Unprecedented ocean and cryosphere change requires urgent action, IPCC report finds
Our oceans are warming, ice sheets are melting, and sea levels are rising – and all at an unprecedented rate, according to a report, published by the Geneva-based Mountain Research Institute.
The most recent report released by the Intergovernmental Panel on Climate Change (IPCC), highlights the severe impact of climate change on the world’s water, from the deepest depths of the ocean to the highest peaks of changing mountains.
The findings of the Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) based on thousands of scientific studies, paint a stark picture of the impacts, outlook, and potential for adaptation to unparalleled and enduring changes in the ocean and cryosphere as a result of global warming, calling for urgent, timely, ambitious, and coordinated action on greenhouse gas emissions.
“The oceans and cryosphere have been taking the heat of climate change for decades” – Ko Barrett, IPCC Vice Chair.
Mountain Research Initiative Executive Director Dr Carolina Adler is a Lead Author of the second chapter of the special report which focuses on the changes occurring in high mountain areas of Himalayas, Hinu Kush, Karakoram, Pamir and elsewhere.
“In this report, we present key evidence on observed and projected trends in warming, and how these trigger physical responses in the ocean and cryosphere,” Adler explains. “These physical responses also lead to impacts on both people and ecosystems that are evident today and are projected to increase in the future. However, despite these significant observed and projected changes, there is still an opportunity to reduce the risk of large impacts and ensure adaptation is more effective through emissions reduction. In essence, we highlight the benefits of ambitious and effective adaptation.”
Impacts on ecosystems and people
The ocean and the cryosphere – the frozen parts of the planet – play a critical role in life on Earth. 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.
Global warming has already reached 1°C above the pre-industrial level, due to past and current greenhouse gas emissions. 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.
Changes in mountains and consequences
“For high mountains, the IPCC SROCC findings confirm the changes we already see in terms of melting glaciers and changes in snow cover, as well as the effects of thawing permafrost – a change that is less visible, and yet is important to note given its role in the increase of mountain hazards such as rockfalls,” said Adler.
Glaciers are retreating in all high mountain regions. Between 2006 and 2015, glacier mass losses across mountain regions averaged at approximately half a meter of thinning per year. Under high emissions scenarios, smaller glaciers such as those found in Europe, eastern Africa, the tropical Andes, and Indonesia are projected to lose more than 80 percent of their current ice mass by 2100. Some glaciers are expected to disappear completely.
The shrinking of the high-mountain cryosphere increasingly exposes the millions of people that rely on mountain glaciers and snowpack – the ‘water towers’ of the world – to both increased flooding and devastating droughts. This, in turn, increases food insecurity, as well as having adverse impacts on livelihoods, health and well-being, infrastructure, transportation, tourism, recreation, and cultural assets – particularly among Indigenous people. This retreat is also altering water availability and quality downstream, with implications for many sectors, such as agriculture and hydropower.
Mountain permafrost amounts to between 27 and 29 percent of global permafrost, with the remainder focused on the Arctic and boreal regions. According to Professor Konrad Steffen, IPCC Lead Author and Director of the Swiss Federal Research Institute WSL: “Due to the ever-warming permafrost, the hillsides in the Alps and elsewhere are becoming unstable, and in the polar regions carbon reserves that have been resting there for thousands of years are being released.”
A quarter of permafrost globally is already likely to melt, the IPCC report has said, and 70 percent or more could be lost if emissions are not curbed. This would result in the release of significant amounts of stored carbon dioxide and methane, further exacerbating the climate emergency.
The changes being seen in high-mountain environments also have implications for the species that live there, as Andreas Fischlin, Professor at the ETH Zurich and Vice-Chair of IPCC Working Group II, points out: “Across the world, the high mountains, in particular, are experiencing significant change. Glaciers are melting, and plants and animals from the lower lands are populating higher elevations or changing their behavior – and, in turn, the habitats of high mountain specialists are contracting.”
There is, according to Adler, some hope, however. “Through an ambitious and concerted reduction of greenhouse gas emissions, we can expect to preserve more of our iconic high mountain landscape – provided we also embed adaptation design and implementation into all aspects of development, management, and governance of our mountain spaces, with community participation at the heart of these measures.”
Melting ice, rising seas
As glaciers and ice sheets in polar and mountain regions loss mass, they are contributing to an increasing rate of sea-level rise, together with the 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 levels 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 – potentially putting areas in which millions currently live underwater.
Sea level rise will increase the frequency of extreme sea-level events, which occur during high tides and intense storms for example. Indications are that with any degree of additional warming, events that used to occur once a century will strike every year on many coasts by 2050, increasing risks for many low-lying coastal cities and small islands.
Increases in tropical cyclone winds and rainfall are also exacerbating extreme sea-level events and coastal hazards. These hazards will be further intensified by an increase in the average intensity, the magnitude of storm surge, and precipitation rates of tropical cyclones, especially if greenhouse gas emissions remain high.
Changing ocean ecosystems
To date, the ocean has provided a buffer against the worst effects of climate change, absorbing over 90 percent of the extra heat trapped in the atmosphere by excess greenhouse gases since the 1970s and somewhere between 20 to 30 percent of the carbon dioxide, which causes ocean acidification. 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 loss of oxygen and changes in nutrient supplies caused by ocean warming and acidification are already affecting the distribution and abundance of marine life in coastal areas, in the open ocean, and on the seafloor. This, in turn, impacts the food security and nutrition of communities that depend upon seafood.
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.
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 affect 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. This article was first published in the Mountain Research Initiative.
Also see: https://youtu.be/5Y09nvF3mTk