»Der Klimawandel erhöht fast überall auf der Welt die Risiken natürlicher und menschlicher Systeme« | Blätter für deutsche und internationale Politik

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»Der Klimawandel erhöht fast überall auf der Welt die Risiken natürlicher und menschlicher Systeme«

Studie des Weltklimarates der Vereinten Nationen (IPCC) zu den Auswirkungen des Klimawandels, April 2014 (engl. Originalfassung)

Climate change will amplify climate-related risks to natural and human systems in most parts of the world. Key regional risks identified with medium to high confidence are presented in Table TS.5. Projected changes in climate and increasing atmospheric CO2 will have positive effects for some sectors in some locations. For extended summary of regional risks and the more limited potential benefits, see introductory overviews for each region below and also Chapters 21-30. [INSERT TABLE TS.5 HERE Table TS.5: Key regional risks from climate change and the potential for reducing risks through mitigation and adaptation. Risks have been identified based on assessment of the relevant scientific, technical, and socioeconomic literature, as detailed in supporting chapter sections. Each key risk is characterized as very low to very high for three timeframes: the present, near-term (here, assessed over 2030-2040), and longer-term (here, assessed over 2080- 2100). Assessed risk levels integrate probability and consequence over the full range of possible outcomes, acknowledging the importance of differences in values and objectives in interpretation of the assessed risk levels. For the near-term era of committed climate change, projected levels of global mean temperature increase do not diverge substantially across emission scenarios. For the longer-term era of climate options, risk levels are presented for global mean temperature increase of 2°C and 4°C above preindustrial levels, illustrating the potential role of mitigation in reducing risks. For the present, risk levels are estimated for current adaptation and a hypothetical highly adapted state, identifying where current adaptation deficits exist. For the future, risk levels are estimated for a continuation of current adaptation and for a highly adapted state, representing the potential for and limits to adaptation. Relevant climate variables are indicated by icons. Risk levels are not necessarily comparable, especially across regions, because the assessment considers potential impacts and adaptation in different physical, biological, and human systems across diverse regional contexts.]

Africa. Climate change will amplify existing stress on water availability and on agricultural systems particularly in semi-arid environments (high confidence).

Increasing temperatures and changes in precipitation are very likely to reduce cereal crop productivity with strong adverse effects on food security (high confidence). Progress has been achieved on managing risks to food production from current climate variability and near-term climate change, but these will not be sufficient to address long-term impacts of climate change. Adaptive agricultural processes such as collaborative, participatory research that includes scientists and farmers, strengthened communication systems for anticipating and responding to climate risks, and increased flexibility in livelihood options provide potential pathways for strengthening adaptive capacities. Climate change is a multiplier of existing health vulnerabilities including insufficient access to safe water and improved sanitation, food insecurity, and limited access to health care and education. Strategies that integrate consideration of climate change risks with land and water management and disaster risk reduction bolster resilient development. [22.3-4, 22.6]

Europe. Climate change will increase the likelihood of systemic failures across European countries caused by extreme climate events affecting multiple sectors (medium confidence).

Sea-level rise and increases in extreme rainfall are projected to further increase coastal and river flood risks and without adaptive measures will substantially increase flood damages (i.e., people affected and economic losses); adaptation can prevent most of the projected damages (high confidence). Heat-related deaths and injuries are likely to increase, particularly in southern Europe (medium confidence). Climate change is likely to increase cereal crop yields in northern Europe (medium confidence) but decrease yields in southern Europe (high confidence). Climate change will increase irrigation needs in Europe, and future irrigation will be constrained by reduced runoff, demand from other sectors, and economic costs, with integrated water management a strategy for addressing competing demands. Hydropower production is likely to decrease in all sub-regions except Scandinavia. Climate change is very likely to cause changes in habitats and species, with local extinctions (high confidence), continental-scale shifts in species distributions (medium confidence), and significantly reduced alpine-plant habitat (high confidence). Climate change is likely to entail the loss or displacement of coastal wetlands. The introduction and expansion of invasive species, especially those with high migration rates, from outside Europe is likely to increase with climate change (medium confidence). [23.2-9]

Asia. Climate change will cause declines in agricultural productivity in many subregions of Asia, for crops such as rice (medium confidence).

