For a while it seemed like switching to clean energy might be enough to stave off climate catastrophe. But even though the United States has cut coal-fired electricity use from 50 percent to 19.5 percent in the last 20 years, the growth of coal in the rest of the world and the rising demand for energy overall — not to mention the extreme weather we are all experiencing — make it clear that we desperately need another solution.
As crazy as it might sound, geoengineering the oceans by adding iron — in effect, fertilizing them — may offer the best, most effective and most affordable way not just to slow the march of global warming but to reverse its course by directly drawing carbon out of the atmosphere. The U.S. government needs to start testing it now, before the climate system spins off into an even more disastrous state.
This geoengineering would in many ways replicate a natural process that has been underway for probably billions of years. Here’s how it works: Iron-rich dust blows off the land and into the seas, fertilizing algae and plankton. The more they grow, the more they convert carbon dioxide in the air to organic carbon, some of which eventually sinks to the watery depths. Studies suggest that this natural process of increasing iron-rich dust in the oceans takes so much carbon out of the atmosphere that at some point along the way it may have helped bring on the ice ages. But human beings have interrupted that natural cycle. Though growing deserts send more dust into the ocean, agricultural practices to preserve topsoil have the opposite effect, keeping dust out of the ocean and likely, in our opinion, contributing to more warming overall.
Dust blowing into the oceans may have played a big role in the ice ages
The more iron dust there was in the ocean, the less carbon there was in the atmosphere and the cooler the average temperature on Earth.
Dust concentration
In parts per million
1.6
Ice
Age
1.2
0.8
0.4
0
CO2 concentration
In parts per million
300
280
260
240
220
200
180
Temperature variation
In degrees Celsius
2
0
−2
−4
−6
−8
200K
Today
400K
years ago
Dust concentration
In parts per million
1.6
Ice Age
1.2
0.8
0.4
0
CO2 concentration
In parts per million
280
260
240
220
200
180
Temperature variation
In degrees Celsius
2
0
−2
−4
−6
−8
400K
years ago
300K
200K
100K
Today
There have already been a significant number of direct scientific experiments into this kind of geoengineering. From 1993 to 2009, about a dozen experiments used ships to deposit iron into ocean patches up to about 10 miles in diameter. The results showed that this approach could alter the exchange of carbon between the air and the sea, increasing the amount of carbon pulled from the atmosphere. They also showed the tremendous impact this approach could have, for a very low cost. One study found that each iron atom can catalyze reactions that convert up to 8,000 molecules of carbon dioxide to plankton or algae.
All of these prior experiments, however, were short-term, lasting only months, and tiny relative to the vastness and variability of the ocean. Key questions remain, including how long the carbon would stay in the ocean. A new round of experiments need to cover a much bigger area, patches at least 200 to 500 miles in diameter, and continue over multiple years. If we did several of these experiments in parallel, in multiple oceans, we could potentially have answers within a decade or less. That would give us the best shot we’ve got against the catastrophic effects of climate change.
This kind of geoengineering has prompted two kinds of worries, both legitimate. First, activists and scientists feared geoengineering might give industries an excuse not to adopt cleaner technologies. Also, there was concern about inadvertent effects, including toxic algae blooms and impacts on commercially important fish species. In 2012, an entrepreneur added 100 tons of iron to the ocean and created a dramatic short-term plankton bloom. Many scientists and policymakers worried about what else could happen if commercial entities scaled up without government oversight. By 2013, a de facto ban on this research was in place.
But today with the impacts of climate change around the world growing ever more dangerous, the most important question is how potential consequences of ocean fertilization compare to the damage we are already doing to the oceans and the rest of the planet by burning huge quantities of fossil fuels. The oceans are warming rapidly. A recent study, published in Nature Climate Change, estimated that even under a low-emission scenario, more than half of marine species are at high or critical risk of extinction by 2100. Coral reefs are at risk from acidification and warming of the ocean surface.
The National Academies recently recommended that we study this and other approaches, and the U.S. government has the capacity to support these studies at scale. It only needs the will and the budget.
The good news is that ocean fertilization should cost less than other options like solar radiation management, a geoengineering approach that has received far more attention, including a recent report from the White House. Ocean fertilization also reduces the ocean acidification that plagues coral reefs and shellfish and should have more long-lasting effects than solar radiation management.
We urgently need more aggressive measures to reduce atmospheric carbon on a large scale. Whatever questions ocean fertilization present, they pale in comparison to what we already know about the escalating climate catastrophe if we continue on our current path.
Mr. Preston is an investor and was the director of technology development at M.I.T. in the 1990s. Mr. Bushnell was the chief scientist at NASA Langley Research Center from 1995 to 2023. Dr. Michaels is an oceanographer and farmer who has conducted research on global ocean carbon and nutrient cycles since 1982.
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