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  Consequences of Global Warming: Regional Impacts

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).


Adaptive Capacity, Vulnerability, and Key Concerns
  • 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]
  • 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]
  • 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]
  • 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.


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).


Figure — Alpine Glacier - circa 1900 (source: Munich Society for Environmental Research).
Figure — Alpine Glacier - recent photograph (source: Munich Society for Environmental Research).

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)

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Copyright 2011, Stephen H. Schneider, Stanford University