Local short- term events such as rainfall and strong winds are really weather rather than climate phenomena, and as such cloud seeding and storm diversion could be excluded from this paper. However, I will mention them briefly, since attempts to modify weather far predate any climate engineering proposals, even if we ignore rain dances and sacrifices to the gods!
The vapour pressure exerted by a water droplet or ice crystal increases with curvature, and therefore very small droplets will evaporate even if the air is greatly supersaturated with respect to flat water surfaces. To form drops some kind of condensation nucleus is therefore needed (a charged ion or particle) to attract together the first water molecules. This is the principle behind cloud seeding. In-situ experiments were begun by Veraart in 1931, soon followed by Schaefer and Langmuir from General Electric in New York. Originally dry ice was dropped from planes through ice clouds. Later silver iodide crystals were released from ground burners, the crystals very effectively mimicing the structure of ice, creating 1015 nuclei per gram of AgI. During the 1940s and 50s the claims of the rainmakers raised many expectations, particularly in Texas, Mexico and Israel, although there was little rain to show for it. In the Blue Ridge Mountains (US) the technique was employed to prevent the formation of large hailstones which damage crops, until farmers the other side of the mountain filed a lawsuit claiming theft of their rain! Recently there has been a little more success at rainmaking in Mexico, and much research continues in Israel (e.g. Rangno 1995). However, success in Israel might not be so welcome elsewhere in the middle east! For several recent papers on rain seeding, see the journal of Applied Meteorology 35 no 9 (1996).
Diverting hurricanes might cause even more conflict than stealing another country's rain. It is theoretically possible by selective cloud seeding, given that a tropical storm derives its energy from the latent heat released as clouds are formed. There have also been proposals, backed by the US Electric Power Research Institute, to develop powerful ionising lasers to deliberately induce lightening in thunderstorms before they reach cities or power installations (Muir 1995). Potentially these might also divert storms.
However, such ideas have never been tried. Weather is too chaotic. If storms can be begun by the flap of a butterfly's wing, who would insure the scientist who might direct a hurricane the wrong way?
The temperature at the Earth's surface adjusts (slowly) such that the energy from incoming solar radiation (sunlight- uv and visible) is balanced by terrestrial radiation (infra red) emitted from the Earth. When greenhouse gases reflect back some of that terrestrial radiation, the surface warms and emits more radiation, until the amount escaping the atmosphere balances the sunlight as before. For a review of radiative forcing, see IPCC 1996 (g) It has been suggested, that to offset the warming effect of the predicted rise in greenhouse gases in the atmosphere, we could instead reduce the incoming solar radiation, by intercepting about 1% of sunlight. To some extent this happens anyway. Sulphate aerosol pollution is produced as a by-product of burning fossil fuel, and this aerosol reflects sunlight both directly, and by seeding the condensation of tiny cloud droplets. In industrial areas principally around 45 degrees north, (central Europe, northern China and India, northern USA), this more than offsets current greenhouse warming as shown clearly by the latest data (Santer et al. 1996). However, this is a local and short lived effect, because the aerosols are rapidly removed from the troposphere as acid rain. Would-be climate engineers desire a longer-lasting effect.Two principle methods have been proposed: giant reflectors in space, and stratospheric dust or aerosols. It has been pointed out by Schneider (1996) that such schemes could never offset global greenhouse warming without creating large regional climate changes, even if the aerosols were much more evenly distributed in the stratosphere than in the troposphere. Terrestrial and solar radiation never balance locally, since the atmosphere and oceans shift a large amount of heat between regions, and cloud cover also varies. A climate engineering "fix" based on reflecting solar radiation would cool most strongly different regions from those where there was most greenhouse warming.
Aerosols or dust in the stratosphere survive much longer than in the troposphere, and are already known to cool the planet, as observed following large volcanic eruptions. In the early 1990s, dust from mount Pinatubo checked global warming, and the observed cooling effect matched well with the most recent model predictions.
It has been suggested that we could deliberately inject either sulphate aerosols or dust into the stratosphere. For a recent review refer to Dickinson (1996).The idea is first credited to the Soviet scientist Budyko (1974) and developed by many others since, mainly in the US, even reaching a US government report (National Academy of Sciences 1992). Originally rockets or rifle shells would have carried the dust, but Penner (1984) suggested that it could be done more easily by a slight modification of commercial jet fuel, and this would be very cheap. In a policy statement to an International Energy Workshop in San Diego in 1992, he presented the dust idea as a "Low-cost no regrets" option for mitigating greenhouse warming, showing that it would cost just 0.1 cents (using coal dust) to cool the planet to compensate for one tonne of Carbon as CO2 in the atmosphere, or 1 cent if SiH4 was used to make inert SiO2 dust (Penner 1993). However, he first attempts to rubbish the whole global warming scenario, and clearly doesn't intend that we carry this out unless, by some strange chance, all those scientists in IPCC happen to be right and we really do find we have a problem. Then, "for intolerable warming, low-cost planetary albedo augmentation may become the method of choice some decades in the future".
Besides being cheap, the aerosol fix is also promoted as "reversible", i.e. you can easily stop if it doesn't work, and within a few years the dust would fall out. On the other hand, most greenhouse gases have a much longer lifetime so if they are to be offset with stratospheric aerosols, we would have to rely on the ability of future generations to keep flying those planes, to keep repairing the shield or be faced with sudden warming.
Even if we are content to pass on that burden, we would also be cutting the amount of sunlight reaching plants on the surface, and presumably also changing its spectral composition. Perhaps the plants would take up less CO2? And do we really want to live under a constant haze in the sky to keep us cool? Do a few scientists and policymakers have the right to impose this on all other life on the planet?
Another obvious objection is that the injected particles might provide a very efficient surface for ozone destruction, as polar stratospheric clouds already do every spring. It seems the engineers have not yet looked at this in any detail.
This idea is very simple, to put gigantic foil sheets up in orbit around the earth, again to reflect sunlight. They would periodically cast a shadow, intercepting incoming light about 1% of the time, and would be assembled in space because such things couldn't be launched from down here.