In Central Asia, cereal production in northern and eastern Kazakhstan could benefit from the longer growing season, warmer winters, and slight increase in winter precipitation, while droughts in western Turkmenistan and Uzbekistan could negatively affect cotton production, increase water demand for irrigation, and exacerbate desertification. The effectiveness of potential and practiced agricultural adaptation strategies is not well understood. Future projections of precipitation at subregional scales and thus of freshwater availability in most parts of Asia are uncertain (low confidence in projections), but increased water demand from population growth, increased water consumption per capita, and lack of good management will increase water scarcity challenges for most of the region (medium confidence). Adaptive responses include integrated water management strategies, such as development of water saving technologies, increased water productivity, and water reuse. Extreme climate events will have an increasing impact on human health, security, livelihoods, and poverty, with the type and magnitude of impact varying across Asia (high confidence). In many parts of Asia, observed terrestrial impacts, such as permafrost degradation and shifts in plant species’ distributions, growth rates, and timing of seasonal activities, will increase due to climate change projected during the 21st century. Coastal and marine systems in Asia, such as mangroves, seagrass beds, salt marshes, and coral reefs, are under increasing stress from climatic and non-climatic drivers. In the Asian Arctic, sea-level rise interacting with projected changes in permafrost and the length of the ice-free season will increase rates of coastal erosion (medium evidence, high agreement). [24.4, 30.5]

Australasia. Without adaptation, further changes in climate, atmospheric CO2, and ocean acidity are projected to have substantial impacts on water resources, coastal ecosystems, infrastructure, health, agriculture, and biodiversity (high confidence).

Freshwater resources are projected to decline in far south-west and far south-east mainland Australia (high confidence) and for some rivers in New Zealand (medium confidence). Rising sea levels and increasing heavy rainfall are projected to increase erosion and inundation, with consequent damages to many low-lying ecosystems, infrastructure, and housing (high confidence); increasing heat waves will increase risks to human health; rainfall changes and rising temperatures will shift agricultural production zones; and many native species will suffer from range contractions and some may face local or even global extinction. Uncertainty in projected rainfall changes remains large for many parts of Australia and New Zealand, which creates significant challenges for adaptation. Some sectors in some locations have the potential to benefit from projected changes in climate and increasing atmospheric CO2, for example due to reduced energy demand for winter heating in New Zealand and southern parts of Australia, and due to forest growth in cooler regions except where soil nutrients or rainfall are limiting. Indigenous peoples in both Australia and New Zealand have higher than average exposure to climate change due to a heavy reliance on climate-sensitive primary industries and strong social connections to the natural environment, and face additional constraints to adaptation (medium confidence). [25.2-3, 25.5-8, Boxes 25-1, 25-2, 25-5, and 25-8]

North America. Many climate-related hazards that carry risk, particularly related to severe heat, heavy precipitation, and declining snowpack, will increase in frequency and/or severity in North America in the next decades (very high confidence).

Climate change will amplify risks to water resources already affected by nonclimatic stressors, with potential impacts associated with decreased snowpack, decreased water quality, urban flooding, and decreased water supplies for urban areas and irrigation (high confidence). More adaptation options are available to address water supply deficits than flooding and water quality concerns (medium confidence). Ecosystems are under increasing stress from rising temperatures, CO2 concentrations, and sea levels, with particular vulnerability to climate extremes (very high confidence). In many cases, climate stresses exacerbate other anthropogenic influences on ecosystems, including land-use changes, non-native species, and pollution. Projected increases in temperature, reductions in precipitation in some regions, and increased frequency of extreme events would result in net productivity declines in major North American crops by the end of the 21st century without adaptation, although some regions, particularly in the north, may benefit. Adaptation, often with mitigation cobenefits, could offset projected negative yield impacts for many crops at 2°C global mean temperature increase above preindustrial, with reduced effectiveness of adaptation at 4°C (high confidence). Although larger urban centers would have higher adaptive capacities, high population density, inadequate infrastructures, lack of institutional capacity, and degraded natural environments increase future climate risks from heat waves, droughts, storms, and sea-level rise (medium evidence, high agreement). Future risks from climate extremes can be reduced, for example through targeted and sustainable air conditioning, more effective warning and response systems, enhanced pollution controls, urban planning strategies, and resilient health infrastructure (high confidence). [26.3-6, 26.8]

Central and South America. Despite improvements, high and persistent levels of poverty in most countries result in high vulnerability to climate variability and change (high confidence).

