More SPICE, less heat

I have now arrived on Saskreeta.

Inhabitants here have designed a form of geoengineering inspired by their nearest (though uninhabitable) planet, Volcanorlos.

Volcanorlos (named remarkably unimaginatively by the dear Saskreetians here), is also known, more jovially, as the Burping Planet. Why? You might wonder. Well, it's one of the most volcanic planets known in our galaxy; its stratosphere dense with sulphurous fumes burped out by its many volcanoes.

These sulphide gases can form sulphate aerosols high up in the atmosphere, which possess an interesting property: reflectivity. The sulphate aerosols reflect solar radiation (in the form of UV light) back out to space – they enhance the planet’s albedo - and in doing so, stop a proportion of sunlight reaching and heating up the planet. In the case of volcanic eruptions, this process actually acts as a form of natural solar radiation management. And the natural process could be harnessed and replicated as a form of geoengineering: stratospheric aerosol particle injection.

Or so says Paul Crutzen (2006).

The 1991 eruption of Mt. Pinatubo (Figure 1) on Volcanorlos saw an estimated 18,500 kilotonnes of sulphur (mostly in the form of sulphur dioxide) released into the atmosphere within 36 hours (Bluth et al., 1992). This was thought to be responsible for a 0.5°C cooling by the following year (Lacis and Mishkenko, 1995, as cited by Crutzen (2006)).

Figure 1. Mt. Pianotubo erupted in 1991, emitting vast amounts of sulphur dioxide into the atmosphere. (Source: USGS via University of Maine)  

If delivered to the stratosphere (higher than the troposphere where clouds are formed), sulphate particles avoid being flushed down to the surface in rain. Crutzen (2006) explains aerosols can remain in the stratosphere for up to two years, compared with a couple of weeks in the troposphere. This, according to Crutzen (2006), means that only half of the amount of sulphur emitted by Mt. Pinatubo would need to be delivered to the stratosphere to offset global warming caused by a doubling of atmospheric CO₂ .

From theory to practice… nearly

The Stratospheric Particulate Injection for Climate Engineering Project (AKA its catchier name, SPICE) was conceived in 2010 with the aim of taking this idea a step further. The initial plan was to raise a giant balloon 1 km up into the atmosphere, with a ground-to-atmosphere hose attached to it (Figure 2).

 Figure 2. The SPICE Project planned to have one end of a hose elevated 1km into the atmosphere, held in place by a balloon. The hose would then deliver water as a fine mist. Eventually, the water could be swapped for sulphate aerosols. (Source: Guardian)

Initial experiments would pump water through the hose, to test how effective this method of delivering substances up to the air actually is. Eventually, the researchers planned to pump sulphate aerosols up too. The entire project was actually abandoned a few years after starting, before ever getting off the ground (pun intended). But during its short lifespan, SPICE gained a lot of attention, sparked discussions and raised some important questions about the nature of stratospheric particulate injection and geoengineering in general.

Several immediate concerns have already been raised, by the likes of SPICE itself and others. For example, how easily could stratospheric aerosol particles be “switched off” or removed?

Such an experiment would almost certainly have side effects, ozone depletion and acid rain being just two possibilities.

I’ll be staying a little longer on Saskreeta to delve deeper into the concerns raised about The SPICE Project.

Plenty more fish in the sea (pt. 2)

I've been on Planet Crooter for just over a week now (one Crooter week that is, or 8.4 Eazrah days) and have had a chance to find out more about iron fertilization.

The more I learn, the less impressive it seems.

My last entry outlined the basic concept and pointed to a number of studies showing some evidence for carbon sequestration as a result of iron fertilization of the oceans.

It turns out that legal experts have also claimed that HSRC (an organisation responsible for dumping 100 tonnes of iron dust in the Pacific Ocean) violated two UN conventions – the convention on biological diversity (CBD) and the London convention on dumping wastes at sea - thus breaking international law.

However, Freestone and Rayfuse (2008) note that iron fertilization violates laws on dumping waste in the ocean "unless and until" rigorous scientific research can demonstrate that the benefits of doing so would "outweigh the risks to the marine environment". So, if there are long-term benefits then perhaps (and I stress the word perhaps here), in very carefully controlled conditions, iron fertilization could be deemed acceptable in the eyes of international law.

