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Environnement
Aditi Mukherji Risks to Ecosystems and Human Systems from Changes in the Ocean and Cryosphere
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Water Systems and security
- The Ocean and Cryosphere in a Changing Climate #SROCC Musée Océanographique de Monaco 25 September 2019
- The world’s ocean and cryosphere have been ‘taking the heat’ from climate change for decades. Consequences for nature and humanity are sweeping and severe.
- Image Source: @ Elza_Bouhassira Photo: Yungdrung Tsewang High Mountains
- Changes in the mountain cryosphere • 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 if emissions continue to increase strongly. • Hazards for people, for example through landslides, snow avalanches or floods will increase as glaciers and permafrost decline. • Changing water availability and quality affects households, agriculture, energy systems, and people both in the region and beyond. • The retreat of the cryosphere will continue to adversely affect recreational activities, tourism and cultural assets.
- Water and changing mountain cryopshere • Mountains are the water towers of the world – runoff per unit generated in the mountains is ~ twice as much from low lands. • For e.g. 10 major rivers of Asia originate from the Hindu Kush Himalayas • Very high confidence that there are changes in seasonality of run-off in snow and glacier dominated river basins across the world – hence impact on water quantity
- Water and changing mountain cryopshere • Robust evidence that peak water in many of the glacier fed rivers has already passed in tropical Andes, Swiss Alps and Western Canada • And peak water will pass by middle of this century in High Mountain Asia and European Alps
- Water and changing mountain cryopshere • There will be significant shifts in downstream nutrients and water quality (DOC, nitrogen, phosphorus) and influence water quality through increases in heavy metals, particularly mercury, and other legacy contaminants (medium evidence, high agreement)
- Societal impacts of changes in water regimes due to cryosphere change • Robust evidence (medium agreement) that water input to hydropower facilities will change in the future due to cryosphere-related impacts on runoff • Medium evidence (medium agreement) that reduction in streamflow due to glacier retreat or reduced snow cover has led to reduced water availability for irrigation of crops and declining agricultural yields in several mountain areas, e.g. in HKH, parts of Andes, though periods before peak flow is reached, water may be temporarily abundant • There have been local responses by farmers to cryospheric changes, e.g. shifting of cropping patterns, out migration, and additional water storage in the form of ice stupas
- Societal impacts of due to water induced hazards • Glacier-related floods, including floods from lake outbursts (GLOFs), are documented for most glacierised mountain ranges and are among the most far-reaching glacier hazards. • High confidence that glacier lakes will increase • Floods originating from the combination of rapidly melting snow and intense rainfall, referred to as rain-on-snow events, are some of the most damaging floods in mountain areas and high confidence these events are on the rise
- Adaptation measures and way forward • Limiting warming to 1.5°C would help people to adjust to changes in water supplies and limit risks related to mountain hazards. • Integrated water management and transboundary cooperation provide opportunities to reduce the impacts of climate-related cryosphere changes on water resources.
- The Hindu Kush Himalaya Global asset for food, energy, water, carbon, and cultural and biological Melting of Himalayan Glaciers Source: ICIMOD
- In a 1.5˚ C world, glaciers in the HKH will lose 36% volume by 2100 A 2˚ C global warming scenario implies a regional warming of around 2.7˚ C and a 49% loss of ice volume Snow covered areas and snow volumes will decrease and snowline elevations will rise; Snow melt induced run-off peak will be stronger and occur earlier in the year Source: HIMAP climate change and cryosphere chapters and Kraaijenbrink et al. 2017, Nature
- What do these changes mean for the region’s water resources? Source: ICIMOD
- Nang, Ladakh, India Communities dependent on glacier and snow melt are feeling the impacts Mukherji, A., A. Sinisalo, M. Nusser, R. Garrard and M. Eriksson. 2019. Source: @ICIMOD
- Not running out of water, but… Contribution to total flow by (a) glacial melt, (b) snowmelt, and (c) rainfall-runoff for major streams during the reference period of 1998–2007. Line thickness indicates the average discharge during the reference period. Source: Lutz et al. (2014) Greater impact for those living closer to glaciers Climate change is expected to drive consistent increases in total runoff of the Indus (due to increased glacier melt), Ganges and Brahmaputra (due to increased precipitation) Source: @ICIMOD
- Mean relative change in 50 year return period of floods RCP 4.5 RCP 8.5 Intensities of ‘once in 50 years’ flood events will increase: 40%–110% in upstream areas 115%–150% in downstream areas Source: Wijngaard et al. 2017, PLOS One Flood magnitudes will increase..
