At the close of a four-year process to examine the impacts of climate change on the world’s ocean and cryosphere and their role in climate mitigation, the Intergovernmental Panel on Climate Change (IPCC) released its findings in Monaco on 25 September, 2019.
The report, the Ocean and the Cryosphere in a Changing Climate (SROCC) shows that impacts are already significant and will be increasingly dangerous if the world doesn’t urgently move on to the least-emissions pathway. This would entail a peak in global emissions by around 2020, with a rapid decline thereafter.
Monaco was the first country to propose, in 2015 to the IPCC that it undertakes a special report on the ocean and climate change. The first Because the Ocean Declaration of November 2015 rallied support for the proposal which was also sponsored within the IPCC by the delegations from China and Spain. The plenary of the IPCC added the cryosphere within the terms of reference and endorsed the proposal in February 2016. Thereafter it has taken four years to prepare and finalize the comprehensive report.
According to the report, scientists are highly confident that, “the global ocean has warmed unabated since 1970 and has taken up more than 90% of the excess heat in the climate system”. Furthermore, they argue that “since 1993, the rate of ocean warming has more than doubled”.
“Climate conditions, unprecedented since the preindustrial period, are developing in the ocean, elevating risks for open ocean ecosystems.”
“Marine heatwaves have very likely doubled in frequency since 1982 and are increasing in intensity”. The panel is “virtually certain” that “by absorbing more CO2, the ocean has undergone increasing surface acidification”, and “a loss of oxygen has occurred from the surface to 1000 metres”.
At the launch of the report held at the Oceanographic Museum of Monaco on 25 September, the co-authors of the report said that their work “highlights the urgency of prioritizing timely, ambitious and coordinated action to address widespread and enduring changes in the ocean and cryosphere.“
The Because the Ocean Secretariat was present in Monaco at the 51st Session of the IPCC where the report’s Summary for Decision-Makers was discussed and finalized. Some of the key ocean-related findings of the report are summarized below.
Breaking the Silos
Policy practitioners in the areas of climate and ocean policies often express frustration for the fact that many ocean and climate advocates tend to work within their respective fields in relative isolation, with little or no synergies with one another. Indeed, the Because the Ocean initiative is one of several recent attempts to break these silos and create a space for climate and ocean experts and advocates to work together.
In this regard, one of the legacies the IPCC SROCC will provide is an unprecedented chance for both the climate and ocean communities to work together. A very timely opportunity little more than three months before UNFCCC COP25 in Santiago, Chile, which the host country has pledged to make a “Blue COP”, with special attention to ocean-related issues.
A Note about Terminology
Every finding in the report is labelled with a degree of confidence, based on the strength of the science behind it, as described in this table. For the purposes of this briefing we have focused on findings with medium (about 5 out of 10 chance) , high (about 8 out of 10 chance) or very high confidence (about 9 out of 10 change).
Reference in the SROCC is made to different emissions scenarios. RCP8.5 refers to a high emissions scenario – a baseline scenario in the absence of climate mitigation targets. RCP2.6 refers to the lowest emissions scenario.
The SROCC is divided into three sections: Observed Changes and Impacts; Projected Changes and Risks; and Responding to Changes: Challenges, Options and Enablers.
Observed Changes and Impacts
- The cryosphere is shrinking. The report includes a detailed assessment of changes in glacier, and ice sheet cover, regional changes in snowfall and degradation of permafrost.
- High confidence that the ocean has warmed unabated since 2005, continuing trends as far back as 1970.
- Very high confidence that marine heat waves are increasing in frequency and severity. High confidence that it is very likely between 84% and 90% of marine heat waves occurring 2006-2015 due to anthropogenic warming.
- High confidence that Arctic sea ice is declining in all months of the year. Medium confidence that around half of observed sea ice loss can be attributed to anthropogenic temperature increase.
- Very likely that the rate of ocean warming has more than doubled since 1993.
- Very likely that stratification in the upper ocean has increased since 1970, impacting ocean oxygen, nutrient supply and net primary production.
- Very likely that “open ocean surface pH has declined by a very likely range of 0.017–0.027 pH units per decade since the late 1980s2, with the decline in surface ocean pH to have already emerged from background natural variability for more than 95% of the ocean surface area.”
- High confidence that the open ocean is losing oxygen primarily due to changing ocean stratification, ventilation and biogeochemistry.
- Medium confidence that the Atlantic Meridional Overturning Circulation (AMOC) has weakened relative to 1850-1900.
- Virtually certain that global sea level is rising, and high confidence that the rate is accelerating due to increasing rates of ice loss from Greenland and Antarctic ice sheets, and from thermal expansion. Very high confidence that glacier and ice sheet contributions exceed the effective thermal expansion.
