Transcript

Intro

Robert Wiblin: Hi listeners, this is the 80,000 Hours Podcast, where each week we have an unusually in-depth conversation about one of the world’s most pressing problems and how you can use your career to solve it. I’m Rob Wiblin, Director of Research at 80,000 Hours.

Today I interview a fascinating and unconventional inventor, who is likely to be both entertaining and informative for most subscribers.

Before that though, this is the show’s fiftieth episode and it’s going to come out around New Year, so I thought it’s a good moment to take a minute to reflect on the year that’s past and where we’re going.

To be honest with you it’s just been an incredible privilege to be able to run this show. Thanks to our donors, Keiran and I are spared the commercial pressures that would otherwise drive us to produce content that’s superficial, or dumbed-down, or misleading, just to get clicks. Instead we just try to produce episodes that we find sincerely interesting and informative ourselves.

As a result, and thanks to people like you recommending the show to their friends, we’ve progressively been able to build up an incredibly highbrow audience. Many of you I meet or get messages from, and the feedback shows both how much you enjoy listening, and the very close attention many of you are paying to each of these interviews.

We’ve produced 95 hours of the show so far, and featured 36 guests in 2018.

I can see from our analytics which episodes you’re most excited to download, and which ones you stick with listening. Whenever Keiran and I worry an interview might have gone too deep into a topic, or be too complicated to hold people’s attention, we’ve found the exact reverse to be the case.

If there’s a level of intellectual challenge that’s too much for you all, we haven’t hit it yet, so I hope next year we can continue to have ever more sophisticated conversations about these topics we all care about, and now with the knowledge that we’ve covered a lot of the basics already.

The second reason we appreciate all of you listeners is your sincere commitment to improving the world. Thanks to our annual impact survey, I’ve been able to read about how many of you are considering totally changing your career plans, or have already done so, on the basis of what you’ve learned listening to this show. It’s an honor to be in the position to help some of the world’s smartest and most caring people have more social impact with their lives.

It’s also a relief to know that this show is not only enjoyable to people, but is making a real contribution to solving the sometimes horrifying problems we talk about here.

I hope that you’ll stick with us into 2019, and that Keiran and I will continue to find guests that can entertain, inform and inspire you.

Alright, with that out of the way, I bring you the eclectic engineer, Dr Dave Denkenberger.

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Robert Wiblin: Today I’m speaking with Dr. David Denkenberger. He did his undergraduate in engineering science from Penn State before doing a master’s at Princeton in mechanical and aerospace engineering and a PhD at the University of Colorado Boulder in their building systems program. He’s now an assistant professor at the University of Alaska Fairbanks in mechanical engineering. He co-founded and directs the Alliance to Feed the Earth in Disasters, otherwise known as ALLFED, and donates half of his income to it. He’s authored or coauthored 94 publications with over 1,300 citations, including the book, Feeding Everyone No Matter What, Managing Food Security After a Global Catastrophe. His food security work has been widely covered by the media, including in Science, Discovery Channel Online and Gizmodo, but most importantly of all, he’s a regular listener to the 80,000 Hours podcast. Thanks for coming on the show, Dave.

Dave Denkenberger: Hi, Rob. Thanks for having me.

ALLFED

Robert Wiblin: We plan to talk about the case for and against working on your approach to feeding the world in the case of a major catastrophe. And I know that at the top of the show, you wanted to clarify and disclaim that all of the things you say here are just your opinion, and not the official views of ALLFED, or the Global Catastrophic Risk Institute, or any other group that you’ve been working with. First though, just describe for listeners what ALLFED actually does and why you think it’s such important work.

Dave Denkenberger: The background is that there are a number of catastrophes that could disrupt agriculture globally, and the most extreme ones could basically collapse agriculture. These are the ones that could block the sun, so they include a large asteroid that caused the extinction of the dinosaurs, a super volcanic eruption like many people think almost caused the extinction of humans about 70,000 years ago, and a nuclear winter and this would be caused by what’s called full-scale nuclear war involving thousands of nuclear weapons between the US and Russia. This causes burning of cities and smoke goes into the atmosphere and it can remain there for a decade.

Dave Denkenberger: In these scenarios, since almost all of our food comes from plants that need the sun to grow, it’s generally assumed that most people would die. We only have a few months of food storage. People who have looked at this problem before have suggested, well, let’s just store up more food, and that would be technically possible, but as a way of visualizing it, you can think of a 160-liter or a 40-gallon oil drum. If that’s full of dry food, that can feed a person for a year, but to have enough food to feed seven billion people for five years, you would need to pile those drums from the earth to the moon and back 40 times.

Dave Denkenberger: As you can imagine, that would be very expensive, many trillions of dollars, and you can’t do it really fast. It would take a while to store up that food, but you would want to do it as fast as practical so that you’re ready to weather disasters that could happen at any time. If you store it up fast, then you inflate the food price and then millions of people more would die of malnutrition than already occurs.

Dave Denkenberger: I wasn’t satisfied with that not very good solution. I was thinking, well, is there another way of producing food when the sun is blocked? In 2011, I was reading this paper called Fungi and Sustainability, and the premise was that after the dinosaur killing asteroid, there would not have been sunlight and there were lots of dead trees and so mushrooms could grow really well. But its conclusion was that maybe when humans go extinct, the world will be ruled by mushrooms again. I thought, why don’t we just eat the mushrooms and not go extinct? I branched out from mushrooms, thinking of all the ways that we could convert either dead vegetation into food or even fossil fuels into food.

