Podcast: Engineering the climate to tackle climate change

Diagram showing examples of geoengineering

Geoengineering examples

14 September 2011 by Richard Hollingham

This week in the Planet Earth podcast, in a geoengineering special edition, we take a closer look at some of the technologies we may have to resort to using to avert dangerous climate change.

In the face of rising levels of atmospheric carbon dioxide, and a collective failure to cut emissions of the greenhouse gas - despite international agreements - the reality is that we might need an emergency back-up plan to combat CO2's effects on our climate.

Broadly speaking, there are two main approaches to geoengineering: either taking carbon dioxide out of the atmosphere or shielding the planet from the Sun's heat.

While no-one is pinning their hopes on any of the solutions in this so-called plan B, we need to figure out if any of the proposed technologies is even viable.

To find out more, Richard Hollingham meets four geoengineering experts who tell him about two solutions being tested: one called SPICE (Stratospheric Particle Injection from Climate Engineer); the other, iron fertilisation, which encourages phytoplankton blooms to absorb CO2.

To assist those who find text-based content more accessible than audio, a transcript of this recording is available below.

Richard Hollingham: When it comes to tackling climate change, is there a plan B? I'm Richard Hollingham and in this special edition of the Plant Earth podcast I will be examining plans to engineer the climate to combat global warming. From a UK project investigating reducing the amount of sunlight that hits the earth...

Hugh Hunt: What we're really testing is other principles, and one of the key things we're interested in the effect of wind on the balloon and on the pipe or on the tether.

Richard Hollingham: So methods of increasing the amount of carbon dioxide absorbed by the oceans.

Matt Watson: The way it might work is that you might spread large quantities of iron into the ocean in a bioavailable form.

Richard Hollingham: Schemes like this are known as geoengineering and there are many more ideas out there, including giant mirrors in space and systems that remove carbon dioxide from the atmosphere. And I'm with Matt Watson from the University of Bristol who is project leader for SPICE - Stratospheric Particle Injection from Climate Engineer. Now, Matt, your project is designed to test the feasibility of injecting sulfur particles into the stratosphere to reflect sunlight. Is that right?

Matt Watson: Yes, that's exactly correct. So what we're interested in is looking at whether or not we can emulate natural systems to see whether or not we can reduce the amount of sunlight hitting the earth's surface and therefore cooling the plant.

Richard Hollingham: When you say the stratosphere, how far up is that?

Matt Watson: The model suggests that the most efficient place to do it is about 20 kilometres.

Richard Hollingham: Now, you're not actually going to do it, you're looking at the feasibility of it, but what's the theory? What's it based on?

Matt Watson: Well, what we have from Mount Pinatubo in the Philippines was an eruption in 1991 that injected around about 20 million tons of sulfur dioxide into the atmosphere. That converted over time to about 30 million tons of sulphate aerosol, very small, very reflective particles and what that does is bounce the suns rays back out into space reducing the amount of energy reaching the earth's surface.

Richard Hollingham: So how does this compare with other geoengineering ideas out there?

Matt Watson: Yes, so geoengineering is a catch-all term for a suite of possible technological solutions to climate change. And they basically fall into two schools. The first of which is a thing called carbon dioxide removal where you actually physically suck carbon dioxide which scientists know is the mechanism by which the planet is heating up, and there are actually even different ways of doing that, you have these things called artificial trees which capture carbon dioxide, there's also a mechanism called biochar where you effectively bury carbon in the ground, through to the second scheme which is called solar radiation management. And what you're doing here is trying to manage the earth's radiation budget, so control the amount of light either coming in or reflecting off either the stratospheric aerosols at 20 kilometres or stratospheric clouds at, maybe, two or three kilometres or the Earth's surface. So, there's even a discussion about painting roofs white, that actually increases what is known as the planetary albedo, so it still bounces radiation back out into space.

Richard Hollingham: Well to find out more about what SPICE involves I visited Hugh Hunt in the engineering department at the University of Cambridge who's developing the technology.

Hugh Hunt: The SPICE project overall is divided up into three bits. The first bit is about trying to establish what particles we might put up into the stratosphere to cool the planet in some way where we don't want to do that. The second part of the project is to figure out how to get those particles up into the stratosphere safely and economically and the third part of the project is to look at what the effect would be on the climate. The part of the project I'm involved in is the second part which is how to get particles up 20 kilometres into the stratosphere.

Richard Hollingham: And the initial project is just to look at the feasibility of this and this is a one kilometre pipe and this is the kit we've got around us. So what is here?

