Drafting Authors: Myles Allen (UK), Mustafa Babiker (Sudan), Yang Chen (China), Heleen de Coninck. (Netherlands/EU), Sarah Connors (UK), Renée van Diemen
24 pages
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3SPM Summary for Policymakers Drafting Authors: Myles Allen (UK), Mustafa Babiker (Sudan), Yang Chen (China), Heleen de Coninck (Netherlands/EU), Sarah Connors (UK), Renée van Diemen (Netherlands), Opha Pauline Dube (Botswana), Kristie L. Ebi (USA), Francois Engelbrecht (South Africa), Marion Ferrat (UK/France), James Ford (UK/Canada), Piers Forster (UK), Sabine Fuss (Germany), Tania Guillén Bolaños (Germany/Nicaragua), Jordan Harold (UK), Ove Hoegh-Guldberg (Australia), Jean-Charles Hourcade (France), Daniel Huppmann (Austria), Daniela Jacob (Germany), Kejun Jiang (China), Tom Gabriel Johansen (Norway), Mikiko Kainuma (Japan), Kiane de Kleijne (Netherlands/EU), Elmar Kriegler (Germany), Debora Ley (Guatemala/Mexico), Diana Liverman (USA), Natalie Mahowald (USA), Valérie Masson-Delmotte (France), J. B. Robin Matthews (UK), Richard Millar (UK), Katja Mintenbeck (Germany), Angela Morelli (Norway/Italy), Wilfran Moufouma-Okia (France/Congo), Luis Mundaca (Sweden/Chile), Maike Nicolai (Germany), Chukwumerije Okereke (UK/Nigeria), Minal Pathak (India), Antony Payne (UK), Roz Pidcock (UK), Anna Pirani (Italy), Elvira Poloczanska (UK/Australia), Hans- Otto Pörtner (Germany), Aromar Revi (India), Keywan Riahi (Austria), Debra C. Roberts (South Africa), Joeri Rogelj (Austria/Belgium), Joyashree Roy (India), Sonia I. Seneviratne (Switzerland), Priyadarshi R. Shukla (India), James Skea (UK), Raphael Slade (UK), Drew Shindell (USA), Chandni Singh (India), William Solecki (USA), Linda Steg (Netherlands), Michael Taylor (Jamaica), Petra Tschakert (Australia/Austria), Henri Waisman (France), Rachel Warren (UK), Panmao Zhai (China), Kirsten Zickfeld (Canada). This Summary for Policymakers should be cited as: IPCC, 2018: Summary for Policymakers. In: Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, and T. Water˜eld (eds.)]. In Press. Summary for Policymakers SPM
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4Introduction This Report responds to the invitation for IPCC ‚ to provide a Special Report in 2018 on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways™ contained in the Decision of the 21st Conference of Parties of the United Nations Framework Convention on Climate Change to adopt the Paris Agreement. 1The IPCC accepted the invitation in April 2016, deciding to prepare this Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty. This Summary for Policymakers (SPM) presents the key ˜ndings of the Special Report, based on the assessment of the available scienti˜c, technical and socio-economic literature 2 relevant to global warming of 1.5°C and for the comparison between global warming of 1.5°C and 2°C above pre-industrial levels. The level of con˜dence associated with each key ˜nding is reported using the IPCC calibrated language. 3 The underlying scienti˜c basis of each key ˜nding is indicated by references provided to chapter elements. In the SPM, knowledge gaps are identi˜ed associated with the underlying chapters of the Report. A. Understanding Global Warming of 1.5°C 4A.1 Human activities are estimated to have caused approximately 1.0°C of global warming 5 above pre-industrial levels, with a likely range of 0.8°C to 1.2°C. Global warming is likely to reach 1.5°C between 2030 and 2052 if it continues to increase at the current rate. ( high con˜dence) (Figure SPM.1) {1.2}A.1.1 Re˚ecting the long-term warming trend since pre-industrial times, observed global mean surface temperature (GMST) for the decade 2006Œ2015 was 0.87°C ( likely between 0.75°C and 0.99°C)6 higher than the average over the 1850Œ1900 period (very high con˜dence). Estimated anthropogenic global warming matches the level of observed warming to within ±20% (likely range ). Estimated anthropogenic global warming is currently increasing at 0.2°C ( likely between 0.1°C and 0.3°C) per decade due to past and ongoing emissions (high con˜dence). {1.2.1, Table 1.1, 1.2.4} A.1.2 Warming greater than the global annual average is being experienced in many land regions and seasons, including two to three times higher in the Arctic. Warming is generally higher over land than over the ocean. ( high con˜dence) {1.2.1, 1.2.2, Figure 1.1, Figure 1.3, 3.3.1, 3.3.2} A.1.3 Trends in intensity and frequency of some climate and weather extremes have been detected over time spans during which about 0.5°C of global warming occurred ( medium con˜dence). This assessment is based on several lines of evidence, including attribution studies for changes in extremes since 1950. {3.3.1, 3.3.2, 3.3.3} 1 Decision 1/CP.21, paragraph 21. 