“Climate collapse is happening in real time. By 2025, we must drastically reduce carbon emissions and expedite the transition to renewable energy.”
On Dec. 30, António Guterres, Secretary-General of the United Nations, noted in his New Year message, “We have just passed a decade of deadly heat. All ten of the hottest years on record, including 2024, have occurred in the last decade.”
According to the United Nations, 2024 is projected to be the hottest year on record. The World Meteorological Organization (WMO) stated that the global average temperature from January to September last year was 1.54 degrees higher than the pre-industrial average. This exceeds the 1.45 degrees increase recorded in 2023, marking the first time that the average temperature has surpassed 1.5 degrees compared to pre-industrial times.
There are predictions that simply reducing plastic emissions and taking passive measures for carbon reduction will not prevent climate collapse. The view is gaining strength that more proactive efforts are needed to mitigate the impacts of climate change. A representative technology is “geoengineering.” Geoengineering is a scientific technology that artificially alters or controls the climate system to prevent global warming.
◇Using the vast ocean as a giant carbon sink
The Earth’s oceans and atmosphere constantly absorb and emit carbon dioxide. Currently, the oceans absorb about one-quarter of carbon emissions, while the land absorbs 30 percent, with the remainder remaining in the atmosphere, warming the planet. The marine technology startup “Captura” has proposed the idea of utilizing the ocean as a carbon sink to address the problem of global warming.
Captura's technology removes carbon dioxide from seawater through an electrochemical process, then returns the water to the ocean to help absorb more carbon dioxide from the atmosphere naturally. This accelerates the carbon absorption that the oceans have done for millions of years.
Captura plans to soon implement innovative carbon removal technology using Pacific seawater on the Big Island of Hawaii. They have already set up experimental facilities at the Port of Los Angeles and confirmed that they can remove about 100 tons of carbon dioxide annually. The new facility under construction in Hawaii is expected to remove more than 10 times the carbon dioxide compared to the Los Angeles experimental facility.
Other startups are researching methods to permanently store carbon dioxide in the ocean by increasing its alkalinity. Canada-based Planetary Technologies is experimenting with adding magnesium hydroxide to seawater to convert carbon dioxide into a stable form. U.S.-based Evercarbon is developing technology to create alkaline substances directly from seawater through electrodialysis. Although carbon dioxide absorbed by seawater will ultimately be released back into the atmosphere, this method aims to permanently reduce carbon dioxide. Both companies will begin full-scale commercial expansion this year.
◇Blocking sunlight entering the Earth
Solar radiation management (SRM), which aims to block sunlight entering the Earth or reflect it back into space to reduce rising temperatures, is also a prominent geoengineering approach. SRM is assessed to inhibit temperature rise more quickly than removing carbon dioxide from the atmosphere.
Techniques for solar radiation management include directly injecting small particles that reflect sunlight into the stratosphere or artificially creating aerosols. The increase in stratospheric aerosols during the 1991 eruption of Mount Pinatubo is inspired by the fact that it lowered the Earth's average temperature by up to 0.5 degrees. Theoretically, it could cool the Earth back to pre-industrial levels in a short period.
Another method involves enhancing the brightness of marine clouds. This is achieved by spraying seawater into the atmosphere in aerosol form to create low-altitude marine clouds or increasing the reflectivity of existing clouds. Additionally, there are methods to increase surface reflectivity by painting building equities or rooftops white.
On Dec. 23 last year, the School of Public Policy at Georgia Institute of Technology stated in the Proceedings of the National Academy of Sciences (PNAS), “Stratospheric aerosol injection (SAI) could reduce temperature-related deaths caused by climate change by saving up to 400,000 lives annually,” and emphasized that “the number of deaths from air pollution or ozone layer destruction caused by solar geoengineering technology would be 13 times more, suggesting that while solar geoengineering involves risks, it could genuinely alleviate suffering, thus warranting a better comparison of risks and benefits.”
◇Environmental impact and lack of regulation… Can geoengineering break through?
Marine carbon removal technologies and solar radiation management technologies aimed at solving the climate crisis are still in the early stages. While they hold immense potential, the lack of research on their environmental impacts is often cited as a limitation.
In the case of technologies utilizing the ocean as a carbon sink, continuous environmental monitoring is necessary to minimize impacts on marine ecosystems during the process of artificially altering seawater’s composition. For example, excessive alkalinity could lead to limestone sedimentation or the re-release of carbon dioxide. Thorough oversight by governments and regulatory agencies and careful technology design are essential.
The same applies to the field of solar geoengineering. Duncan McLaren, a postdoctoral researcher at the University of California, and Olaf Cory, a professor at the University of Leeds, stated in an editorial published in the journal Science that “the approach of ‘research first, regulation later’ in solar geoengineering is not suitable for solving problems,” and emphasized the need for establishing common norms.
Currently, the field of solar geoengineering is drawing attention as a technology with the potential to mitigate climate change issues. However, the environmental and political risks mostly remain in unknown territory. Notably, the lack of a regulatory framework to manage the direction of technology, ownership, and control is raising concerns about unfair or harmful outcomes.
Thus, the researchers argue, “Current researchers supporting SRM must reduce uncertainties through additional research and lay the groundwork for subsequent regulations.” However, as controversies surrounding geoengineering experiments and commercial activities rise, the credibility of the approach focused on research while delaying regulation is declining.
They emphasize that “the geopolitical divides surrounding SRM technology and conflicting worldviews make resolving this issue difficult,” and that a common framework centered around a non-deployment policy is necessary to create a foundation that can prevent indiscriminate commercialization, development, and deployment and to cautiously manage SRM research.
References
PNAS (2024), DOI: https://doi.org/10.1073/pnas.2401801121
Science (2025), DOI: https://doi.org/10.1126/science.adr9237