intensity of heavy rains and tropical
cyclones (medium confidence), and region-specific changes in
the frequency of tropical cyclones, would alter the risks to life,
property, and ecosystems from flooding, storm surges, and wind damage.
[5.3.4]
- Some species with restricted climatic niches and which are
unable to migrate due to fragmentation of the landscape, soil
differences, or topography could become endangered or extinct (high
confidence). Australian ecosystems that are particularly vulnerable
to climate change include coral reefs, arid and semiarid habitats in
southwest and inland Australia, and Australian alpine systems.
Freshwater wetlands in coastal zones in both Australia and New Zealand
are vulnerable, and some New Zealand ecosystems are vulnerable to
accelerated invasion by weeds. [5.3.2]
|
Europe |
- Adaptive capacity is generally high in Europe for human
systems; southern Europe and the European Arctic are more vulnerable
than other parts of Europe. [5.4 and 5.4.6]
- Summer runoff, water availability, and soil moisture are
likely to decrease in southern Europe, and would widen the difference
between the north and drought-prone south; increases are likely in
winter in the north and south (high confidence). [5.4.1]
- Half of alpine glaciers and large permafrost areas could
disappear by end of the 21st century (medium confidence).
[5.4.1]
- River flood hazard will increase across much of Europe (medium
to high confidence); in coastal areas, the risk of flooding,
erosion, and wetland loss will increase substantially with implications
for human settlement, industry, tourism, agriculture, and coastal
natural habitats. [5.4.1 and 5.4.4]
- There will be some broadly positive effects on agriculture
in northern Europe (medium confidence 6); productivity will
decrease in southern and eastern Europe (medium confidence).
[5.4.3]
- Upward and northward shift of biotic zones will take
place. Loss of important habitats (wetlands, tundra, isolated habitats)
would threaten some species (high confidence). [5.4.2]
- Higher temperatures and heat waves may change traditional
summer tourist destinations, and less reliable snow conditions may
impact adversely on winter tourism (medium confidence). [5.4.4]
|
Latin America |
- Adaptive capacity of human systems in Latin America is
low, particularly with respect to extreme climate events, and
vulnerability is high. [5.5]
- Loss and retreat of glaciers would adversely impact runoff
and water supply in areas where glacier melt is an important water
source (high confidence). [5.5.1]
- Floods and droughts would become more frequent with floods
increasing sediment loads and degrade water quality in some areas (high
confidence). [5.5]
- Increases in intensity of tropical cyclones would alter
the risks to life, property, and ecosystems from heavy rain, flooding,
storm surges, and wind damages (high confidence). [5.5]
- Yields of important crops are projected to decrease in
many locations in Latin America, even when the effects of CO2
are taken into account; subsistence farming in some regions of Latin
America could be threatened (high confidence). [5.5.4]
- The geographical distribution of vector-borne infectious
diseases would expand poleward and to higher elevations, and exposures
to diseases such as malaria, dengue fever, and cholera will increase
(medium confidence). [5.5.5]
- Coastal human settlements, productive activities,
infrastructure, and mangrove ecosystems would be negatively affected by
sea-level rise (medium confidence). [5.5.3]
- The rate of biodiversity loss would increase (high
confidence). [5.5.2]
|
North America |
- Adaptive capacity of human systems is generally high and
vulnerability low in North America, but some communities (e.g.,
Indigenous peoples and those dependent on climate-sensitive resources)
are more vulnerable; social, economic, and demographic trends are
changing vulnerabilities in subregions. [5.6 and 5.6.1]
- Some crops would benefit from modest warming accompanied
by increasing CO2, but effects would vary among crops and
regions (high confidence), including declines due to drought in
some areas of Canada’s Prairies and the U.S. Great Plains, potential
increased food production in areas of Canada north of current
production areas, and increased warm-temperate mixed forest production (medium
confidence 6). However, benefits for crops would decline at an
increasing rate and possibly become a net loss with further warming (medium
confidence). [5.6.4]
- Snowmelt-dominated watersheds in western North America
will experience earlier spring peak flows (high confidence),
reductions in summer flows (medium confidence), and reduced
lake levels and outflows for the Great Lakes-St. Lawrence under most
scenarios (medium confidence); adaptive responses would offset
some, but not all, of the impacts on water users and on aquatic
ecosystems (medium confidence). [5.6.2]
- Unique natural ecosystems such as prairie wetlands, alpine
tundra, and cold-water ecosystems will be at risk and effective
adaptation is unlikely (medium confidence). [5.6.5]
- Sea-level rise would result in enhanced coastal erosion,
coastal flooding, loss of coastal wetlands, and increased risk from
storm surges, particularly in Florida and much of the U.S. Atlantic
coast (high confidence). For more information on water
cycle-related impacts of climate change in the U.S., see Gleick
et al., 2000.[5.6.1]
- Weather-related insured losses and public sector disaster
relief payments in North America have been increasing; insurance sector
planning has not yet systematically included climate change
information, so there is potential for surprise (high confidence).
