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Globally sea levels are estimated to rise 1.1 metre by 2100, if countries are not able to restrict emissions “well below” 2 degrees Celsius above pre-industrial levels, as stated in the 2015 Paris climate agreement, according to a new report by the Intergovernmental Panel on Climate Change (IPCC) on September 25, 2019.
But, even if countries are able to restrict emissions, it is still estimated to rise 30-60 centimetres by 2100.
While, during the 20th century the global sea level rose by around 15 cm, it is currently accelerating by 3.6 millimetre annually, revealed the IPCC’s Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC).
This is likely to have a direct impact on the lives of 680 million people living in low-lying coastal zones, according to the report.
Greenhouse gas emissions have pushed the current global emissions to 1°C above the pre-industrial level.
Any degree of additional warming is likely to bring extreme sea-level events every year by the mid-century in many regions, triggering risks for people living in the low-lying coastal cities and small islands, showed the report.
“Some island nations are likely to become uninhabitable due to climate-related ocean and cryosphere change,” stated the SROCC report.
Increasing warming of oceans and melting of Greenland and West Antarctica ice sheets have significantly contributed to the rise in sea level, said Valérie Masson-Delmotte, Co-Chair of IPCC Working Group I.
The rising sea temperatures have also doubled the frequency of marine heatwaves since 1982. At 2°C warming, its frequency will be 20 times higher; and if emissions continue to increase it will occur 50 times more often, the report noted.
The oceans have, until now, absorbed more than 90 per cent of the excess heat in the climate system. If global warming is limited to 2°C, they will absorb 2-4 times more heat than between 1970 and the present.
However, the increased warming of sea water will decrease the mixing between water layers and, as a result, the supply of oxygen and nutrients essential for marine life.
Oceans are also major source of carbon sink: Since the 1980s, the waters have absorbed 20-30 per cent of human-induced carbon dioxide emissions (CO2), causing ocean acidification.
Continued carbon uptake by the ocean by 2100 will exacerbate ocean acidification, leading to major consequences for marine life and coastal habitats.
The SROCC report was approved by 195 IPCC member governments. It provides evidence for the benefits of limiting global warming to the lowest possible level.
The report has identified the areas of concern and suggests that there is urgent need for timely, ambitious and coordinated action to address the unprecedented and enduring changes in the ocean and cryosphere.
“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,” said Hoesung Lee, Chair of the IPCC.
The study, analysed by the team of more than 100 authors from 36 countries, also revealed that small glaciers in Europe, eastern Africa, the tropical Andes and Indonesia will likely lose more than 80 per cent of their current ice mass by 2100.