- The more decisively and 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.
- Our ocean and cryosphere – They sustain us. They are under pressure. Their changes affect all our lives. The time for action is now.
- More Information: Website: http://ipcc.ch IPCC Secretariat: ipcc-sec@wmo.int IPCC Press Office: ipcc-media@wmo.int @IPCC_CH @IPCCNews @IPCC_Climate_Change www.vimeo.com/ipcc www.youtube.com/c/ipccgeneva Find us on:
Notes de l'éditeur
- The front and the back cover of the report pays tribute to the various regions addressed in this assessment, from the polar regions to tropical shores. The ocean and cryosphere – the frozen parts of our planet – might feel remote to some people. But they impact all of us, for weather and climate, food and water, or for energy, trade, transport, for health and wellbeing, for culture and identity. The ocean and the cryosphere are critical for all life on earth. And this report has shown, that if greenhouse gas emissions continue to increase, global warming will drastically alter the ocean and cryosphere. However, if we reduce emissions sharply, consequences for people and their livelihoods will still be challenging. But they will be potentially more manageable for those who are most vulnerable. The report reveals the benefits of ambitious and effective adaptation for sustainable development. Conversely there may be escalating costs and risks associated with delayed action.
- The launch of the IPCC Special Report on the Ocean and Cryosphere in a Changing Climate is the conclusion of two years of hard work. The commissioning of this report responds to government proposals including from our generous host, the Principality of Monaco, and builds on the completion of the Special Report on 1.5°C Warming and the Special Report on Climate Change and Land. This report will build a strong foundation for the upcoming IPCC 6th Assessment Report and the Synthesis Report. This report was written by 104 authors from 36 countries, including authors from 19 developing countries or countries with economies in transition. 31 percent of the authors were women. Almost 7,000 scientific publications were referenced in the report, which received more than 31,000 expert and government review comments.
- This report is unique because - for the first time - the IPCC has produced an in-depth report examining the farthest corners of the Earth – from the highest mountains and remote polar regions to the deepest oceans. We have found that even and especially in these places human-caused climate change is evident. This report documents the melting of high mountain glaciers and polar ice sheets which contain the freshwater for our future. It documents the thawing of permafrost which is the frozen foundation for communities and wildlife habitats of the north. It shines a light on coastal and low-lying areas where sea-level rise and associated impacts threaten the lives and livelihoods of large segments of the population And it documents the ways in which for decades the ocean has been acting like a sponge - absorbing carbon dioxide and heat to regulate the global temperature. But it can’t keep up. Taken together, these changes show that “the world’s ocean and cryosphere have been ‘taking the heat’ for climate change for decades. The consequences for nature and humanity are sweeping and severe.” This report highlights the urgency of timely, ambitious, coordinated, and enduring action. What’s at stake is the health of ecosystems, wildlife, and, importantly, the world we leave our children. The Co-Chairs will now take you on a deeper dive into the topic. Hand over to Panmao
- Melting glaciers, snow and ice in mountain regions are very visible symbols of climate change. A total of 670 million people in high mountain regions. They are increasingly exposed to hazards and changes in water availability.
- Glaciers, snow, ice and permafrost are declining and will continue to do so. 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 if emissions continue to increase strongly. As glaciers retreat and snow cover shrinks, warm-adapted plant and animal species migrate upslope. This changes species richness: Warm-adapted species increase. Cold- and snow-adapted species decrease and risk eventual extinction, especially without conservation. The retreat of the high mountain cryosphere will continue to adversely affect recreational activities, tourism, and cultural assets.
