Global Warming Has “Profound Consequences” for Oceans, Cryosphere

Knowledge assessed in the report outlines climate-related risks and challenges that people around the world are exposed to today and that future generations will face. It presents options to adapt to changes that can no longer be avoided, manage related risks and build resilience for a sustainable future. The assessment shows that adaptation depends on the capacity of individuals and communities and the resources available to them.

The IPCC notes that more than 100 authors from 36 countries assessed the latest scientific literature related to the ocean and cryosphere in a changing climate for the report, referencing about 7,000 scientific publications.

The IPCC says that the Special Report is a key scientific input for world leaders gathering in forthcoming climate and environment negotiations, such as the UN Framework Convention on Climate Change Conference (COP25) in Chile in December

“The world’s ocean and cryosphere have been ‘taking the heat’ from climate change for decades, and consequences for nature and humanity are sweeping and severe,” said Ko Barrett, Vice-Chair of the IPCC. “The rapid changes to the ocean and the frozen parts of our planet are forcing people from coastal cities to remote Arctic communities to fundamentally alter their ways of life,” sheadded.

“By understanding the causes of these changes and the resulting impacts, and by evaluating options that are available, we can strengthen our ability to adapt,” she said. “The Special Report on the Ocean and Cryosphere in a Changing Climate provides the knowledge that facilitates these kinds of decisions.”

Major Changes in High Mountains Affecting Downstream Communities
People in mountain regions are increasingly exposed to hazards and changes in water availability, the report said.

Glaciers, snow, ice and permafrost are declining and will continue to do so. This is projected to increase hazards for people, for example through landslides, avalanches, rockfalls and floods.

Smaller glaciers found for example in Europe, eastern Africa, the tropical Andes and Indonesia are projected to lose more than 80 percent of their current ice mass by 2100 under high emission scenarios. The retreat of the high mountain cryosphere will continue to adversely affect recreational activities, tourism, and cultural assets.

As mountain glaciers retreat, they are also altering water availability and quality downstream, with implications for many sectors such as agriculture and hydropower.

“Changes in water availability will not just affect people in these high mountain regions, but also communities much further downstream,” said Panmao Zhai, Co-Chair of IPCC Working Group I.

“Limiting warming would help them adapt to changes in water supplies in mountain regions and beyond, and limit risks related to mountain hazards,” he said. “Integrated water management and transboundary cooperation provides opportunities to address impacts of these changes in water resources.”

Melting ice, Rising Seas
Glaciers and ice sheets in polar and mountain regions are losing mass, contributing to an increasing rate of sea level rise, together with expansion of the warmer ocean.

While sea level has risen globally by around 15 cm during the 20th century, it is currently rising more than twice as fast – 3.6 mm per year – and accelerating, the report showed.

Sea level will continue to rise for centuries. It could reach around 30-60 cm by 2100 even if greenhouse gas emissions are sharply reduced and global warming is limited to well below 2°C, but around 60-110 cm if greenhouse gas emissions continue to increase strongly.

“In recent decades the rate of sea level rise has accelerated, due to growing water inputs from ice sheets in Greenland and Antarctica, in addition to the contribution of meltwater from glaciers and

the expansion of warmer sea waters,” said Valérie Masson-Delmotte, Co-Chair of IPCC Working

Group I.

“This new assessment has also revised upwards the projected contribution of the Antarctic ice sheet to sea level rise by 2100 in the case of high emissions of greenhouse gases,” she said. “The wide range of sea level projections for 2100 and beyond is related to how ice sheets will react to warming, especially in Antarctica, with major uncertainties stillremaining.”

More Frequent Extreme Sea Level Events
Sea level rise will increase the frequency of extreme sea level events, which occur for example during high tides and intense storms. Indications are that with any degree of additional warming, events that occurred once per century in the past will occur every year by mid-century in many regions, increasing risks for many low-lying coastal cities and small islands.

Without major investments in adaptation, they would be exposed to escalating flood risks, the report shows. Some island nations are likely to become uninhabitable due to climate-related ocean and cryosphere change, the report said, but habitability thresholds remain extremely difficult to assess.

Increases in tropical cyclone winds and rainfall are exacerbating extreme sea level events and coastal hazards. Hazards will be further be intensified by an increase in the average intensity, magnitude of storm surge and precipitation rates of tropical cyclones, especially if greenhouse gas emissions remain high.

