The world's oceans are warming at an alarming rate, melting glaciers, depleting fish populations, supercharging tropical cyclones, and threatening the livelihoods of millions of people who live in coastal areas and the Arctic, according to a new report from the United Nations' body in charge of monitoring climate change.
The sobering report, released Wednesday by the Intergovernmental Panel on Climate Change, lays bare the destructive and irreversible changes already playing out on Earth's ice sheets, glaciers, and oceans, and warns that the hazards posed by unprecedented warming will only worsen if greenhouse gas emissions continue at their current rate.
"The world’s ocean and cryosphere have been 'taking the heat' from climate change for decades, and consequences for nature and humanity are sweeping and severe," Ko Barrett, vice-chair of the IPCC, said in a statement. "The rapid changes to the ocean and the frozen parts of our planet are forcing people from coastal cities to remote Arctic communities to fundamentally alter their ways of life."
Drawing from nearly 7,000 scientific publications, the IPCC's "Special Report on the Ocean and Cryosphere in a Changing Climate" found that global warming has caused widespread shrinking of Earth's cryosphere — ice sheets, glaciers, snow cover, and frozen ground — and unabated warming of oceans.
The report follows one published last month focusing on the impacts of climate change on land and comes on the heels of the UN Climate Action Summit and a massive climate strike movement that drew millions to the streets last week.
Scientists say rising global temperatures are caused by the burning of fossil fuels and emissions of other potent greenhouse gases. When nearly 200 countries signed the Paris climate accord aimed at preventing catastrophic climate change, they agreed to limit warming to at least 2 degrees Celsius, and ideally to 1.5 degrees Celsius. But even if the world succeeds in dramatically cutting climate pollution and limiting man-made global warming to only 1.5 degrees, there’s no escaping a series of negative impacts — rising seas, steep declines in coral reefs, and more extreme weather.
According to the report, the world's oceans have absorbed more than 90% of the warming that has occurred on Earth over the last 50 years, with the rate of ocean warming more than doubling since 1993. As a result of increasing rates of ice loss from the Greenland and Antarctic ice sheets, ocean levels rose around 15 centimeters during the 20th century and are currently rising at a rate of 3.6 millimeters per year — and accelerating.
Warming oceans will lead to more frequent tropical cyclones, according to the report, which said that extreme sea-level events that have historically occurred once each century will occur every year by 2050, increasing flooding risks for low-lying coastal cities and island communities. As a result, some small islands, which are home to 65 million people globally, are at risk of becoming uninhabitable, the report said.
Glacial melt, reductions in snow cover, and thawing of permafrost are also projected to increase the risk of landslides, avalanches, rockfalls, and floods in mountain regions.
"Many small glaciers, for instance, in Washington state in the Western US, will disappear within the next decades or within, at [the] latest, in a century," Regine Hock, one of the report's more than 100 authors, said on a press call.
In the Arctic region, where 4 million people live, some communities, especially indigenous peoples, have already had to adjust their travel and hunting patterns in response to changes in seasonal ice and snow conditions, the report said. Some communities have also planned for relocation.
Warming of the world's oceans has also disrupted the abundance of fish and shellfish stocks in some regions, leaving communities that depend on seafood at risk of decreased food security.
"The open sea, the Arctic, the Antarctic and the high mountains may seem far away to many people," said IPCC chair Hoesung Lee 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 wellbeing, for culture and identity."
Significantly reducing greenhouse gas emissions, protecting and restoring ecosystems, and carefully managing the use of natural resources, the report said, would limit the impact of climate change on oceans and ice-covered regions around the world.