Explaining Ocean Warming: Causes, Scale, Effects and Consequences Edited by D
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Explaining Ocean Warming: Causes, scale, effects and consequences Edited by D. Laffoley and J. M. Baxter September 2016 IUCN GLOBAL MARINE AND POLAR PROGRAMME The designation of geographical entities in this book, and the presentation of the material, do not imply the expression of any opinion whatsoever on the part of IUCN concerning the legal status of any country, territory, or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. The views expressed in this publication do not necessarily refect those of IUCN. Published by: IUCN, Gland, Switzerland Copyright: © 2016 International Union for Conservation of Nature and Natural Resources Reproduction of this publication for educational or other non-commercial purposes is authorized without prior written permission from the copyright holder provided the source is fully acknowledged. Reproduction of this publication for resale or other commercial purposes is prohibited without prior written permission of the copyright holder. Citation: Laffoley, D. & Baxter, J. M. (editors). 2016. Explaining ocean warming: Causes, scale, effects and consequences. Full report. Gland, Switzerland: IUCN. 456 pp. Individual chapters within this report should be referenced as: Author(s). 2016. Title of chapter. In: Laffoley, D., & Baxter, J.M. (editors). 2016. Explaining ocean warming: Causes, scale, effects and consequences. Full report. Gland, Switzerland: IUCN. pp. xxx. ISBN: 978-2-8317-1806-4 DOI: http://dx.doi.org/10.2305/IUCN.CH.2016.08.en Cover photos: Clockwise from top: King penguins (Aptenodytes patagonicus) on Middle Beach (Brothers Point in distance), Macquarie Island, Southern Ocean. (© Robbie Kilpatrick/australian antarctic Division, November 2015, Image RS31770,Image antarctica); a colony of black coral with small crabs moving amongst the branches (image courtesy of Department of BIS, UK); seagrass (Zostera marina) © SNH/Ben James; Hurricane Catarina on March 26th, 2004, off SE Brazil. Image courtesy of NASA. Layout by: Unit Graphics, Serbia Available from: IUCN (International Union for Conservation of Nature) Global Marine and Polar Programme (GMPP) Rue Mauverney 28 1196 Gland Switzerland Tel +41 22 999 0000 Fax +41 22 999 0002 [email protected] www.iucn.org/resources/publications The cascading efects of climate 2 -related changes in the ocean A.K. Magnana, J.-P. Gattusob,a a Institute for sustainable development and international relations, Sciences Po, France b Sorbonne Universités, UPMC Univ Paris 06, CNRS-INSU, Laboratoire d’Océanographie de Villefranche-sur-mer, France Summary • The ocean moderates anthropogenic climate change by absorbing signifcant parts of the heat and CO2 that accumulate in the atmosphere. The ocean also receives all water from melting ice. • This regulating function happens at the cost of profound alterations of the ocean’s physics and chemistry, especially leading to ocean warming and acidifcation, and consequently sea-level rise. • These changes signifcantly affect the ocean’s ecology (organisms and habitats) and, consequently, ecosystem services and coastal human societies (e.g. fsheries, aquaculture, tourism, food security). • As atmospheric CO2 increases, the solutions (i.e. mitigate, protect, repair, adapt) become fewer and less effective, thus decreasing the long-term ability of humankind to cope with both on-set and gradual changes in the ocean. • Such an assessment provides further compelling arguments for rapid and ambitious CO2 emission reductions at the international level, notably through the revision cycle of countries’ 2030 pledges (i.e. Intended Nationally Determined Contributions, INDCs) approved by the Paris Agreement in 2015. Ocean Warming 47 . The cascading efects of climate-related changes in the ocean 2.1 Introduction organisms and keystone species, including ecosystem Together, the atmosphere and the ocean allow life engineers; to identify commonalities and develop unifying on the Blue Planet. These life-support systems are, concepts; to focus on species, processes and ecosystems however, altered by human activities, as exemplifed by considered most vulnerable or most resilient to ocean contemporary climate change that generates worldwide change; and to cover the range of processes from sub- disturbance in extreme events patterns, gradual cellular to ecosystem dynamics and biogeochemical environmental changes, widespread impacts on life and cycling. A ffth one of course deals with better understanding natural resources, and multiple threats to human societies. the interactions with human societies, from impacts to an impressive body of knowledge on “emerging” issues short- to long-term responses. a third reason is that the such as ocean warming and acidifcation has recently societal side of the problem has been understudied up to accumulated. Regarding ocean acidifcation, the number now. Yet, as climate change will amplify, changes in the of scientifc papers increased by 35% per year between ocean as well as impacts on society will also increase. 