Ranzi, Roberto

English

Hydraulic Engineering Repository

Article, Published VersionRanzi, RobertoClimate Change impact, adaptation and mitigation in thewater sector: new hints from the IPCC AR6HydrolinkVerfügbar unter/Available at: https://hdl.handle.net/20.500.11970/110518Vorgeschlagene Zitierweise/Suggested citation:Ranzi, Roberto (2022): Climate Change impact, adaptation and mitigation in the watersector: new hints from the IPCC AR6. In: Hydrolink 2022/3. Madrid: International Associationfor Hydro-Environment Engineering and Research (IAHR). S. 68-71.https://www.iahr.org/library/hydrolink?hid=472.Standardnutzungsbedingungen/Terms of Use:Die Dokumente in HENRY stehen unter der Creative Commons Lizenz CC BY 4.0, sofern keine abweichendenNutzungsbedingungen getroffen wurden. Damit ist sowohl die kommerzielle Nutzung als auch das Teilen, dieWeiterbearbeitung und Speicherung erlaubt. Das Verwenden und das Bearbeiten stehen unter der Bedingung derNamensnennung. Im Einzelfall kann eine restriktivere Lizenz gelten; dann gelten abweichend von den obigenNutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte.Documents in HENRY are made available under the Creative Commons License CC BY 4.0, if no other license isapplicable. Under CC BY 4.0 commercial use and sharing, remixing, transforming, and building upon the materialof the work is permitted. In some cases a different, more restrictive license may apply; if applicable the terms ofthe restrictive license will be binding.68  |  #HydrolinkMagazine IAHR.orgIN DEPTH >  CLIMATE CHANGE3 | 2022Climate Change impact, adaptation and mitigationin the water sector: new hints from the IPCC AR6By Roberto RanziIn August 2021 the Intergovernmental Panel onClimate Change (IPCC), during its 54th sessionfinalized the first part of the Sixth AssessmentReport (AR6), Climate Change 2021: The PhysicalScience Basis 1, prepared by Working Group I (WGI).Later, in spring 2022 also the reports of WorkingGroup II (WGII)2 and Working Group III (WGIII) onImpact, Adaptation and Vulnerability and on Mitiga-tion were published on-line3. The full Working GroupIII report is published only in draft form, while theSummary for policymakers has been approved. Theconcern of scientists, media, and decision makersabout the trends of warming, melting of ice sheets4,rate of sea level rise and other impacts on the hydro-sphere and the biosphere is very high.The thousands of pages of the IPCC reports andtheir summaries for policymakers provide a soundbasis for an up-to-date approach for the assessmentof the impact, the design of adaptation and mitiga-tion measures in water engineering, a topic of highinterest for IAHR.Some of the headline statements and the summaryconclusions from the IPCC reports which have ahigh or at least medium level of consensus are ofspecial interest for the water sector and are summa-rized in the following. Parts of these reports arecited verbatim in this article in order to conveyaccurately to the readers of Hydrolink the messageof the IPCC.IAHR.org #HydrolinkMagazine  |  69IN DEPTH >  CLIMATE CHANGE 3 | 2022• It is virtually certain that the Arctic will continue to warmmore than the global surface, with high confidence abovetwo times the rate of global warming. Additional warmingis projected to further amplify permafrost thawing, and lossof seasonal snow cover, of land ice and of Arctic sea ice(high confidence). There is low confidence in the projecteddecrease of Antarctic sea ice.• It is virtually certain that global mean sea level will continueto rise over the 21st century. Relative to 1995-2014, thelikely (with medium confidence) global mean sea level riseby 2100 is 0.28-0.55 m under the very low GHG emissionsscenario (SSP1-1.9), 0.44-0.76 m under the intermediateGHG emissions scenario (SSP2-4.5), and 0.63-1.01 m under the very high GHG emissions scenario (SSP5-8.5).• Precipitation is projected to increase over high latitudes,the equatorial Pacific and parts of the monsoon regions,but decrease over parts of the subtropics and in limitedareas of the tropics.• Increases in frequency and intensity of hydrological droughtsbecome larger with increasing global warming in someregions (medium confidence). There will be an increasingoccurrence of some extreme events unprecedented in theobservational record with additional global warming, evenat 1.5°C of global warming.• It is very likely that heavy precipitation events will intensifyand become more frequent with additional global warming.At the global scale, extreme daily precipitation events, withreturn period of 10 years, are projected to intensify by about7% for each 1°C of global warming (high confidence).• There is strengthened evidence since AR5 that the globalwater cycle will continue to intensify as global temperaturesrise (high confidence), with precipitation and surface waterflows projected to become more variable over most landregions within seasons (high confidence) and from year toyear (medium confidence).