2 The assessment covers literature accepted for publication by 15 May 2018. 3 Each ˜nding is grounded in an evaluation of underlying evidence and agreement. A level of con˜dence is expressed using ˜ve quali˜ers: very low, low, medium, high and very high, and typeset in italics, for example, medium con˜dence. The following terms have been used to indicate the assessed likelihood of an outcome or a result: virtually certain 99Œ100% probability, very likely 90Œ100%, likely 66Œ100%, about as likely as not 33Œ66%, unlikely 0Œ33%, very unlikely 0Œ10%, exceptionally unlikely 0Œ1%. Additional terms (extremely likely 95Œ100%, more likely than not >50Œ100%, more unlikely than likely 0Œ<50%, extremely unlikely 0Œ5%) may also be used when appropriate. Assessed likelihood is typeset in italics, for example, very likely . This is consistent with AR5. 4 See also Box SPM.1: Core Concepts Central to this Special Report. 5 Present level of global warming is de˜ned as the average of a 30-year period centred on 2017 assuming the recent rate of warming continues. 6 This range spans the four available peer-reviewed estimates of the observed GMST change and also accounts for additional uncertainty due to possible short-term natural variability. {1.2.1, Table 1.1}
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5A.2 Warming from anthropogenic emissions from the pre-industrial period to the present will persist for centuries to millennia and will continue to cause further long-term changes in the climate system, such as sea level rise, with associated impacts (high con˜dence), but these emissions alone are unlikely to cause global warming of 1.5°C (medium con˜dence). (Figure SPM.1) {1.2, 3.3, Figure 1.5} A.2.1 Anthropogenic emissions (including greenhouse gases, aerosols and their precursors) up to the present are unlikely to cause further warming of more than 0.5°C over the next two to three decades ( high con˜dence) or on a century time scale (medium con˜dence). {1.2.4, Figure 1.5} A.2.2 Reaching and sustaining net zero global anthropogenic CO2 emissions and declining net non-CO2 radiative forcing would halt anthropogenic global warming on multi-decadal time scales ( high con˜dence ). The maximum temperature reached is then determined by cumulative net global anthropogenic CO 2 emissions up to the time of net zero CO 2 emissions ( high con˜dence) and the level of non-CO2 radiative forcing in the decades prior to the time that maximum temperatures are reached (medium con˜dence). On longer time scales, sustained net negative global anthropogenic CO 2 emissions and/or further reductions in non-CO2 radiative forcing may still be required to prevent further warming due to Earth system feedbacks and to reverse ocean acidi˜cation ( medium con˜dence ) and will be required to minimize sea level rise ( high con˜dence). {Cross-Chapter Box 2 in Chapter 1, 1.2.3, 1.2.4, Figure 1.4, 2.2.1, 2.2.2, 3.4.4.8, 3.4.5.1, 3.6.3.2} A.3 Climate-related risks for natural and human systems are higher for global warming of 1.5°C than at present, but lower than at 2°C ( high con˜dence). These risks depend on the magnitude and rate of warming, geographic location, levels of development and vulnerability, and on the choices and implementation of adaptation and mitigation options (high con˜dence). (Figure SPM.2) {1.3, 3.3, 3.4, 5.6}A.3.1 Impacts on natural and human systems from global warming have already been observed ( high con˜dence). Many land and ocean ecosystems and some of the services they provide have already