2000 and 2013 compared to an increase of 4.8% per year Whatever the global mitigation efforts will be in the coming for all scientifc felds (Riebesell and Gattuso, 2014; Yang et decades, some impacts are already unavoidable due to al., 2015). Another signifcant indicator is the development latency in the climate and ocean systems. This means that of three chapters specifcally dedicated to the ocean dealing with climate and ocean changes is not only about in the contribution of the IPCC Working Group 2 to the “avoiding the unmanageable” (i.e. prevent dangerous Fifth assessment Report (aR5). These chapters together physical and biological changes through massive GHG represent a more than 400-page synthesis of the existing emission mitigation), but also about “managing the literature, at the global (Pörtner et al., 2014; Wong et al., unavoidable” (i.e. adaptation) (Bierbaum et al., 2007). 2014) and regional (Hoegh-Guldberg et al., 2014) levels. Scientists also undertook massive efforts to disseminate This chapter does not pretend to provide answers to their understandings outside of the scientifc community, the challenges raised above. It rather seeks to lay some and now the issue of ocean climate-related changes is the foundations for future transdisciplinary research on ocean subject of numerous policy concerns (e.g. Goal 14 of the changes and their consequences on human societies. It is Sustainable Development Goals1, Our Ocean Conferences mainly inspired from a scientifc paper (Gattuso et al., 2015) in 2014 in the USA and in 2015 in Chile, and Ocean days and on a Policy Brief (Magnan et al., 2015a) that provide and side events at the 21st Conference of the Parties to a synthesis of the recent and future changes to the ocean UNFCCC2 in 2015). Progress to develop the scientifc and its ecosystems, as well as to the goods and services understanding of what is happening in the ocean as well provided to humans. This chapter follows the “chain of as to better include the ocean-related issues in policy impacts” principle to emphasize cascading effects, going agenda at various scales, must, however, be reinforced from changes in the ocean’s physics and chemistry to for at least three reasons. First, and although COP 21 marine and coastal species, and then to human societies allowed some major progress, the source of the problem, through the ocean’s ecosystem services. It considers i.e. the high concentration of greenhouse gases (GHG) in the global scale and focuses on key organisms and the atmosphere, has not yet been eradicated. Mitigation ecosystem services for which robust scientifc studies have efforts at the global scale must thus be pursued, not to been recently published (Howes et al., 2015; Weatherdon say drastically accelerated. Here the scientifc community, et al., 2015). The chapter notably explores two contrasting including the ocean community, has a major role to play to GHG emission scenarios developed by the IPCC for the “keep the pressure on” through advances in knowledge, end of the 21st Century: the high emissions trajectory from processes at work to impacts and thresholds (Briggs (Representative Concentration Pathway 8.5, RCP8.5) et al., 2015; Stocker, 2015; Magnan et al., 2016). Second, and a stringent emissions scenario (RCP2.6). The latter Science still faces key research challenges to develop scenario is consistent with the Paris Agreement3 of keeping multiple-driver studies at the community to ecosystem mean global temperature increase below 2°C in the 21st levels, and to fnd answers to societal problems. Riebesell Century. We then discuss possible solutions and end and Gattuso (2015) emphasize four of these challenges with four key messages to be considered in international regarding ocean acidifcation: to concentrate on reference climate negotiations under the UNFCCC. 1 http://www.un.org/sustainabledevelopment/oceans/ 3 UNFCCC. The Paris agreement (FCCC/CP/2015/L.9/Rev.1). available at: 2 United Nations Framework Convention on Climate Change http://unfccc.int/resource/docs/2015/cop21/eng/l09r01.pdf. 48 Ocean Warming Ocean Warming Warming Ocean ascading efects 49 Figure 2.1 The chain of impacts of ocean acidifcation, ocean warming and sea-level rise. Sources: the authors, derived from Pörtner et al. (2014), Hoegh-Guldberg et al. (2014). The cascading efects of climate-related changes in the ocean Figure 2.2 Distribution of heat, carbon dioxide and ice-melt water in the main Earth reservoirs and consequences for the ocean. 2.2 Cascading