The latest Intergovernmental Panel on Climate Change (IPCC) Special Report highlights the urgency of prioritising timely, ambitious and coordinated action to address unprecedented and enduring changes in the ocean and cryosphere (the frozen parts of the planet).
The IPCC Special Report on the Ocean and Cryosphere in a Changing Climate was produced by more than 100 authors from 36 countries, using the latest scientific literature and referencing around 7000 scientific publications, and will be a key input to the upcoming UN Framework Convention on Climate Change Conference (COP25) in Chile this December.
It reveals the benefits of ambitious and effective adaptation for sustainable development and, conversely, the escalating costs and risks of delayed action.
Dr Carol Turley, PML Senior Scientist and Review Editor for the Special Report, said:
“The latest Intergovernmental Panel on Climate Change Special Report on the Ocean and Cryosphere in a Changing Climate highlights the urgency of prioritizing urgent, ambitious and coordinated action to address unprecedented and enduring changes in the ocean and cryosphere -the frozen parts of the planet.
Global warming has already reached 1°C above the pre-industrial level, due to past and current greenhouse gas emissions. The ocean is warmer, more acidic and less productive. Melting glaciers, ice sheets and expanding seas are causing sea level rise, and coastal extreme events are becoming more severe. There is overwhelming evidence that this is resulting in profound consequences for ecosystems and people.
Hundreds of millions people in high mountain regions and in low-lying coastal zones and small island developing states depend directly on these systems. However, the ocean and the cryosphere play a critical role for life on Earth so all of us will be impacted indirectly. The level of that impact will depend on how society around the world responds to the challenge of reducing our CO2 emissions.
The report does give hope as 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. Urgently reducing greenhouse gas emissions limits the scale of ocean and cryosphere changes. Many of the ecosystems and the livelihoods that depend on them can be preserved – if we act now.”
Major changes in high mountains affecting downstream communities
People in high mountain regions are increasingly exposed to hazards and changes in water availability, as glaciers, snow, ice and permafrost decline, leading to landslides, avalanches and other dangers. Smaller glaciers across the world are projected to lose more than 80% of current ice mass under a high emission scenario, affecting water availability and quality, and requiring integrated water management and transboundary cooperation to address these impacts.
Melting ice, rising seas
With glaciers and ice sheets losing mass, sea levels are rising; the global sea level has risen by around 15cm during the 20th century, but is now rising twice as fast, and accelerating. Levels could rise by around 30-60 cm by 2100 even if emissions are sharply reduced, but by around 60-110 cm if emissions continue to grow.
More frequent extreme sea level events
This sea level rise will increase the frequency of extreme events such as high tides and intense storms, with indications that any degree of additional warming will lead to once-in-a-century events occurring every year in many regions. Major investments in adaptation will be required to avoid the escalating flood risks, and some island nations are likely to become uninhabitable.
Changing ocean ecosystems
To date, the ocean has taken up more than 90% of excess heat in the climate system, causing disruptions to species throughout the ocean food web, with impacts on marine ecosystems and the people that depend on them. Marine heatwaves have doubled in frequency since 1982, and are projected to continue increasing in frequency, duration, extent and intensity.
This warming, in addition to ocean acidification caused by carbon dioxide emissions, are affecting the distribution and abundance of marine life across the seas. Tackling this will require not only efforts to reduce emissions, but also reductions in other stressors such as pollution - even so, policies around fisheries management and marine-protected areas will be required to offer communities opportunities to adapt.
Declining Arctic sea ice, thawing permafrost
Declines in sea ice are continuing rapidly, but could be limited to an ice-free September only once a century if global warming is stabilised at 1.5°C, as compared to once every three years at 2°C warming. Permafrost ground, which holds large amounts of organic carbon, is projected to undergo widespread thawing in the 21st century, even if global warming is limited.
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. This is the first IPCC report that highlights the importance of education to enhance climate change, ocean and cryosphere literacy.
“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.
Roberts continued: “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."