- What is more, the retreat of glaciers and thawing permafrost increases hazards for people living in those regions, for example through landslides, avalanches and rockfalls. Changes in water availability for households, agriculture and energy will not just affect people in these high mountain regions, but also communities much further downstream. Limiting warming would help people to adjust to changes in water supplies and limit risks related to mountain hazards. Integrated water management and transboundary cooperation provide opportunities to address impacts of these changes in water resources. Now we move from high mountains to polar regions. Hand over to Valérie
- What is more, the retreat of glaciers and thawing permafrost increases hazards for people living in those regions, for example through landslides, avalanches and rockfalls. Changes in water availability for households, agriculture and energy will not just affect people in these high mountain regions, but also communities much further downstream. Limiting warming would help people to adjust to changes in water supplies and limit risks related to mountain hazards. Integrated water management and transboundary cooperation provide opportunities to address impacts of these changes in water resources. Now we move from high mountains to polar regions. Hand over to Valérie
- Timing of peak water from glaciers in different regions (Figure 2.1) under two emission scenarios for Representative Concentration Pathways RCP2.6 and RCP8.5. Peak water refers to the year when annual runoff from the initially glacier-covered area will start to decrease due to glacier shrinkage after a period of melt induced increase. The bars are based on Huss and Hock (2018) who used a global glacier model to compute the runoff of all individual glaciers in a region until year 2100 based on 14 General Circulation Models (GCMs). Depicted is the area of all glaciers that fall into the same 10-year peak water interval expressed as a percentage of each region’s total glacier area, i.e., all bars for the same RCP sum up to 100% glacier area. Shadings of the bars distinguish different glacier sizes indicating a tendency for peak water to occur later for larger glaciers. Circles/diamonds mark timing of peak water from individual case studies based on observations or modelling (Table SM2.10). Circles refer to results from individual glaciers regardless of size or a collection of glaciers covering <150 km2 in total, while diamonds refer to regional-scale results from a collection of glaciers with >150 km2 glacier coverage. Case studies based on observations or scenarios other than RCP2.6 and RCP8.5 are shown in both the left and right set of panels.
- What is more, the retreat of glaciers and thawing permafrost increases hazards for people living in those regions, for example through landslides, avalanches and rockfalls. Changes in water availability for households, agriculture and energy will not just affect people in these high mountain regions, but also communities much further downstream. Limiting warming would help people to adjust to changes in water supplies and limit risks related to mountain hazards. Integrated water management and transboundary cooperation provide opportunities to address impacts of these changes in water resources. Now we move from high mountains to polar regions. Hand over to Valérie
- What is more, the retreat of glaciers and thawing permafrost increases hazards for people living in those regions, for example through landslides, avalanches and rockfalls. Changes in water availability for households, agriculture and energy will not just affect people in these high mountain regions, but also communities much further downstream. Limiting warming would help people to adjust to changes in water supplies and limit risks related to mountain hazards. Integrated water management and transboundary cooperation provide opportunities to address impacts of these changes in water resources. Now we move from high mountains to polar regions. Hand over to Valérie
- What is more, the retreat of glaciers and thawing permafrost increases hazards for people living in those regions, for example through landslides, avalanches and rockfalls. Changes in water availability for households, agriculture and energy will not just affect people in these high mountain regions, but also communities much further downstream. Limiting warming would help people to adjust to changes in water supplies and limit risks related to mountain hazards. Integrated water management and transboundary cooperation provide opportunities to address impacts of these changes in water resources. Now we move from high mountains to polar regions. Hand over to Valérie
- Figure 2.7 | Anticipated changes in high mountain hazards under climate change, driven by changes in snow cover, glaciers and permafrost, overlay changes in the exposure and vulnerability of individuals, communities, and mountain infrastructure.