- Regional differences in sea level rise, within +/-30% result from land ice loss and variations in ocean warming and circulation.
- High confidence that anthropogenic climate change has led to increased precipitation, winds and extreme sea level events associated with some tropical and extra-tropical cyclones.
Observed Impacts on Ecosystems
- High confidence that there have been geographical shifts in marine species. Medium confidence that this has consequences for species interactions affecting their abundance, and causing cascading impacts on ecosystem structure and fisheries.
- In many regions, declines in fish and shellfish stocks have already reduced catches. However high confidence that abundance of some species has increased due to expansion of suitable habitat. But medium confidence that overall, ocean warming in the 20th century has contributed to an overall decrease in maximum catch potential. Medium confidence that there are changes in species composition of fisheries catches since the 1970s in many shelf seas ecosystems.
- High confidence that coastal ecosystems are under stress from combination of ocean warming, intensified marine heat waves, ocean acidification, loss of oxygen and sea level rise, plus adverse effects from human activities on ocean and land. High confidence that impacts are already being observed on species, biodiversity, and ecosystem functioning and services.
- High confidence that nearly 50% of coastal wetlands have been lost over the 20th century as compared with preindustrial time. Ranges of seagrass meadows and kelp forests are contracting at low latitudes. High confidence also that mangrove encroachment into subtropical salt marshes is leading to loss of food and habitat for dependent fauna.
- Very high confidence that marine heatwaves have negatively impacted marine organisms and ecosystems in all ocean basins over the last two decades, including critical foundation species.
- Very high confidence that frequency of large-scale coral bleaching events have increased since 1997 causing worldwide reef degradation.
- High confidence that calcified organisms (e.g. barnacles and muscles) are affected by extreme temperature events and acidification.
Observed Impacts on People
- High confidence that changes in the ocean have modified or degraded marine ecosystem services leading to impacts on fisheries and food, trade and transport, challenging their governance.
- Medium confidence that both positive and negative impacts include health and well-being, indigenous culture, tourism and recreation.
- High confidence that harmful algal blooms are expanding in range and increasing in frequency due to both climatic (warming, acidification and oxygen loss) and non-climatic (eutrophication and pollution) drivers.
- High confidence that shipping activity in the Arctic summer will increase due to reduction in sea ice..
- High confidence that coastal communities are exposed to climate-related hazards, including tropical cyclones, extreme sea level and flooding, marine heatwaves, sea ice loss, and permafrost thaw.
Projected Changes and Risks
Projections differ depending on which emissions scenario is assumed. Obviously, in general impacts are projected to be more severe under a high emissions scenario as compared with a lower one.
- Virtually certain that the ocean will continue to warm through the 21st century accompanied by loss of Arctic sea ice, loss of oxygen, increased acidification, increasingly frequent marine heat waves and further weakening of the AMOC.
- High confidence that upper ocean stratification will increase throughout the 21st
- Very high confidence that globally, frequency, duration and spatial extend of marine heatwaves will intensify, and medium confidence that frequency will increase by around a factor of 50 by 2081-2100 under RCP8.5, and factor of around 20 under RCP2.6. Medium confidence that the Arctic Ocean and tropical ocean will experience the largest frequency increases.
- Continued carbon uptake by the ocean to 2100 is virtually certain to exacerbate ocean acidification.
- Very likely oxygen loss between 100 and 600 m depth projected to emerge over 59–80% of the ocean area by 2031–2050 under RCP8.5. Very likely projected time of emergence prior to 2100 for five primary drivers of marine ecosystem change (surface warming and acidification, oxygen loss, nitrate content and net primary production change) for over 60% of the ocean area under RCP8.5 and over 30% under RCP2.6.
- Extreme El Niño and La Niña events likely to occur more frequently and to intensify.
- High confidence that sea level will continue to rise at an increasing rate, and (currently rare) extreme sea level events will occur frequently by 2050, especially in tropical regions.
- High confidence under all future emissions scenarios, many low-line megacities and small islands at almost all latitudes will experience extreme sea level events (and severe flooding) annually by 2050.
Projected Risks for Ecosystems
- Medium confidence that global rates of biomass production as well as standing stocks will decrease in ocean ecosystems and from the surface to deep seafloor. Very likely further poleward shifts in species distribution, and medium confidence that global fisheries catch potential will decrease in the 21st century due to warming by 20.5–24.1% by the end of the 21st century relative to 1986–2005 under RCP8.5. High confidence that the rate and magnitude of decline will be highest in the tropics. Medium confidence that ocean acidification, oxygen loss and sea ice reduction will exacerbate these problems.