changed due to global warming ( high con˜dence). (Figure SPM.2) {1.4, 3.4, 3.5} A.3.2 Future climate-related risks depend on the rate, peak and duration of warming. In the aggregate, they are larger if global warming exceeds 1.5°C before returning to that level by 2100 than if global warming gradually stabilizes at 1.5°C, especially if the peak temperature is high (e.g., about 2°C) ( high con˜dence). Some impacts may be long-lasting or irreversible, such as the loss of some ecosystems (high con˜dence). {3.2, 3.4.4, 3.6.3, Cross-Chapter Box 8 in Chapter 3} A.3.3 Adaptation and mitigation are already occurring (high con˜dence). Future climate-related risks would be reduced by the upscaling and acceleration of far-reaching, multilevel and cross-sectoral climate mitigation and by both incremental and transformational adaptation (high con˜dence). {1.2, 1.3, Table 3.5, 4.2.2, Cross-Chapter Box 9 in Chapter 4, Box 4.2, Box 4.3, Box 4.6, 4.3.1, 4.3.2, 4.3.3, 4.3.4, 4.3.5, 4.4.1, 4.4.4, 4.4.5, 4.5.3}
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660503 0002 0001 00040302010003210˜˚˛˚˝˙Billion tonnes CO˜ per year (GtCO˜/yr)Billion tonnes CO˜ (GtCO˜)Watts per square metre (W/m˚)˜˚˛˝Observed monthly global mean surface temperatureEstimated anthropogenic warming to date and likely rangeFaster immediate CO˜ emission reductions limit cumulative CO˜ emissions shown in panel .Maximum temperature rise is determined by cumulative net CO˜ emissions and net non-CO˜ radiative forcing due to methane, nitrous oxide, aerosols and other anthropogenic forcing agents.Global warming relative to 1850-1900 (°C)CO˜ emissions decline from 2020 to reach net zero in or †“‘“Cumulative CO˜ emissions in pathways reaching net zero in and †“‘“Non-CO˜ radiative forcing or 1960198020202060210019802020206021001980202020602100198020002020201720402060208021002.01.51.00.50Likely Faster CO˜ reductions (blue in ˜ & ˚) result in a ˛˝˙˛ˆˇ˘ of limiting warming to 1.5°C of net non-CO˜ radiative forcing (purple in ) results in a of limiting warming to 1.5°C Global CO˜ emissions reach while net non-CO˜ radiative forcing is (grey in ˜, ˚ & )Figure SPM.1 | Panel a: Observed monthly global mean surface temperature (GMST, grey line up to 2017, from the HadCRUT4, GISTEMP, CowtanŒWay, and NOAA datasets) change and estimated anthropogenic global warming (solid orange line up to 2017, with orange shading indicating assessed likely range). Orange dashed arrow and horizontal orange error bar show respectively the central estimate and likely range of the time at which 1.5°C is reached if the current rate of warming continues. The grey plume on the right of panel a shows the likely range of warming responses, computed with a simple climate model, to a stylized pathway (hypothetical future) in which net CO 2 emissions (grey line in panels b and c) decline in a straight line from 2020 to reach net zero in 2055 and net non- CO2 radiative forcing (grey line in panel d) increases to 2030 and then declines. The blue plume in panel a) shows the response to faster CO 2 emissions reductions (blue line in panel b), reaching net zero in 2040, reducing cumulative CO 2 emissions (panel c). The purple plume shows the response to net CO 2 emissions declining to zero in 2055, with net non-CO 2 forcing remaining constant after 2030. The vertical error bars on right of panel a) show the likely ranges (thin lines) and central terciles (33rd Œ 66th percentiles, thick lines) of the estimated distribution of warming in 2100 under these three stylized pathways. Vertical dotted error bars in panels b, c and d show the likely range of historical annual and cumulative global net CO 2 emissions in 2017 (data from the Global Carbon Project) and of net non-CO2 radiative forcing in 2011 from AR5, respectively. Vertical axes in panels c and d are scaled to represent approximately equal effects on GMST. {1.2.1, 1.2.3, 1.2.4, 2.3, Figure 1.2 and Chapter 1 Supplementary Material, Cross-Chapter Box 2 in Chapter 1}
