Inspirations: Terraforming Earth with Iron

  • Iron sulphide could encourage marine algal growth.
  • Small-scale experiments have shown it moving carbon from the atmosphere to the deep ocean.
  • It could offset global warming, but the large-scale effects are unpredictable.
  • In 2012, Russ George provoked controversy by boosting fish stocks in an unregulated experiment.


Marine algal bloom south of Cornwall, UK (Mike Peel [Wikimedia Commons])

In 1988, oceanographer John Martin was giving a lecture at the Woods Hole Oceanographic Institute. Perhaps he became a little carried away with his research, because he put on his best Dr Strangelove accent and said, “give me a half tanker of iron, and I will give you an ice age”.

He was being flippant – but not that flippant. The research behind his quip is still being discussed as a way to restore fisheries and, as Martin was hinting at, to counteract global warming. To put it another way, Martin was talking about terraforming our own planet. Thirty years and several small-scale experiments later, oceanographers and marine biologists are still discussing and debating whether Martin’s half-tanker of iron would actually work and if it did, what it would actually do.

To put it another way: could we and should we?

Where should the iron go?

Martin’s research revolved around sampling station PAPA in the Gulf of Alaska, roughly half way between the Canadian Pacific coast and the southern end of the Aleutian Islands. Those waters are packed full of the sort of nutrients that marine algae need to grow, but Martin found that not much algae actually growing there. After a few experiments, he concluded that there was one nutrient missing: iron. Marine algae don’t need much iron, but without the trace amounts they do need, they couldn’t do much with all the nitrates and phosphates around them.

The oceanic ecosystem is vast, as we’d expect on a planet that hides more than two thirds of its surface under the sea. Before Martin’s experiment, no one had thought much about trying to manipulate it because it was assumed that such a massive system would need


(Miwok Follow [CC / Flickr])

an impractically massive manipulation. When Martin showed that all the North Pacific algae needed to grow was a trace amount of iron, he had identified a manipulation on a small enough scale that it might be possible to do it. His idea of iron fertilisation went on to become one of the key suggestions in the field of geoengineering:  intentionally manipulating the earth’s climate.

Sampling station PAPA was in what is called a ‘high nutrient low chlorophyll zone’, or HNLC. The HNLCs encircle the earth in the sub-Arctic regions of the Atlantic and Pacific oceans, and also in the sub-Antarctic zones of the Southern Ocean, which is the ocean that encircles Antarctica. The high nutrients refer to all the goodies floating around that algae need to reproduce into more algae. A quick way of measuring how much algae there is in the water is to measure how much chlorophyll there is – that’s the green stuff that plants and algae use to harvest energy from sunlight – so low chlorophyll means not much algae.

From iron to an ice age

Martin’s quip about an ice age came out of research on global warming, which was a fairly recent research area at the time. Before talking about what chucking iron in the sea has to do with global warming, I realise there are still a few people who think that two centuries of pumping carbon into the atmosphere cannot possibly have any consequences, so it’s worth looking at some headline figures compiled by the


Historic global temperature and atmospheric carbon dioxide levels derived from Antarctic ice core data (National Oceanic and Atmospheric Administration)

International Panel on Climate Change. The IPCC is an international consortium of scientists that compiles data from many different sources into a report that is updated every few years.

Their latest report was released in 2014 and is vast and highly technical, but it’s worth looking at some of the headline figures in their synthesis report: the most important being that the global temperature rose by 0.85°C (0.5°F) between 1880 and 2012, and continues to rise by around 0.05°C per year. If that doesn’t sound like much, it’s worth remembering that the difference between 1880 and the coldest point of the last ice age was around 6°C (3.3°F), and that rate of increase adds up to another degree (0.6°F) every twenty years.