Hugh Hunt: If we were to think about putting 20/30 kilograms per sec up 20 kilometres into the stratosphere - well we wouldn't do that in one go because the design issues are rather difficult, no one's been able to do that up until now. So, we're starting with something much more manageable which is to put a balloon, a normal blimp sized balloon at one kilometre and take pretty much an ordinary garden hose sized pipe and to use an ordinary garden pressure washer to pump water up to that one kilometre.

Richard Hollingham: Which is what we've got here. We've got an ordinary...

Hugh Hunt: Yeah, so this here is a pressure washer. It's rated at 150 bar.

Richard Hollingham: This is the sort of thing people clean patios or driveways with-

Hugh Hunt: Yeah it is.

Richard Hollingham: You can buy this is any DIY shop.

Hugh Hunt: You do. It's got enough pressure to get the water up to a kilometre and we've got some pretty ordinary hose here. This hose is like your ordinary garden hose, it is fibre reinforced and that means it can withstand high pressure and also withstand tension.

Richard Hollingham: You're just pulling on it there and you can't stretch that.

Hugh Hunt: We've got to be sure that the materials we use are going to be safe.

Richard Hollingham: So you have the pressure washer at the bottom, one kilometre pipe and it's being held aloft by a balloon and I've got a large balloon here.

Hugh Hunt: I've got a balloon, it's just a party balloon, but what it means is I can hold up a picture of what the thing might look like.

Richard Hollingham: So you've got the pressure washer on the ground here, the hose connected to the pressure washer and that piece of hose, which you can't really stretch, going up to the balloon above your head, and we will put pictures of this on the Planet Earth Online Facebook page. If that works what's the next stage?

Hugh Hunt: So the idea is to spray water at a kilometre, really because it's not objectionable. The quantities of water we're talking about is of the order of, maybe, a litre per minute which is one tenth of what a good shower would be. What we're really testing is other principles and one of the key things we're interested in is the effect of wind on the balloon and on the pipe or on the tether. The idea being that if in heavy winds the whole thing falls over then we have to think about how we might design it so that it doesn't fall over.

I think it's just going to look rather dull, it's going to look like a balloon on the end of a string and you might if you get your binoculars out see the stream of water coming up. One of the things we're trying to get across is that that is probably what it would look like were we to put something at 20 kilometres with a bigger pipe and a bigger balloon. Well, scaled up it would probably look exactly the same. And were we to think about putting some up at 20 kilometres we would only need, maybe, ten or 20 of these around the planet to affect the kind of global cooling that we might be looking for.

Richard Hollingham: And with the 20 kilometre project the water isn't the thing you're ultimately going to use or might use when you're talking about geoengineering, you prefer the phrase climate engineering.

Hugh Hunt: Yes I do prefer the phrase climate engineering because in a way it doesn't matter whether the climate changes because of manmade interference or otherwise. If we find that the climate is getting warmer then we might like to in someway modify the climate. Climate engineering sounds like we understand what we mean. I also think it's important to distinguish between carbon sequestration at source which is taking carbon out of the chimney stacks at power stations and then putting it straight into the ground. That really is dealing with the manmade source of carbon dioxide. The nice thing about the term climate engineering is that it is clear that we are dealing with climate as it is or as it may be than trying to change it in some way.

Richard Hollingham: Hugh Hunt in his Cambridge laboratory. And as I mentioned you can see some pictures of Hugh with his balloon and pressure washer, as well as a short video on our Facebook page. To find it search for Plant Earth Online. Now, Matt, this all sounds relatively straight forward. Are there any dangers with the SPICE experiment itself? Let's talk first of all about this one kilometre pipe.

Matt Watson: Ok, well the SPICE project itself as you've correctly highlighted is a feasibility study. 90% of it is going to be conducted wither on a computer or in the lab so, for example, we're going to try and characterise the optical properties of different particles, their chemical impacts on the stratosphere, again in the lab, and we're also going to do a lot of modelling. The thing that seems to have caught most people's imagination is the fact that we're actually going to get out and try this delivery system of one pipe and balloon that Hugh's been talking about and there are risk associated with that, for example, we have to close air space above it and we have to make sure that we have strategies in place to make sure that, for example, if the pipe snapped we can retrieve the balloon carefully and we can bring it down in a controlled manner etc. As for the environmental impact we're only pumping water and we've actually gone to great lengths to make sure even that doesn't have an environmental signature. We're very mindful of the fact that there are arguments against geoengineering per se, but actually this particular experiment, I think, is exceptionally safe.

Richard Hollingham: What about if it was then developed, not necessarily by you but to 20 kilometres and firstly put water through, then start putting sulfur particles through. What are the dangers of that?

