Iron Dust Could Reverse the Course of Climate Change

For a while it seemed 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 past 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.

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 needs 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.