Ocean warming is “greatest hidden challenge of our generation,” according to IUCN
This article was originally published on Mongabay and is republished with permission.
- A report released by the International Union for Conservation of Nature (IUCN) on Monday finds that the effects of global warming on oceans are not a concern for the future — fish, marine mammals, seabirds, and even humans are already being impacted by rising temperatures in oceanic waters.
- More than 93 percent of the global warming that has resulted from human activities since the 1970s was absorbed by Earth’s oceans, and data show a “sustained and accelerating upward trend in ocean warming,” according to the report.
- Entire groups of species such as plankton, fish, jellyfish, turtles and seabirds have been driven up to 10 degrees of latitude towards the Earth’s poles as they seek to keep within the environmental conditions to which they’re adapted.
Global warming is changing Earth’s oceans and those impacts will last for decades even if we rein in greenhouse gas emissions from human activities, according to new research.
A report released by the International Union for Conservation of Nature (IUCN) on Monday finds that the effects of global warming on oceans are not a concern for the future — fish, marine mammals, seabirds, and even humans are already being impacted by rising temperatures in oceanic waters.
“This is no longer a single story of ocean warming challenges to coral reefs, but a rapidly growing list of alarming changes across species at ecosystem scales, and across geographies spanning the entire world,” the IUCN said in a statement about the findings of the report, which was compiled by 80 scientists in 12 countries around the world.
“It is pervasive change, driven by ocean warming and other stressors already operating in ways we are only beginning to understand… Ocean warming may well turn out to be the greatest hidden challenge of our generation.”
More than 93 percent of the global warming that has resulted from human activities since the 1970s was absorbed by Earth’s oceans, and data show a “sustained and accelerating upward trend in ocean warming,” according to the report. If the amount of heat that was trapped in the top two kilometers (about 1.2 miles) of the ocean between 1955 and 2010 had gone into the lower 10 kilometers (about 6.2 miles) of the atmosphere instead, the Earth’s ambient temperature would be 36-degrees-Celsius warmer today, the report says.
The warming of ocean waters has led to major changes described in the report, above and beyond the impacts on coral reefs that have made headlines as a global bleaching event has been ongoing since 2014. Entire ecosystems have been impacted, the researchers say, from polar to tropical regions and from coastlines to the deep ocean seabed.
Entire groups of species such as plankton, fish, jellyfish, turtles and seabirds have been driven up to 10 degrees of latitude towards the Earth’s poles as they seek to keep within the environmental conditions to which they’re adapted. This has meant the loss of breeding grounds for some turtles and seabirds, as well as impacts on the breeding success of many birds and sea mammals.
Pacific green sea turtle. Photo by Rhett Butler.
“We now know that the changes in the ocean are happening between 1.5 and 5 times faster than those on land,” the IUCN said. “Such range shifts are potentially irreversible, with great impacts on ecosystems. What this will result in, decades down the line, is less clear. It is an experiment where, rather than being a casual observer in the lab, we have unwittingly placed ourselves inside the test-tube.”
Sea-level rise and the melting of glaciers and ice sheets are increasing at an accelerating rate, and will have significant consequences for humanity in addition to marine species and ecosystems, the report warns. There is likely to be an increase in mean global ocean temperature of one to four degrees Celsius by 2100, with the greatest ocean warming occurring in the Southern Hemisphere and contributing to the subsurface melting of Antarctic ice shelves.
Meanwhile, there is likely to be Arctic warming and ice loss. Within the next few decades, the report finds, Arctic sea ice could essentially disappear during the summer. “Since the 1990s the atmosphere in the polar regions has been warming at about twice the average rate of global warming,” the report states.
Aside from impacts to ecosystems and biodiversity, the report looks at what rising ocean temperatures could mean for future warming scenarios, as well. There is currently as much as 2.5 Gigatons of frozen methane hydrate stored in the sea floor at depths of 200 to 2,000 meters (0.12 to 1.2 miles). “Increasing water temperature could release this source of carbon into the ocean and ultimately into the atmosphere,” per the report, which would mean that the impacts of global warming on the oceans could in turn lead to even more accelerated global climate change in the future.
But it’s not just rising temperatures imperiling the health of oceans in the future. “Warming, ocean acidification and de-oxygenation have been termed the deadly trio, as one or more of these processes are known to play an important role in all of the major mass extinction events that have taken place,” the report notes. “Evidence points not only to all three of these processes currently occurring in the ocean, but that they are occurring at unprecedented rapid rates and over short timescales.”
Nearly 200 countries signed the Paris Climate Agreement in December, and the United States and China just announced that they were formally joining the accord, bring it that much closer to entering into force. But that won’t mean that the effects of global warming on Earth’s oceans will slow down any time soon. “[T]he very nature of the deep sea will result in it continuing to experience the effects for decades, if not centuries, even after complete cessation of CO2 emissions,” the report finds.
“By absorbing a disproportionate amount of heat from global warming and by taking up the rapidly increasing emissions of carbon dioxide, the ocean has shielded the world from even more rapid changes in climate,” the authors of the report write. “However, the extent to which it can continue to do so in the near and distant future is far from clear.”
Throughout the report, a consistent theme is that our knowledge of the impacts of global warming on Earth’s oceans and our capacity to adequately study ocean warming are currently lacking: “The global community is increasingly committing itself to a high-carbon future which it is poorly equipped to understand, let alone cope with.”
Because the United Nations Framework Convention on Climate Change (UNFCCC), the treaty under which the Paris Climate Agreement was adopted, governs climate law between nation states, the authors write, the UNFCCC should acknowledge the role played by the deep sea in influencing the global climate by setting aside greater resources for studying the deep sea and predicting the impacts of climate change.
“It is important that this is undertaken if we are to not only protect the fauna inhabiting the deep sea, but to safeguard the many resources, functions and services that the deep sea currently provides,” the authors write.
The Great Barrier Reef near Cairns, Queensland, Australia. Photo by Rhett Butler.
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