Climate panel: Oceans are in trouble and so are we
Report warns failure to cut emissions will have dire consequences
The planet is in hot water — literally — and that will have dire consequences for humanity, warns a new United Nations report on the state of the world’s oceans and ice.
Over the next century, climate change will make the oceans warmer and more acidic. Melting ice sheets will drive up sea levels at an accelerating pace. And the population of animals in the sea could drop by as much as 15%, according to the sobering assessment by the U.N. Intergovernmental Panel on Climate Change.
“The oceans and ice are in trouble, so we’re all in trouble,” said Michael Oppenheimer, a climate scientist at Princeton and a lead author of the report.
But while some damage is inevitable at this point, the report makes clear that society’s efforts to reduce greenhouse gas emissions in the coming decades will determine how bad things ultimately get.
It’s “the difference between an unmanageable problem and one that humans can deal with,” Oppenheimer said.
The analysis, released Wednesday at a meeting of scientists and policymakers in Monaco, follows close on the heels of the U.N. Climate Action Summit in New York, which failed to elicit ambitious commitments from the world’s biggest polluters. Yet the report underscores just how costly delaying action will be.
Thus far, the world’s oceans have been the quiet hero of the warming world. They have absorbed about a quarter of the carbon dioxide humans have pumped into the atmosphere since the dawn of the industrial revolution, and 90% of the resulting heat.
“But it can’t keep up,” said Ko Barrett, deputy administrator for research at the National Oceanic and Atmospheric Administration and a vice chair of the IPCC.
The report illustrates how climate change has already started to alter the chemistry and circulation of the oceans, and how that exacts a heavy toll on marine ecosystems. Coastal communities, which will be home to a billion people by 2050, are also feeling the impacts, starting with rising seas.
Over the last century, sea level rise was primarily driven by runoff from melting mountain glaciers in places like Alaska and the Andes, as well as by the expansion of seawater as it warmed. Now, the massive ice sheets in Greenland and Antarctica have taken over as the largest contributors, and they are increasing sea levels faster than ever.
Since 2006, sea levels have risen at a rate of 0.14 of an inch per year — more than double the rate over the previous century.
The big question will happen next?
Based on new research since the last IPCC assessment came out in 2014, the authors increased their estimates of projected future sea levels.
Compared with the turn of the 21st century, sea levels will increase about 1.5 feet by 2100 and will rise a total of 3 feet by the year 2300 — if society rapidly reduces greenhouse gases.
That will present plenty of challenges, “but things will evolve slowly, giving humans plenty of time to plan,” Oppenheimer said.
On the other hand, if countries fail to curb emissions in the next few decades, the world will see about 3 feet of sea level is: What rise by the end of the century — and much more after that.
In the worstcase scenario, where parts of the Antarctic ice sheet start to collapse, we could be in for as much as 17 feet of sea level rise by 2300. That would probably outpace society’s ability to adapt, Oppenheimer said.
No one knows exactly where the tipping point lies, but scientists have already seen troubling signs of rapid ice loss in places like Antarctica’s Thwaites Glacier, which alone contains enough water to raise sea levels by 2 feet.
“That is very worrying,” said Regine Hock, a glaciologist at the University of Alaska Fairbanks and an author of the report. “The indications are there that instability might be on its way.”
Regardless of how much sea levels rise over the long term, they will cause problems for coastal communities in the short term because of increasingly devastating storm surges and high tides.
By 2050, flood events that used to occur only once a century will happen at least once every year in many places in the world, even under a bestcase scenario, according to the report.
On top of that, hurricanes will intensify, and extreme El Niño and La Niña events are forecast to happen twice as often by the end of the century. That’s true no matter how quickly countries reduce greenhouse gas emissions.
Many of these episodes will be unlike anything in living memory, and will require communities to plan for unprecedented impacts. “If we do business as usual, we won’t be prepared for them,” said Somin Cheong, a human geographer at the University of Kansas and an author of the report.
The assessment also looked at how climate change is affecting fish populations and the communities that depend on them.
Warming waters have put many marine animals on the move. One analysis found that some fish species along the West Coast could migrate as much as 600 miles north under a highemissions scenario. Creatures that can’t relocate, like corals, could simply be eradicated.
Some animals will thrive in their new homes and others will hit dead ends, forcing fishing industries to adapt. But on the whole, unmitigated climate change will decrease the potential catch of global fisheries by 20%, the report concluded.
There is no onesizefitsall approach to making coastal communities more resilient, Cheong said, but governments could help by improving early warning systems for disasters, encouraging residents to plan for climate change when they rebuild, or, in some cases, considering retreating altogether. But there are also reasons to be hopeful. The ocean holds the potential to accomplish roughly a quarter of the greenhouse gas reductions needed to meet the Paris climate targets, according to a report released Monday by the High Level Panel for a Sustainable Ocean Economy, a group of scientists and world leaders convened by the World Resources Institute.
For instance, seagrass meadows, salt marshes and mangrove habitats can sequester huge amounts of what scientists call “blue carbon.” Preserving and restoring them yields other benefits too, like buffering coastlines from storms and serving as nurseries for economically important fish.
Even so, there’s no escaping the grim picture painted by the IPCC report. If climate change continues unabated, “the consequences for humanity are sweeping and severe,” Barrett said.
“What’s at stake is the health of ecosystems, wildlife and — importantly — the world we leave our children.”
A storm surge from Hurricane Dorian cut Cedar Island off from mainland North Carolina earlier this month. A U.N. climate report projects that if the world fails to curb emissions in the next few decades, it will see a 3foot rise in sea levels by the end of the century — and a rise of up to 17 feet by the year 2300.