[5.6.1]
- Vector-borne diseases — including malaria, dengue fever,
and Lyme disease — may expand their ranges in North America;
exacerbated air quality and heat stress morbidity and mortality would
occur (medium confidence); socioeconomic factors and public
health measures would play a large role in determining the incidence
and extent of health effects. [5.6.6]
|
Polar |
- Natural systems in polar regions are highly vulnerable to
climate change and current ecosystems have low adaptive capacity;
technologically developed communities are likely to adapt readily to
climate change, but some indigenous communities, in which traditional
lifestyles are followed, have little capacity and few options for
adaptation. [5.7]
- Climate change in polar regions is expected to be among
the largest and most rapid of any region on the Earth, and will cause
major physical, ecological, sociological, and economic impacts,
especially in the Arctic, Antarctic Peninsula, and Southern Ocean (high
confidence). [5.7]
- Changes in climate that have already taken place are
manifested in the decrease in extent and thickness of Arctic sea ice,
permafrost thawing, coastal erosion, changes in ice sheets and ice
shelves, and altered distribution and abundance of species in polar
regions (high confidence). [5.7]
- Some polar ecosystems may adapt through eventual
replacement by migration of species and changing species composition,
and possibly by eventual increases in overall productivity; ice edge
systems that provide habitat for some species would be threatened (medium
confidence). [5.7]
- Polar regions contain important drivers of climate change.
Once triggered, they may continue for centuries, long after greenhouse
gas concentrations are stabilized, and cause irreversible impacts on
ice sheets, global ocean circulation, and sea-level rise (medium
confidence). [5.7]
|
Small Island States |
- Adaptive capacity of human systems is generally low in
small island states, and vulnerability high; small island states are
likely to be among the countries most seriously impacted by climate
change. [5.8]
- The projected sea-level rise of 5 mm per year for the next
100 years would cause enhanced coastal erosion, loss of land and
property, dislocation of people, increased risk from storm surges,
reduced resilience of coastal ecosystems, saltwater intrusion into
freshwater resources, and high resource costs to respond to and adapt
to these changes (high confidence). [5.8.2 and 5.8.5]
- Islands with very limited water supplies are highly
vulnerable to the impacts of climate change on the water balance (high
confidence). [5.8.4]
- Coral reefs would be negatively affected by bleaching and
by reduced calcification rates due to higher CO2 levels (medium
confidence); mangrove, sea grass beds, and other coastal ecosystems
and the associated biodiversity would be adversely affected by rising
temperatures and accelerated sea-level rise (medium confidence).
[4.4 and 5.8.3]
- Declines in coastal ecosystems would negatively impact
reef fish and threaten reef fisheries, those who earn their livelihoods
from reef fisheries, and those who rely on the fisheries as a
significant food source (medium confidence). [4.4 and 5.8.4]
- Limited arable land and soil salinization makes
agriculture of small island states, both for domestic food production
and cash crop exports, highly vulnerable to climate change (high
confidence). [5.8.4]
- Tourism, an important source of income and foreign
exchange for many islands, would face severe disruption from climate
change and sea-level rise (high confidence). [5.8.5]
|
a Because the available
studies have not employed a common set of climate scenarios and
methods, and because of uncertainties regarding the sensitivities and
adaptability of natural and social systems, the assessment of regional
vulnerabilities is necessarily qualitative.
b The regions listed in
this table are graphically depicted in Figure TS-2 of the Technical
Summary of IPCC, 2001b.
Many regional effects have the
potential to further alter the climate on a large scale, as depicted in
the figure below.
Figure— Potentially sensitive ‘switch point’
areas in which local effects might trigger larger-scale changes.
