Earth’s oceans are under severe strain from climate change, a major new United Nations report warns, which threatens everything from the ability to harvest seafood to the well-being of hundreds of millions of people living along the coasts.
Rising temperatures are contributing to a drop in fish populations in many regions, and oxygen levels in the ocean are declining while acidity levels are on the rise, posing risks to important marine ecosystems, according to the report issued Wednesday by the Intergovernmental Panel on Climate Change, a group of scientists convened by the United Nations to guide world leaders in policymaking.
In addition, warmer ocean waters, when combined with rising sea levels, threaten to fuel ever more powerful tropical cyclones and floods, the report said, further imperiling coastal regions and worsening a phenomenon that is already contributing to storms like Hurricane Harvey, which devastated Houston two years ago.
“The oceans are sending us so many warning signals that we need to get emissions under control,” said Hans-Otto Pörtner, a marine biologist at the Alfred Wegener Institute in Germany and a lead author of the report. “Ecosystems are changing, food webs are changing, fish stocks are changing, and this turmoil is affecting humans.”
What on Earth Is Going On?
Sign up for our weekly newsletter to get our latest stories and insights about climate change — along with answers to your questions and tips on how to help.
Advertisement
For decades, the oceans have served as a crucial buffer against global warming, soaking up roughly a quarter of the carbon dioxide that humans emit from power plants, factories and cars, and absorbing more than 90 percent of the excess heat trapped on Earth by carbon dioxide and other greenhouse gases. Without that protection, the land would be heating much more rapidly.
But the oceans themselves are becoming hotter and less oxygen-rich as a result, according to the report. If humans keep pumping greenhouse gases into the atmosphere at an increasing rate, the risks to human food security and coastal communities will increase sharply, particularly since marine ecosystems are already facing threats from plastic pollution, unsustainable fishing practices and other man-made stresses.
“We are an ocean world, run and regulated by a single ocean, and we are pushing that life support system to its very limits through heating, deoxygenation and acidification,” said Dan Laffoley of the International Union for Conservation of Nature, a leading environmental group that tracks the status of plant and animal species, in response to the report.
The report, which was written by more than 100 international experts and is based on more than 7,000 studies, represents the most extensive look to date at the effects of climate change on oceans, ice sheets, mountain snowpack and permafrost.
Changes deep in the ocean or high in the mountains are not always as noticeable as some of the other hallmarks of global warming, such as heat waves on land, or wildfires and droughts. But the report makes clear that what happens in these remote regions will have ripple effects across the globe.
For instance, as ice sheets in Greenland and Antarctica melt and push up ocean levels, the report said, extreme flooding that was once historically rare could start occurring once a year or more, on average, in many coastal regions this century. How quickly this happens depends largely on the ability of humanity to reduce emissions of greenhouse gases that are heating the planet.
Around the world, glaciers in the mountains are receding quickly, affecting the availability of water for millions of people who depend on meltwater downstream to supply drinking water, irrigate agricultural land and produce electricity through dams and hydropower.
But some of the report’s starkest warnings concern the ocean, where major shifts are already underway.
The frequency of marine heat waves — which can kill fish, seabirds, coral reefs and seagrasses — have doubled since the 1980s. Many fish populations are migrating far from their usual locations to find cooler waters, throwing local fishing industries into disarray. Floating sea ice in the Arctic Ocean is declining at rates that are “likely unprecedented for at least 1,000 years,” the report said.
There have even been unwelcome surprises. The report notes that some pathogens are proliferating in warmer waters, including vibrio, a bacteria that can infect oysters and other shellfish, and that already sickens some 80,000 Americans who eat raw or undercooked seafood each year. “That’s a good example of how changes in the ocean can affect even people who live far from the coasts,” said Sherilee Harper, a public health expert at the University of Alberta and an author on the report.
More at: https://www.nytimes.com/2019/09/25/...tion=click&module=Top Stories&pgtype=Homepage
Rising temperatures are contributing to a drop in fish populations in many regions, and oxygen levels in the ocean are declining while acidity levels are on the rise, posing risks to important marine ecosystems, according to the report issued Wednesday by the Intergovernmental Panel on Climate Change, a group of scientists convened by the United Nations to guide world leaders in policymaking.
In addition, warmer ocean waters, when combined with rising sea levels, threaten to fuel ever more powerful tropical cyclones and floods, the report said, further imperiling coastal regions and worsening a phenomenon that is already contributing to storms like Hurricane Harvey, which devastated Houston two years ago.
“The oceans are sending us so many warning signals that we need to get emissions under control,” said Hans-Otto Pörtner, a marine biologist at the Alfred Wegener Institute in Germany and a lead author of the report. “Ecosystems are changing, food webs are changing, fish stocks are changing, and this turmoil is affecting humans.”
What on Earth Is Going On?
Sign up for our weekly newsletter to get our latest stories and insights about climate change — along with answers to your questions and tips on how to help.
Advertisement
For decades, the oceans have served as a crucial buffer against global warming, soaking up roughly a quarter of the carbon dioxide that humans emit from power plants, factories and cars, and absorbing more than 90 percent of the excess heat trapped on Earth by carbon dioxide and other greenhouse gases. Without that protection, the land would be heating much more rapidly.
But the oceans themselves are becoming hotter and less oxygen-rich as a result, according to the report. If humans keep pumping greenhouse gases into the atmosphere at an increasing rate, the risks to human food security and coastal communities will increase sharply, particularly since marine ecosystems are already facing threats from plastic pollution, unsustainable fishing practices and other man-made stresses.
“We are an ocean world, run and regulated by a single ocean, and we are pushing that life support system to its very limits through heating, deoxygenation and acidification,” said Dan Laffoley of the International Union for Conservation of Nature, a leading environmental group that tracks the status of plant and animal species, in response to the report.
The report, which was written by more than 100 international experts and is based on more than 7,000 studies, represents the most extensive look to date at the effects of climate change on oceans, ice sheets, mountain snowpack and permafrost.
Changes deep in the ocean or high in the mountains are not always as noticeable as some of the other hallmarks of global warming, such as heat waves on land, or wildfires and droughts. But the report makes clear that what happens in these remote regions will have ripple effects across the globe.
For instance, as ice sheets in Greenland and Antarctica melt and push up ocean levels, the report said, extreme flooding that was once historically rare could start occurring once a year or more, on average, in many coastal regions this century. How quickly this happens depends largely on the ability of humanity to reduce emissions of greenhouse gases that are heating the planet.
Around the world, glaciers in the mountains are receding quickly, affecting the availability of water for millions of people who depend on meltwater downstream to supply drinking water, irrigate agricultural land and produce electricity through dams and hydropower.
But some of the report’s starkest warnings concern the ocean, where major shifts are already underway.
The frequency of marine heat waves — which can kill fish, seabirds, coral reefs and seagrasses — have doubled since the 1980s. Many fish populations are migrating far from their usual locations to find cooler waters, throwing local fishing industries into disarray. Floating sea ice in the Arctic Ocean is declining at rates that are “likely unprecedented for at least 1,000 years,” the report said.
There have even been unwelcome surprises. The report notes that some pathogens are proliferating in warmer waters, including vibrio, a bacteria that can infect oysters and other shellfish, and that already sickens some 80,000 Americans who eat raw or undercooked seafood each year. “That’s a good example of how changes in the ocean can affect even people who live far from the coasts,” said Sherilee Harper, a public health expert at the University of Alberta and an author on the report.
More at: https://www.nytimes.com/2019/09/25/...tion=click&module=Top Stories&pgtype=Homepage
