IPCC – Special Report on the Ocean and Cryosphere in a Changing Climate

Date: 23rd September 2019

On September 25th, the IPCC will publish its Special Report on the Ocean and Cryosphere in a Changing Climate. Despite the inextricable links between the ocean and climate, this is the first oceanic report that the IPCC has undertaken.

The ocean and climate work together as part of the Earth System of our planet. Because of the close links between the two, the ocean has borne the brunt of the climate crisis, standing between humanity and its worst impacts. It has absorbed most of the excessive heat and much of the excessive carbon dioxide but at a cost, which is detrimental to its health and our survival. Ocean scientists have long understood the catastrophic impact that climate breakdown has on the ocean and the consequences this has for human wellbeing and survival, in turn. This report should be an alarm call – if we do not protect the ocean from the ravages of climate breakdown, it will be to our own detriment. The ocean is at the heart of the ecosystem of our planet.


Dr Lucy Woodall – Department of Zoology, Oxford University, UK

“The impacts of climate change such as sea level rise, acidification and ocean warming are causing massive transformations in the ocean. From the shallow coastal reefs to the deepest ocean, as scientists we witness and document these effects on all parts of the planet. The ocean controls so many of our planetary processes, so the consequences of climate change on the ocean must be considered when we debate the health of the planet. They are one and the same.”

Prof. Dan Laffoley – IUCN Global Marine and Polar Programme

“The IPCC report shows us that our ocean world is in deep, deep trouble as ‘the Earth’ is far more dependent on ‘the ocean’ than its name implies. We are an ocean world, run and regulated by that single ocean. We are now pushing that life support system to its very limits by heating, acidifying and deoxygenating the very system that keeps us alive. We are well past ‘wake up calls’ – what we need now is enlightened self-interest in delivering the actions that protect the planet and climate, which in turn support each and every one of us.”

Prof. Jason Hall-Spencer – University of Plymouth, UK

“Human carbon dioxide emissions are speeding up the sixth mass extinction of life on this planet by causing sea level rise and coastal habitat loss. Surface seawater warming and acidification are killing tropical coral reefs and hypoxic events are causing ecosystem collapse.”

Prof. Alex Rogers – University of Oxford, UK

“Climate change is impacting the entire ocean through heating, acidification and deoxygenation. The ocean has absorbed 93% of the excess heat generated by global warming. Responses to this by marine life include changes in distribution (species moving away from the Equator), negative impacts on ocean productivity, and coral bleaching, which threatens to near destroy the most biodiverse ecosystem in the ocean. The changes are unpredictable and there are continuous surprises for scientists, including the recent increase in marine heatwaves and the detection of a new form of coral bleaching that simply kills corals and speeds up the erosion of their skeletons, which is the backbone of the coral reef ecosystem. Unless CO2 emissions are limited to prevent heating of more than 1.5oC, we will see increasingly extreme and less predictable consequences for the ocean as tipping points are passed.”

Mirella von Lindenfels – International Programme on the State of the Ocean

“This is not just about sea level rise. A declining ocean will impact on human lives in countless different ways, whether you live inland or on the coast, on high ground or low. The ocean is like the human heart, it makes all life possible and we need to take measures to protect that heart urgently by reducing all the needless strains placed upon it, from overfishing to pollution.”

Julie Packard – Executive Director of the Monterey Bay Aquarium

“The bottom line is that we need the ocean. And right now, the ocean needs us. It’s not too late to take courageous climate action and safeguard the ocean from further damage.”

Chris Scholin – President and CEO of the Monterey Bay Aquarium Research Institute.

“It’s time to double down on our investment in ocean and climate research, technology and conservation. We are in a race to explore and understand our ocean as it undergoes massive change as a result of human activity. The sooner we act, the healthier our ocean will be.”


Please note that all the facts used in this document can be found in the comprehensive, referenced briefings found here.

You can access spokespeople on all these issues here.



Prof. Jason Hall-Spencer – University of Plymouth, UK

“Studies at carbon dioxide seeps worldwide show that organisms with shells or skeletons, such oysters and corals, are sensitive to ocean acidification and that degraded reefs provide less coastal protection and less habitat for commercially important fish and shellfish. This amplifies the risks to marine goods and services from climate change, causing shifts to seaweed dominance, habitat degradation and a loss of biodiversity in coastal waters worldwide.

“Human carbon dioxide emissions are speeding up the sixth mass extinction of life on this planet by causing sea level rise and coastal habitat loss. Surface seawater warming and acidification are killing tropical coral reefs and hypoxic events are causing the ecosystem collapse.”