Such proposals, it seems, have kept many physicists amused, and the orbits of the various parasols, mirrors and "solar sails" are spelled out in some details in Fogg's "Terraforming" book (Fogg 1995, pp 173-182). None seem very realistic yet, and they certainly wouldn't come cheap, but I guess the idea might be being promoted by those who fell by the wayside with the demise of the US Star Wars (Strategic Defence Initiative) programme. Recalling how so much money was spent on this, whose only result was to distract from the task of nuclear disarmament, I wouldn't be so surprised if they try to persuade another US president to take a personal fancy to such ideas. After all, it's more glamorous than some other fixes, for example, growing seaweed (below)! And politically much simpler to explain to an electorate than resisting the car-culture.
Solar radiation might also be deliberately reflected locally by altering the surface "albedo". There have even been rumours recently about "painting the deserts white", although I have not traced their source.
The effect of such schemes would probably be small compared to natural feedbacks which change in albedo in response to climate change. For instance, the northward movement of forests and reduction in snow cover in Siberia and Canada would be expected to cause increased absorption of sunlight. On the other hand simple climate models suggest that cloud cover is expected to increase, but these models do not yet take into account seeding by sulphate aerosols. The latter may be partially provided by marine algae, and thus would be influenced by ocean fertilisation schemes (see below)
Nobody denies that the deep ocean has an enormous capacity to store carbon dioxide. This is principally due to the high alkalinity of seawater, such that for every 100 molecules of CO2 stored in it, roughly 98 of these are found as1 bicarbonate ions, 1 has been converted further to a carbonate ion, and only one remains as CO2.
(for chemists: CO2 + H2O <==> HCO3- + H+ <==> CO32-+ 2H+)
Thus a little CO2 in air (at 1 atmosphere pressure) can be in equilibrium with about 100 times more "total CO2" in the equivalent volume of seawater.
The problem is that most of the ocean water is not in contact with the atmosphere. Transfer of CO2 between the surface ocean and the deep ocean is slow, and occurs by two main processes: subduction of cold salty waters, particularly in the North Atlantic , and the biological "pump" whereby organic particles sink below the mxed surface layer. Only a small fraction of these particles eventually reach the sediment, the longest-term sink of carbon, but on the timescale of a thousand years or so removal to the deep water itself is sufficient. If this happened faster, the pulse of CO2 in the atmosphere from fossil fuel burning would be much smaller, and thus the greenhouse warming less dramatic, although the long-term equilibrium climate change would be unaffected.
So climate engineers want to get CO2 into the deep ocean faster. There are various proposals: CO2 could be pumped there directly, soaked up by changing the alkalinity fo the water, or absorbed into an enhanced biological pump by "fertilisation" of the ocean with nutrients. For a general review of enhancing ocean CO2 sinks, see DeBaar (1992),
Surface seawater is also typically supersaturated with respect to calcium carbonate, and it might be expected that precipitation of this solid (directly, or into shells or corals etc.) would be a good way to remove CO2 from the system. Paradoxically, it actually does the opposite, by decreasing the alkalinity. While ocean chemists have long understood this, it seems that some engineering consultants have yet to work it out, proposing, for example, to increase the growth of calcareous seaweeds. Governments who prefer to trust such private consultants may be wasting their money.
Another related effect of the seawater carbonate chemistry is often ignored by the engineers, as pointed out by Orr and Sarmiento (1992). For every ten units of CO2 you remove from the surface ocean, about 9 are replaced from the vast pool of bicarbonate ions in the water, and only about 1 would be replaced from the atmosphere. So if, for instance, seaweed was used as a fuel, the main effect would be to shift CO2 temporarily from the ocean to the atmosphere. It may be better than burning fossil fuel, but is not an efficient way to solve the problem!
The principle nutrients limiting the growth of ocean algae are nitrate, phosphate, and in some places, iron (more on this below). To some extent we are already increasing the nutrient supply to coastal waters, through agricultural and sewage runoff. However, further from shore the nitrate and phosphate are supplied mainly by upwelling of deep water. Over much of the ocean, where warm surface water rests stably above cold deep water, the nutrient supply is poor and little grows.
So there have been many proposals to grow more algae by augmenting the nutrient supply. Not only might this enhance the biological carbon pump, but it might also provide a fuel or even food for fish.
On the other hand, our ability to predict the many feedbacks intrinsic to marine ecology is still very poor (for a summary see IPCC 1996 (e)). For instance, the important role of bacteria in recycling nutrients is just beginning to be uncovered. Plankton may also produce other gases which affect climate: notably nitrous oxide and methane which are much more potent greenhouse gases than CO2, dimethyl sulphide which oxidises to form sulphate aerosols which seed clouds (see above), and also smaller quantities of hydrocarbons and halocarbons which affect atmospheric chemistry.
At least in surface waters you could easily measure some effects of a perturbation. However, once the surplus algae sank deeper, there is little consensus as to their fate. One concern is that the extra supply of organic carbon could use up all the oxygen in parts of the deep ocean. This might lead to the production of a lot of methane, or nitrous oxide. Fuhrman and Capone (1991) review some of these concerns.
Furthermore, there has been little consideration of the effect on any life in the sea bigger than algae. As a general rule, biodiversity in the sea decreases in highly productive algal blooms. And suppose we really could predict the effect on all the plankton, krill, fish, whales: how then would this help us make a decision whether to go ahead or not?
In any case, the science is very far from making such predictions. Consider, for example, the failure of the scientific management of fish stocks, or the poor understanding of toxic algal blooms. Marine ecology is a complex non-linear system that behave chaotically, with many surprises in store.
Seaweed dominated the early ocean-algae climate engineering proposals. The idea was to set up kelp farms, eventually covering tens of thousands of square kilometres of the open ocean, originally with the intention of producing methane. In the 1970s $20million of research was funded by the (then) American Gas Association, only to find that it would cost them 6 times more than the energy they would gain. The vast cost comes from the need to supply nitrate and phosphate to the surface ocean. Either you can add man-made chemicals, in amounts well exceeding the total world production of fertiliser, or use a lot of energy to pump up nutrient rich water from the sea floor. It has also been pointed out (Orr and Sarmiento 1992)that such water is usually supersaturated in CO2, which would then be released to the atmosphere...