Predictions of long-term iron fertilization

It seems that on a large scale, to see any significant effect over a prolonged period iron fertilization would have to be performed continuously (Aumont and Bopp, 2006).

Cao and Caldeira (2010) have run predictions to see what we could hope to gain from continuous iron fertilization. They reckon that by 2100, "globally sustained ocean iron fertilization" could have reduced atmospheric carbon dioxide from 965 ppm (the Intergovernmental Panel on Climate Change's (IPCC) A2 emission scenario for 2100) to 833 ppm. That's a 14% reduction. Good, some might say, but not good enough. Especially considering this estimation is highly optimistic. (Not least because Cao and Caldeira's predictions assumed sustained global iron fertilization since 2008!) This prediction is fairly consistent with Aumont and Bopp's (2006) claim that long term carbon sequestration from iron fertilization is negligible.

But, even if iron fertilization doesn't seem jaw-droppingly impressive as a means of carbon sequestration, I keep wondering: is something still better than nothing? Could it still be part of a wider plan to reduce atmospheric CO2?

The answer to this, I’m afraid, is no. Even such reductions in atmospheric CO2 as were predicted by Cao and Caldeira (2010) or Aumont and Bopp (2006) would come at a high price elsewhere, deeper down. Carbon could be sequestered and stored in the deep ocean but, Cao and Caldeira warn, this would lead to a rise in deep-sea CO2 concentrations, and risk serious deep-sea ocean acidification (see Figure 1).

Figure 1. Left panels show simulated changes in pH (relative to pre-industrial values) in the year 2100. Right panels show how the simulated horizontal mean pH changes with year and ocean depth. Row a) shows simulations for IPCC emission scenario A2. Row b) shows simulations for IPCC emission scenario A2, with sustained global ocean iron fertilization (OIF). Row c) shows simulations for IPCC CO2 concentration scenario A2, with sustained OIF. From Cao and Caldeira (2010). 

Deep sea ocean acidification is dangerous, for one thing, but it could also be totally counterproductive to the efforts of iron fertilization that caused it in the first place. Oceans are in constant motion: waves, tides, currents, mixing, and upwelling (just to name a few of the things they do). Upwelling is basically the process of deep water moving upwards, to replace surface water that's blown away by winds. If deep water is acidic (as predicted by Cao and Caldeira (2010)), then upwelling will eventually mean this deep acidic water (acidic with dissolved CO2) reaches the surface again, and it will be less able to take in much CO2 from the atmosphere.

Quite a hazardous outcome, and certainly not one that could be deemed beneficial enough to see a lifting of the international ban on dumping waste in oceans!

And as if this isn’t convincing evidence against iron fertilization, Aumont and Bopp (2006) note that when iron fertilization is stopped sequestered carbon is re-exposed to the atmosphere quite rapidly, again undoing all the hard work.

This, put together with wider environmental concerns (eg: ocean-oxygen levels could be accidentally depleted, or toxic algae may start to grow) seems clear to me that this is not a form of geoengineering Eazrah should be considering putting into action.

I'll shortly be leaving Planet Crooter, and my quest for promising geoengineering continues.

Plenty more fish in the sea (pt. 1)

I’ve arrived at the first stop on my quest, Eazrah’s nearest galactic neighbour, Planet Crooter.

I was greeted warmly by the inhabitants here and have spent a few days speaking with them about the current state of both our planets' climates, and what action is being taken to control them. They told me about a form of geoengineering here called iron fertilization, though many inhabitants claim it is not really geoengineering at all. I’ll explain why later on.

This is the idea:

1. Iron powder is dissolved into the oceans

(The focus is kept on regions of “high-nutrient, low-chlorophyll” (HNLC) surface water. HNLC means there are lots of nutrients necessary for life in the water, but there’s not much chlorophyll – a pigment crucial for phytoplankton and algae to photosynthesize – indicating there’s not much photosynthesis or plant growth going on. As the water is rich in other nutrients, it’s thought that iron (of lack thereof) limits phytoplankton growth.)

