Contrasting futures for the ocean give a stark warning to governments ahead of Paris climate negotiations

Paris, Thursday, 2nd July 2015

The ocean moderates anthropogenic atmospheric warming at the cost of profound alterations of its physics, chemistry, ecology, and ecosystem services. The Oceans 2015 Initiative has published a paper in Science evaluating and comparing the risks of impacts on marine and coastal ecosystems and the goods and services they provide under two potential carbon dioxide (CO2) emissions pathways over this century. Jean-­‐Pierre Gattuso, Senior Scientist at CNRS and lead author of the paper says “the oceans have been minimally considered at previous climate negotiations; our study provides compelling arguments for a radical change at COP21”.

Atmospheric CO2 has increased by more than 40% over the industrial period, which has driven a series of major environmental changes. Yet, the global ocean is a “climate integrator’’ that (1) absorbed 93% of the earth’s additional heat since the 1970s, keeping the atmosphere cooler but increasing ocean temperature and rising sea level; (2) captured 28% of human-­‐caused CO2 emissions since 1750, but acidifying the ocean; and (3) collected virtually all water from melting ice, furthering sea‐level rise. (…)

From moderate to very high risks

Ocean changes associated with a stringent emissions pathway —i.e., consistent with the Copenhagen Accord’s goal of a global atmospheric temperature increase of less than 2°C by 2100 — already carries  high risks of impacts for warm‐water corals and mid‐latitude bivalves. The risk of other impacts will remain moderate if we do not exceed this scenario. Higher emissions pathways, such as the business‐as‐usual path we are currently following, would greatly aggravate the situation: almost all marine organisms the Oceans 2015 Initiative team considered (e.g., corals, pteropods, finfish, and krill) would face very high risk of impact, such as mass mortalities or species displacement. Likewise, the risk of impact on ecosystem services such as coastal protection (e.g., by oyster beds, coral reefs and mangroves), aquaculture, tourism and capture fisheries would become high or very high by 2100. For example, substantial declines for tropical fisheries are projected as soon as mid 21st century, even under low‐emissions pathways. This study also shows that the policy options to address ocean impacts (mitigate, protect, repair, adapt) narrow as the ocean warms and acidifies, i.e. as the world moves away from the +2°C path. For example, one cannot manage coral reef resilience if there is no healthy reefs remaining. Some options are also antagonistic, for example, solar radiation management could limit the increase in temperature but would reduce the incentive to cut CO2 emissions, thereby providing no relief from ocean acidification. “Given the extent of the expected changes, no country is in a safe position, making this issue a worldwide problem that challenges the traditional North/South divide”, said Alexandre Magnan, scientist at IDDRI and coauthor of the paper.

Push to consider ocean issues at COP21

Four key messages are articulated. (1) The ocean strongly influences the,climate system and provides important services to humans. (2) Impacts on key marine and coastal organisms, ecosystems, and services from anthropogenic CO2 emissions are already detectable across various latitudes, and several will face high risk of impacts well before 2100, even with stringent CO2 emissions scenarios. (3) Immediate and substantial reduction of CO2 emissions is required more than ever to prevent massive and effectively irreversible impacts on ocean ecosystems and their services. (4) As CO2 increases, the protection, adaptation and repair options for the ocean become fewer and less effective.

Given the contrasting futures outlined in this paper, the ocean provides further compelling arguments for rapid, rigorous and ambitious CO2 emissions reductions. Any new global climate agreement that does not minimize the impacts on the ocean will be incomplete and inadequate.

Source: Gattuso J.­‐P.,  Magnan A., Billé R., Cheung W. W. L., Howes E. L., Joos F., Allemand D., Bopp L., Cooley S., Eakin C. M., Hoegh‐Guldberg O., Kelly R. P., Pörtner H.‐O., Rogers A. D., Baxter J. M., Laffoley D., Osborn D., Rankovic A., Rochette J., Sumaila U. R., Treyer S. & Turley C., 2015. Contrasting futures for ocean and society from different anthropogenic CO2 emissions scenarios. Science. (…)

Scientific contacts:

Jean‐Pierre Gattuso, gattuso(at)obs-­‐, +33 493 763 859
Alexandre Magnan, alexandre.magnan(at), +33 650 813 927 (…)

Press release.

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