Nevertheless, in the heat of the greenhouse effect and with Carbon taxes/credits in sight, the seaweed idea has been revived, mainly by the US Electric Power Research Institute. They say it would cost about $200/tonne C sequestered. Engineers have devised grand schemes with diagrams showing the tracks of supertankers moving about the farms harvesting the seaweed. A more sensible review can be found in Ritschard (1992).
I have not yet found any mention of the potential effect on marine ecology. After all, it's not something we would expect electricity companies to investigate.
Both the European Community and the Japanese have recently supported research investigating coastal fertilisation to increase both the biological carbon sink, and the supply of fish. Such projects have received much scorn from academic marine biologists, who say they are simplistic and may do far more harm than good, for instance encouraging jellyfish, anoxia or toxic algal blooms. (see Mackenzie 1996). Nevertheless they have found support due to commercial backing. Norsk Hydro (one of the world's biggest manufacturer of fertilisers, incidentally) wishes to add nitrate and phosphate to the Norwegian sea and is already experimenting in fjords. Meanwhile Mitsubishi is funding a similar proposal off Japan, claiming it might not only capture carbon dioxide, but also produce a lot of sardines (Matuo et al 1995)!
Others are more ambitious still. Jones (1996) calculates the nitrogen needed to soak up the entire projected anthropogenic global CO2 emissions. He also claims to get 260 kilos of fish per tonne of nitrogen...
Of all climate engineering proposals, fertilisation of the Southern Ocean with iron has raised the most controversy. Perhaps this is because experiments designed to investigate whether iron is the key limiting nutrient are already underway and well publicised, with four papers appearing in one recent issue of nature (vol 383 no 6600), remarkable for any topic.
The idea has been around for about 7 years, and is credited to John Martin who first developed the clean laboratory techniques to measure how little iron there was dissolved in open seawater. The concentration is low because it falls out as a precipitate from alkaline seawater, so the only supply to the open ocean is atmospheric dust. This led him to suggest that iron might be the limiting nutrient, which would explain an old puzzle: Why, in the Southern Ocean and the Equatorial Pacific, is the algal growth much less than would be expected from the supply of nitrate and phosphate? If iron was the answer, as suggested by bottle incubations of the algae in these waters, it might also be a feedback controlling ice ages. Atmospheric dust increases during glacial periods. This dust could fertilise the Southern Ocean and the algae would soak up enough CO2 to reduce the greenhouse effect, enhancing the ice age.
This led to his famous quote at a conference, "give me half a tanker of Iron, and I'll give you an ice age". It was a joke. But once this idea was out, for the "biggest manipulation of nature ever attempted by man", it seemed inevitable that scientists would want to try it out, albeit on a small scale. The proposal briefly caught the attention of the US media, with portrayals of irresponsible mad scientists in white coats about to take over the world. It was feared especially that the possibility of a technofix to global warming would weaken resolve to reduce CO2 emissions. To calm the uproar the scientists adopted a resolution, including "The American Society of Limnology and Oceanography urges all governments to regard the role of iron in marine productivity as an area for further research and not to consider iron fertilisation as a policy option that significantly changes the need to reduce emissions of CO2". The story is summarised by Chisholm and Morel (1991) in the preface to a special issue of Limnology and Oceanogrphy (36 no 8) on the topic.
However, the scientists were determined to continue research, on the grounds that we need to understand ice ages in order to predict future climate. Plans were hatched for the "first real experiment in oceanography" (i.e. you tinker with the ocean rather than just observe it), adding iron to a 80km2 patch of the Pacific Ocean west of the Galapagos Islands. This was possible due to a new method using the gas sulphur hexafluoride to trace the patch. During the first experiment in 1993, the algae grew well but there seemed to be little effect on the CO2 (Watson et al 1994). In the summer of 1995 the experiment was repeated with multiple iron additions and was much more "successful". In particular, there was a large decrease in CO2 in the water (Cooper et al 1996) and the algae also produced a lot of Dimethyl Sulphide (Turner et al 1996) which might seed clouds over the ocean (see above) and thus have an additional cooling effect. The DMS cooling is very hard to quantify but might be considerably greater than the reduction in CO2 greenhosue warming.
As it happens, models predict that the same amount of CO2 would have been soaked up anyway, once this surface water of the equatorial Pacific, which doesn't mix well with deep water, moved to a region of higher iron supply and nitrate became limiting. This is not true, however, around Antarctica, where surface water is subducted down and the carbon removed from contact with the atmosphere. The key test would be to repeat the experiment in the Southern Ocean. The UK team, my colleagues here in UEA, are looking for funds to carry this out.
Prof Andy Watson does not rule out the possibility that this could one day lead to a climate engineering fix ."We are interested in the possibility that something as relatively simple as this could be used." But his model predicts that even a continuous widespread iron fertilisation could only reduce atmospheric CO2 by 60ppm by 2100, a tenth of that needed to offset "Business-As-Usual" fossil fuel emissions. Peng and Broeker (1991) predicted a similar limitation.
On the other hand, one country (eg Australia) or even a multinational corporation might like to claim this 60ppm for their own credit, in a future world of carbon emission taxes or quotas (This is considered more in section 4.4.1). Iron Fertilisation is cheap, perhaps as low as 5$ per tonne of Carbon fixed, compared to $200 for many other proposed sinks. You need to add iron continuously, but not much. Aeroplanes could deliver dust, or rusting tankers or discarded oil rigs could produce it in situ. A more sophisticated approach might employ purpose-designed slow-release floating granules.
The prospect of the ecology of the Southern Ocean being traded off against national or corporate carbon emissions quotas in some crazy Cost-Benfit Analysis raises many ethical questions to which I will return later. But even putting that aside, the scientists are far from being able to predict the effect on that ecology, as already noted in the general points on ocean fertilisation (above).