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8B.2.3 Increasing warming ampli˜es the exposure of small islands, low-lying coastal areas and deltas to the risks associated with sea level rise for many human and ecological systems, including increased saltwater intrusion, ˚ooding and damage to infrastructure ( high con˜dence). Risks associated with sea level rise are higher at 2°C compared to 1.5°C. The slower rate of sea level rise at global warming of 1.5°C reduces these risks, enabling greater opportunities for adaptation including managing and restoring natural coastal ecosystems and infrastructure reinforcement (medium con˜dence). (Figure SPM.2) {3.4.5, Box 3.5} B.3 On land, impacts on biodiversity and ecosystems, including species loss and extinction, are projected to be lower at 1.5°C of global warming compared to 2°C. Limiting global warming to 1.5°C compared to 2°C is projected to lower the impacts on terrestrial, freshwater and coastal ecosystems and to retain more of their services to humans ( high con˜dence). (Figure SPM.2) {3.4, 3.5, Box 3.4, Box 4.2, Cross-Chapter Box 8 in Chapter 3} B.3.1 Of 105,000 species studied,9 6% of insects, 8% of plants and 4% of vertebrates are projected to lose over half of their climatically determined geographic range for global warming of 1.5°C, compared with 18% of insects, 16% of plants and 8% of vertebrates for global warming of 2°C ( medium con˜dence ). Impacts associated with other biodiversity-related risks such as forest ˜res and the spread of invasive species are lower at 1.5°C compared to 2°C of global warming ( high con˜dence). {3.4.3, 3.5.2} B.3.2 Approximately 4% (interquartile range 2Œ7%) of the global terrestrial land area is projected to undergo a transformation of ecosystems from one type to another at 1°C of global warming, compared with 13% (interquartile range 8Œ20%) at 2°C (medium con˜dence). This indicates that the area at risk is projected to be approximately 50% lower at 1.5°C compared to 2°C (medium con˜dence). {3.4.3.1, 3.4.3.5} B.3.3 High-latitude tundra and boreal forests are particularly at risk of climate change-induced degradation and loss, with woody shrubs already encroaching into the tundra (high con˜dence) and this will proceed with further warming. Limiting global warming to 1.5°C rather than 2°C is projected to prevent the thawing over centuries of a permafrost area in the range of 1.5 to 2.5 million km2 (medium con˜dence). {3.3.2, 3.4.3, 3.5.5} B.4 Limiting global warming to 1.5°C compared to 2°C is projected to reduce increases in ocean temperature as well as associated increases in ocean acidity and decreases in ocean oxygen levels (high con˜dence). Consequently, limiting global warming to 1.5°C is projected to reduce risks to marine biodiversity, ˜sheries, and ecosystems, and their functions and services to humans, as illustrated by recent changes to Arctic sea ice and warm-water coral reef ecosystems ( high con˜dence). {3.3, 3.4, 3.5, Box 3.4, Box 3.5}B.4.1 There is high con˜dence that the probability of a sea ice-free Arctic Ocean during summer is substantially lower at global warming of 1.5°C when compared to 2°C. With 1.5°C of global warming, one sea ice-free Arctic summer is projected per century. This likelihood is increased to at least one per decade with 2°C global warming. Effects of a temperature overshoot are reversible for Arctic sea ice cover on decadal time scales ( high con˜dence). {3.3.8, 3.4.4.7} B.4.2 Global warming of 1.5°C is projected to shift the ranges of many marine species to higher latitudes as well as increase the amount of damage to many ecosystems. It is also expected to drive the loss of coastal resources and reduce the productivity of ˜sheries and aquaculture (especially at low latitudes). The risks of climate-induced impacts are projected to be higher at 2°C than those at global warming of 1.5°C ( high con˜dence). Coral reefs, for example, are projected to decline by a further 70Œ90% at 1.5°C (high con˜dence) with larger losses (>99%) at 2°C (very high con˜dence). The risk of irreversible loss of many marine and coastal ecosystems increases with global warming, especially at 2°C or more ( high con˜dence). {3.4.4, Box 3.4} 9 Consistent with earlier studies, illustrative numbers were adopted from one recent meta-study.
