The ocean under climate change – a message for COP21

The world’s oceans are in a state of decline. Climate change is already having a profound impact on ocean ecosystems. Increased ocean temperatures, sea level rise, altered weather patterns, changes in ocean currents, melting sea ice, and the effects of ocean acidification are upon us. These impacts are being exacerbated by man-made stresses such as overfishing, habitat loss and land-based sources of pollution.
The Our Common Future under Climate Change conference brings together some of the world’s leading marine scientists for an up-to-the minute assessment of the state of the global ocean under climate change, and discussion of two key questions: will the new climate treaty that emerges from the United Nations climate negotiations in Paris in December contain adequate commitments to protect the ocean – and specifically, will a 2 degree limit to global warming be sufficient to prevent the worst damage to the global ocean foreseen in risk scenarios.

The CFCC15 programme features 3 sessions on the state of the oceans under climate change, building on the unprecedented level of recognition given to ocean issues in the most recent report from the Intergovernmental Panel on Climate Change in 2014.
One of the lead conveners at the CFCC15 sessions, Jean-Pierre Gattuso of France’s CNRS-UPMC, Laboratoire d’Océanographie, outlines what the conference can expect to hear.
“The Ocean is critical to life on Earth through its regulation of atmospheric gases, stabilisation of planetary heat, and provision of food and resources to well over 3 billion people worldwide. Despite its importance, however, our understanding of impacts of key climate change drivers such as ocean warming and acidification has been relatively limited. The recent consensus report from WGII of the IPCC AR5 addresses this deficit ( by including a number of ocean-focused chapters for the first time. AR5 has identified serious risks to marine ecosystems, fisheries, and coastal livelihoods.
The sessions at CFCC15 will provide an integrated and updated perspective on the changes, risks and projections for both natural and human systems. The ensuing discussions will facilitate the construction of key messages for the COP21 negotiation process on the Ocean and associated issues.
On the opening day of Conference, Tuesday July 7, we have a large session presenting the latest assessments of ocean impacts and feedbacks, how marine species are shifting their ranges, the state of fisheries and threats to food security, and regional challenges for people, industry and ecosystems in a rapidly warming and acidifying ocean. On Wednesday we look in more depth at ocean changes including those affecting coral systems, and on Thursday we have a session focussing on the specific challenges facing the Mediterranean. One of the world’s iconic  – and most overfished – seas is confronted with a wide range of challenges induced by climatic change: extreme events, sea-level change, ocean acidification, and significant risks for food production, water availability, biodiversity and other sectors.
We believe the focus on oceans at this Conference underlines the critical importance of their role in regulating our Earth system, and the risks we face in losing their vital services. However, despite the ocean’s critical role in global ecosystem processes and services, international climate negotiations have only minimally touched on ocean impacts. These three sessions will bring compelling arguments for changing this situation”
Key Ocean Statistics and Information presented in the IPCC 5th assessment report in 2014:
  • Oceans cover more than 70% of the planet
  • The living organisms of the Ocean create half the oxygen (O2) humankind uses to breathe and burn fossil fuels.
  • Oceans provide 20% of the animal protein consumed by 3 billion people.
  • Climate change causes oceans to warm and stratify (where the naturally occurring different layers of warmer and colder and less or more salty water do not mix effectively, disrupting normal nutrient supply for marine species) and sea level to rise, as well as Arctic summer sea ice to shrink.
  • Ocean warming accounts for more than 90% of the energy accumulated in the climate system.
  • Warming causes oceans to lose oxygen overall and during an expansion of hypoxic (depleted oxygen) water layers.
  • The accumulation of anthropogenic CO2 in ocean surface waters disturbs water chemistry and causes acidification.
  • Ocean warming has caused geographical shifts in the distribution of marine species, with some migrating further north, away from equatorial waters.
July 7th Climate Change and Ocean Systems: Impacts and Feedbacks, Lead Conveners: J.-P. Gattuso (CNRS and Université Pierre et Marie Curie, Laboratoire d’Océanographie de Villefranche, Villefranche-sur-mer – France); E. Poloczanska, CSIRO, Oceans and Atmosphere Flagship, Global Change Institute, University of Queensland, Brisbane, Australia
July 8th Ocean Change: Understanding and projecting the impacts of warming and acidification on natural and human systems Lead Conveners: J.-P. Gattuso (CNRS and Université Pierre et Marie Curie, Laboratoire d’Océanographie de Villefranche, Villefranche-sur-mer – France); O. Hoegh-Guldberg (University of Queensland, Global Change Institute, Brisbane – Australia)
July 9th The Mediterranean Basin in a warmer and drier world: challenges and opportunities Lead Conveners: J. Guiot (CNRS, Aix-Marseille University, CEREGE, Aix-en-Provence – France); W. Cramer (CNRS-IMBE, Aix-en-Provence – France; J.-P. Gattuso (CNRS and Université Pierre et Marie Curie, Laboratoire d’Océanographie de Villefranche, Villefranche-sur-mer – France)
Jean-Pierre Gattuso and other marine experts involved in the Oceans 2015 Initiative produced this short film to explain the threats facing the Ocean under climate change.  It was released during World Ocean Day at Unesco, Paris. French, Chinese, Spanish and Arabic versions are also available.
Our Common Future under Climate Change, Zoom blog, 24 June 2015. Article and movie.

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