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Summary for PolicymakersSPMSummary for Policymakers3SPMDrafting AuthorsMyles 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 asIPCC, 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. Waterfield eds.]. In Press.Summary for PolicymakersSPMSPMSummary for Policymakers4IntroductionThis 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 findings of the Special Report, based on the assessment of the available scientific, technical and socio-economic literature2relevant 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 confidence associated with each key finding is reported using the IPCC calibrated language.3The underlying scientific basis of each key finding is indicated by references provided to chapter elements. In the SPM, knowledge gaps are identified associated with the underlying chapters of the Report.A. Understanding Global Warming of 1.5°C4A.1 Human activities are estimated to have caused approximately 1.0°C of global warming5above 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 confidence Figure SPM.1 {1.2}A.1.1 Reflecting the long-term warming trend since pre-industrial times, observed global mean surface temperature GMST for the decade 2006–2015 was 0.87°C likely between 0.75°C and 0.99°C6higher than the average over the 1850–1900 period very high confidence. 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 confidence. {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 confidence {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 confidence. 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 finding is grounded in an uation of underlying evidence and agreement. A level of confidence is expressed using five qualifiers very low, low, medium, high and very high, and typeset in italics, for example, medium confidence. The following terms have been used to indicate the assessed likelihood of an outcome or a result virtually certain 99–100 probability, very likely 90–100, likely 66–100, about as likely as not 33–66, unlikely 0–33, very unlikely 0–10, exceptionally unlikely 0–1. Additional terms extremely likely 95–100, more likely than not 50–100, more unlikely than likely 0–99 at 2°C very high confidence. The risk of irreversible loss of many marine and coastal ecosystems increases with global warming, especially at 2°C or more high confidence. {3.4.4, Box 3.4}9 Consistent with earlier studies, illustrative numbers were adopted from one recent meta-study.SPMSummary for Policymakers910 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 difficult to value and monetize.B.4.3 The level of ocean acidification due to increasing CO2concentrations 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, calcification, survival, and thus abundance of a broad range of species, for example, from algae to fish high confidence. {3.3.10, 3.4.4}B.4.4 Impacts of climate change in the ocean are increasing risks to fisheries and aquaculture via impacts on the physiology, survivorship, habitat, reproduction, disease incidence, and risk of invasive species medium confidence but are projected to be less at 1.5°C of global warming than at 2°C. One global fishery model, for example, projected a decrease in global annual catch for marine fisheries 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 confidence. {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 confidence. Regions at disproportionately higher risk include Arctic ecosystems, dryland regions, small island developing states, and Least Developed Countries high confidence. 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 confidence. {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 confidence. Lower risks are projected at 1.5°C than at 2°C for heat-related morbidity and mortality very high confidence and for ozone-related mortality if emissions needed for ozone ation remain high high confidence. Urban heat islands often amplify the impacts of heatwaves in cities high confidence. 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 confidence. {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 confidence. 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 confidence. 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 confidence. {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 confidence. 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 confidence. {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 century10medium confidence. This excludes the costs of mitigation, adaptation investments and the benefits 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 confidence. {3.5.2, 3.5.3} SPMSummary for Policymakers10B.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 confidence. 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 confidence. {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 five Reasons for Concern RFCs for global warming to 2°C high confidence. 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 confidence; from moderate to high risk between 1°C and 1.5°C for RFC2 Extreme weather events medium confidence; from moderate to high risk between 1.5°C and 2°C for RFC3 Distribution of impacts high confidence; from moderate to high risk between 1.5°C and 2.5°C for RFC4 Global aggregate impacts medium confidence; and from moderate to high risk between 1°C and 2.5°C for RFC5 Large-scale singular events medium confidence. 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 confidence. There are a wide range of adaptation options that can reduce the risks of climate change high confidence. 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 confidence. The number and availability of adaptation options vary by sector medium confidence. {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., efficient 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 confidence. {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 confidence. 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 confidence. {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-specific implications for vulnerable regions, ecosystems and human health medium confidence. {Cross-Chapter Box 12 in Chapter 5, Box 3.5, Table 3.5} SPMSummary for Policymakers1110 Here, impacts on economic growth refer
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