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Due to global warming, the oceans are becoming warmer, more acidic and less productive, and the worst thing is that some of these effects are “irreversible” according to the latest Special Report of the Intergovernmental Panel on Climate Change (IPCC)
Scientists warn that it is necessary to initiate large-scale and coordinated actions in the face of the climate crisis that is causing permanent changes in the sea and the cryosphere.
Strategies must focus on reducing greenhouse gas emissions, at least to slow down the catastrophic changes that are already happening in seas and oceans.
The goal is to have more time to conserve ecosystems and for populations to prepare for the imminent rise in water.
Strategies such as building large levees around large coastal megacities like New York or anticipating the inevitable displacement of some populations, especially small island states that could become uninhabitable by the end of the century, must already be considered.
We are not facing a problem in theory, the climate crisis is already happening. Bruce Glavovic of Massey University in New Zealand comments that this "will redefine the coastlines of the world in January, where populations are concentrated.
Global warming has already reached 1 ° C above the pre-industrial level, due to past and current greenhouse gas emissions. Also, glaciers and ice sheets in the polar and mountain regions are losing mass, contributing to an increasing rate of sea level rise, along with the expansion of the warmer ocean.
In a world warming to +2 ° C, many megacities and small islands would be hit by an extreme event between now and 2050 at least once a year, rather than once every 100 years as before.
The IPCC Special Report provides key data for world leaders gathering in upcoming negotiations on climate and the environment, such as the United Nations Framework Convention on Climate Change (COP25) Conference in Chile in December.
Make human life sustainable
The result of the report shows that adaptation to the climate crisis depends on the capacity of individuals and communities and the resources available.
“If we cut emissions sharply, the consequences for people and their livelihoods will remain challenging, but potentially more manageable for the most vulnerable. We will increase our capacity to build resilience and there will be more benefits for sustainable development“Argued one of the scientists.
Rapid changes are forcing people from coastal cities to remote Arctic communities to alter their ways of life
Melting ice, rising seas
While sea level worldwide has risen by around 15cm during the 20th century, it is currently rising more than twice as fast (3.6mm per year) and accelerating, according to the IPCC.
Sea level will continue to rise as forecast for centuries. This could reach a rate of around 30 to 60 cm by 2100 even if greenhouse gas emissions are drastically reduced and global warming is limited to well below 2 ° C. If emissions continue to increase strongly, it could reach around 60 to 110 cm.
“In recent decades, the rate of sea level rise has accelerated due to rising water from the ice sheets in Greenland and Antarctica, in addition to the contribution of glacier melt and the expansion of warmer waters in the sea, ”said Valérie Masson-Delmotte, Co-Chair of IPCC Working Group I.
Increasingly frequent extreme events
Rising sea levels will also increase the frequency of extreme ocean-related events, which occur, for example, during high tides and intense storms.
There are indications that any additional degree of warming will lead to events that occurred once a century in the past, occurring every year in the middle of the century in many regions. This fact increases the risk of catastrophes in many low-lying coastal cities and small islands.
Some island nations are likely to become uninhabitable due to oceanic and cryospheric climate change, according to the report, but habitability thresholds remain extremely difficult to assess.
Some island nations are likely to become uninhabitable due to oceanic and cryospheric climate change
The risks will be further intensified by increases in average intensity, storm surge magnitude, and precipitation rates from tropical cyclones, especially if greenhouse gas emissions continue to increase.
“Various adaptation approaches are already being implemented, often in response to flood events. The report highlights the diversity of options available for each context and for developing integrated responses that anticipate future sea level rise on a full scale, ”concluded Masson-Delmotte.
Changes in ocean ecosystems
The report also highlights that warming andchemical changes of the oceans are already altering species throughout the ocean's food web, with impacts on marine ecosystems and the people who depend on them.
To date, the ocean has absorbed more than 90% of the excess heat in the climate system. By 2100, the ocean will absorb between two and four times more heat than between 1970 and the present if global warming is limited to 2 ° C, and five to seven times more with higher emissions. "The warming of the ocean reduces the mixing between the layers of water and, as a consequence, the supply of oxygen and nutrients for marine life", explain the scientists.
Additionally, marine heat waves have doubled in frequency since 1982 and are projected to increase further in frequency, duration, extent, and intensity. Its frequency will be 20 times higher at 2 ° C of warming, compared to pre-industrial levels. They would occur 50 times more often if emissions continue to increase.
Warming and acidification of the oceans, loss of oxygen, and changes in nutrient supply are already affecting the distribution and abundance of marine life in coastal areas, in the open ocean, and on the sea floor.
Marine heat waves have doubled in frequency since 1982 and are increasing in intensity
"Reducing greenhouse gas emissions will limit the 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.
Landslides and avalanches in high mountains
On the other hand, people in mountainous regions are increasingly exposed to hazards and changes in water availability, according to the report.
Glaciers, snow, ice, and permafrost are and will continue to decline. This is projected to pose risks to people, for example through landslides, avalanches, rockslides and floods.
Smaller glaciers in Europe, East 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 withdrawal of the high mountain cryosphere will continue to negatively affect recreational activities, tourism and cultural assets.
"Changes in water availability will not only affect people in these high mountain regions, but also communities downstream," said Panmao Zhai, Co-Chair of IPCC Working Group I.
Source: Intergovernmental Panel on Climate Change