The chart shows regions in which specific local phenomena may result in
points of sensitivity for larger-scale and possibly rapid changes in regional
or global climatic conditions. (Source: Grubb 2004, from J. Schellnhuber and H. Held, adapted
from ‘How Fragile is the Earth System?', in J. Briden, and T. Downing,
T.(Eds.), Managing the Earth: the Eleventh Linacre Lectures, Univ.
Press, Oxford, 2002).
The climate policy community is
therefore faced not only with the need to estimate the impacts of a wide
range of plausible climatic futures, but also with the imperative of estimating
the relative adaptive capabilities of future societies so as to assess the
equity implications of the consequences of global warming. This complicates
the negotiations of solutions, as many of the typically proposed mitigative
activities could slow the economic growth rates of those very countries
that need to build adaptive capabilities by growing economically (e.g., IPCC, 2001c). Yet, if these countries are allowed to
emit unabated amounts of greenhouse gases, the risks of severe climate change
impacts, including irreversibilities, will increase. The best way to approach
this dilemma is to assess the range of possible climate change outcomes,
their costs, and the distribution of those costs, and then to weigh those
impacts against the costs and benefits of a host of mitigation options carried
out in various countries. This must be done keeping in mind that there are large
inequities in access to resources that make it difficult to achieve agreements
protecting the global commons. Side payments or other schemes to redress
the inequity issue will have to be part of future climate policy negotiations
if they are to be acceptable to a majority of nations.
Conclusion
The absence of highly confident
assessments about "dangerous" climate change and the impacts of climate
change in general (see also "Assessing
the science to address UNFCCC Article 2") is likely to remain
a feature of this policy debate landscape, and thus there is a
critical need for a public literate in how climate science works, what
subjective probabilities are, and how effective risk-management
trade-offs can be made across time and income groups. It is my hope
that this website, the literature cited, and its external links will
help in that process.
Figure — What will happen to the Snows of Kilimanjaro? (source: PAGES).
The snows of Kilimanjaro are expected to disappear completely within
the next few decades, though some dispute this is true (see Revkin,
2004 for a review of the debate).
Above: Pictures of Shrinking Glaciers — see Researchers Track Glacial Melt with Old Photos, New
Technology. Source: http://www.gletscherarchiv.de.
Figure —
A geographic information system representation of glacier shrinkage from 1850 to 1993 in Glacier
National Park. The BlackfeetJackson glaciers are in the center.
The yellow areas reflect the current area of each glacier; other colors
represent the extent of the glaciers at various times in the past.
(Courtesy: C. Key, USGS and R. Menicke, National Park Service) (Source: USGS - Understanding Climate Change Effects on
Glacier National Park's Natural Resources)
Next: Climate Policy
Links
Articles
- United States Geological Survey (USGS)/Status and
Trends of the Nation’s Biological Resources (Schneider and Root)
- Kinzig, A.P., S. Carpenter, M. Dove, G. Heal, S.
Levin, J. Lubchenco. S.H. Schneider, and D. Starrett, 2000: Nature
and Society: An Imperative for Integrated Environmental Research.
Executive Summary, NSF Meeting, June 5-8, Tempe, Arizona, November
2000, 6 pp
- Kinzig, A.P., J. Antle, W. Ascher, W. Brock, S.
Carpenter, F. S. Chapin III, R. Costanza, K.L. Cottingham, M. Dove, H.
Dowlatabadi, E. Elliot, K. Ewel, A. Fisher, P. Gober, N. Grimm, T.
Groves, S, Hanna, G. Heal, K. Lee, S. Levin, J. Lubchenco, D. Ludwig,
J. Martinez-Alier, W. Murdoch, R. Naylor, R. Norgaard, M. Oppenheimer,
A. Pfaff, S. Pickett, S. Polasky, H.R. Pulliam, C. Redman, J.P.
Rodrigez, T. Root, S.H. Schneider, R. Schuler, T. Scudder, K. Segersen,
M.R. Shaw, D. Simpson, A.A. Small, D. Starrett, P. Taylor, S, van der
Leeuw, D.H. Hall, M. Wilson (eds.), 2000: Nature and Society: An Imperative for Integrated
Environmental Research, NSF Workshop, June, Tempe, Arizona, in
press.
- Rosenzweig, C., F.N. Tubiello, R. Goldberg, E.
Mills, J. Bloom, 2002: “Increased
crop damage in the US from excess precipitation under climate change”
For more climate information, see:
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