The main reason for the rising global temperature is carbon dioxide, which is produced by fossil fuels. Since the industrial revolution, we’ve been digging up carbon that has been buried for the last 300 million years, in the form of coal and oil, and burning into


Atmospheric carbon dioxide measured at the Mauna Loa Observatory in Hawaii (Earth System Research Laboratory)

carbon dioxide. Since the days of James Watt and Matthew Bolton, carbon-releasing technology has spread across the world so that every year, more carbon was released than the last. That trend at least has levelled off in the last three years thanks largely to the spread of renewable technologies, but we’re still pumping huge quantities of carbon dioxide into the atmosphere.

We only have to step outdoors and look up to understand that the atmosphere is a large place, but that doesn’t mean its capacity is unlimited. The IPCC’s physical science report tells us that the atmosphere contained some 278 parts per million carbon dioxide in 1750, before the industrial revolution got started, and rose to 390.5 parts per million in 2011. The year after the report was published, it broke 400 parts per million. As carbon dioxide rises, so does the Earth’s temperature.

So what does all this have to do with iron and oceans?

Sending carbon to Davy Jones’s locker

The answer lies in the physical properties of carbon dioxide. It’s a very stable compound, so once it’s found its way into the atmosphere, it tends to stay there. The only natural process that removes it is, as we all learned at secondary school, photosynthesis: the process by which plants gather water and carbon dioxide and use the energy from sunlight to make glucose and oxygen. What they didn’t tell us, at least at my secondary school, is that most photosynthesis happens not in the leaves of plants, but in single-celled marine algae floating close to the top of the ocean surface.

Martin’s insight was that while algae require a lot of different nutrients to divide, they stop when the first one runs out. In the HNLCs, the first to run out is iron. With more


The sub-Arctic Pacific Ocean: a shipwreck off Unalaska in the Aleutian Islands (NOAA Photo Library [CC / Flickr])

iron, algae could divide more and convert all the nutrients floating around in those oceans into more algae. Those algae would then be eaten by animal plankton, which in turn would be eaten by fish and so the carbon drawn from the air would move up the food chain.

What particularly interested Martin was that some of that carbon would sink. Because photosynthesis depends on sunlight, the subpolar oceans are highly seasonal, with algae and animals growing and dividing in the long days of the summer and then dying off when the winter closes in. Here in Britain, anyone who visits the coast at different times of year can watch the sea turn from blue during the winter to chlorophyll-green in the summer as it becomes saturated with photosynthesising algae. There is even more growth in the subpolar oceans because the longer days mean more sunlight.

When the algae and many of the animals that feed on it die, many simply disintegrate. They become the fertiliser for next year’s burst of growth. But some of them sink into the deep ocean. As they do, they take the carbon that forms them to a place where it can’t find its way back into the atmosphere. If enough carbon was to sink, Martin reasoned, global warming could be consigned to history.

EIFEX’s diatoms

Martin himself retired soon after his quip about the ice age, and he died a few years later in 1993. It was left to others to see whether his idea worked in practice. Several small-scale studies have shown that a small amount of iron in the right place can indeed cause a lot of algal growth. One of the more convincing was the so-called European Iron Fertilization Experiment (EIFEX) led by Victor Smetacek of the Alfred Wegener Institute for Polar and Marine Research. Smetacek and his international colleagues were able to trace the massive growth of a bloom of algae called diatoms, and then follow them as they died and at least half of them sank to a kilometre. They lost track of them after that, though it’s safe to assume that they kept sinking.

The EIFEX team weren’t able to measure how much carbon they removed from the atmosphere. There have been a lot of attempts to work out exactly how much carbon will be sent to the depths by a ton of iron. The lower estimates say that it would remove about 1,000 tons, which is a lot but probably not enough for it to be feasible to throw around enough iron. The higher estimates are that a ton of iron could sink over 100,000 tons of carbon, which would make it worth a try. One of the more cited models estimated that iron fertilisation could reasonably be used to remove a gigaton of carbon (that’s


Icebergs in the Southern Ocean (David Stanley [CC / Flickr])

1,000,000,000 tons) of carbon from the atmosphere per year. That would slow down the rise in carbon levels but while we’re pumping 10 gigatons (The level measured in 2014 was 9,855,000,000 tons) up there every year, it wouldn’t turn the rise into a decline.

