Will stashing more CO2 in the ocean help slow climate change?

The Ocean’s Role in Climate Change Mitigation

The ocean is Earth’s climate hero.

The Importance of the Ocean in Carbon Dioxide Absorption

For decades, ocean waters have helped hold back the juggernaut of global warming, absorbing at least a third of the carbon dioxide emitted by human activities since the Industrial Revolution began.

Now, the world may ask the ocean to do even more. That would require tinkering with the chemistry and biology of the ocean to increase how much carbon it takes up.

Such an approach is worth considering because the window for limiting warming by reducing carbon emissions alone is closing fast, climate simulations suggest. Forestalling the worst impacts of climate change by 2100 will require actively pulling carbon back out of the atmosphere — at a scale possible only with the ocean’s help, some scientists say.

The Sustainable Development Goals and Climate Change Targets

Earth is on track to warm by about 3.2 degrees Celsius by the end of the century, relative to pre­industrial times, according to the Intergovernmental Panel on Climate Change. Even if all nations meet their current emission-reduction pledges, the world would still warm by about 2.7 degrees (SN: 10/26/21).

That’s higher than the target of 1.5 to 2 degrees set by the 2015 Paris Agreement, an international climate treaty signed by 195 parties. In fact, Earth’s average temperature is likely to surpass the 1.5-degree benchmark as soon as the mid-2030s (SN: 12/15/23). Each uptick in the thermostat increases the risk of devastating consequences, including deadly heat waves, more intense storms and inundations of coastal cities due to melting ice and rising seas.

Technologies that remove carbon from the atmosphere could help turn the thermostat back down by the end of the century. “The latest IPCC report notes that to meet the [Paris Agreement] climate goals, we have to employ carbon dioxide removal technologies,” says geochemist Gabriella Kitch of the U.S. National Oceanic and Atmospheric Administration in Silver Spring, Md.

Carbon dioxide removal, or CDR, is in its infancy, currently drawing only about 2 billion metric tons of CO₂ per year out of the atmosphere. That’s a small fraction of the 37 billion tons of CO₂ emitted each year by humans’ energy consumption. Most of that CDR comes from forests, whether via planting new trees, regrowing old forests or better managing existing growth (SN: 7/9/21).

To stay on track with Paris Agreement goals, the world needs to ramp it up, removing 10 billion to 15 billion tons of CO₂ annually by 2050, Kitch says. By the end of the century, that would need to add up to a grand total of 400 billion to 1,000 billion tons of atmospheric CO₂, a range that depends on how quickly we also reduce carbon emissions.

Land-based CDR, including planting trees, restoring coastal ecosystems and building facilities that directly capture CO₂ from the air, can get us part of the way there, Kitch says. But all of the carbon uptake from land-based approaches would add up to only about 10 billion tons annually, Kitch says. Such calculations need to ensure sufficient land area for food, water and biodiversity preservation, she adds. “That gets us to 2050, but what about beyond that?”

The Ocean’s Potential for Carbon Uptake

That’s where the ocean comes in. “The big advantage of the ocean is its capacity,” Kitch says. “The ocean can store about 19 times the amount of carbon that can be stored on land.”

There are a few basic ways to enhance the ocean’s current carbon uptake: Increase the ocean’s abundance of photosynthesizing organisms, increase the water’s alkalinity so it can absorb more acidic CO₂ and build huge facilities at sea that suck carbon directly out of the water.

But CDR in the big blue is largely untested — and in that sense, the ocean’s vastness is both a feature and a bug. Ocean waters are complex and always in motion, making shifts in chemistry fiendishly difficult to monitor. And there’s little baseline data on large swaths of the ocean, which will make it hard to evaluate how well CDR is working. And current observational technologies, such as sensors, may not be up to the challenge.

On top of that, there are also long-standing concerns about environmental impacts, of which there’s very little data. Changes to regional water properties might create ripple effects through ecosystems, critics note. Fostering phytoplankton blooms, for instance, could shift local food webs or even produce greenhouse gases. Treating large parcels of seawater to remove carbon could pose risks to local wildlife.

But the biggest challenge of all is time. Researchers are racing to explore these uncharted waters before the climate crisis worsens.

How Carbon Dioxide Removal Could Slow Climate Change

Carbon dioxide can linger in the atmosphere for centuries before it’s taken up by plants or incorporated into the molecular structure of rocks. Those natural carbon “sinks” are too slow to match the pace of emissions from fossil fuel burning and other human activities, however.

CDR can be thought of like “a time

SDGs, Targets, and Indicators

SDG 13: Climate Action

• Target 13.1: Strengthen resilience and adaptive capacity to climate-related hazards and natural disasters
• Target 13.2: Integrate climate change measures into national policies, strategies, and planning
• Target 13.3: Improve education, awareness-raising, and human and institutional capacity on climate change mitigation, adaptation, impact reduction, and early warning
• Target 13.5: Take urgent action to combat climate change and its impacts

SDG 14: Life Below Water

• Target 14.1: By 2025, prevent and significantly reduce marine pollution of all kinds
• Target 14.2: By 2020, sustainably manage and protect marine and coastal ecosystems to avoid significant adverse impacts
• Target 14.3: Minimize and address the impacts of ocean acidification
• Target 14.7: Increase the economic benefits to small island developing states and least developed countries from the sustainable use of marine resources

SDG 15: Life on Land

• Target 15.1: By 2020, ensure the conservation, restoration, and sustainable use of terrestrial and inland freshwater ecosystems and their services
• Target 15.2: By 2020, promote the implementation of sustainable management of all types of forests, halt deforestation, restore degraded forests, and substantially increase afforestation and reforestation globally
• Target 15.5: Take urgent and significant action to reduce the degradation of natural habitats, halt the loss of biodiversity, and protect and prevent the extinction of threatened species

SDG 17: Partnerships for the Goals

• Target 17.16: Enhance the global partnership for sustainable development, complemented by multi-stakeholder partnerships that mobilize and share knowledge, expertise, technology, and financial resources

Table: SDGs, Targets, and Indicators

Copyright: Dive into this article, curated with care by SDG Investors Inc. Our advanced AI technology searches through vast amounts of data to spotlight how we are all moving forward with the Sustainable Development Goals. While we own the rights to this content, we invite you to share it to help spread knowledge and spark action on the SDGs.

Fuente: sciencenews.org

Join us, as fellow seekers of change, on a transformative journey at https://sdgtalks.ai/welcome, where you can become a member and actively contribute to shaping a brighter future.