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As the Earth warms due to climate change, oceans are heating up, becoming more acidic, and losing oxygen. These changes threaten marine life, food webs, and global fisheries. Scientists agree that cutting greenhouse gas emissions is essential, but current efforts are not enough to keep global warming below the 1.5-2 degrees Celsius targets set by the Paris Agreement. Because of this, researchers are exploring climate intervention strategies as possible additions to emissions cuts.
These climate intervention strategies hold promise, but little is known about their potential impacts on the ocean.
In an effort to summarize what is known, as well as to identify some of the most pressing questions still to answer, a group of 26 researchers from around the world has published a review article in the American Geophysical Union journal Reviews of Geophysics. Kelsey Roberts, a visiting scholar in Cornell’s Department of Earth and Atmospheric Sciences, is first author on the article, titled “Potential Impacts of Climate Interventions on Marine Ecosystems.”
“Our oceans are already feeling the massive impacts of climate change. They will also be on the front lines of any climate intervention, yet we still lack a clear picture of how these approaches could impact marine life,” Roberts said. “We brought together a diverse, elite team of experts across many different domains and perspectives to map out the current state of knowledge and identify the most critical research gaps.”
Two of the most frequently discussed categories of climate interventions are carbon dioxide removal (CDR) and solar radiation modification (SRM). The goal of CDR methods is to remove carbon dioxide from the atmosphere and store it for long periods of time, often using the oceans as the place where the CO2 is stored.
Researchers are studying a variety of biological and chemical methods to increase the amount of CO2 stored in the oceans, including fertilizing the oceans with nutrients to foster phytoplankton growth, farming large amounts of seaweed, sinking plant material from land deep in the ocean, and adding alkaline materials to seawater.
If successful, each of these methods would certainly increase the amount of CO2 in the oceans, but they could also disrupt ecosystems and alter food webs.
SRM methods aim to cool the planet by reflecting solar radiation away from Earth and back into space. Examples include adding particles to the upper atmosphere or brightening clouds over the ocean. These methods could lower temperatures quickly, but they come with major uncertainties and risks, such as changes in rainfall, ocean circulation, and marine productivity. In addition, if SRM were stopped suddenly, rapid warming could occur.
The authors of the review make it clear that not enough is known about the how CDR and SRM interventions would impact the oceans. While climate interventions might reduce some effects of global warming, they also pose significant ecological risks. Their effects depend strongly on how, where, and at what scale they are used. There are large gaps in scientific understanding, especially regarding food webs and fisheries. The authors argue that these approaches cannot replace emissions reductions and require much more research before any large-scale use.
Co-author Daniele Visioni, assistant professor in Department of Earth and Atmospheric Sciences in the College of Agriculture and Life Sciences, has been a vocal proponent of the pressing need for more research into the possible effects of climate interventions.
“There are no easy choices in front of us, except one: to provide our future selves more, better information with which to make decisions about climate interventions,” said Daniele, who is also a faculty fellow at the Cornell Atkinson Center for Sustainability. “By mapping out what we know and don’t know, we hope to have provided the scientific community a path forward towards responsible, meaningful interdisciplinary research.”
