No place on earth will be spared impacts of climate change, experts warn
- September 26, 2019
- Category: Water issues, Arctic & Antarctica, Agriculture, Environmental, Global
The latest Special Report by the UN’s Intergovernmental Panel on Climate Change (IPPC) is warning that no place on earth will be spared the impacts of climate change.
As ice melts in the planet’s frozen regions, oceans warm and sea levels rise, The Ocean and Cryosphere in a Changing Climate, says that the projected responses of the ocean and cryosphere to past and current human-induced greenhouse gas emissions and ongoing global warming include:
- climate feedbacks
- changes over decades to millennia that cannot be avoided
- thresholds of abrupt change
The IPCC is calling for “timely, ambitious and coordinated action” to address what it describes as “unprecedented and enduring changes in the ocean and cryosphere.”
The report warns:
“Ocean warming, acidification and deoxygenation, ice sheet and glacier mass loss, and permafrost degradation are expected to be irreversible on timescales relevant to human societies and ecosystems.”
According to the scientists, societies worldwide will be exposed, and challenged to adapt, to changes in the ocean and cryosphere even if current and future efforts to reduce greenhouse gas emissions keep global warming well below 2°C.
The global ocean covers 71% of the Earth surface and contains about 97% of the Earth’s water, while around 10% of Earth’s land area is covered by glaciers or ice sheets.
A total of 670 million people in high mountain regions and 680 million people in low-lying coastal zones depend directly on these systems. Four million people live permanently in the Arctic region, and small island developing states are home to 65 million people.
Coastal communities, small islands, polar areas and high mountains are particularly exposed to the impacts, while other communities further from the coast are also exposed to changes in the ocean, such as through extreme weather events.
Coasts are home to approximately 28% of the global population, including around 11% living on land less than 10 meters above sea level. The low-lying coastal zone is currently home to around 680 million people (nearly 10% of the 2010 global population). This is projected to reach more than one billion by 2050.
Around 670 million people (nearly 10% of the 2010 global population), including Indigenous peoples, live in high mountain regions in all continents except Antarctica. In high mountain regions, population is projected to reach between 740 and 840 million by 2050.
“Overwhelming evidence global warming is resulting in profound consequences for ecosystems and people”
The report says that global warming has already reached 1°C above the pre-industrial level, due to past and current greenhouse gas emissions and that there is overwhelming evidence that this 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.
Hoesung Lee, Chair of the IPCC commented:
“The open sea, the Arctic, the Antarctic and the high mountains may seem far away to many people.”
“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.”
“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,” Lee said.
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 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.
Major changes in high mountains have serious implications for agriculture and hydropower
People in mountain regions are increasingly exposed to hazards and changes in water availability, the report says. In addition, as the mountain glaciers retreat, they are also altering water availability and quality downstream, with implications for many sectors such as agriculture and hydropower.
The ongoing decline of glaciers, snow, ice and permafrost is projected to increase hazards for people, for example through landslides, avalanches, rockfalls and floods.
Under high emission scenarios, 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.
Panmao Zhai, Co-Chair of IPCC Working Group I commented:
“Changes in water availability will not just affect people in these high mountain regions, but also communities much further downstream.”
“Limiting warming would help them adapt to changes in water supplies in mountain regions and beyond, and limit risks related to mountain hazards.”
“Integrated water management and transboundary cooperation provides opportunities to address impacts of these changes in water resources.”
Melting ice contributing to rising sea levels
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. Significant sea level rise contributions from Antarctic ice sheet mass loss, which earlier reports did not expect to manifest this century, are already being observed.
The report warns that 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 – and it 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.
Valérie Masson-Delmotte, Co-Chair of IPCC Working Group I said:
“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.”
“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.”
“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, the report says. 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.
Beyond 2100, sea level will continue to rise for centuries due to continuing deep ocean heat uptake and mass loss of the Greenland and Antarctic ice sheets and will remain elevated for thousands of years
The report flags up the three coastal megacities of Shanghai, New York and Rotterdam which have all had both historical and recent experience with damaging extreme sea level events. High, and in many cases, growing population density and total population, and high exposure of people and infrastructure to global mean sea level rise and extreme sea level events characterize coastal megacities.
Without major investments in adaptation, they would be exposed to escalating flood risks, the report shows. Some small island nations are likely to become uninhabitable due to climate-related ocean and cryosphere change, the report says, but habitability thresholds remain extremely difficult to assess.
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 says.
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.
The ocean has also 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.
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.
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 and in the future, some regions, notably tropical oceans, will see further decreases.
“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.”
Declining Arctic sea ice and widespread permafrost thaw projected to occur in 21st century
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.
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.
The report warns that if greenhouse gas emissions continue to increase strongly, there is a potential that around 70% near-surface permafrost could be lost,
The permafrost also holds large amounts of organic carbon, almost twice the carbon in the atmosphere, and have the potential to significantly increase the concentration of greenhouse gases in the atmosphere if they thaw.
IPCC calls 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 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.
However, the Special Report says the scale and cross-boundary dimensions of changes in the ocean and cryosphere will challenge the ability of communities, cultures and nations to respond effectively within existing governance frameworks, commenting:
“Profound economic and institutional transformations are needed if climate-resilient development is to be achieved. Changes in the ocean and cryosphere, the ecosystem services that they provide, the drivers of those changes, and the risks to marine, coastal, polar and mountainecosystems, occur on spatial and temporal scales that may not align within existing governance structures and practices.”
Click here to download The Ocean and Cryosphere in a Changing Climate in full