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910 Here, impacts on economic growth refer to changes in gross domestic product (GDP). Many impacts, such as loss of human lives, cultural heritage and ecosystem services, are dif˜cult to value and monetize. B.4.3 The level of ocean acidi˜cation due to increasing CO 2 concentrations associated with global warming of 1.5°C is projected to amplify the adverse effects of warming, and even further at 2°C, impacting the growth, development, calci˜cation, survival, and thus abundance of a broad range of species, for example, from algae to ˜sh ( high con˜dence). {3.3.10, 3.4.4} B.4.4 Impacts of climate change in the ocean are increasing risks to ˜sheries and aquaculture via impacts on the physiology, survivorship, habitat, reproduction, disease incidence, and risk of invasive species ( medium con˜dence) but are projected to be less at 1.5°C of global warming than at 2°C. One global ˜shery model, for example, projected a decrease in global annual catch for marine ˜sheries of about 1.5 million tonnes for 1.5°C of global warming compared to a loss of more than 3 million tonnes for 2°C of global warming ( medium con˜dence). {3.4.4, Box 3.4} B.5 Climate-related risks to health, livelihoods, food security, water supply, human security, and economic growth are projected to increase with global warming of 1.5°C and increase further with 2°C. (Figure SPM.2) {3.4, 3.5, 5.2, Box 3.2, Box 3.3, Box 3.5, Box 3.6, Cross-Chapter Box 6 in Chapter 3, Cross-Chapter Box 9 in Chapter 4, Cross-Chapter Box 12 in Chapter 5, 5.2} B.5.1 Populations at disproportionately higher risk of adverse consequences with global warming of 1.5°C and beyond include disadvantaged and vulnerable populations, some indigenous peoples, and local communities dependent on agricultural or coastal livelihoods (high con˜dence). Regions at disproportionately higher risk include Arctic ecosystems, dryland regions, small island developing states, and Least Developed Countries ( high con˜dence). Poverty and disadvantage are expected to increase in some populations as global warming increases; limiting global warming to 1.5°C, compared with 2°C, could reduce the number of people both exposed to climate-related risks and susceptible to poverty by up to several hundred million by 2050 (medium con˜dence). {3.4.10, 3.4.11, Box 3.5, Cross-Chapter Box 6 in Chapter 3, Cross-Chapter Box 9 in Chapter 4, Cross-Chapter Box 12 in Chapter 5, 4.2.2.2, 5.2.1, 5.2.2, 5.2.3, 5.6.3} B.5.2 Any increase in global warming is projected to affect human health, with primarily negative consequences ( high con˜dence). Lower risks are projected at 1.5°C than at 2°C for heat-related morbidity and mortality (very high con˜dence) and for ozone-related mortality if emissions needed for ozone formation remain high (high con˜dence). Urban heat islands often amplify the impacts of heatwaves in cities ( high con˜dence). Risks from some vector-borne diseases, such as malaria and dengue fever, are projected to increase with warming from 1.5°C to 2°C, including potential shifts in their geographic range (high con˜dence). {3.4.7, 3.4.8, 3.5.5.8} B.5.3 Limiting warming to 1.5°C compared with 2°C is projected to result in smaller net reductions in yields of maize, rice, wheat, and potentially other cereal crops, particularly in sub-Saharan Africa, Southeast Asia, and Central and South America, and in the CO2-dependent nutritional quality of rice and wheat (high con˜dence). Reductions in projected food availability are larger at 2°C than at 1.5°C of global warming in the Sahel, southern Africa, the Mediterranean, central Europe, and the Amazon (medium con˜dence). Livestock are projected to be adversely affected with rising temperatures, depending on the extent of changes in feed quality, spread of diseases, and water resource availability ( high con˜dence). {3.4.6, 3.5.4, 3.5.5, Box 3.1, Cross-Chapter Box 6 in Chapter 3, Cross-Chapter Box 9 in Chapter 4} B.5.4 Depending on future socio-economic conditions, limiting global warming to 1.5°C compared to 2°C may reduce the proportion of