- Medium confidence that enhanced stratification will reduce nutrient supply and lead to net primary production decline by 7-16% for RCP8.5 by 2081-2100. in the tropical ocean.
- In contrast, medium confidence that net primary production will increase in the Arctic (and possibly around Antarctica, but that is low confidence).
- Medium confidence that the geographical range of Arctic marine species (including marine mammals, birds and fish) will contract, while the range of some sub-Arctic fish communities is projected to expand.
- High confidence of decrease in deep-sea (3000-6000 m depth) seafloor biomass.
- Medium confidence that in the Southern Ocean, the habitat of Antarctic krill will contract southwards.
- Medium confidence that there will be decreased calcification, bio-erosion and dissolution of non-living components of cold-water coral communities. Cold-water corals will be particularly vulnerable when both temperature and oxygen conditions are outside species’ tolerance range.
- High confidence that all coastal ecosystems will be at high to very high levels of risk under RCP8.5 by 2100. Very high confidence that coral reefs will be at high or very high risk even at global warming of 1.5°C. High confidence that the same will be true for seagrass meadows and kelp forests.
- High confidence that globally, 20-90% of coastal wetlands will be lost by 2100 depending on projected sea level rise and habitat degradation.
- High confidence that salinization and hypoxia in estuaries will continue, and medium confidence that this will lead to higher risks for benthic and pelagic biota.
- High confidence that almost all warm water coral reefs will suffer significant losses of area and local extinctions, even at 1.5°C.
Projected Risks for People
- Medium confidence that climate change impact on fish catches will affect income, livelihoods and food security of resource-dependent communities. Decrease in seafood availability will elevate the risk of nutritional health impacts on some coastal communities.
- Medium confidence that communities with high consumption of seafood are at risk from increased exposure to toxic contaminants in marine plants and animals (bioaccumulation of e.g. persistent organic pollutants and mercury) as well as to waterborne Vibrio pathogens and harmful algal blooms.
- High confidence that low-lying coastal communities in cities, small islands, deltas, river mouths and the Arctic will experience substantially exacerbated risks. Medium confidence that urban atoll islands and low-lying Arctic communities will be at moderate to high risk even under low-emission scenarios.
- High confidence that vulnerable communities in coral reef environments and polar regions are expected to face adaptation limits – even under a low emission scenario – well before the end of the century.
- Medium confidence that some island nations may become uninhabitable.
- High confidence that ambitious adaptation has potential to reduce risk in many locations, which in turn could facilitate adaptation beyond 2100.
Responding to Changes
- Current governance structures are not well-suited to deal with the multiple risks stemming from climate change. High confidence that governance systems are often too fragmented across administrative boundaries and sectors to address increasing and cascading risks in an integrated way.
- High confidence that options for assisting the functional integrity of marine ecosystems in the future include protection, restoration, ecosystem-based management and the reduction of pollution and other stressors.
- “Networks of protected areas, on land and at sea, help maintain existing ecosystem services and can also facilitate the poleward and attitudinal movements of populations, species and ecosystems that are already occurring in response to warming and sea-level rise (high confidence).”
- High confidence that terrestrial and marine habitat restoration, and ecosystem management tools (assisted species relocation, coral gardening) can be locally effective in enhancing ecosystem-based adaptation.
- Medium confidence that strengthening the responsiveness and precautionary approaches of existing fisheries management strategies will reduce negative climate change impacts on fisheries, with benefits for regional renewable resource economies.
- Medium confidence that sustainable fisheries management practices will reduce climate risks but has limited ability to address ecosystem change.
- High confidence that blue carbon ecosystems can contribute to climate mitigation for some countries, but medium confidence that mitigation potential is relatively modest at the global scale (0.5% of global current emissions annually).
The report closes with a section on enablers, and the need for cross-boundary cooperation and coordination among different actors. Need for education and climate literacy, monitoring and forecasting, funding and institutional support.
- High confidence that a key enabler in responding to sea level rise includes taking a long-term perspective when making short-term decisions, and explicitly accounting for uncertainty and risks post-2050.
- High confidence that climate resilient, sustainable development requires coordinated and sustained implementation of a low emission pathway and adaptation actions.
- High confidence that this will require profound economic and institutional transformations.
- The authors have very high confidence that the report “reveals the benefits of ambitious mitigation and effective adaptation for sustainable development” and,warns of “the escalating costs and risks of delayed action”.
- “The potential to chart Climate Resilient Development Pathways varies within and among ocean, high mountain and polar land regions”.
- “Realising this potential depends on transformative change”.
- “This highlights the urgency of prioritising timely, ambitious, coordinated and enduring action”.