2. Influx of iron into the water stimulates tiny organisms – phytoplankton and algae – to grow into colonies (they call it a plankton bloom, see figure 1)

3. The growth of these organisms effectively sucks organic carbon out of the water...

4. ... meaning less carbon can travel from the water back into the atmosphere. There's also a greater capacity for carbon dioxide to dissolve into the ocean from the atmosphere

5. When the phytoplankton and algae die they sink to the ocean floor, trapping carbon on the ocean bed. This part is the carbon sequestration

Figure 1. The natural-coloured top image is a spectacular plankton bloom off Kamchatka. The bottom image shows scientist-estimations of chlorophyll concentrations in this area. Regions of high chlorophyll concentration correspond with densely plankton-populated water. (Images by Robert Simmon and Jesse Allen, based on MODIS data, via NASA)

I'll explain a little more...

Some scientists speculated that a lack of iron was limiting biological activity in HNLC regions. In an early experiment Coale et. al. (1996) tested this out in a HNLC part of the Pacific Ocean. They saw that when iron was dissolved into the water, algae and phytoplankton populations did indeed start to grow. They also saw a significant drawdown of carbon from the surface water, suggesting iron fertilization had potential as a method of carbon sequestration.

Boyd et. al. (2000) then tested out the same thing in the Southern Ocean. They saw that although there was some increase in algae and phytoplankton, they couldn’t prove there was much carbon sequestration occurring. But then in 2009, Pollard et. al. (amongst others) did confirm carbon sequestration as a result of (natural) iron fertilization in the Southern Ocean.


Mixed results really: it seemed like iron fertilization did stimulate plankton growth, but it was unclear whether it would lead to significant carbon sequestration.

Then came the largest-scale “experiment” of iron fertilization. But it wasn’t performed out of scientific endeavour. A businessman, set on earning money from carbon credits, convinced a small marine restoration organisation, Haida Salmon Restoration Corporation (HSRC), to release 100 tonnes of iron sulphate into the north-eastern Pacific Ocean to boost salmon populations. (The idea being that a plankton bloom would boost fish populations, including salmon.)

In terms of salmon, the “experiment” was a success. But from a geoengineering perspective, it seemed there was little carbon sequestration as most of the phytoplankton were eaten by fish before they had a chance to die, sink to the seafloor and lock carbon away.

The move was also controversial with environmentalists here: there are plenty of reasons why anyone using iron to artificially create plankton blooms should be careful. From risking depleting surface-water oxygen, to accidentally encouraging toxic phytoplankton or algae species blooming.


So far I'm not too impressed with iron fertilization. The evidence suggesting it leads to carbon sequestration is weak, but some evidence does exist so I think it deserves more attention. Maybe the benefits of iron fertilization are more significant over a longer time scale? I’ll stay on Planet Crooter a little longer to find out.

A journey across space

Geoengineering (noun): “deliberate large-scale manipulation of the planetary environment to counteract anthropogenic climate change” -

The Royal Society

Greetings, fellow space traveller! You are joining me on a journey across space – a journey that my home planet, Eazrah, dearly depends on.

I have been sent on this mission by our Eazling leaders, to discover new technologies from around the galaxy that could help to save our planet.

Figure 1. My vessel for the mission. 

Eazrah is facing a crisis. Its climate is changing dramatically because atmospheric levels of gases like carbon dioxide and methane have become so high they’ve caused global temperatures to get too hot. We’ve been warned that the higher temperatures could cause droughts so extreme that crops cannot grow. Most of the beautiful ice-lands are melting too, and causing sea levels to rise and swallow up entire coastal cities.

But nobody has done anything to stop it. Not really. Carbon dioxide and methane are still being pumped out into the atmosphere every day and the temperature is still rising.

As a last resort, our leaders want to look for alien “geoengineering” technologies that will either suck carbon dioxide out of the atmosphere, or to reduce the amount of sunlight hitting the planet’s surface and heating it up.

My objective is simple: find a technology that’s been developed on an alien planet to remove atmospheric carbon dioxide or manage solar radiation to control global temperatures.

Many of the Eazlings are wary of using such large-scale technologies to control global temperature. Some worry that inadvertent damage could be done by the techniques. Others are concerned it will take too long to implement a successful geoengineering plan on the scale needed to avoid the disaster brought by climate change. And some Eazlings claim we need to address the fundamental reasons why we’ve let climate change get to this point – make changes to our system, rather than using a techno-fix to carry on with business as usual.

But one thing is for certain: we desperately need something to be done to prevent ongoing climate change. So I'm exploring any technologies that could be part of a plan to do that.