Extract from the Executive Summary of Chapter 6 Ocean Systems of IPCC Working Group II on ocean acidification
Rising atmospheric CO2 over the last century and into the future not only causes ocean warming but also changes carbonate chemistry in a process termed ocean acidification (WGI AR5 Sections 3.8.2, 6.4.4). Impacts of ocean acidification range from changes in organismal physiology and behavior to population dynamics (medium to high confidence) and will affect marine ecosystems for centuries if emissions continue (high confidence). Laboratory and field experiments as well as field observations show a wide range of sensitivities and responses within and across organism phyla (high confidence). Most plants and microalgae respond positively to elevated CO2 levels by increasing photosynthesis and growth (high confidence).Within other organism groups, vulnerability decreases with increasing capacity to compensate for elevated internal CO2 concentration and falling pH (low to medium confidence). Among vulnerable groups sustaining fisheries, highly calcified corals, mollusks, and echinoderms are more sensitive than crustaceans (high confidence) and fishes (low confidence). Trans-generational or evolutionary adaptation has been shown in some species, reducing impacts of projected scenarios (low to medium confidence). Limits to adaptive capacity exist but remain largely unexplored. {6.3.2, Box CC-OA}
Few field observations conducted in the last decade demonstrate biotic responses attributable to anthropogenic ocean acidification, as in many places these responses are not yet outside their natural variability and may be influenced by confounding local or regional factors. Shell thinning in planktonic foraminifera and in Southern Ocean pteropoda has been attributed fully or in part to acidification trends (medium to high confidence). Coastward shifts in upwelling CO2-rich waters of the Northeast Pacific cause larval oyster fatalities in aquacultures (high confidence) or shifts from mussels to fleshy algae and barnacles (medium confidence), providing an early perspective on future effects of ocean acidification. This supports insight from volcanic CO2 seeps as natural analogs that macrophytes (seaweeds and seagrasses) will outcompete calcifying organisms. During the next decades ecosystems, including cold- and warm-water coral communities, are at increasing risk of being negatively affected by ocean acidification, especially as ocean acidification will be combined with rising temperature extremes (medium to high confidence, respectively). {6.1.2, 6.3.2, 6.3.5}
IPCC: The Intergovernmental Panel on Climate Change (IPCC) was established by the United Nations Environmental Programme (UNEP) and the World Meteorological Organization (WMO) in 1988 to assess the scientific, technical and socio-economic information relevant for the understanding of human induced climate change, its potential impacts and options for mitigation and adaptation. The IPCC has completed four full assessment reports, guidelines and methodologies, special reports and technical papers. For more information on the IPCC, its activities and publications please see the IPCC homepage.
Working Group II: In its reports, Working Group II assesses the scientific, technical, environmental, economic and social aspects of the vulnerability (sensitivity and adaptability) to climate change of, and the negative and positive consequences for, ecological systems, socio-economic sectors and human health, with an emphasis on regional sectoral and cross-sectoral issues.
Chapter 6: Ocean Systems: Pörtner, H.-O., D.M. Karl, P.W. Boyd,W.W.L. Cheung, S.E. Lluch-Cota, Y. Nojiri, D.N. Schmidt, and P.O. Zavialov, 2014: Ocean systems. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Field, C.B., V.R. Barros, D.J. Dokken, K.J. Mach, M.D. Mastrandrea, T.E. Bilir, M. Chatterjee, K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, E.S. Kissel, A.N. Levy, S. MacCracken, P.R. Mastrandrea, and L.L.White (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 411-484. 6
