Special Report on the Ocean and Cryosphere in a Changing Climate

Choices made now are critical for the future of our ocean and cryosphere


The World Meteorological Organization today welcomed a landmark global report by the Intergovernmental Panel on Climate Change that underscores the urgency of timely, ambitious and coordinated action to address unprecedented and enduring changes in the ocean and cryosphere.

The IPCC Special Report on the Ocean and Cryosphere in a Changing Climate was approved on 24 September by the 195 IPCC member governments, gathered in Monaco. It spotlights the benefits of ambitious and effective adaptation for sustainable development and, conversely, the escalating costs and risks of delayed action.

“Water in its liquid or frozen state covers most of our Earth. The interplay between the ocean, cryosphere and greenhouse gas emissions influences climate and weather worldwide. Understanding this helps us to lessen the impacts of extreme events,” said WMO Deputy Secretary-General Elena Manaenkova, who attended the approval session.

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. Hand in hand with the ocean, it plays a critical role for life on the planet.

According to a separate report released on Sunday by WMO, the global average temperature has increased by 1.1°C since the pre-industrial period, and by 0.2°C compared to 2011-2015.

The IPCC report points to overwhelming evidence that global warming, which is stoked by past and current greenhouse gas emissions, is resulting in profound consequences for ecosystems and people. The ocean is warmer, more acidic and less productive. Melting glaciers and ice sheets are causing sea level rise, and coastal extreme events are becoming more severe.

Urgently reducing greenhouse gas emissions limits the scale of ocean and cryosphere changes. Ecosystems and the livelihoods that depend on them can be preserved.

“The open sea, the Arctic, the Antarctic and the high mountains may seem far away to many people,” said Hoesung Lee, Chair of the IPCC. “But we depend on them and are influenced by them directly and indirectly in many ways – for weather and climate, for food and water, for energy, trade, transport, recreation and tourism, for health and wellbeing, for culture and identity.”

A total of 670 million people in high mountain regions and 680 million people in low-lying coastal zones depend directly on the ocean and cryosphere systems. Four million people live permanently in the Arctic region, and small island developing states are home to 65 million people.

“If we reduce emissions sharply, consequences for people and their livelihoods will still be challenging, but potentially more manageable for those who are most vulnerable,” Mr Lee said. “We increase our ability to build resilience and there will be more benefits for sustainable development.”

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.

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 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, known for short as COP25, in Chile in December.

It provides new evidence for the benefits of limiting global warming to the lowest possible level – in line with the goal that governments set themselves in the 2015 Paris Agreement on climate change, of keeping warming below 2.0°C or, better still, 1.5°C.

“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,” she added.

“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 report is also timely given that the UN General Assembly has-approved the UN Decade of Ocean Science for Sustainable Development, which runs from 2021 to 2030.


Major changes in high mountains

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% 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.”

WMO expert Rodica Nitu, Project Manager of the Global Cryosphere Watch programme, welcomed the report.

“It conveys with authority the sense of urgency in addressing the hydro-climatic impacts of the changing cryosphere, whether in polar regions or high mountains, as well as their effects downstream, at lower latitudes, on lowlands, including the significant impact on the rising of the sea level, and the increase of greenhouse gas emissions,” she said.

“WMO, through its Global Cryosphere Watch programme in particular, is committed to work with the international community and its Members, to translate the strong science of this report into policy action, by addressing the cryosphere observations, data, and information gaps, and contribute to limiting the scale of risks and impacts of emerging threats from significant changes in the cryosphere, coupled with the ongoing expansion of people and infrastructure, whether in the polar regions, the high mountain valleys, at sea level.”

“One of the most compelling messages of the report is that on the importance of education to enhance climate change, ocean and cryosphere literacy, as a prerequisite for sustained action,” she added.

At the 18th World Meteorological Congress in June this year, WMO reiterated its commitment to governments to ensure enhanced and sustained cryosphere observations, data, and information by enhancing its programmes to include cryosphere specific functions within the framework of hydrological, climate,and maritime weather services, as well as early warning systems for polar and mountain regions. As a first step towards delivering on this commitment, WMO will host a High Mountain Summit on 29-31 October in Geneva.


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, the IPCC report said.

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 still remaining.”


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 Ms Masson-Delmotte.

