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Expanding Ocean-Climate Action

The climate crisis is fully upon us; recent data show the globe hasn’t been this hot in 100,000 years. The two trillion tons of carbon dioxide (CO2) pollution humans have added to the biosphere since the industrial revolution have trapped an almost unfathomable amount of excess heat energy on our planet, referred to somewhat neutrally as the earth’s “energy imbalance”. That energy imbalance is driving dangerous change across the entire planet, with around 90 percent of the excess heat energy absorbed into the ocean, leading to devastating impacts like marine heat waves that bleach coral reefs, stressing marine life that cannot migrate to cooler waters, disrupted ocean mixing and nutrient exchange, and rising sea levels. At the same time, direct absorption of CO2 into the ocean has made the ocean about 30 perecent more acidic than it was 200 years ago. 

These interlocking stresses to the ocean—all from the same source—work together to significantly impair ocean ecosystems, coastal communities, and the blue economy. They are cumulative and increasing, and together they threaten to push us past critical tipping points that will change our climate and the earth as we know it.

While deep and lasting reductions in greenhouse gas emissions is non-negotiable, it has also become crystal clear, at this stage, reductions alone won’t keep global warming from exceeding 1.5 degrees Celsius, nor even guarantee that we won’t surpass 2 degrees Celsius, the upper limit agreed in the Paris Accord. While innovation in clean energy and climate solutions over the past 20 years has driven major progress in deployments of renewables, it still represents less than 10 percent of total global energy production. Meanwhile emissions continue to increase and our collective risk increases alongside it.

What’s worse, we are underestimating the full extent of the threat, as most of the earth systems models we rely on for forecasting rates of change and severity don’t include key sources of greenhouse gases, such as the emissions from thawing permafrost. Permafrost is just one of multiple global “tipping points” where abrupt changes may have widespread and profound impacts on the stability of the whole system.

We desperately need an expanded discussion around what is needed to protect and restore our ocean and climate, and to grow our toolbox of climate actions. Yes, we must rapidly shift to low carbon options, and the ocean can help in that race. But additional new tools are needed, including significant expansion of carbon removal—cleaning up the legacy carbon in the atmosphere that is already past safe levels—and accelerated research and development of all possible actions that might help slow down the passing of critical tipping points. These are not alternatives to emissions reductions, rather they are part and parcel of an expanded ocean-climate agenda to seek to stabilize and ultimately reverse climate disruption.

There is good news on the first of these new fronts. The past few years have seen significant advances on ocean-based carbon removal techniques that might harness the ocean’s natural carbon sequestering abilities to help mitigate climate change and protect ocean health. The deep ocean already holds more carbon than any other part of Earth’s biosphere and has the potential to safely take up even more. The sheer size of the ocean also means that any marine carbon dioxide removal solutions proven to be viable and safe have the potential to be developed at climate-relevant scales.

A number of marine carbon dioxide removal (mCDR) approaches are being explored—all of them requiring additional development and field testing to better understand their potential. For instance, researchers are exploring how to accelerate natural ocean processes that lead to deep sea storage of carbon. The approach entails adding alkaline materials which interact with dissolved CO2 in seawater and results in carbon sequestration services over 10s to 100s of thousands of years. Other potential methods are more novel, including the use of electricity to rearrange seawater molecules to extract carbon.

Yet even if wildly successful, carbon dioxide removal, combined with rapid decarbonization, still does not eliminate the growing risk of exceeding tipping points in critical ecosystems. One of the most at risk is Arctic sea ice, critical to the global climate system because of its contributions to Earth’s reflectivity (albedo), its role in keeping the Arctic region cold (e.g. permafrost frozen, Greenland ice sheet intact) and its influence on global weather patterns. Arctic sea ice is also one of the fastest disappearing systems on the planet.

The Arctic region has warmed three to four times faster than the global average, and summer sea ice is expected to disappear as early as 2035. Given the near-term risks associated with continued loss of sea ice, scientists are researching pathways to slow down sea ice loss. For example, global strategies like solar radiation management could help cool the region by reflecting or refracting a small amount of incoming solar energy, as could locally targeted approaches like thickening sea ice or enhancing low-lying marine clouds to increase albedo in the summer or thinning clouds in the winter to allow more heat to escape.

These actions do not substitute for rapid and deep emissions reductions. They complement it by increasing our chances of keeping key parts of the climate system functioning while we achieve a wholesale transition away from fossil energy. To better understand the potential of such tools, we must invest in the necessary rigorous research, development, and demonstration (RD&D). RD&D is crucial in assessing the complexities of climate interventions, comparing them to inaction, and providing insights into the potential consequences, risks, and benefits of different strategies. 

A growing ocean-climate community has begun to advocate for this enhanced level of research. For example, recently more than 400 renowned scientists from across the globe published an open letter calling for the acceleration of responsible RD&D to determine which mCDR approaches may ultimately prove to be safe, equitable, and feasible. Ocean Visions has outlined a comprehensive program to help advance the science, technology, and policy priorities needed to rigorously evaluate mCDR in the near-term. While still nascent in comparison, pathways like marine cloud brightening, surface albedo modification, and mixed phase cloud thinning must be given more serious consideration against the backdrop of the risks they may help ameliorate.

The severity and accelerating pace of the ocean-climate emergency, and the increasing risks we face, calls us to do everything we can to avoid catastrophic outcomes. This includes exploring all possible tools alongside decarbonization to avoid irreversible change. It is our responsibility to future generations, and to the millions of voiceless species with whom we share the planet, to do so. Ethical considerations, governance mechanisms, and international cooperation are critical issues in the mix. But with concerted action, we can achieve climate mitigation and then move beyond towards actively healing the ocean and the climate.

The time is now to come together to explore a greater range of strategies to address the ocean-climate crisis and help ensure the ocean’s health for generations to come.