It has been also suggested, that iron fertilisation could alter the dynamics of the Southern Ocean to increase the natural flux of Iron-rich water from depths to the surface, resulting in a runaway iron fertilisation. This physical feedback might be initiated by a decrease in sunlight penetration through the algae. So it is quite possible, that we could underestimate the feedbacks and go too far, creating another ice age after all...
It is not surprising that iron fertilisation has raised so much controversy. Of all climate engineering proposals, it is perhaps the easiest and cheapest to carry out, very elegant, and yet it carries the most unpredictable consequences. It also involves the pristine ocean around Antactica, the part of the world least affected by our pollution so far. Experiments have already been "successful", and the organisers need to publicise the results to help secure more funding, for they have so far avoided commercial sponsorship and rely on research council funds. Perhaps because it is investigated openly by independent ocean scientists, the idea retains more credibility than it would if backed by industry. Some claim that we should push ahead with research, to ensure the results are open for the world to judge, before any commerical venture can get established. There is already an international race among oceanographers to get the money for the next experiment. But the Southern Ocean belongs to none of us, perhaps more rightly to whales, krill, penguins, algae, all life on earth. Respect for this seems to have been lost in the race to be first with clever science.
Another "joke" I heard along the lines of the iron fertilisation, was that we could add silicate to the North Atlantic, to alter the balance between different types of ocean algae (J. Young, EHux conference, April 1995). This might encourage diatoms, which need the silicate for their cell walls, rather than coccolithophores, which secrete calcium carbonate plates. As carbonate ions are removed from seawater, its alkalinity decreases and CO2 is driven into the air. Diatoms only make organic carbon and thus pull CO2 from the air.
Imagine the genetic engineers let loose on this kind of problem. Suppose they could design some new algae, that pumped CO2 as efficiently as possible out of the surface ocean, was resistant to iron deficiency, or produced loads of dimethyl sulphide. They could then give them some special advantage over other species. Just release a few cells to the sea, sit back and watch the planet cool. But then how to stop it?
Genes are already identified for charcteristics suitable for capturing CO2 from power station flue gases in lakes of algae (more below). Presumably it's not so far from there to modifying typical marine algae. The Japanese fund "Research Initiatives for Innovative Technology for the Earth" (RITE 1994, see also below) already sponsors projects entitled "Gene Manipulation Reinforcement of the Carbon Fixation Capability of Photosynthetic Organisms", "Creation of Iron Deficiency-resistant Plants", and "Biological elimination of atmospheric CO2 by enhanced pump activities and the SuperRuBisCO". The last of these sounds particularly alarming, it's also worryingly close to my own field of work, regarding air-sea CO2 exchange and the physiological response of algae to low CO2, which I had thought was so harmless... I notice they have already identified the gene for this response (Fukuzawa 1995). Perhaps we can only hope, that over 4 billion years, all the successful kinds of marine algae have already evolved.
Dissolving lime in the oceans is the opposite chemical process to the coccolith formation mentioned just above. Indeed, it has even been shown that you can combine coccolith cultures, waste concrete and seawater to fix atmospheric CO2 (Takano and Matsunaga 1995)!
That works in the laboratory. But H Kheshgi of the Exxon Research and Engineering Company (Kheshgi, 1994) was more ambitious: He proposed increasing the alkalinity of the ocean surface mixed layer, by adding lime (CaO) in situ. The lime dissolves quickly, and would reduce the CO2 in the water locally, pulling it in from the air. But to get this lime, you have to heat limestone (CaCO3) with coal in kilns, driving off CO2. This produces almost as much CO2 as the seawater would take up (80%), except that you have it conveniently in one place, and perhaps it might be possible to store it compressed out of the way (see below). The whole process seems extremely inefficient. Soda ash (Na2CO3) could be used instead, but there isn't enough of it available.
To soak up as much CO2 as we currently add to the atmosphere each year, you would need to start with about 30 billion tonnes of limestone, about ten times the rate it is currently mined. Imagine the scale of superquarries that would be dug for this purpose, they would dwarf those for roadbuilding, already facing intense oppostion. On the other hand, once fully mixed into the ocean, the long term change would be almost negligible. But the lime could never be added evenly across the ocean surface, it would have to be added at a few localised points. There, it would surely have a dramatic effect on marine ecology. Or it might just reprecipitate (perhaps with the help of some coccolithophores...) before dispersing enough to affect much CO2.
People have always dreamed of greening the world's deserts. Their potential as a CO2 sink as well as a food source has revived interest in such grand schemes. One such proposal from the Japan Gas Association and RITE (Ozawa et al 1995) includes generation of clouds by evapotranspiration from coastal mangroves and lagoons, and artificial mountains to promote rainfall, along with underground dams and new cities. They even provide an "artists impression" of this new landscape.
A slightly less ambitious scheme was proposed by Glenn (1992) at the US Electric Power Research Institute, using halophytes. These are plants, usually found in salt marshes, that thrive in saline conditions. The idea is that, perhaps with a bit of genetic engineering, they could be adapted to desert lands irrigated with seawater, or lake/river water that has become too salty for any other purpose. Glenn estimated that world-wide there are 130million hectares of suitable land, and that this could sequester about 0.7 billion tonnes Carbon annually, at a cost of about $200/tonne. It is suggested that some of the crop could be ploughed back into the "soil", the rest could be buried dry. He also recommends a particular oilseed crop, that is edible, tasty, nutritious, and could also be a fuel. The main problem is that you need a lot of excess irrigation to leach out the salts that would otherwise build up. Presumably you also leach out nutrients at the same time, so where do you replace them from? This question is not addressed.
Some other obvious points seem to have been overlooked. If you make the desert wet (or even just grow trees on it), it becomes darker, thus absorbing considerably more sunlight and warming the planet. There would also be very high evaporation, and water vapour itself is a greenhouse gas. On the other hand, if more clouds formed as a result, they reflect sunlight. We should also recall, that rice paddy fields are a very large source of methane, and these salt marshes might be likewise.
