Global warming and climate change are changing ocean temperatures to such an extent that coastal cities could see frequent flooding and cyclones, while also wreaking havoc on marine ecosystems and seafood supplies. This findingcomes from more than 100 scientists from 36 countries who worked on a just-released report for the United Nations’ Intergovernmental Panel on Climate Change (IPCC).
The report, focusing on oceans and cryospheres (ice, snow, glaciers and permafrost) is the last of three special reports put out by the IPCC, with the previous two focusing on global warming and the planet’s land, respectively.
Melting ice is leading to rising sea levels and an expanding, warmer ocean, according to the report. This is dangerous, as sea levels are rising at more than 3.6 mm per year — for context, sea levels rose only 150mm during the entire 20th century. This means that sea levels could rise by around 300 to 600 mm by 2100, even if greenhouse gas emissions are sharply reduced. However, if greenhouse gas emissions continue to increasemore than their current rate, sea levels could rise by 600 to 1100 mm.
A significant rise in sea level will lead to extreme sea-level events like storm surges, surface waves, extreme high tides, changes in coastal geometry and even disasters like floods and cyclones. Extreme sea-level events have occurred only once a century, historically — but they’re now slated to occur yearly, at least. This is further exacerbated by tropical cyclone winds and rainfallrelated to climate change and can prove devastating to marine ecosystems and people who live on the coast. Some island nations could become uninhabitable, according to the report.
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Oceans have also been bearing a lot more climate change-induced wreckage than is visible; they’ve taken up more than 90% of excess heat in the climate system. Apart from that, oceans have also taken up 20% to 30% of human-induced carbon dioxide, leading to acidification. Ocean warming and acidification reduces the supply of oxygen and nutrients that support marine life, affecting the distribution and population of water creatures in coastal areas, the ocean and seafloor. This also means that people who depend on a seafood-heavy diet will face nutritional and food security issues.
According to the report, people in mountainous regions are also facing increasing exposure to water-related hazards and changes, due to a decline in glaciers, snow, ice, and permafrost. Disasters that could occur include landslides, avalanches, floods, and rockfalls. “Changes in water availability will not just affect people in these high mountain regions, but also communities much further downstream,” Panmao Zhai, co-chair of the IPCC Working Group I, said in a statement, while referring to altering water availability affecting agriculture and hydro-power.
Smaller glaciers present in Europe, eastern Africa, the tropical Andes, and Indonesia could also lose more than 80% of their ice by 2100, if greenhouse gas emissions continue at the current rate.
“The open sea, the Arctic, the Antarctic, and the high mountains may seem far away to many people,” Hoesung Lee, chairperson of the IPCC, said in a statement, “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 well-being, for culture and identity.”
Lee added, “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. … We increase our ability to build resilience and there will be more benefits for sustainable development.”