“The marine meteorological community is encouraged that the report brings global attention to the fact that changing climate has already, and will continue to, increase frequency and severity of extreme maritime weather conditions,” said Sarah Grimes, Acting Chief of Marine Meteorology and Ocean Affairs at WMO.

“Such conditions are extremely dangerous and damaging to people and property at sea and in coastal zones, notwithstanding negative effects to livelihoods and the global blue economy. Flooding in particular, has been highlighted as a serious issue, given increasing sea levels, storminess and resultant waves and surges, impacting millions of vulnerable people living at the coast, especially in small island developing states. Global recognition of marine and coastal hazards is critical for persuading policy-makers to determine and prioritize appropriate adaptation and mitigation measures,” she added.

Through activities such as the Coastal Inundation Forecasting Initiative (CIFI),  Worldwide Met-Ocean Information and Warning Service (WWMIWS), marine capacity development training, and the upcoming International Symposium on Extreme Maritime Weather, run by WMO and the International Maritime Organization, WMO is helping its Members establish and strengthen early warning and forecast systems for coastal and marine weather hazards.


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% 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% of human-induced carbon dioxide emissions since the 1980s, causing ocean acidification. Continued carbon uptake by the ocean by 2100 will exacerbate ocean acidification.

The IPCC report also notes that 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 sea floor.

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.


Declining Arctic sea ice, thawing permafrost

The extent of Arctic sea ice is declining in every month of the year, and it is getting thinner. If global warming is stabilized at 1.5°C above pre-industrial levels, the Arctic ocean would only be ice-free in September – the month with the least ice – once in every hundred years. For global warming of 2°C, this would occur up to one year in three.

Some people living in the Arctic, especially indigenous peoples have already adjusted their traveling and hunting activities to the seasonality and safety of land, ice and snow conditions, and some coastal communities have planned for relocation. Their success in adapting depends on funding, capacities, and institutional support, the report shows.

Permafrost ground that has been frozen for many years is warming and thawing and widespread permafrost thaw is projected to occur in the 21st century. Even if global warming is limited to well below 2°C, around 25% of the near-surface (3-4 meter depth) permafrost will thaw by 2100. If greenhouse gas emissions continue to increase strongly, there is a potential that around 70% near-surface permafrost could be lost.

Arctic and boreal permafrost hold large amounts of organic carbon, almost twice the carbon in the atmosphere, and have the potential to significantly increase the concentration of greenhouse gases to the atmosphere if they thaw. It is unclear whether there is already a net release of carbon dioxide or methane due to the ongoing thaw of the Arctic permafrost. In the future, increased plant growth can increase the storage of carbon in soils and offset carbon release from permafrost thaw, but not at the scale of large changes on the long term.

Wildfires are disturbing ecosystems in most tundra and boreal as well as mountain regions.


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.

The report 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 climate impacts.

It 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,” Ms Roberts said.

The IPCC is the UN body for assessing the science related to climate change. It was established by the United Nations Environment Programme and WMO in 1988 to provide policymakers with regular scientific assessments concerning climate change, its implications and potential future risks, and to put forward adaptation and mitigation strategies.

IPCC assessments provide governments, at all levels, with scientific information that they can use to develop climate policies. IPCC assessments are a key input into the international negotiations to tackle climate change. IPCC reports are drafted and reviewed in several stages, thus guaranteeing objectivity and transparency.

The IPCC assesses the thousands of scientific papers published each year to inform policymakers about the state of knowledge on climate change. The IPCC identifies where there is agreement in the scientific community, where there are differences and where further research is needed. It does not conduct its own research.

“The IPCC Special Report on the Ocean and Cryosphere in a Changing Climate is a landmark assessment that not only emphasizes the dire impacts of climate change on our ocean and cryosphere, but also highlights the need to further study these crucial regions of our planet,” said Mike Sparrow, Senior Scientific Officer in the World Climate Research Programme, a partnership between WMO, the Intergovernmental Oceanographic Commission of UNESCO, and the International Science Council.

“We will steer our future activities to ensure we meet the important scientific priorities identified,” he added.

To produce its reports, the IPCC mobilizes hundreds of scientists worldwide. Only a dozen permanent staff work in the IPCC’s Secretariat, which is located in WMO’s Geneva base.

The IPCC has three working groups: Working Group I (the physical science basis of climate change); Working Group II (impacts, adaptation and vulnerability); and Working Group III (mitigation of climate change).

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