However, this idea may get further support. For instance, if transferable carbon taxes/credits are introduced, the oil producing states, most of which are in desert regions, might like to gain some carbon credit. Will they try to green the oilfields?
There are plenty of good reasons to plant trees, and carbon storage is but one of them. A review of the issues can be found in Marland (1992). I will not dwell long on this topic, partly because it is too vast and already well known. Although reforestation might be considered climate engineering, it takes place within national boundaries rather than exploiting the "global commons", and also it can hardly be considered a new unknown technology! Trees can be planted by people locally and they know what to expect as a result.
However, there are a few common misconceptions. For instance, mature forest does not take up carbon, only young forest is a net sink. As the forest matures, it approaches equilibrium where growth equals decay. So this is only a long term solution, if you continually harvest the wood and then store it somehow. It has also been suggested that we fertilise existing forests to maximise carbon uptake, this would likwise provide only a temporary sink.
On the other hand, some grasslands or peat bogs in particular, can be a permanent sink for carbon, as more accumulates on top each year. Recent reposrts suggest that this carbon sink may be equal or greater in magnitude than the world's trees. Also, if a peat bog is dried out by planting trees, the previously anaerobic peat becomes accessible to soil micororganisms, which release it as CO2, or worse, as methane. So it is not always wise, from a climate perspective, to put trees where there were none recently before.
Judging from the number of papers, I guess that far more research money has been poured into this topic than all of the others here put together. It attracts funding because a company could dispose of just its own CO2, and thereby avoid taxes or emissions quotas. I'm not sure whether this strictly counts as "climate engineering". However, it is usually placed in comparison with the other proposals here, and discussed in the same journals. The deep ocean is also a "global commons" rather than the propoerty of the company, and as such we all have a right to be concerned with its use. And this topic raises many of the same ethical and scientific dilemmas, as do the proposals above.
For general reviews see DeBaar (1992), Ormerod (1994), Kheshgi (1994b), Reimer (1996). For more detail see the conference proceedings in "Energy Conversion and Management" (1992,1993,1995,1996).
A lot of technology has been developed, to separate CO2 from stack gases, on the assumption that this is the key to the pollution problem. But burning fossil fuel produces so much CO2, that really the major problem is where to put it afterwards. As mentioned above, the deep ocean has an enormous capcity, and is the natural medium-term sink for carbon. Note that the best long-term sink is not in seawater, but fixed by photosynthesis back into the oil and coal from which it came. Unfortunately these take millions of years to form.
The gas would first have to be liquefied, and then pumped down pipelines (for which the technology doesn't exist yet) to below 1500m depth (for environmental reasons -see below). It would then mix with seawater, forming a very acidic plume which would spread out across the sea floor.
Originally it was thought 3000m was necessary, because above this height the pressure is insufficient to keep the CO2 as a liquid. However, various groups then claimed shallow injection was possible (e.g. Drange and Haugan 1992) because, so long as you could get enough CO2 to dissolve before the bubbles rose to the air, then the resulting dense CO2 solution in seawater would sink naturally. They looked for sites where ocean currents already descended continental slopes.
A complicating factor is that when concentrated CO2 and water are mixed, they react to form solid compounds known as clathrates. In trial experiments, the clathrates blocked the end of the CO2 pipe. A lot of research then followed on this topic. Indeed, it has been proposed that the clathrates may be useful, because they sink rapidly, so this helps to solve the depth problem. The Japanese are particularly keen on the idea of deliberate clathrate formation.
I have read some amusing paragraphs from these engineers, tagged on at the end of the papers to show some environmental concern. They are worried primarily about the fish being confused by all these rising bubbles and falling clathrate particles, perhaps trying to eat them, perhaps becoming psychologically disturbed! We are assured that they are looking into this problem, but it would only be confined to a small local area around the end of the pipe. Well, maybe so. But there are far more worrying implications, both to the regional and global environment.
CO2 is an acidic gas, and the liquid CO2/seawater mixture would be highly acidic. It could therefore kill most marine life, perhaps over a large area of the sea floor. Usually the chemistry of the benthic environment changes very little, so even a small perturbation may have disastrous effects (for pH tolerance see IEA 1996). Perhaps the engineers view the deep sea as worthless mud with a few worms in it. However, marine ecologists have recently estimated that there are so many different species of benthic organisms, that the biodiversity is comparable to the tropical rainforests. We just don't know much about it yet. Again, does this give us a right to destroy such life to satisfy our thirst for burning oil?
Finally a few of these questions are being considered, for instance in a paper from MIT (Auerbach et al 1996) or at an International Energy Agency Workshop on environmental impacts (IEA 1996). The marine biologists came up with some fairly restrictive criteria, such as "no species should be driven to extinction" and "no significant destruction of ecological processes at basin scales", for which there must be no acidic strata which could form a barrier to migration. To be sure of that, and to protect diversity of shelf slopes, CO2 should be released below 1500m. On the other hand, a pure "CO2 lake" sitting on the sea bed (it's denser than water) would be disasterous for life in the sediment.
Harrison et al (1995) also raise an additional concern: they suggest that the high concentration of CO2 in the seawater would reduce its capacity to hold other gases, particularly oxygen, and therefore the bottom water might become anoxic. Methane could then form, although they assert it wouldn't rise to the sea surface.
But how can we sure that the CO2-rich water will not return to the surface? Deep ocean currents do change over time, sometimes suddenly, rarely predictably, depending on finely balanced physics. Or instead of upwelling slowly to the surface, the CO2-rich water might become unstable while the CO2 is still concentrated, rising suddenly as plumes of gas. Methane does this occasionally from the sea bed, indeed, there is a theory that this may account for the mysterious loss of ships in the "Bermuda triangle", which would sink in the froth. And only last year, we may recall the natural disaster of lake Nyos in Cameroon, where a plume of CO2 that suddenly bubbled up from the bottom, asphyxiated all humans and animals within a few miles of the lake. This CO2 had been accumulating from quiet volcanic activity in the rocks, but so far nobody can explain why it suddenly destabilised when it did. Pumping liquid CO2 to the bottom of the sea, could lead to similar disasters; until we understand what triggers them, we cannot deny the possibility.