• Global warming of 1.5°C and 2°C will be exceeded duringthe 21st century unless deep reductions in carbon dioxide(CO2) and other greenhouse gas emissions occur in thecoming decades.The IPCC AR6 report depicts scenarios consistent with, but, tosome extent, even more severe than the AR5 and poses respon-sibilities to the decision makers on the active measures to betaken to mitigate the effect of the projected global warming.The water engineering community including IAHR is alsochallenged in order to properly address at the regional and localscale the impact of combined climatic and anthropogenic chan-ges in the water cycle and revise the design and managementcriteria in the water sector.The science basis and impact on the water sectorThe current state of the climateIt is indisputable that human activities are causing climatechange, making extreme climate events, including heat waves,heavy rainfall, and droughts, more frequent and severe.• The likely range of total human-caused global surface tem-perature increase from 1850–1900 to 2010–2019 is 0.8°Cto 1.3°C, with a best estimate of 1.07°C.• Human influence is very likely the main driver of the globalretreat of glaciers since the 1990s and the decrease inArctic sea ice area between 1979–1988 and 2010–2019.However there has been no significant trend in Antarcticsea ice area from 1979 to 2020 due to regionally opposingtrends and large internal variability.• It can be stated with high confidence that global mean sealevel increased by 0.20 [0.15 to 0.25] m between 1901 and2018. The average rate of sea level rise was 1.3 [0.6 to 2.1]mm yr-1 between 1901 and 1971, increasing to 1.9 [0.8 to 2.9]mm yr-1 between 1971 and 2006, and further increasing to3.7 [3.2 to 4.2] mm yr-1 between 2006 and 2018. Thermalexpansion explained 50% of sea level rise during 1971–2018,while ice loss from glaciers contributed 22%, ice sheets 20%and changes in land water storage 8%.• In 19 out of 45 macroregions of the world an increase ofheavy precipitation (drawn from one to five days precipitation)is observed, in 8 of them a low agreement is reached on thetype of change and in none of them a decrease is assessed.• Increased adverse impacts of inland flooding and flood orstorm induced damages in coastal areas are observedworldwide, especially in Asia, Australasia, North Americaand mountain regions.• In 12 out of 45 macroregions of the world an increase ofagricultural and ecological drought, due to increased landevapotranspiration, is observed, in 28 a low agreement isreached on the type of change and just in one of them adecrease is assessed.Possible Climate FuturesA set of five new illustrative emissions scenarios (named SSPx-y ‘Shared Socio-economic Pathway’ differently from the Repre-sentative Concentration Pathways (RCPs) in the 5th AssessmentReport) labelled with x=1,..5, with radiative forcing, y, set toy=1.9, 2.6, 4.5, 7.0 and 8.5 Wm-2, is considered in AR6.• In the mid term (2041-2060) and long term (2081-2100)the very likely range of mean global surface temperatureincrease compared to 1850-1900 ranges from 2.0°C to2.4°C and 2.7°C to 4.4°C, respectively, according to theSSP3-4.5 and SSP5-8.5 scenarios.70  |  #HydrolinkMagazine IAHR.orgIN DEPTH >  CLIMATE CHANGE3 | 2022Adaptation measuresThe WGII report focused on the transformation and systemtransitions in energy; land, ocean, coastal and freshwater eco-systems; urban, rural and infrastructure; and industry and society.Chapter 4 of the WGII Report is fully dedicated to impact andadaptation in the water sector.Land ocean and ecosystem transitionIPCC recognizes with high confidence that adaptation to water-related risks and impacts is well documented. For inland flooding,combinations of non-structural measures like early warningsystems and structural measures like levees have reduced lossof lives. Enhancing natural water retention, e.g., by restoringwetlands and rivers, land use planning such as no build zonesor upstream forest management, can further reduce flood risk.On-farm water management, water storage, soil moistureconservation and irrigation are some of the most commonadaptation responses and provide economic, institutionalor ecological benefits and reduce vulnerability. Irrigation needsappropriate management to avoid potential adverse outcomes,which can include accelerated depletion of groundwater andother water sources and increased soil salinization. However,the effectiveness of most water-related adaptation options toreduce projected risks declines with increasing warming.Small islandsObserved adaptation measures in small islands during droughtevents includes community water sharing, as well as usingalternative water resources such as water purchased fromprivate companies, desalination units or accessing deeper ornew groundwater resources and rainwater harvesting.Urban, rural and infrastructure transitionWith medium confidence it is perceived that combined eco-system-based and structural adaptation responses are beingdeveloped, and there is growing evidence of their potential toreduce adaptation costs and contribute to flood control, sanita-tion, water