The European: Mr. Caldeira, your name is closely related to geoengineering and the idea to put sulfur particles into the stratosphere that would then shield solar radiation. Could you give our readers a little background on this? How did this idea come about?
Caldeira: Over the last century, people have come to understand that greenhouse gas emissions cause the planet to warm up. Since the 1960s at least people have suggested that the warming effect of greenhouse gases could be at least partially counteracted by reflecting additional sunlight to space. In the 1970s Mikhail Budyko, a Russian climatologist, proposed putting sulfate aerosols in the stratosphere which is one of the things that volcanoes do. In 1991, Mount Pinatubo in the Philippines put enormous amounts of sulfur into the stratosphere and the next year the earth cooled by about half a degree Celsius. The material falls out of the stratosphere within the time scale of a year or so but had the material been maintained in the stratosphere, it would likely have been enough to offset at least on a global mean basis all of the warming expected for this century. My colleagues and I have evaluated a number of geoengineering approaches. Concerning the approach of putting sulfur particles into the stratosphere, the amounts of material needed are not that much. A single firehose if you kept it continuously spraying would be more than enough to put enough material into the stratosphere to offset all of the century’s emissions. And it might be relatively cheap.
The European: How much would it cost?
Caldeira: Well, nobody has done it and until then nobody really knows. But it is likely that the indirect costs would be more than the direct costs. I think what more people are worried about is when you do some of these things that some people get damaged. In the 1960s, there was a program in the US to look at steering hurricanes and it eventually was abandoned. I think it came out of the concern that if a hurricane was going to hit a major city and it was deflected to hit some rural area that people in this rural might potentially be killed; that people could be damaged that would not have been damaged otherwise. I think that these legal liability issues make most people shy away from thinking they could actually do large scale experiments.
The European: Nevertheless, the idea of cooling the planet by putting sulfur into the stratosphere sounds very tempting and like a solution to all our problems.
Caldeira: I think it is all about risk management. Do we really trust the models and the projections of how these things would work? There are at least two dimensions of things you need to be concerned about. One is that models, like the computer model simulations we worked with, are simplified representations of reality. It is hard to predict what the unanticipated consequences would be and you can be sure that something unanticipated will happen when you monkey with a system as complex as our planet. And the other dimension is: how do social, political and economic systems react to this? You can imagine a situation where maybe technically the system would work but maybe that leads people to relax about emissions reductions or somehow two countries disagree about what temperature there should be on the planet. You could get all kinds of international conflict.
The European: But unless you try, you cannot manage risk. How much risk do we need to take in order to save the planet?
Caldeira: This is going to be a tough question that we might end up having to deal with. From an environmental point of view, you minimize risk by reducing interference in natural systems. So I think that not putting aerosols in the stratosphere is the least risky option. My basic feeling is that things would have to get pretty bad before you want to deploy a system like this because the potential risk of something going wrong is pretty high. And also politically, whoever decides to deploy such a system would have to take all of the political heat of getting blamed for every bit of bad weather on the planet. The other kind of issue is: who would deploy it? Let’s say crops were failing throughout the world and let’s say a country was threatened with massive famine and starvation and if its leader thought that deploying a system like this would save their population it would be hard to imagine that a politician could resist the pressure to do this. I would say that politicians would have to feel that they are pretty much backed up against the wall and see this as the only way out.
The European: Is there any international law regulating the deployment of such systems? Obviously, they would influence the whole planet…
Caldeira: There is a treaty against using weather systems as a means of conducting war. But there is very little regulation around just modifying climate for the purposes of offsetting greenhouse warming. There are some discussions looking at what kind of governance might be necessary.
The European: So, if I had enough money I could put up such a system and nobody could stop me?
Caldeira: I guess that somebody could stop you. The question is: is there a law against it? If you are within the territorial boundaries of a country then you will be subject to whatever the environmental regulations of that particular country are. Some countries might just count is as pollution. In the United States there are environmental regulations against putting sulfur in the atmosphere beyond a certain amount. And in international waters, I think it depends on the flag of the ship you are on. And if this particular country does not have any regulations on that….anyway, I think that if somebody started doing this on a big scale, they would be stopped, regardless of what the legality is.
The European: To come back to the climate situation: how bad is our climate situation?