If that CO2 that we had stored over several decades, suddenly came back up and into the atmosphere in just a year or two, the effect on the global climate could be catastrophic. For a sudden pulse of CO2 could cause enough warming, to trigger climate feedback processes that lead to a runaway greenhouse effect. It would have been much better to have put the CO2 into the atmosphere, year by year as it was produced.
It also takes a lot of energy to pump anything down to such a pressure under the ocean, and you have to burn a lot more fossil fuel to make this extra energy, so this process is extremely inefficient. There seems to be some disagreement in the literature as to exactly how much more energy is needed, but it is at least 30-40% extra. Part of the confusion arises because both CO2 "capture" from flue gases (essentially an entropy problem) and CO2 "disposal" (transport, pressurising) cost energy, but where one stops and the other begins is arbitrary. Also, the costs are much higher for conventional power stations than for new ones purpose-designed for CO2 capture. The overview by Ormerod (1994) helps to clarify this. The IEA (Riemer 1996) asserts that capture is considerably more costly than disposal.
Not only is all this expensive to the consumer, but in the long term it also makes the problem worse, because to get that extra energy you have to burn more fossil fuel... So you end up disposing more CO2 (eg 40%) into the deep ocean than you would have put into the atmosphere if it had gone up in smoke as at present. Over hundreds of years through ocean circulation and diffusion, the CO2, including that "extra" CO2, will find its way back into equilibrium with the atmosphere. The graphs by Kheshgi (1994b) illustrate this problem well. Effectively this is putting an extra burden on future generations in order to avoid a problem now. This is an issue of intergenerational equity, which wouldn't usually be noticed in any cost-benefit analyses because the future is so rapidly discounted.
Bacastow and Dewey (1996) also point out that as the global climate warms and CO2 increases in the atmosphere, the deep ocean's buffering capcity for CO2 uptake decreases, and so deep ocean disposal becomes a less favourable option.
Despite all these technical and environmental problems, each year there are more papers on this topic. They want to conduct a small scale experiment soon, so there will be another IEA workshop to plan this and choose a site. It is proposed that the trace gas sulphur hexafluoride, which is a greenhouse gas 25000 times more potent than CO2, will be released alongside the CO2, to track the fate of the dense high-CO2 water (VanScoy 1996). A five year experiment in a fjord (a relatively closed system) has also been proposed to investigate the effect on benthic biology.
After all, the sponsors will want a return for their money. These include British Coal, the Dutch government, the US Electric Power Research Institute and Department of Energy, Statoil, Exxon, Norsk Hydro, the Japanese Electric Power Research Institute, Tokyo Electric Power Company, Mitsubishi, and the Japanese Ministry of International Trade and Industry through NEDO and RITE (more later).
Although the ocean is a much bigger sink, some CO2 might be stored more easily and reliably (?) underground, in aquifers or depleted oil and gas wells. Indeed, such projects are already underway, both in Texas and below the North Sea from a Norwegian platform.
This CO2 currently being pumped back underground was not captured from power station flue gas: without carbon emission taxes or quotas this process is still too expensive for large-scale operation. It comes from under the rocks in the first place, mixed with the oil and gas deposits. Gas from the Sleipner Vest gas field off Norway contains 9.5% CO2, most of which has to be separated from the methane before it can be sold. The recent introduction of a carbon tax (180$/t C) in Norway encouraged Statoil to set up an installation to pump the CO2 (about one million tonnes a year) into a sandstone aquifer 1000m under the platform (see IPCC 1996 (b) and European Chemical News 1996). This is seen as a pilot project, perhaps leading eventually to the burial of up to 1/3 of all Europe's CO2 emissions. The paper by Haugen and Eider (1996) outlines the large-scale European proposals, whilst Pearce J.M. et al (1996) consider the lessons which can be learnt from the Texan "enhanced oil recovery" schemes. In such schemes the CO2 is pumped into an oil well such that it's pressure forces out more oil, preferably without the CO2 and oil becoming mixed together, though this is not always straightforward.
To bury 1/3 of Europe's CO2 emissions clearly requires much more than separation of the CO2 initially mixed with natural gas. Yet to separate CO2 from the flue gases of conventional power stations is very expensive and inefficient. Statoil envisages instead a "hydrogen" economy whereby the fuel is converted into CO2 and H2 rather than being oxidised completely in combustion (Kaarstad 1995). The hydrogen (note it's highly explosive!) would be used to power transport, whilst the CO2 could be buried.
Perhaps the greatest danger with these schemes is that the pressurised CO2 would not stay in the aquifers under the rocks. If CO2 stored for several decades suddenly reemerged as a sudden pulse to the atmosphere, the resulting sudden greenhouse warming could be catastrophic. On the other hand, perhaps the rocks are slightly more secure than the deep ocean, for which the same applies?
Liquefying the CO2 and pumping it down also requires a lot of energy so the process is once again inefficient, requiring considerably more CO2 to be produced in the first place, as above for ocean storage.
Another concern is that the CO2 could contaminate groundwater in nearby aquifers, making it acidic and unsuitable for many purposes.
Even if these concerns could be met, it is unlikely that enough suitable storage locations are available to remove a large fraction of world CO2 emissions. However, there is now a very wide range of figures describing the available capacity, depending upon how secure you want the CO2 to be. Some such figures are given in an IEA report (1996b page 18), and are of the order of 200Gt Carbon, compared to 750Gt in today's atmosphere. Note that not much of this capacity will be conveniently situated near the sources of the CO2. The largest site, for instance, may be below Indonesia.