- What is more, the retreat of glaciers and thawing permafrost increases hazards for people living in those regions, for example through landslides, avalanches and rockfalls. Changes in water availability for households, agriculture and energy will not just affect people in these high mountain regions, but also communities much further downstream. Limiting warming would help people to adjust to changes in water supplies and limit risks related to mountain hazards. Integrated water management and transboundary cooperation provide opportunities to address impacts of these changes in water resources. Now we move from high mountains to polar regions. Hand over to Valérie
- Kyetrak glacier
- Relative change in the 50-year return period of flood under RCP 4.5 and 8.5. In the most parts of the IGB the 50-year return level is projected to increase with relative increase upto about 300% under RCP 8.5 climate scenarios. Largest increase is projected for upstream headwaters in UIB and UGB (mainly due to increase in rainfall Some decrease in Kabul river basin, mainly due to decrease in snow and icemelt Regional differences due to different precipitation trends among the regional level. Precipitation increases
- Changes in polar regions influence people’s life around the world, where ever they live.
- The Greenland and Antarctic ice sheets are losing mass. These ice sheets are now key drivers of sea level rise (in addition to expansion of the warming water). Because ice sheets will continue to melt in response to past and current warming, the planet will experience global sea level rise for decades and centuries to come. 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.
- Permafrost, frozen soil and rock, is thawing, with the potential of adding more greenhouse gases to the atmosphere. Even if global warming is limited to well below 2°C, around one quarter of the near-surface (3-4 meter depth) permafrost will thaw by 2100. If greenhouse gas emissions continue to increase strongly around 70% near-surface permafrost could be lost. People living in the Arctic, especially Indigenous peoples are already adjusting their travel and hunting activities to the seasonality and safety of land, ice, and snow conditions. But their success in adapting depends on funding, capacities and institutional support. Four million people live permanently in the Arctic region…
- …and small island developing states are home to 65 million people. 680 million people in low-lying coastal zones. And they are vulnerable to sea level rise and coastal extreme events.
- During the 20th century, the global mean sea level rose by about 15 centimetres. It is currently rising more than twice as fast and the pace will further accelerate reaching up to 1.10 m in 2100 if emissions are not sharply reduced. Sea level rise will increase the frequency of extreme sea level events, which occur for example during high tides and intense storms. Many low-lying coastal cities and small islands will be exposed to risks of flooding and land loss annually by 2050. Without major investments in adaptation, they would be exposed to escalating flood risks.
- So what can communities and cities at the coast do to adapt? The scientific literature addresses various adaptation approaches, including protection, accommodation, ecosystem-based adaptation, coastal advance and managed relocation. (please explain) People with the highest exposure and vulnerability are often those with the lowest capacity to respond. Hand over to Hans
- Marine life is already being affected by warming and changes in ocean chemistry, with impacts on the people that depend on them.
- To date, the ocean has absorbed 90% of the heat in the climate system. It will take up 2 to 4 times more heat than between 1970 and the present by 2100 if global warming is limited to 2°C and up to 5 to 7 times more at higher emissions (compared to 1970). Warming in the ocean reduces mixing between water layers and therefore limits 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. They are especially harming warm-water corals, kelp forests and the distribution of marine life. By absorbing human-induced carbon emissions, the ocean is becoming more acidic. This is already making it harder for some marine species to build their shells and skeletons. It has taken up between 20 to 30% of these carbon dioxide emissions, and continued uptake will exacerbate ocean acidification by 2100.
- An ocean that is warmer, more acidic and is losing oxygen has implications for marine life, its distribution and productivity. Changes in the ocean cause shifts in the distribution of fish populations. This has 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. In addition to cutting greenhouse gas emissions, reducing other pressures such as pollution will further help marine life deal with changes in their environment. Policy frameworks, such as fisheries management and marine-protected areas, offer opportunities for people to adapt to changes and minimize risks for our livelihoods, while enabling a more resilient ocean. Hand over to Debra
- What we see is that human-induced climate change has a major footprint on the systems that we depend upon – from the top of the mountains to the depth of oceans. These changes will continue for generations to come.
- This new IPCC Special Report highlights the urgency of prioritizing timely, ambitious and coordinated action to address widespread and enduring changes in the ocean and cryosphere. It provides the best available scientific knowledge to empower people, communities and governments to tackle the unprecedented transitions in all aspects of society, including energy, land and ecosystems, urban and infrastructure as well as industry that would be needed to deliver on the Paris Agreement. 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 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.