Enter DMS

But perhaps it wouldn’t have to. Lowering carbon dioxide levels in the atmosphere is not an end unto itself, but a means to the end of halting the rise in global temperature. As marine algae photosynthesise, they produce a chemical called dimethyl sulphide, or DMS. When DMS is released into the atmosphere, much of it reacts with oxygen to form sulphides.

While carbon dioxide warms the Earth by reflecting heat back toward it, sulphides have the opposite effect: they reflect heat from the sun away from the Earth. The process is less direct than the ‘greenhouse’ process of carbon dioxide: sulphides encourage the formation of clouds, which reflect heat away before it gets caught up in the greenhouse effect of carbon dioxide. Iron fertilisation would offset global warming not only by sequestering carbon in the deep ocean, but also by generating clouds that keep heat out of the atmosphere.

Why, then, do we not see ships full of iron sulphide heading for the subpolar oceans to cool down the Earth?

The law of unintended consequences

The answer is that even the exponents of iron fertilisation are cautious about it. Geoengineering involves tinkering with a vast and complex system in ways that can’t be


(Defence Images [CC / Flickr])

properly tested beforehand. The best mathematical models in the world are only as good as the data, which is woefully incomplete. The only way to find out what the effects of tinkering with the Earth is to try it, and then we all have to live with the consequences, for better or worse.

Martin himself suggested one danger, which is that overdoing it would lower the Earth’s temperature so far that it would cause another ice age. Carbon dioxide was down to 200 parts per million at the height of the last ice age, and a dropping the Earth’s temperature by a few degrees would be just as bad as raising it by a few degrees. In fact, it now appears that it’s unlikely to be a problem: ocean fertilisation simply won’t remove that much carbon.

A more pressing worry is that when dead algae sink into the deep ocean, it’s not just carbon they’re taking with them but all the other nutrients that would otherwise have fertilised next year’s bloom. Fertilisation might work very well for a few years but after


(Davide D’Amico [CC / Flickr])

that, the rest of the nutrients simply may not be there. A few gigatons of carbon might have been removed, but at the cost of sterilising vast tracts of ocean that supply commercial fisheries and feed great whales.

Another concern is that the clouds formed by DMS release would tend to move rainfall from the subtropics to the tropics. The result would be floods in places like Bangladesh and Bolivia and more droughts and wildfires in places like Australia and California – as if there aren’t enough already.

Time to move on?

There’s no way to tell how realistic these models are, and it’s quite possible that the problems caused by checking global warming with iron fertilisation would be less serious than the problems caused by not checking climate change with iron fertilisation. We are, after all, already engaged in a massive geoengineering project by pumping all that carbon up there in the first place.


(Tim Donnelly [CC / Flickr])

In 2009, a group of scientists summed up the concerns in an editorial for the Nature journal. The title summed up their position: Ocean fertilization: time to move on. They were not advocating against geoengineering in itself, but arguing that the risks of ocean fertilisation outweigh the likely benefits.

While most of the interest in ocean fertilisation has come from academic scientists, who have always abided by the precautionary principle and kept their experiments to a small scale, there is no law against it. Resolutions have been passed by the International Maritime Organization and under the United Nations Convention on Biodiversity, allowing small scale research studies but condemning large-scale attempts at geoengineering. However, they amount to no more than a voluntary agreement by the signing governments to not do it. They don’t include sanctions for anyone who takes it into their head to try it.

Lessons from salmon

Which is exactly what entrepreneur Russ George did in 2012, when he dumped 120 tons of iron sulphide in the North Pacific. George’s experiment was on too small a scale to have an appreciable effect on atmospheric carbon, but that wasn’t what he was trying to do. He had recently formed a company called the Haida Salmon Restoration Corporation,


Coho salmon (BLM Oregon & Washington [CC / Flickr])

which claimed to be working with the Haida Nation – indigenous Canadians living mostly on the Haida Gwaii archipelago off the coast of British Columbia – with the aim of restoring their fisheries.