  • Today, the ocean absorbs over one million tonnes/1 billion kg of CO2 from the atmosphere every hour and as the CO2 dissolves in seawater, it forms carbonic acid and decreases the pH of the ocean, driving the water towards acidity.
  • The massive increase in our carbon emissions means that this chemical process is happening on an unprecedented scale, causing what is collectively known as ocean acidification.
  • Ocean acidification is now occurring about 10 times faster than anything experienced over the last 300 million years. It is expected to increase by 170% by 2100 if things continue as they are, causing sweeping changes to the chemistry of seawater and threatening marine life.
  • Without the ocean absorbing CO2 , the rate and severity of climate change would be far greater.
  • Many sea creatures – including mussels, clams, coral, oysters and certain phytoplankton and zooplankton species – require calcium carbonate to build their shells and skeletons, a process disrupted by acidification.
  • As these species are at the bottom of marine food-webs, the effects ripple up to fish, seabirds and marine mammals. Declining harvests attributed to ocean acidification are already being reported, for example in the US Pacific Northwest’s oyster industry.
  • The world’s coral reefs, already under existential threat from ocean heating, are also severely impacted by ocean acidification, with many corals and calcifying algae unable to adapt to changing.
  • Ocean acidification will accelerate as long as concentrations of atmospheric CO2 continue to rise. The long time lags of the marine carbon cycle make urgent action to cut CO2 emissions even more imperative if we are to avert the worst, most destabilising consequences.

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Mirella von LindenfelsInternational Programme on the State of the Ocean

“How will we breathe if the ocean cannot? Half our oxygen comes from the ocean and it is running out of breath. A robust High Seas treaty in 2020 is an essential step towards protecting the ocean and increasing its resilience to climate breakdown.”

Craig DownsExecutive Director, Haereticus Environmental Laboratory

“Where deoxygenation is occurring, it is creating dead zones in our ocean. There are things we can do immediately to reduce the impact of deoxygenation such as reducing pollution and such approaches are vital we if are going to help the ocean maintain its life-giving functions.”


  • Oxygen is vital to life in the ocean. As the sea temperature rises, oxygen becomes less soluble via a process known as deoxygenation.
  • Reduced oxygen levels in coastal areas are associated with the run-off of nutrients from fertilisers and sewage and this is being exacerbated by global heating and is now affecting the open ocean.
  • Low oxygen waters are described as hypoxic. Hypoxic water has oxygen concentrations below 2mg per litre – a level so low that it is detrimental to most organisms and very few species can survive. Since 1950, more than 500 coastal sites have reported oxygen concentrations below this level.
  • In the open ocean, oxygen-minimum zones have expanded by 4.5 million km2 – about the same size as the European Union – and the total volume of seawater completely devoid of oxygen (anoxic) has more than quadrupled.
  • Impacts of deoxygenation on the ocean include:
    • reduced growth and reproduction, altered behaviour, and increased disease and mortality in marine animals,
    • increased mortality of corals and associated fauna,
    • amplification of ocean acidification because increased respiration by marine organisms increases CO2, and
    • a contribution to global heating (due to the microbes that proliferate at very low oxygen levels producing more nitrous oxide – a powerful greenhouse gas).
  • Global heating driven by rising greenhouse gas emissions is having a pervasive and accelerating effect on the ocean. The most direct impact is the heating of the ocean itself, which recent studies show is occurring faster and deeper than previously thought.
  • Of the eight priority issues identified by the International Programme on the State of the Ocean (IPSO) to be addressed to help avert ecological disaster in the global ocean, ocean heating is the highest priority. It is the pre-eminent factor driving change in the ocean.

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Prof. Dan Laffoley – IUCN Global Marine and Polar Programme

“The IPCC report shows us all that the ocean is critical to life on Earth. It helps regulate our climate and provides conditions for life –- if it gets too warm species die, if it gets too cold species also die. The ocean keeps conditions just right for life on Earth. What the IPCC report now shows is that we are pushing that ocean – our ocean – to dangerous limits, and that matters, not just to us, but to all life on Earth.”

Mirella von Lindenfels – International Programme on the State of the Ocean

“Heating is one of the three deadly factors present in every mass extinction event in Earth’s history. Along with acidification and deoxygenation, heating is pushing our ocean towards catastrophe. If we allow the ocean to heat unchecked we will start to lose vital ecosystem functions, sea levels will rise and biodiversity will decline. This will impact on all humankind, not just people living near to or depending on the coast.”


