Iron Fertilization (Climate Week #4)

“Give me a half a tanker of iron and I will give you another ice age.” Or at least, that’s what oceanographer John Martin said in 1988 about a radical and bizarre way of stopping climate change: dumping iron in the ocean. This is one of several geoengineering solutions to climate change, solutions that deliberately alter the environment to fight climate change.

To understand what iron has to do with climate change, you need to understand that most photosynthesis (the process plants use to take carbon dioxide out of the sky) doesn’t happen on land. The majority (50-85% depending on the estimate) actually happens in the ocean, done by microscopic algae called phytoplankton. These “wandering plants” take nutrients from the water, and carbon dioxide from the air, in order to make more phytoplankton. Then, the phytoplankton are either eaten by other marine creatures or sink to the ocean floor, preventing the carbon dioxide being released back into the atmosphere.

Iron is a necessary nutrient for photosynthesis – and it’s often the limiting nutrient. It turns out there are large parts of the ocean (HNLCs, or High Nutrient Low Chlorophyll zones) that have all the nutrients for phytoplankton growth, except for iron. While iron naturally enters the ocean through volcanic eruptions, upwellings of nutrient rich water, and iron dust from the land, the iron doesn’t have to be natural in origin to be effective.

The basic plan is this: take huge amounts of iron, in a form easily dissolved in water such as iron sulphate. Use ships to dump large amounts of this dissolvable iron in otherwise nutrient rich water. Large scale algal blooms are created, taking huge amounts of carbon dioxide out of the atmosphere into the deep ocean.

Give me a half a tanker of iron and I will give you another ice age.

How much iron would be required to actually make this work? How much would it cost? Would doing this cause ecological damage or other unintended consequences? Could it actually be effective at a large scale? Could there be a way to do this artificially on land, without risking damage to the oceans?

I’ll explore those questions in later posts.

It’s an unusual, even radical solution. And there are many people who not only dislike technological solutions to climate change on general principle, but who also don’t like that iron fertilization takes carbon dioxide out of the sky before we learn how to stop emitting it – potentially giving humans permission to pollute even more and make the problem worse.

Considering the dire situation we’re in with climate change, I think we need all options on the table – including the radical ones.