resources management, landslide prevention andcoastal protection. Responses to ongoing sea level rise andland subsidence in low-lying coastal cities and settlementsand small islands include protection, accommodation, advanceand planned relocation. These responses are more effectiveif combined and/or sequenced, planned well ahead, alignedwith sociocultural values and development priorities, andunderpinned by inclusive community engagement processes.Coastal cities and settlements play a key role in moving towardhigher climate resilient development, as almost 900 millionpeople lived within the Low Elevation Coastal Zone, below10 m of elevation above sea level in 2020. Therefore, theseareas make key contributions to climate resilient developmentthrough their vital role in national economies.Adaptation in the agricultural sectorWater-related adaptation in the agricultural sector makes upthe majority of documented local, regional and global evidenceof implemented adaptation. Water and soil conservation measures(e.g., reduced tillage, contour ridges or mulching) are frequentlydocumented as adaptation responses to reduce water-relatedclimate impacts in the agricultural sector. The use of non-con-ventional water sources, that is, desalinated and treated waste-water, is emerging as an important component of increasingwater availability for agriculture. While desalination has a highpotential in alleviating agricultural water stress in arid coastalregions, proper management and water quality standards fordesalinated irrigation water are essential to ensure continuedor increased crop productivity. In addition to the energy intensity,risks of desalinated water include lower mineral content, highersalinity, crop toxicity and soil sodicity. Similarly, wastewaterreuse can be an important contribution to buffer against theincreasing variability of water resources. However, wastewateruse guidelines that ensure the adequate treatment to reduceadverse health and environmental outcomes due to pathogensor other chemical and organic contaminants are essential.Energy system transitionWithin energy system transitions, the most feasible adaptationoptions support infrastructure resilience, reliable power systemsand efficient water use for existing and new energy generationsystems. Energy generation diversification, including renewableenergy resources and generation that can be decentralised de-pending on context (including wind and small scale hydroelectric)and demand side management can reduce vulnerabilities to cli-mate change, especially in rural populations. Adaptations forhydropower are effective in most regions up to 1.5°C to 2°C,with decreasing effectiveness at higher levels of warming. Hydro-power can also play a role in compensating for the intermittencyof other renewable energies. E.g., integrating hydro, solar andwind power in energy generation strategies in the Grand EthiopianRenaissance Dam can potentially deliver multiple benefits, inclu-ding decarbonisation, compliance with environmental flow normsand reduce potential conflicts among Nile riparian countries5.Cross-cutting optionsEffective adaptation options for water-borne diseases includeimproving access to potable water, reducing exposure of waterand sanitation systems to flooding and extreme weather events,and improved early warning systemsEnabling climate resilient developmentStructural vulnerabilities to climate change can be reducedthrough carefully designed and implemented legal, policy, andprocess interventions. This includes rights-based approachesthat focus on capacity- building, meaningful participation ofthe most vulnerable groups, and their access to key resources,including financing, to reduce risk and adapt. Evidence showsthat climate resilient development processes link scientific,Indigenous, local, practitioner and other forms of knowledge,and are more effective and sustainable because they are locallyappropriate and lead to more legitimate, relevant and effectiveactions. Governance for climate resilient development is enabledby adequate and appropriate human and technological resources,information, capacities and finance.IAHR.org #HydrolinkMagazine  |  71IN DEPTH >  CLIMATE CHANGE 3 | 2022MitigationThe WGIII report about mitigation, focused primarily on GHGemissions and the energy sector. Only the Summary for Policy-makers has been approved so far. The final draft of the fullreport is available online but cannot be cited yet. So only shorthints, relevant for the IAHR community are reported here.Sustainable urban planning and infrastructure design in-cluding green roofs and facades, networks of parks and openspaces, management of urban forests and wetlands, urban agri-culture, and water-sensitive design can deliver both mitigationand adaptation benefits in settlements. These options can alsoreduce flood risks, pressure on urban sewer systems, urbanheat island effects, and can deliver health benefits from reducedair pollution. There could also be trade-offs. For example, increa-sing urban density