“Various adaptation approaches are already being implemented, often in response to flooding events, and the report highlights the diversity of options available for each context to develop integrated responses anticipating the full scale of future sea level rise,” said Masson-Delmotte.

Changing Ocean Ecosystems
Warming and changes in ocean chemistry are already disrupting species throughout the ocean food web, with impacts on marine ecosystems and people that depend on them, the report said.

To date, the ocean has taken up more than 90 percent of the excess heat in the climate system. By 2100, the ocean will take up 2 to 4 times more heat than between 1970 and the present if global warming is limited to 2°C, and up to 5 to 7 times more at higher emissions. Ocean warming reduces mixing between water layers and, as a consequence, the supply of oxygen and nutrients for marine life.

Marine heatwaves have doubled in frequency since 1982 and are increasing in intensity. They are projected to further increase in frequency, duration, extent and intensity. Their frequency will be 20 times higher at 2°C warming, compared to pre-industrial levels. They would occur 50 times more often if emissions continue to increase strongly.

The ocean has taken up between 20 to 30 percent of human-induced carbon dioxide emissions since the 1980s, causing ocean acidification. Continued carbon uptake by the ocean by 2100 will exacerbate ocean acidification.

Ocean warming and acidification, loss of oxygen and changes in nutrient supplies, are already affecting the distribution and abundance of marine life in coastal areas, in the open ocean and at the seafloor.

Shifts in the distribution of fish populations have reduced the global catch potential. In the future, some regions, notably tropical oceans, will see further decreases, but there will be increases in others, such as the Arctic. Communities that depend highly on seafood may face risks to nutritional health and food security.

“Cutting greenhouse gas emissions will limit impacts on ocean ecosystems that provide us with food, support our health and shape our cultures,” said Hans-Otto Pörtner, Co-Chair of IPCC Working Group II. “Reducing other pressures such as pollution will further help marine life deal with changes in their environment, while enabling a more resilient ocean.”

“Policy frameworks, for example for fisheries management and marine-protected areas, offer opportunities for communities to adapt to changes and minimize risks for our livelihoods,” he added.****

Knowledge for Urgent Action
The report finds that strongly reducing greenhouse gas emissions, protecting and restoring ecosystems, and carefully managing the use of natural resources would make it possible to preserve the ocean and cryosphere as a source of opportunities that support adaptation to future changes, limit risks to livelihoods and offer multiple additional societal benefits.

“We will only be able to keep global warming to well below 2°C above pre-industrial levels if we effect unprecedented transitions in all aspects of society, including energy, land and ecosystems, urban and infrastructure as well as industry. The ambitious climate policies and emissions reductions required to deliver the Paris Agreement will also protect the ocean and cryosphere – and ultimately sustain all life on Earth,” said Debra Roberts, Co-Chair of IPCC Working Group II.

SROCC provides the best available scientific knowledge to empower governments and communities to take action, embedding that scientific knowledge on unavoidable change and plausible futures into their own context, to limit the scale of risks and climateimpacts.

The report gives evidence of the benefits of combining scientific with local and indigenous knowledge to develop suitable options to manage climate change risks and enhance resilience. This is the first IPCC report that highlights the importance of education to enhance climate change, ocean and cryosphere literacy.

“The more decisively and the earlier we act, the more able we will be to address unavoidable changes, manage risks, improve our lives and achieve sustainability for ecosystems and people around the world – today and in the future,” Roberts said.

Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC)
The IPCC Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) is the third in a series of Special Reports produced in the IPCC’s Sixth Assessment Cycle. The report was prepared under the joint scientific leadership of IPCC Working Groups I and II, with support from the Working Group II Technical Support Unit.

The word “cryosphere” – from the Greek kryos, meaning cold or ice – describes the frozen components of the Earth system, including snow, glaciers, ice sheets and ice shelves, icebergs and sea ice, ice on lakes and rivers as well as permafrost and seasonally frozen ground.

The Summary for Policymakers presents the key findings of the Special Report, based on the assessment of the available scientific, technical and socio-economic literature relevant to the ocean and cryosphere in a changing climate.

The Summary for Policymakers of the Special Report on the Ocean and Cryosphere in a Changing Climate as well as additional information are available at https://www.ipcc.ch/srocc

SROCC in Numbers
The report was prepared by 104 authors and review editors from 36 countries, 19 of which are

developing countries or economies in transition.

6,981 publications were referenced in the whole report (Final Draft).

The drafts of the report received 31,176 comments from 80 countries and the EU.