the world population exposed to a climate change-induced increase in water stress by up to 50%, although there is considerable variability between regions ( medium con˜dence). Many small island developing states could experience lower water stress as a result of projected changes in aridity when global warming is limited to 1.5°C, as compared to 2°C (medium con˜dence). {3.3.5, 3.4.2, 3.4.8, 3.5.5, Box 3.2, Box 3.5, Cross-Chapter Box 9 in Chapter 4} B.5.5 Risks to global aggregated economic growth due to climate change impacts are projected to be lower at 1.5°C than at 2°C by the end of this century 10 ( medium con˜dence ). This excludes the costs of mitigation, adaptation investments and the bene˜ts of adaptation. Countries in the tropics and Southern Hemisphere subtropics are projected to experience the largest impacts on economic growth due to climate change should global warming increase from 1.5°C to 2°C ( medium con˜dence). {3.5.2, 3.5.3}
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10B.5.6 Exposure to multiple and compound climate-related risks increases between 1.5°C and 2°C of global warming, with greater proportions of people both so exposed and susceptible to poverty in Africa and Asia ( high con˜dence). For global warming from 1.5°C to 2°C, risks across energy, food, and water sectors could overlap spatially and temporally, creating new and exacerbating current hazards, exposures, and vulnerabilities that could affect increasing numbers of people and regions (medium con˜dence). {Box 3.5, 3.3.1, 3.4.5.3, 3.4.5.6, 3.4.11, 3.5.4.9} B.5.7 There are multiple lines of evidence that since AR5 the assessed levels of risk increased for four of the ˜ve Reasons for Concern (RFCs) for global warming to 2°C ( high con˜dence ). The risk transitions by degrees of global warming are now: from high to very high risk between 1.5°C and 2°C for RFC1 (Unique and threatened systems) ( high con˜dence ); from moderate to high risk between 1°C and 1.5°C for RFC2 (Extreme weather events) (medium con˜dence); from moderate to high risk between 1.5°C and 2°C for RFC3 (Distribution of impacts) (high con˜dence); from moderate to high risk between 1.5°C and 2.5°C for RFC4 (Global aggregate impacts) (medium con˜dence); and from moderate to high risk between 1°C and 2.5°C for RFC5 (Large-scale singular events) (medium con˜dence). (Figure SPM.2) {3.4.13; 3.5, 3.5.2} B.6 Most adaptation needs will be lower for global warming of 1.5°C compared to 2°C ( high con˜dence). There are a wide range of adaptation options that can reduce the risks of climate change ( high con˜dence). There are limits to adaptation and adaptive capacity for some human and natural systems at global warming of 1.5°C, with associated losses (medium con˜dence). The number and availability of adaptation options vary by sector (medium con˜dence). {Table 3.5, 4.3, 4.5, Cross- Chapter Box 9 in Chapter 4, Cross-Chapter Box 12 in Chapter 5} B.6.1 A wide range of adaptation options are available to reduce the risks to natural and managed ecosystems (e.g., ecosystem- based adaptation, ecosystem restoration and avoided degradation and deforestation, biodiversity management, sustainable aquaculture, and local knowledge and indigenous knowledge), the risks of sea level rise (e.g., coastal defence and hardening), and the risks to health, livelihoods, food, water, and economic growth, especially in rural landscapes (e.g., ef˜cient irrigation, social safety nets, disaster risk management, risk spreading and sharing, and community- based adaptation) and urban areas (e.g., green infrastructure, sustainable land use and planning, and sustainable water management) (medium con˜dence). {4.3.1, 4.3.2, 4.3.3, 4.3.5, 4.5.3, 4.5.4, 5.3.2, Box 4.2, Box 4.3, Box 4.6, Cross-Chapter Box 9 in Chapter 4}.B.6.2 Adaptation is expected to be more challenging for ecosystems, food and health systems at 2°C of global warming than for 1.5°C (medium con˜dence). Some vulnerable regions, including small islands and Least Developed Countries, are projected to experience high multiple interrelated climate risks even at global warming of 1.5°C ( high con˜dence). {3.3.1, 3.4.5, Box 3.5, Table 3.5, Cross-Chapter Box 9 in Chapter 4, 5.6, Cross-Chapter Box 12 in Chapter 5, Box 5.3} B.6.3 Limits to adaptive capacity exist at 1.5°C of global warming, become more pronounced at higher levels of warming and vary by sector, with site-speci˜c implications for vulnerable regions, ecosystems and human health ( medium con˜dence). {Cross-Chapter Box 12 in Chapter 5, Box 3.5, Table 3.5}