  • The ocean has absorbed 93% of the excess heat trapped by human-emitted greenhouse gases since the 1970s. This has tempered global heating but has caused the temperature of the ocean to rise, with multiple knock-on effects including deoxygenation.
  • The average global sea surface temperature has increased by approximately 0.13oC over the past 100 years meaning a total rise of over 1oC. Long-term effects have been detected at a depth of 700m. Modelling studies predict a likely increase in mean global ocean temperature of 1-4°C by 2100.
  • The ocean is heating up to 40% faster on average than indicated by the IPCC in 2013.
  • Even incremental heat changes can have a profound effect on ocean chemistry, ecosystems and sea levels. If all the heat absorbed by the ocean since the 1950s was suddenly added to the atmosphere, air temperatures would soar by around 36oC.
  • Impacts include:
    • Deoxygenation
    • Accelerated sea level rise
    • Reduced ocean mixing
      As the ocean warms, there is increased stratification (layering of water of different salinity and density) in the upper layers, resulting in reduced movement of nutrients from deeper layers.
    • Reduced biodiversity
      Heating and associated deoxygenation are driving the extinction of vulnerable species and causing non-native species from different biogeographic regions to spread beyond their range and become established across the ocean.
    • Weather changes
      Warmer waters are bringing more frequent marine heatwaves – periods of extreme warm sea surface temperature that persist for days to months. There is also evidence of a recent increase in global wave power as a consequence of oceanic warming.
    • Acceleration of polar ice melt
    • Redistribution of important ocean species
      Ocean heating has already begun to cause a change in distribution of many marine species including invertebrates, fish and marine mammals. This will lead to local extinctions and cause permanent changes.
    • Impacts on coral reefs
      Since the 1980s, rising sea surface temperatures due to global warming have triggered unprecedented mass bleaching of corals, including three pan-tropical events in 1998, 2010 and 2015/16.

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Prof. Alex Rogers – Oxford University, UK

“It may be unexpected that the deep ocean could be affected by global warming but this affects surface primary production, the food supply of much of the deep sea, and also oxygen levels, by slowing the mixing of oxygen-rich surface waters with the deep. No part of the ocean is unaffected by climate change.”

“The deep sea has a sparse food supply, is cold and dark, and the animals inhabiting it grow very slowly and are often extremely fragile. This is why activities such as deep-sea bottom trawling have rapidly depleted populations of deep-sea fish like orange roughy and devastated communities of deep-sea corals, which have shown little or no recovery over decades. We need to protect the deep ocean from further damage.”

“With little understanding of the potential impacts, states are preparing to mine deep-sea ecosystems including the abyssal planes and seafloor massive sulphides associated with hydrothermal vents and seamounts – all rich feeding and breeding grounds for marine life. Added to this we see the development of other threats to the deep sea including the accumulation of marine debris and microplastics and the effects of climate breakdown. It is too fragile and important an area to risk.”


  • The deep ocean refers to the sea and seabed below 200m. It makes up 90% of the Earth’s marine environment, and is the largest biome (community of plants and animals living together) on the planet.
  • It is at the heart of the Earth system, playing a central role in regulating currents and climate and storing the carbon that might otherwise contribute to global heating.
  • It is a highly vulnerable and fragile environment already challenged by:

    – Deep-sea fishing
    Industrial fishing operations have increasingly turned to exploiting deep-sea species. The main method used is bottom trawling – huge nets armed with steel plates and heavy rollers that destroy everything in their path.

    – Deep-sea mining
    Many companies are exploring the deep ocean with a view to beginning mining operations. The deep seabed between 1000 and 6000m depth contains large concentrations of metals of commercial interest.

    In the past 50 years, the ocean has absorbed 93% of excess heat generated by greenhouse gas emissions. As the ocean warms, stratification in the upper layers increases, resulting in a reduction in the movement of nutrients from deeper layers.
  • Recent science has confirmed the vulnerability of the deep ocean to climate change. The long-term effects of ocean warming have been detected to a depth of at least 700m.
  • The heating of the deep ocean has clear implications for species that have evolved to live in the cold and for the thermohaline circulation system.

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  • The cryosphere, particularly the Arctic and Antarctic, play a vital role in regulating the climate and ocean systems that sustain the Earth by:

    – reflecting heat from the sun, helping to regulate our planet’s temperature,

    – storing most of the world’s freshwater, and

    – influencing the Earth’s system of circulating water in the ocean, which transports heat from the tropics toward the poles and increases the ability of the ocean to absorb CO2 from the atmosphere.
  • Polar regions are also highly sensitive to human activity and the cryosphere is one of the first places where scientists are able to identify global changes in climate.
  • Climate change-related impacts:

    – Sea level rise, which is one of the most obvious consequences, e.g. a rise of many metres is possible and global sea levels are already rising at 3.1mm per year.