Matt Watson: Well, ok, so within an increase in scale comes an increase in complexity. The engineering challenges to put a balloon and pipe at 20 kilometres is actually much more significant, at one kilometre you have to pass through very, very turbulent parts of the atmosphere that are moving at great speed, possibly in different directions for not much change in height. Actually, I don't think water is particularly benign in the stratosphere because there's not much water up there, so I'm not sure you would want to pump water in the stratosphere. We would actually have to think about what one might pump up there. If you then got to something that was climatologically active there are a huge range of possible side effects, all of which need effecting how do the particles impact ozone, how do they change rainfall patterns, what do they do the radiation budget and all of these things are things that SPICE is going to begin to approach.

Richard Hollingham: Why do something so complicated? Why invest the money in this? Why not plant more trees or pain the roofs of houses white? They are an awful lot simpler and we know they will work.

Matt Watson: Well I guess I will have to call you on that last one; I'm not convinced they will work. The critical thing about geoengineering technology is that none of them should get a free ride. There's been a lot of stuff written in the press recently about how some stuff is safe and some stuff isn't. I'm afraid that's utterly pre-emptive. We have no idea what stuff is safe and what stuff isn't. White roofs, for example, looks pretty safe but it's not clear that it would have the desired effect. Planting trees, actually there are huge environmental issues with planting trees. What do you do about biodiversity, what do you do about changing the earth's reflectivity and the same goes for cloud whitening and for stratospheric aerosols. All of this stuff needs to be thought of exceptionally carefully before we do anything.

Richard Hollingham: Well one of the most controversial ideas for engineering our climate is to increase the amount of carbon dioxide absorbed by the seas. Various ocean fertilisation schemes have been studied by scientists at the National Oceanography Centre in Southampton, where with the wind howling outside I spoke to Richard Sanders and Richard Lampitt.

Richard Lampitt: Relation fertilisation in its simplest sense is just the deliberate introduction of nutrients of various sorts into the ocean in order to make them produce more. These nutrients are either what we call macronutrients, which are nitrate, phosphate and silicate or the might be micronutrients needing very quantities such as iron.

Richard Hollingham: Richard Sanders, is this a natural process that goes on anyway.

Richard Sanders: There are some places in the world's oceans where we see that these macronutrients that Richard Lampitt has just described are present in vast access and in those environments we feel that occurs because these micronutrients aren't there in sufficient quantities for growth to occur. And in those regions, principally the southern ocean, but other places, there are some small oases of life associated with subantarctic islands, polar islands where natural processes are eroding volcanic rocks and bringing to the sea surface these micronutrients, iron in particular and stimulating productivity. So, yes, this iron fertilisation is a natural phenomenon that occurs in many places in the oceans.

Richard Hollingham: And the oceans have a major role anyway, don't they, in storing carbon?

Richard Sanders: That's right. The totality of the processes that occur in the upper ocean biologically that sequester carbon, we refer to that as the biological carbon pump, and that's a hugely important process going on in the background performing a really valuable service for humanity and for all other animals and plants on the planet. It's storing massive quantities of carbon dioxide biologically in the ocean's interior and if it didn't exist or if it changed really our world would be a different place to the one we see today.

Richard Hollingham: So, Richard Lampert, how would this work?

Richard Lampitt: So the way it might work is that you might spread large quantities of iron into the ocean in a bio available form. So that is you've got a lot of research to do this to make sure that the iron is available for the microscopic plants, the phytoplankton for them to take it up.

Richard Hollingham: When you say a large amount of iron, how much?

Richard Lampitt: Well there is actually rather quite a lot of disagreement about how much iron is required, but one does need to bear in mind that the volcanoes and rivers and, as Richard Sanders was saying, the islands themselves produce absolutely vast quantities. So there is an enormous natural cycle of iron in the globe and we're talking about much, much smaller quantities instead of produced by volcanic activity, for instance.

Richard Hollingham: So what are the side effects of doing this if it was done on a large scale?

Richard Lampitt: One of the key issues in any of the research that we are wanting to carry out is that the first thing will it work, will it actually remove the carbon dioxide from the atmosphere and the second is what are the potential side effects and how likely is it that they are going to take place. And some of these are quite significant and serious and they may actually make the whole process not work. For instance, one could release some gases at the same time such as nitrous oxide which have a very high greenhouse warming potential. So you fertilise an area of ocean, you reduce some carbon dioxide, remove carbon dioxide but actually want you do is release the nitrous oxide. So, those sort of side effects are ones which are absolutely a central part to any research that we carry out. There are a variety of others and one of the key issues is to establish what are these side effects, and how likely is it that they will occur if this was carried out on a large scale.