Caldeira: I have a very high degree of uncertainty in regard to how bad climate change would be for humans. I also study coral reefs and the effects of carbon dioxide on coral reefs. And I think that if we continue on our current path for a few more decades, they will be essentially a thing of the past. The question is how adaptable humans are. And it is difficult to predict how social systems and our social networks respond. We saw with the subprime mortgage crisis a couple of years ago that bad real estate investments in the United States and Ireland and a few other places led to a approximately 5% GDP drop throughout the world. This shows that we are economically linked and that disruption in one place propagates out to the rest of the world. I think that climate change is likely to be at least as big a problem as the subprime mortgage problem. I think that climate change is going to be felt regionally. You are going to have heat waves or drought in certain regions. The question is how much economic disruption that will cause. I don’t know whether our economy is like a house of cards that will then just collapse or whether it is a house of bricks and we don’t really have to worry about those little regional things. I have really no idea.
The European: Does politics react to the research you and your colleagues are doing? Do they approach you and ask you for advice?
Caldeira: First of all, as scientists, we are evaluating these approaches and trying to predict what might happen if they were deployed. We make a pretty clear distinction between research and development. But this distinction between researching something and advocating it is often lost. I get a full range from people thinking it is a mistake that we did not deploy one of these systems last year and that we better do something desperately fast to others thinking that I am working for oil companies trying to figure out a way to keep burning more oil and coal. Often the level of discourse is not very civilized. In the United States the political discourse has become very polarized and uncivil. There is a sort of fundamental lack of respect in how people are talking to each other in political discourse these days around here. As to politics, the policy world is becoming aware of these things. In a way, I am a little surprised in how fast these things have gone from being pure research topics to something that people consider as a policy option. But I think there is a danger of people thinking of those systems as “the one” solution. I think it is entirely likely that if we deploy one of these systems that bad stuff will start happening.
The European: What would bad stuff be?
Caldeira: One thing could be just unpredicted shifts in climate systems. Or maybe there could be impacts on ecosystems. We know that from Mount Pinatubo – the aerosols dropped out of the stratosphere within a year or two. After that in both the Amazon River and the Ganges there was very low river flow and droughts were experienced. I don’t think that the world would come to an end. I guess the more dangerous thing might be the feedbacks –socially, politically or environmentally – that maybe take a few decades to really manifest themselves. If you keep going for many decades and then you turn the system off, you would be hit pretty suddenly with all that warming you have been masking. And then you might just be stuck with it…
The European: Geoengineering really interferes into nature. Some people even say that you are playing God. Do you think that there are borders that science should not cross?
Caldeira: One of the problems is that we have 7 billion people on this planet. If we had 70 million instead, a hundred times fewer people, then we could deal with nature pretty easily. One of the biggest transformations to the planet we have done is removing natural ecosystems and replacing them with agricultural systems. For many centuries we have been transforming this planet into something that is more molded for human use. My own perspective is that the less we do the better off we are likely to be but the problem is that civilization is getting so large both in terms of how much each individual consumes and how many people there are that our drive for consumption is transforming both the land surface and the atmosphere. So then this question of whether it is okay to interfere more to try to alleviate some of the symptoms of past interference is a pretty dangerous road to go down. But I think it is at least possible that things will get bad enough that that trade-off seems attractive.
The European: What would you say should we do to save our planet?
Caldeira: I think the best thing to do is to transform our energy system into one that does not use the atmosphere as a waste dump. We have grown up culturally over thinking of the atmosphere as something infinite. And so people would just put up smoke stacks and use it as a waste dump. I think we just have to move beyond this conceptual framework of thinking that this is okay.
The European: Do we need an emergency for that?
Caldeira: When we were still hunters and gatherers our conception of big temporal scales was worrying about whether we had enough nuts to last the next winter and our conception of big spatial scales was worrying about the village in the next valley, that they would not come over and crush our heads in the middle of the night. And suddenly we find ourselves in a modern world where we have to think about century scale problems and global scale problems without the emotional preparation to deal with that. So we are more or less like kids fouling their play room. I would like to say that suddenly we are coming to our senses and reduce emissions and we won’t need to put those kinds of things in the stratosphere but I don’t see much of this evidence yet.
The European: So we are waiting for the emergency?
Caldeira: I think that there is enough risk that I want these systems developed. But how bad things are really going to get I don’t know. I don’t want to be too callous but if you look at the response of the west when there are wars and famines in Africa – most people more or less just ignore it and life in the west goes on. I don’t know whether climate change is going to be something that will stay confined to poor countries mostly or whether it is going to be something that is going to rock the whole planet. Just being callous and in the view of how politics works, my guess is that if the worst effects stay isolated to poor and marginalized places that Europe and North America won’t deploy this kind of systems and will just of go on with their day. But if these kind of climate events start propagating and damaging the economies of Europe and North America then I think that politicians would be motivated to look at deploying these things.