One amusing idea, is to store the CO2 on site as giant insulated balls of dry ice. W Seifritz from Stuttgart has been looking into this (Seifritz 1993): he reckons 400m diameter spheres would be the easiest to keep cool. One such sphere would store enough for 6.4 GigaWatt-years of electricity production, although about 25% of that energy would have to be expended on freezing the CO2 in the first place. These giant golf balls would be designed to leak slowly, rather than being kept cold for ever. That way, Seifritz argues, we can delay the release of CO2 to the atmosphere, to emerge gradually over 800 years, and slowly find its own way into the ocean. By this time he expects the fossil fuel will have run out and we will have had to find more renewable sources of energy anyway. Will people in 800 years time thank him for this kind consideration?!
Rather than maintaining giant golf balls, Honjou and San (1995) propose shipping the CO2 to Antarctica in tankers, and then storing it within the ice sheet. They suggest that by storing the CO2 in certain locations in midwinter, it should be possible to get it to -78C without extra cooling. It would then be insulated in caves in the ice. This is clearly a ludicrous proposition, for the stored CO2 would be a certain time-bomb if global warming did begin to melt, or even warm, the antarctic ice sheet...
Dry ice has also been proposed as an alternative method of deep ocean disposal. Murray et al (1996) suggest that "torpedos" of dry ice (heavier than water) could be dropped from the sea surface and would penetrate the sediment far enough that most of the CO2 would react with porewater and be trapped as a solid, thus minimising the impact on the ocean water itself.
The most seriously considered idea, for on-site treatment of waste CO2, brings us back to the algae again, but this time they would be in vast artificial lakes, covering tens of square kilometres for a medium-sized power station. It's really a form of solar power, which is why you need a large surface area, and uses photosynthesis to convert the CO2 back into organic carbon. This might eventually be recycled as a fuel, chemical feedstock, or even food. They would be very strange algae, thriving on warm CO2-rich stack gases bubbling through the acidic water. Various attempts are being made to culture and genetically engineer algae specifically for this purpose. They also need to be tolerant of sulphate, nitate and other pollution from the fossil fuel combustion. It is reckoned that such frothing pea-soup reservoirs, would be four time more efficient than a tropical rainforest, at capturing solar energy. Maybe, but I know which I'd prefer to have outside my door!
There are many papers on this topic in the IEA conference proceedings (e.g. Brown 1996). Many of these are from projects sponsored by RITE.
This proposal is not directly concerned with global warming, more with damage from the increased UV flux passing through holes in the ozone layer. On the other hand, stratospheric ozone destruction is intimately linked to climate change, both because ozone is a greenhouse gas, and because surface warming results in stratospheric cooling and therefore more polar stratospheric clouds which provide the surface for ozone-destroying chemistry.
The destruction of ozone is catalysed by free radicals of chlorine or nitrogen oxides, derived mainly from CFCs or aircraft exhaust respectively The suggestion was (see Baum 1994), to add ethane or propane to the stratosphere to soak up the chlorine radicals, forming hydrochloric acid. About 50,000 tonnes would be needed in the Antarctic stratosphere each spring. However, to predict exactly what will happen, you have to solve simultaneously about 150 equations describing chemical reactions. Some simplifications have to be made, yet it isn't intuitive, which reactions will matter. Ralph Cicerone, who came up with this idea, found later that introducing a couple of new reactions, previously thought unimportant, changed the balance substantially. Now he is not so enthusiastic about the proposal. Perhaps we should be relieved!
Despite the discovery this summer of what are claimed to be fossil bacteria from a Martian meteorite, it is generally accepted that the suface of Mars today is not hospitable. James Lovelock first noted that the chemistry of Mars' atmosphere, unlike our own, was in chemical equilibrium, and thus told his colleagues in NASA that the planet must be dead before any probe was sent there (the story is told in "The Ages of Gaia", Lovelock 1988). Lovelock went on to propose suggestions for bringing Mars to life, by first creating CFCs using energy from nuclear reactors, and by the resultant greenhouse effect melting the icecaps which contain water and frozen CO2. More subtle manipulation would follow, and eventually seeding by algae and bacteria.
Lovelock did not expect that his proposal would be taken seriously, but many academics were inspired to develop it further, and even to extend the idea to other planets. Martyn Fogg's book on "Terraforming" (Fogg 1994) spells out the various proposals in meticulous detail, for example explaining equations describing the physics of parasols in space or even of shifting planet's orbits. There is also a substantive chapter on engineering the climate on earth. Fogg also notes various ethical concerns about terraforming, but these are somewhat lost in the overall mood of technological optimism.
Whether or not we feel we have the right to take over another planet, we would almost certainly make blunders. Consider, for instance, the escape of hydrogen. Mars' gravity is less than Earth's and its atmosphere thin and with little oxygen. Sunlight can split water molecules, and in such conditions the light hydrogen could easily be lost to space. After melting the oceans, we could then lose them forever. Or what if the nuclear explosions made the planet too radioactive for any advanced life to survive? Or if there still survives the remains of life from long ago, which we unwittingly destroy?
In any case, it's a long way off yet, and most people would say, that we have far more important things to worry about down here on Earth.
The funders of research are usually indicated either at the beginning or end of a paper. Before reading such small print I had the impression that climate engineering was primarily the domain of a few eccentric academics. It is no longer so. Such professors may receive most publicity, but I was concerned to find most climate engineering research is now funded by industry, particularly those with a vested interest in continued high consumption of fossil fuels. In addition to direct sponsorship, there are many projects funded by government supported institutes set up for industrial research and development.
The table below is given only for purposes of illustration: there are many more sponsors involved and each is likely to back a range of proposals.
| Sponsor | Example proposal |
|---|---|
| Statoil | CO2 storage in aquifers |
| Norsk Hydro | Ocean Fertilisation, CO2 disposal |
| Exxon | Liming the Ocean |
| British Coal | CO2 capture and disposal |
| Mitsubishi | Ocean Fertilisation to grow fish |
| Hitachi | CO2 fixation (through RITE) |
| Japan Gas Association | Greening Deserts |
| Japan Central Research Institute of Electric Power Industry | CO2 capture, ocean fertilisation |
| American Gas Association | Seaweed |
| RWE and DMT (Germany) | Sponsors of IEA |
| International Energy Agency | Overviews of many projects, see below |
| US Electric Power Research Institute | Many projects, see below |
| Research Institute for Innovative Technology for the Earth | Many projects, see below |
I have not included here the many private engineering consultancies which have been hired to investigate proposals. Sometimes it is clear that they have little experience in global biogeochemistry, and make blatant errors or just discover what is already textbook knowledge to academics. However, it seems that certain governments trust such consultancies more than their own universities or research labs...