George kept his activities quiet until after the event, when they were uncovered by The Guardian. The revelations were met with a storm of protest out of all proportion to the mere hundred tons of iron, aimed more at the principle of unregulated attempts to manipulate the environment than the specific experiment. The Guardian article quotes oceanographer John Cullen:

History is full of examples of ecological manipulations that backfired.

Others were concerned that unaccountable fertilisation schemes like George’s might provoke a backlash against potentially useful research. Victor Smetacek, who headed the EIFEX trial, was quoted in New Scientist:

I am disturbed and disappointed, as this will make legitimate, transparent fertilisation experiments more difficult.

George’s experiment might have attracted less criticism if it could have been written off


Sockeye salmon (Alaska Region U.S. Fish & Wildlife Service [CC / Flickr])

as an unsuccessful cowboy escapade, but that’s difficult to do for one simple reason: it does appear to have worked.

Exactly how well is rather difficult to establish. Satellite images show that there was a much more chlorophyll in the fertilised area than there had been the year before. The Corporation’s website confidently asserts that there were far more salmon in the year after the experiment than there had been for years, but cites an article in The Globe and Mail newspaper rather than a technical report. The Fraser River Panel reported that the number of salmon returning to the Fraser to spawn doubled in the year after George’s experiment (it’s in the figure on p.27), which does support the Corporation’s assertion. Unfortunately, the Canadian Department of Fisheries and Oceans only report up to 2011.

Nobody was measuring how much carbon it sent to the deep as George was interested in building up a fishery rather than geoengineering.

Carbophobes vs carbophiles

The experiment earned some bravos among the chorus of raspberries, notably by


Scanning electron micrograph of diatoms (Amada44 [Wikimedia  Commons])

aerospace engineer Robert Zubrin, who has spoken and written a lot on the subject of terraforming and whose main claim to fame is his work on solar sails that I’ve pontificated about before. Perhaps it’s not surprising that praise for ocean fertilisation comes from a man used to thinking big. He refers to a quadrupling of salmon stocks in the year after the experiment, but only cites Russ George’s blog as a source, which is hardly an impartial estimate.

Zubrin’s view is that of a maverick. He actively welcomes the rise in carbon dioxide in the atmosphere as a boon for plant growth and food production, and sees George’s experiment as a way of taking advantage of that. He dismisses the ‘antihuman ravings’ of George’s detractors, who he labels as ‘carbophobes’.

There is a whole other debate to be had about Zubrin’s ‘carbophilia’, to adopt his own terminology, though the whole concept of ocean fertilisation would be moot if it wasn’t for the fact that there’s more to plant and algal growth than how much carbon dioxide there is in the atmosphere.

While George’s one-off experiment is unlikely to have done any lasting damage, nobody seems to think that it would be a good idea for anyone with a hundred tons of iron to throw it wherever they wanted more fish. That would be to carry out geoengineering as an incidental consequence, which is what we call ‘pollution’.

Fertilisation or pollution?

Though pollution is hardly a rare phenomenon, as the Haida Salmon Restoration Corporation states on a section of its website titled ‘Geoengineering’ – hinting, perhaps, at grander ambitions than restoring salmon:


(Jutta M. Jenning [CC / Flickr])

One must ask, why is it OK to dump billions of liters of known hazardous material into our fresh water and oceans, but media-based controversy arises when placing 120 tons of a known nutrient back into the ocean, that has been scientifically shown to be in necessary and beneficial?

As we’ve seen, there are answers to the rhetorical question. The effects of ocean fertilisation are not all positive. It’s not for one small company to decide what is best for the world, though I type those words knowing full well that it would not be the first small company to do so.

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Posted in Inspirations, Wednesday Pontification

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