to reduce travel demand, could imply highvulnerability to heat waves and flooding.Electricity systems powered predominantly by renewablesare becoming increasingly viable and in some countries andregions this is already happening. It will be more challengingto supply the entire energy system with renewable energy.Even though operational, technological, economic, regulatory,and social challenges remain, a variety of systemic solutionsto accommodate large shares of renewables in the energy sys-tem have emerged. A broad portfolio of options such as, integra-ting systems, coupling sectors, energy storage, smart grids,demand- side management, sustainable biofuels, electrolytichydrogen and derivatives, and others will ultimately be neededto accommodate large shares of renewables in energy systems.It has to be noted that IPCC considers the potential contributionof hydropower to net emission reduction relatively low, about0.4 GtCO2-eq yr-1, i.e. one tenth of that of solar or wind energy.However, hydropower is still the predominant source of renew-able energy and accounts for about 16% share in global totalelectricity generation. Its potential of further development re-mains high but depends on the assessment of environmentaland social impacts in the planning stages. Fundamental is therole of Pumped Hydroelectric Storage (PHS) which representsthe largest fraction of electricity storage capacity globally.Marine energy also has a high potential of development,some tens of PWh yr-1, similar to that of hydropower, as energycan be extracted from tides, waves, ocean thermal energy con-version, currents, and salinity gradients.The IPCC reports state with high confidence that restora-tion of mangroves and coastal wetlands sequester carbon, whilealso reducing coastal erosion and protecting against stormsurges, thus, reducing the risks from sea level rise and extremeweather.Concluding remarksThe huge amount of data, information, scenarios collected overten years and presented in the almost 10,000 pages of theWGI, WGII and WGIII IPCC AR6 reports provides a sound basisfor addressing the complex challenges posed by global warming,its impact on natural and anthropic systems and the adaptationmeasures to be taken to reduce the associated risks. The watersector is considered more mature than others but the potentialof knowledge, technologies, solutions, developed in the hydro-community is fundamental to address such challenges. A multi-disciplinary approach paying attention to social, environmental,cultural, economic, communication aspects is needed to coordi-nate the efforts of professionals and researchers in the watersector in their contribution for the solution of the problemsfaced by the mankind in adapting to the multi-faceted changestriggered by the global warming.References1 | IPCC, 2021: Summary for Policymakers. In: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Reportof the Intergovernmental Panel on Climate Change [Masson- Delmotte, V., P. Zhai, A. Pirani, S. L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. I.Gomis, M. Huang, K. Leitzell, E. Lonnoy, J. B. R. Matthews, T. K. Maycock, T. Waterfield, O. Yelekçi, R. Yu and B. Zhou (eds.)]. Cambridge University Press. In Press.2 | IPCC, 2022: Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovern-mental Panel on Climate Change [H.-O. Pörtner, D.C. Roberts, M. Tignor, E.S. Poloczanska, K. Mintenbeck, A. Alegría, M. Craig, S. Langsdorf, S. Löschke, V. Möller,A. Okem, B. Rama (eds.)]. Cambridge University Press. Cambridge University Press, Cambridge, UK and New York, NY, USA. 3056 pp., doi:10.1017/9781009325844.3 | IPCC, 2022: Climate Change 2022: Mitigation of Climate Change. Summary for Policymakers. Contribution of Working Group III to the Sixth Assessment Reportof the Intergovernmental Panel on Climate Change. www.ipcc.ch4 | Colosio, P., Tedesco, M., Ranzi, R., and Fettweis, X., 2021: Surface melting over the Greenland ice sheet derived from enhanced resolution passive microwavebrightness temperatures (1979–2019), The Cryosphere, 15, 2623–2646, https://doi.org/10.5194/tc-15-2623-2021.5 | Sterl, S., Fadly D., Liersch S., Koch H., and Thiery W., 2021: Linking solar and wind power in eastern Africa with operation of the Grand Ethiopian RenaissanceDam. Nature Energy, 6(4), 407– 418, doi:10.1038/s41560-021-00799-5.Roberto RanziPhD Roberto Ranzi is Professor of Hydraulic structures and River basin monitoring and restoration at the Universityof Brescia, Italy.Professor Ranzi is Chair of the IAHR Technical Committee on Climate Change Adaptation.http://roberto-ranzi.unibs.it

Climate Change impact, adaptation and mitigation in the water sector: new hints from the IPCC AR6

http://henry.baw.de/bitstream/20.500.11970/110518/1/HydroLink_2022_03_Climate_Change_Impact_adaptation_and_mitigation_in_the_water_sector_new_hints_from_the_IPCC_AR6.pdf

Climate Change impact, adaptation and mitigation in the water sector: new hints from the IPCC AR6

Abstract

Similar works

Full text

Available Versions

Hydraulic Engineering Repository