I also observed that most of the independent academics who submit papers describing direct climate engineering applications come from departments or institutes specialising not in environmental or earth sciences, ecology, meteorology or oceanography, but rather in chemical engineering, biotechnology, or industrial technology.
In 1991 the International Energy Agency set up a Greenhouse Gas Research and Development Programme, for the purpose of collating and directing research into technical responses to climate change. The programme has its headquarters in Cheltenham, UK, on a site provided by British Coal which also has research labs there dedicated to CO2 disposal. The IEA programme is funded mostly by governments, although these are encouraged to invite participation from industries within their country, and there are three direct industrial sponsors: RWT and DMT of Germany, and EPRI (below). The programme's income in 1995 was £721,000. This funds little detailed research directly, acting more to bring people together and summarise their results, most notably by setting up a series of conferences on CO2 capture and disposal (the proceedings are in published in various issues of Energy Conversion and Management). There is also a series of workshops underway on ocean storage of CO2, expected to lead soon to the design of a small scale experiment.
Recently, it was decided to broaden the remit to include other greenhouse gases, for instance reducing methane emissions from natural gas flaring and leakage: generally this is a cheaper way to prevent the same greenhouse warming. Many publications are availiable from the programme, whose address and web page are given with the references
RITE was set up in 1990 by the Japanese Ministry for International Trade and Industry (MITI), through the New Energy Development Organisation (NEDO). It is run from it's own laboratory in Kyoto's Kansai Science City, and had 486 employees in 1995. There are three headquarters labs, for global systems analysis, for plant physiology, microbiology and genetics, and for chemical CO2 fixation and catalysis. Additionally RITE supports international joint projects for which it publicly invites proposals. The total budget in 1995 was 60m US$, and 500m US$ was earmarked for the first 10-year projects. It should be noted that much of this is spent on developing environmentally friendly technology not linked directly to climate change. Nevertheless, 140m US$ was earmarked for "Biological CO2 fixation and utilization", and 70m US$ for "CO2 fixation in desert area using biological function".
Looking through the research projects, it seems that many of them are at the very detailed process level, far removed from the global environment. These are intended to develop commercial technological products for use at a local scale, not yet to manipulate the world's oceans or atmosphere. Some seem very sensible, for example reducing methane emissions from rice paddy fields, preventing acid rain in developing countries, or bio-recycling of waste water. Nevertheless the emphasis is very much on finding a techical fix to every problem, including climate change. "RITE recognise the urgency of accelerating progress in global environmental research, which is still largely at the basic or 'idea' level ." (my emphasis). It seems to imply that climate engineering is a necessary and inevitable successor to basic climate research. I am most concerned at RITE's focus on biotechnology, a fundamental research area being "improvement of catalytic functions of microbial CO2-fixing enzymes", perhaps initially for capture of CO2 from flue gases or to develop plants to green the deserts, but surely leading eventually to algae in the open ocean.
A colleague of mine suggested applying for RITE sponsorship of the next Iron Fertilisation experiment in the Southern Ocean, but the professors decided to avoid this, not wishing to promote the "technofix" implications of the experiment, and also concerned about the strings which might be attached.
For RITE does not intend to get nothing back for all this money. The grant application form states "Research findings may be presented at academic conferences etc. following the conditions prescribed by and upon the approval of RITE and NEDO, the commissioner of the programme. Intellectual property, such as inventions developed through the entrusted research, will be jointly owned by NEDO and the inventor." In other words, this technology "for the Earth" will be patented with the intention of making money for the organisation. RITE filed 86 patents in 1994.
Clearly the Japanese government (MITI) thinks there will be a large market for such technology. Moreover, they are keen to demonstrate it to the world. Japan has volunteered to host the 3rd Conference of the Parties of the UN Climate Convention, in Kyoto in December 1997, just next door to the headquarters of RITE.
An American summing up an IEA conference said "I assume the Japanese incentive, besides self interest and preservation, is also dedicated to the noble objective of world social order". Gaining a competetive advantage and intellectual property rights seem a more likely explanation.
Information about RITE and reports of its research projects can be obtained from the address given with the references.
EPRI was founded in 1973, and now has an annual research budget of £500m, funded by power and fossil fuel companies from all corners of the world. Most of this is spent on technology for generating and delivering electricity, however EPRI has also been interested in climate engineering proposals for a long time. For instance, they supported much of the research on giant seaweed farms, and of course CO2 capture and disposal. In 1991, EPRI hosted a conference on "geoengineering" jointly with the Scripps Institute of Oceanography. The review by Alpert (1992)of biospheric CO2 sinks, with costs, came from EPRI, as did Glenn (1992)'s paper on greening the deserts.
Perhaps this long experience has shown EPRI that climate engineering alone is unlikely to save the fossil fuel industry from curbs on CO2 emissions. In any case, the focus seems to have shifted, towards creating cost benefit analyses of climate change, which can be used to show that it isn't economic (from the US$ point of view) to prevent the climate change in the first place. EPRI will spend 8m US$ in 1997 on a new integrated cost-benefit analysis. It is also worth noting that EPRI was responsible for the controversial paper of Wigley, Richels and Edmonds (1996) advocating delaying a reduction in CO2 emissions. The use of such analyses by the industry lobby in the climate negotiations is discussed later.
EPRI also employs many climate modellers to investigate uncertainties in global climate models. Whilst this work may be useful, it is explicit that the principal aim is not to save the world from global warming, but to avoid unnecessary regulatory burdens on the fossil fuel industry.
EPRI has a comprehensive web site, the address is given with the references.