Richard Sanders: One of the most important side effects perhaps might be alterations to the marine ecosystem. By its very nature you add iron to the surface of the ocean and stimulate plankton growth, we're growing different communities of organisms. It may only be that they're larger but they're likely going to be different as well. That increase in surface biomass or that changed surface biomass can propagate down through the water column and up the food chain and we may have different communities of grazers or fish communities or benthic organisms living. Now, at some level it becomes a value judgement about whether or not this is an important thing, but before we can start having those discussions about whether or not this is important we need to actually have some hard evidence about what the likely consequences for marine food webs and marine ecology are going to be.

Richard Hollingham: Richard Sanders and Richard Lampitt at the National Oceanography Centre. So, what do people think of these ideas. Well the natural Environment Research Council recently carried out a public dialogue investigating attitudes to geoengineering. The findings suggested that participants felt it might one day be necessary but they found some technologies more acceptable than others. Richard Lampitt was an advisor for the study.

Richard Lampitt: The thinking is that we really need to bring people, the public, the general public along with us. We need to have their support and we need to have them believe that what the scientific community are trying to do is not some devilish plan to provide resources for our own research, but actually to help the planet, to help to make sensible decisions in the future. So to bring people along with us is really helpful so that they understand and can support what we're doing.

Richard Hollingham: When you look though at the summary of the results, the level of support for ocean based methods such as iron fertilisation was low. There was also a majority opposed to the idea of injecting sulphate particles high up in the stratosphere, two projects we've been talking about and the most ambitious does that surprise you?

Richard Lampitt: No, it doesn't really surprise me. I think people are nervous, and rightly so, but people are nervous about some of these schemes that have been proposed and I think what we've got to do is to get the evidence together to do the research so that we can make sensible decisions in the future and to engage, to talk with people, to ensure that they understand what we're doing and so that we can also take advantage of their insights. When some of these issues, the ethical ones for instance, are not ones which the scientific community is well geared up to engage in but there are significant ethical issues here. So we need to engage in both directions.

Richard Hollingham: Well, Matt Watson from the University of Bristol is still with me. Hugh referred to all this, this geoengineering earlier as climate engineering which in a way sounds scarier.

Matt Watson: Yes, well, one of the reasons one might want to avoid geoengineering is that there is already a word geoengineering which means something quite different to geoengineers of that flavour. Climate engineering I think is a perfectly acceptable badge because this stuff is scary, it should be scary if we're in the position...we're so far down the road in terms of climate change that we're having to think about these things, people should be concerned about it. Personally I'm not an advocate of deployment of geoengineering but I feel passionate that we have to think about these things before we get to the point where we might have to deploy them without really researching them properly. I think the future is uncertain enough to justify undertaking the research but that shouldn't be a mandate for deployment.

Richard Hollingham: Many people and I think this came out in the study, and certainly many environmentalists don't even like the idea of investigating these proposals.

Matt Watson: Yes, and maybe they have a point. I think a very sagely colleague of mine told me last week that essentially how you feel about geoengineering is broadly tied to how you feel about the success of carbon dioxide reduction. Make no mistake about it the right thing to do is to reduce carbon dioxide emissions, that's absolutely what we should be doing and no geoengineering project should be allowed to undermine that effort but if you believe, as most climate scientists do, that we are approaching or even past the point of no return these things have to remain on the table until they're shown to be too dangerous or too risky to pursue further.

Richard Hollingham: Isn't there a danger here that by you developing the technology someone else will simply do it?

Matt Watson: Yes, I think that's a perfectly valid question actually. So we were challenged by the research councils who are paying for this research to actually go away and think about that problem. They asked us that very question but they also asked us what other applications could this technology be used for both positive and negative, and so we've gone away and we've thought about that. There's not a clear answer actually to be completely honest. I think is somebody is going to deploy without a mandate, particularly in terms of sulphate aerosol or any other aerosol that might reflect light, I think they would do it whether or not we'd done the research or not and actually because we're trying to be objective you could argue that we don't know whether or not this technology is going to work or not and therefore if we find out it doesn't work that's less likely to make people who are reckless deploy. So, I think the other option is just to stick your head in the sand and hope that nothing bad happens and that's less palatable.

Richard Hollingham: Matt Watson, thank you very much. You can share your opinions on our Facebook page and for more information and features on geoengineering, or if you prefer climate engineering, as well as technologies, just carbon capture and storage do visit Planet Earth online. I'm Richard Hollingham, thanks for listening.