    – Loss of biodiversity, e.g. a keystone species, krill, has moved four degrees of latitude south to find more favourable conditions.

    – Effects on current and climate, e.g. there are concerns it will disrupt or stop thermohaline circulation.

    – Population effects, e.g.  all these impacts will adversely impact populations around the world with a disproportionate impact on indigenous peoples in the Arctic.

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Dr Craig Downs – Haereticus Laboratories, USA

Marine pollution, such as sewage, sunscreens, fertilisers, and plastics, can act synergistically with climate change factors, increasing the detrimental impacts of both. Longer, warmer summers interacting with sewage can give rise to bigger and more enduring dead zones. Endocrine disruptors from sunscreens and plastics can reduce the fertility of marine organisms, while acidified areas reduce the ability of surviving juveniles to recruit and restore an area. Together, climate change and marine pollution are a guarantee for the destruction of marine vitality.

Mirella von Lindenfels – International Programme on the State of the Ocean

“However hard it may be to deal with pollution, it is not as hard as living with the consequences of it. Pollution is undermining the health and resilience of the ocean, literally eroding its ability to withstand the impacts of climate breakdown and actually exacerbating these. We can tackle this now if the will exists to do so.”


  • Marine pollution is defined by the 1982 UN Convention on the Law of the Sea as: “the introduction by man, directly or indirectly, of substances or energy into the marine environment … which results or is likely to result in such deleterious effects as harm to living resources and marine life.” (UNCLOS, 1982)
  • Over 80% of it originates from land-based activities.
  • It can change the physical, chemical, and biological state of the ocean and coastal areas, posing a threat to marine wildlife and ecosystems, and the industries and livelihoods dependent on them, such as fisheries and tourism. Toxic chemicals also become concentrated in the food chain and can impact human health. 
  • The three most significant forms of oceanic and coastal pollution are:

    Nitrogen-phosphorous pollution from agriculture, sewage, and urban and industrial run-off. Nitrogen and phosphorus pollution, also called nutrient or eutrophic pollution (eutrophication), has a global impact on ocean bodies and is particularly concentrated in coastal areas near the estuaries of major rivers.

    A serious impact of eutrophication is the algal blooms that can be toxic to marine ecosystems. When the dense algal blooms die off, their decomposition severely depletes the dissolved oxygen in the water, potentially causing ‘dead zones’ where the oxygen levels are so low that fish and other organisms struggle to survive.

    Chemical pollution that comprises, but is not limited to, pesticides, petroleum, pharmaceuticals and personal care products, heavy metals and industrial discharge.

    The chemicals come from a range of sources including crude oil and other petroleum products, anti-foulants, pesticides, pharmaceuticals and personal care products. It is estimated that the total amount of chemicals entering the ocean rose by 12% between 2003 and 2012. Although the level coming from North America and Europe dropped by 60% during that period, in the Pacific it rose by 50%.

    The most dangerous pollutants are the persistent, bioaccumulative and toxic substances. Even chemicals banned decades ago, such as polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs), are still found in high concentrations in deep-sea creatures despite being banned by the 2001 Stockholm Convention.

    Pollutants recognised as endocrine disruptors and teratogens, which impact the ability of marine species to reproduce or reduce offspring survival rates, present a growing concern. Personal care products, in particular, contain cryptic chemicals that have a significant impact on human and ocean health

    Plastic-debris pollution is flagged as a major threat by the 2019 IPBES Assessment, which warns that it has increased tenfold since 1980, affecting at least 267 species, including 86% of marine turtles, 44% of seabirds and 43% of marine mammals.

    An important 2015 study calculated that 275 million tonnes of plastic waste was generated in 192 coastal countries in 2010, with 4.8 to 12.7 million tonnes entering the ocean.

    It is estimated that between 1.15 and 2.41 million tonnes of plastic waste enters the ocean every year from rivers. Other sources are coastal mismanagement, abandoned fishing gear and microplastic particles from household cleaners, personal care products and viscous clothing. Plastics have been found in the depths of the Mariana Trench and embedded in ice in the Arctic.

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Dr Jason Hall SpencerPlymouth University, UK

“Marine invasive species are spreading rapidly throughout the ocean due to human carelessness and lack of vigilance. The Suez Canal is like a cut artery bleeding voracious non-native fish and jellyfish into the Mediterranean Sea with no biosecurity measures in place at all.”


