Oceans face dire threats from climate change. They also hold answers.

Rising seas. Retreating glaciers. Thawing tundra. Acidifying oceans.

The impacts from climate change to the Earth’s oceans and frozen regions – water and ice – are severe, and are getting worse, with potentially devastating consequences, from more frequent flooding and more severe storms to dwindling fish stocks and diminishing snowpacks. A major United Nations report released Wednesday highlights the threat to those regions – the observed changes and what we can expect in the future.

But the ocean – while increasingly under threat – is also a source of some of the most promising solutions for mitigating carbon emissions and combating climate change. That’s the message from a less prominent U.N. report released this week, this one focused on quantifying the ocean-based solutions to climate change.

“The ocean has been a significant victim of climate change and ocean acidification, and it’s time we woke up and realized the seriousness and the severity of the changes,” says Jane Lubchenco, a former administrator of the National Oceanic and Atmospheric Administration. But, she adds, “the ocean is not just a victim, it’s also a source of some very powerful solutions, and we had not appreciated until this report how significant those solutions are. … It’s dismal, but it’s not hopeless.”

Taken together, ocean-based solutions can cover up to a quarter of the emissions reductions needed to keep warming below 2.0 – a massive amount. And the urgency of action was put into stark relief Wednesday by the special report approved by the Intergovernmental Panel on Climate Change (IPCC) – the product of more than 100 international scientists and the most comprehensive look yet taken at the Earth’s oceans, poles, glaciers, tundra, and high mountain regions. It shines a light on some of the most remote corners of the globe, where, in some cases, the effects of climate change are most severe.

Warning signs

The IPCC report “documents the ways in which for decades the ocean has been acting like a sponge, absorbing carbon dioxide and heat to regulate the global temperature, but it can’t keep up,” said Ko Barrett, vice chair of the IPCC, in a call with reporters on Tuesday.

Many of the effects of climate change are already being observed, and are accelerating. Since 1993, the rate of ocean warming has doubled, and since 1982, marine heat waves – which can be devastating to fish and other marine life – have doubled in frequency and become more intense.

Mountain glaciers, critical sources of fresh water for populations around the world, are receding, and widespread permafrost thaw – which could exacerbate warming as methane is released – is predicted for this century. Oceans are becoming more acidic and losing oxygen. Fish stocks are migrating north.

The report also has significant data, and projections, about sea-level rise, which is accelerating and is now predominantly due to melting ice sheets in Greenland and Antarctica. It projects a mean sea-level rise of 2.8 feet by 2100 under a high-emissions scenario – higher than previous reports have put it. Hundred-year floods are likely to become annual events by 2100, under both low- and high-emissions scenarios.

Against this backdrop of possible consequences, the report from the High Level Panel (HLP) for a Sustainable Ocean Economy offers an array of solutions that also, fittingly, come from the ocean.

Up till now, most mitigation strategies have been focused on land, whether shutting down coal plants, increasing renewables, or restoring forests, says Ove Hoegh-Guldberg, a marine scientist at the University of Queensland in Australia and the HLP report’s lead author.

“The idea that there are options in the ocean is really important,” he says. And “they’re not just small options. They actually can take care of 20% or more of the emissions that are separating us from where we are today and where we should be when it comes to achieving the 1.5 degree C target. … It’s a game changer.”

Potential benefits

Dr. Hoegh-Guldberg cites five main areas where the ocean can offer climate solutions: renewable energy, shipping and transport, protection and restoration of coastal and marine ecosystems, shifting diets to seafood, and carbon storage in the seabed.

Taken together, these five strategies could reduce global emissions by up to 11 billion metric tons of carbon dioxide equivalents by 2050.

Each area, of course, also comes with its own challenges. There are big costs associated with decarbonizing shipping and scaling up offshore wind and other forms of renewable energy. Getting large numbers of people to eat more sustainable seafood isn’t easy. Carbon seabed storage isn’t yet ready for deployment at a broad scale. And to be effective at the levels Dr. Hoegh-Guldberg outlines, these strategies will require significant political will, funding, and cooperation of industry and government.

But pursuing these strategies could also pay out big benefits that go beyond emissions reductions. Take mangroves, salt marshes, sea grasses, and marine ecosystems. Restoring and protecting such “blue carbon” ecosystems  – and simply recognizing their value – won’t just help in terms of the carbon they store, says Dr. Lubchenco, it will also help coastal communities be more resilient: restoring fisheries, protecting coastlines against storm surges, providing critical habitat for wildlife.

“This is the low-hanging fruit. This is an opportunity to really make something happen,” says Dr. Lubchenco, who is co-chair of the HLP expert group, and co-authored a separate paper this week on ocean-based solutions in Science. “These are carbon-rich hotbeds, and they need to be protected and restored.”

“Too big to ignore”

With all the solutions outlined, work needs to be done to make sure they’re done sustainably and don’t cause unintended damage, says Dr. Hoegh-Guldberg. Seabed carbon storage, which is already being done at a small scale in Norway, and which essentially squirts liquified CO2 into the deep ocean floor, could theoretically reduce emissions by 0.5 to 2 billion metric tons by 2050. But he notes that it is a nascent technology that has risks.

“If you have a leakage of this, and you acidify the deep ocean, what are the consequences?” asks Dr. Hoegh-Guldberg. Unlike the other four strategies, which are ready for implementation, that one still needs research, he says.

Still, he and Dr. Lubchenco emphasize that this report is not simply an exercise in wishful thinking. Solid examples of all of these strategies are happening around the globe; what’s needed is scale, and firm commitments from nations and companies.

The 14 nations that make up the High Level Panel collectively represent 30% of the world’s coastlines, 20% of fishery catches, and 20% of shipping, says Dr. Lubchenco. All of them have stepped forward with various ocean commitments, including investments in offshore renewable energy and commitments to making shipping low- or zero-carbon.

The report this week offers a rare occasion to spotlight the effects of global warming on Earth’s most remote regions – and to consider what those effects will mean for humans. But it’s also a chance to broaden our notion of where we can find solutions, say ocean advocates.

“The narrative for most of human history has been, the ocean is too big to fail,” says Dr. Lubchenco. As awareness has grown about the massive problems facing the ocean – plastic pollution, warming seas, overfishing, acidification, dead zones – that narrative, she says, has shifted to: “It’s too big to fix.”

“I think there is a narrative that is finally emerging,” she says, in this report and with other activities this week, “that is a new narrative, that says actually, the ocean is so central to our future, it is so important to food security, to climate mitigation and adaptation … that it is too big to ignore.”