Climate change impacts on agricultural productivity are expected to exhibit large spatial variability, for example with sustained or increased productivity through mid-century in southeast South America and decreases in productivity in the near-term (by 2030) in Central America, threatening food security of the poorest populations (medium confidence). Reduced precipitation and increased evapotranspiration in semi-arid regions will increase risks from water-supply shortages, affecting cities, hydropower generation, and agriculture (high confidence). Ongoing adaptation strategies include reduced mismatch between water supply and demand, and water-management and coordination reforms (medium confidence). Conversion of natural ecosystems, a driver of anthropogenic climate change, is the main cause of biodiversity and ecosystem loss (high confidence). Climate change is expected to increase rates of species extinction (medium confidence). In coastal and marine systems, sea-level rise and human stressors increase risks for fish stocks, corals, mangroves, recreation and tourism, and control of diseases (high confidence). Climate change will exacerbate future health risks given regional population growth rates and vulnerabilities due to pollution, food insecurity in poor regions, and existing health, water, sanitation, and waste collection systems (medium confidence). [27.2-3]

Polar Regions. In the Arctic, climate change and often-interconnected non-climate-related drivers, including environmental changes, demography, culture, and economic development, interact to determine physical, biological, and socioeconomic risks, with rates of change that may be faster than social systems can adapt (high confidence).

Thawing permafrost and changing precipitation patterns have the potential to affect infrastructure and related services, with particular risks for residential buildings, for example in Arctic cities and small rural settlements. Climate change will especially impact Arctic communities that have narrowly based economies limiting adaptive choices. Increased Arctic navigability and expanded land- and freshwater-based transportation networks will increase economic opportunities. Impacts on the informal, subsistence-based economy will include changing sea-ice conditions that increase the difficulty of hunting marine mammals. Polar bears have been and will be affected by loss of annual ice over continental shelves, decreased ice duration, and decreased ice thickness. Already, accelerated rates of change in permafrost thaw, loss of coastal sea ice, sea-level rise, and increased intensity of weather extremes are forcing relocation of some indigenous communities in Alaska (high confidence). In the Arctic and Antarctic, some marine species will shift their ranges in response to changing ocean and sea ice conditions (medium confidence). Climate change will increase the vulnerability of terrestrial ecosystems to invasions by non-indigenous species, the majority expected to arrive through direct human assistance (high confidence). [6.3, 6.5, 28.2-4]

Small Islands. Small islands have high vulnerability to climatic and non-climatic stressors (high confidence).

Diverse physical and human attributes and their sensitivity to climate-related drivers lead to variable climate change risk profiles and adaptation from one island region to another and among countries in the same region. Risks can originate from transboundary interactions, for example associated with existing and future invasive species and human health challenges. Sea-level rise poses one of the most widely recognized climate change threats to low-lying coastal areas on islands and atolls. Projected sea-level rise at the end of the 21st century, superimposed on extreme sea-level events, presents severe coastal-flooding and erosion risks for low-lying coastal areas and atoll islands. Wave over-wash will degrade groundwater resources. Coral reef ecosystem degradation associated with increasing sea surface temperature and ocean acidification will negatively impact island communities and livelihoods, given the dependence of island communities on coral reef ecosystems for coastal protection, subsistence fisheries, and tourism. [29.3-5, 29.9, 30.5, Figure 29-1, Table 29-3, Box CC-CR]

The Ocean. Warming will increase risks to ocean ecosystems (high confidence).

Coral reefs within coastal boundary systems, semi-enclosed seas, and sub-tropical gyres are rapidly declining as a result of local non-climatic stressors (i.e., coastal pollution, overexploitation) and climate change. Projected increases in mass coral bleaching and mortality will alter or eliminate ecosystems, increasing risks to coastal livelihoods and food security (medium to high confidence). An analysis of the CMIP5 ensemble projects loss of coral reefs from most sites globally to be very likely by 2050 under mid to high rates of ocean warming. Reducing non-climatic stressors represents an opportunity to strengthen ecological resilience. The highly productive high-latitude spring bloom systems in the Northeastern Atlantic are responding to warming (medium evidence, high agreement), with the greatest changes being observed since the late 1970s in the phenology, distribution, and abundance of plankton assemblages, and the reorganization of fish assemblages, with a range of consequences for fisheries (high confidence). Projected warming increases the likelihood of greater thermal stratification in some regions, which can lead to reduced O2 ventilation and encourage the formation of hypoxic zones, especially in the Baltic and Black Seas (medium confidence). Changing surface winds and waves, sea level, and storm intensity will increase the vulnerability of ocean-based industries such as shipping, energy, and mineral extraction. New opportunities as well as international issues over access to resources and vulnerability may accompany warming waters particularly at high latitudes. [5.3-4, 6.4, 28.2-3, 30.3, 30.5-6, Table 30-1, Figures 30-4 and 30-10, Boxes 6-1, CC-CR, and CC-MB]

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