  • An invasive species is one that has been introduced by human activity – deliberately or accidentally – to geographic areas outside its native range and caused ecological or economic impacts in that location.
  • Marine invasive species can have a devastating impact on biodiversity, ecosystems, fisheries, human health, tourism and coastal development and are very difficult and expensive to tackle. The IUCN Global Invasive Species Database lists 59 invasive species in the marine realm. They can:

    – disrupt native habitats,

    – cause the extinction of flora and fauna (by consumption and by out-competing for space and resources),

    – overwhelm important vulnerable ecosystems such as coral reefs and mangroves,

    – decrease water quality,

    – increase competition and predation among species, and
    spread disease.
  • The major routes for invasive species are:

    – navigational canals – transporting species via inland waterways,

    – aquaculture – escape/overspill of non-native species introduced for farming,

    – aquarium trade – deliberate and accidental release of exotic species,

    – plastic pollution – transport of invasive species attached to plastic waste, and

    – shipping – through ballast water and biofouling of ship hulls. This is the most significant vector for the introduction of marine invasive species. As much as 10 billion tonnes of ballast water is carried around the world per year, carrying up to 7,000 species of aquatic plants, microbes and animals every hour of every day. In addition, biofouling, where species attach to ships hulls, anchors and other equipment, is a related problem.

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  • About 80% of the world’s trade is carried by sea. As well as a large and growing carbon footprint, shipping is responsible for chemical waste, air pollution, dumping of sewage, noise pollution and the transfer of invasive species across the ocean.
  • Over 10 billion tonnes of goods are transported by sea every year, and the industry expanded by 4% from 2017 to 2018, the fastest rate in five years.
  • Impacts include:

    – spills and discharge of oil and other chemicals,

    – transfer of invasive species in ballast water and on ship hulls,

    – release of biocides from the toxic chemicals in antifouling paints, dumping of garbage and sewage,

    – physical damage caused by anchors, wave disturbance and striking marine mammals,

    – damage to natural habitats near ports and shipping routes, including seagrass meadows, coral reefs and mangroves, and

    – contribution to global heating and air pollution through emission of sulphur dioxide, nitrogen oxides and CO2 (WWF, n.d.).
  • Shipping is a major and growing source of global greenhouse gas emissions and air pollution.For the period 2007–2012, shipping accounted for approximately 3.1% of annual global CO2.
  • If shipping were a country it would be the sixth biggest carbon emitter. Mid-range forecasted scenarios show that, by 2050, CO2 emissions from international shipping could grow by between 50% and 250%, depending on economic growth and energy developments.
  • Global nitrogen oxide (NOx) and sulphur oxide (SOx) emissions from shipping represent about 15% and 13% of the total from anthropogenic sources. NOx and SOx emissions are responsible for around 400,000 premature deaths from lung cancer and cardiovascular disease and around 14 million childhood asthma cases every year.

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Tony LongCEO, Global Fishing Watch

“The IPCC report shows that the ocean is bearing the brunt of the climate crisis – our planet’s life support system is under attack. We know that overfishing, one of many pressures, has severely weakened our ocean’s immune system, diminishing its ability to withstand the impacts of climate change. We also know that ending overfishing will contribute to mitigating climate change impacts. Stamping out illegal fishing, in particular, is one of the most immediate and do-able actions the world can take to strengthen the ocean, making it more capable of withstanding climate change impacts.” 


  • In 2015, fish accounted for about 17% of animal protein consumed by the global population and provided about 3.2 billion people with almost 20% of their average per capita intake.
  • Fishing has had the greatest impact on marine biodiversity in the past 50 years. The percentage of stocks fished at biologically unsustainable levels increased from 10% in 1974 to 33.1% in 2015. Industrial fishing now covers 55% of the ocean and overfishing is exacerbated by widespread illegal, unreported and unregulated (IUU) fishing.
  • 90% of fish stocks are now either fully fished (59.9%) or overfished at biologically unsustainable levels (33.1%). The number of underfished stocks have reached the lowest levels ever recorded at just 7%.
  • Catches from wild fisheries peaked in 1996 at around 130 million tonnes per year and have been declining by 1 million tonnes per year since then – not because we are choosing to catch fewer fish but because they are no longer there.
  • Reasons for overfishing include: harmful subsidies (e.g. tax relief on fuel); poor fisheries science; poor decision-making mechanisms; lack of precautionary management; lack of transparency; absence of high seas governance; and IUU fishing.

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