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1110 Here, impacts on economic growth refer to changes in gross domestic product (GDP). Many impacts, such as loss of human lives, cultural heritage and ecosystem services, are dif˜cult to value and monetize. 1.01.52.001.01.52.00Global mean surface temperature change relative to pre-industrial levels (˜C)Global mean surface temperature change relative to pre-industrial levels (˜C)2006-2015˙ˇImpacts and risks associated with the Reasons for Concern (RFCs)Purple indicates very high risks of severe impacts/risks and the presence of significant irreversibility or the persistence of climate-related hazards, combined with limited ability to adapt due to the nature of the hazard or impacts/risks. Red indicates severe and widespread impacts/risks. Yellow indicates that impacts/risks are detectable and attributable to climate change with at least medium confidence. White indicates that no impacts are detectable and attributable to climate change.Five Reasons For Concern (RFCs) illustrate the impacts and risks of di˚erent levels of global warming for people, economies and ecosystems across sectors and regions.Heat-related morbidity and mortalityLevel of additional impact/risk due to climate changeUnique and threatened systemsExtreme weather events Global aggregate impactsLarge scale singular eventsDistribution of impactsWarm-watercoralsTerrestrialecosystemsTourism2006-2015HVHVHHHHHMM-HHMMMMMHMHHHMHHMMHMHMHMHMHImpacts and risks for selected natural, managed and human systemsConfidence level for transition: L=Low, M=Medium, H=High and VH=Very highMangrovesSmall-scalelow-latitudefisheriesArcticregionCoastal floodingFluvial floodingCrop yieldsUndetectableModerateHighVery highFigure SPM.2 | Five integrative reasons for concern (RFCs) provide a framework for summarizing key impacts and risks across sectors and regions, and were introduced in the IPCC Third Assessment Report. RFCs illustrate the implications of global warming for people, economies and ecosystems. Impacts and/or risks for each RFC are based on assessment of the new literature that has appeared. As in AR5, this literature was used to make expert judgments to assess the levels of global warming at which levels of impact and/or risk are undetectable, moderate, high or very high. The selection of impacts and risks to natural, managed and human systems in the lower panel is illustrative and is not intended to be fully comprehensive. {3.4, 3.5, 3.5.2.1, 3.5.2.2, 3.5.2.3, 3.5.2.4, 3.5.2.5, 5.4.1, 5.5.3, 5.6.1, Box 3.4} RFC1 Unique and threatened systems: ecological and human systems that have restricted geographic ranges constrained by climate-related conditions and have high endemism or other distinctive properties. Examples include coral reefs, the Arctic and its indigenous people, mountain glaciers and biodiversity hotspots. RFC2 Extreme weather events: risks/impacts to human health, livelihoods, assets and ecosystems from extreme weather events such as heat waves, heavy rain, drought and associated wild˜res, and coastal ˚ooding. RFC3 Distribution of impacts: risks/impacts that disproportionately affect particular groups due to uneven distribution of physical climate change hazards, exposure or vulnerability. RFC4 Global aggregate impacts: global monetary damage, global-scale degradation and loss of ecosystems and biodiversity. RFC5 Large-scale singular events: are relatively large, abrupt and sometimes irreversible changes in systems that are caused by global warming. Examples include disintegration of the Greenland and Antarctic ice sheets.
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