Robert Wiblin: Is anyone else working on this? Has anyone else had this idea? It seems obvious in retrospect.

Dave Denkenberger: Well, interestingly, Carl Shulman at Future of Humanity Institute did a blog post as soon after I thought of these ideas, before I published the first paper and the book. Yeah, he was thinking that route. Other than that, it seems like it really hasn’t been thought about.

Robert Wiblin: Yeah. I just love this idea. Whether it’s practical or not, I’m just so fond of it because you’ve taken a problem that most people have just thought of as inevitable and basically accepted that if there’s a nuclear war, then maybe billions of people would die of starvation. I guess bringing an engineering mindset that you’ve been trained in, you’ve just seen this as a practical challenge to overcome and pretty quickly come up with a bunch of seemingly plausible ways that we could actually just feed everyone even if the sun were completely blocked out, which is amazing.

Dave Denkenberger: Yeah, that’s right. I do think that that engineering mindset is really important in that certainly, it’s important to know what the problems are and ideally prevent them, but realistically, they still could happen. I think that there should be more work done on this resilience end of the spectrum.

Most likely causes of a global food shortage/ likelihood

Robert Wiblin: You’ve written some blog posts and, in fact, I think published a paper now trying to estimate the cost effectiveness of working on this problem. I think you think that if your cost effectiveness is correct, you would be able to save lives by working on feeding people in these catastrophes for between $0.20 and $400 per life, which would be pretty extraordinarily effective if it were true. I suspect that that’s probably a bit too overoptimistic, although the project is probably worth doing anyway, even if it’s not quite as effective as that. I guess we’ll discuss the cost effectiveness analysis later and which parts of it might be too optimistic or not optimistic enough perhaps.

Robert Wiblin: First, maybe let’s just dive into thinking about the nature of the problem that you’re solving and the concrete solutions that you’ve come up with for it. Not all listeners I imagine will be convinced that a mass starvation of humanity is a terribly likely risk. Let’s go through, what are the major possible causes of a global food shortage and how likely might they be?

Dave Denkenberger: I mentioned asteroid and super volcano, but as the existential risk community has pointed out, generally the natural catastrophes can’t be that bad because they can’t be happening every century or we would have been doomed long ago, though of course there is the possibility that we’ve been extremely lucky, which people have tried to adjust for. I think still, even adjusting for that, the natural catastrophes are lower probability.

Probability of asteroids/ supervolcanoes as GCRs

Robert Wiblin: Do we have any estimate of the probability of an asteroid or super volcano that would cause a risk to human food supply?

Dave Denkenberger: Yeah. If you’re talking about blocking the sun then it really is around one in I think 10 million years or 100 million years for an asteroid, and the volcano is more likely, more like one in 100,000 or a million years.

Robert Wiblin: How robust are those estimates? Because I know we’ve had a couple of volcanoes erupt and changed the biosphere during the million years or so that humanity has been around.

Dave Denkenberger: The latest estimate I saw on the super volcanoes was actually coming up with a larger number that they happen more frequently. Apparently it’s difficult to identify further back than a few million years. There’s some uncertainty there. There’s also uncertainty whether the super volcanic eruption would actually block the sun well enough and long enough to cause mass starvation. It’s the same with nuclear war as well. I’ve written a paper that tries to go through all the uncertainties of, well, how many nuclear weapons would be detonated? Which cities would be hit? What fraction of the combustible material actually burns quickly? How much of that turns into smoke? How much of that smoke makes it into the upper atmosphere? How much do the particles block the sun? How much does it impact agriculture? As you can imagine, there’s uncertainty in all of those steps so it adds up.

Nuclear winter

Robert Wiblin: Yeah. It seems like there’s this question of how bad nuclear winter would be or how likely it is to happen is pretty controversial. Is seems to be people have strong views on both sides. Have you had a chance to really dive into that and form a strong view?

Dave Denkenberger: Well, I did dive into it in the course of writing that paper. Yeah, I think you’re right that there seems to be two camps. One is if there’s full-scale nuclear war, there’s going to be nuclear winter. The other camp is even if there is full-scale nuclear war, there’s not going to be nuclear winter. What I came up with was defining it as global agricultural collapse, which means basically the plants we’re growing now, where they are, are not going to be able to grow. Now we’ll get into whether we might be able to move them or not, but if we just use that definition, then I was getting around 20% chance if full scale nuclear war then you would have global agricultural collapse.

Dave Denkenberger: One reason of mine it was relatively low compared to many analysts was because I considered two scenarios that wouldn’t be quite as bad that might still be described as full-scale nuclear war. One of those is called the industrial strike where you’re trying to disable industry but not trying to kill people. The other one is the counterforce strike where you’re trying to disable the other person’s nuclear weapons. Both of those, you’re not hitting city centers and so the fires would not be as bad.

Robert Wiblin: Do you know what the crux of the debate is about? How is it that people can disagree so much about whether a nuclear winter is likely?

Dave Denkenberger: Well, I think it’s because just there are so many levels of uncertainty. People point out in World War II, one of the cities had a firestorm which is defined as a stationary fire. The entire city burns at once. One of them had a mass fire but didn’t all burn it once. This actually affects how much of the smoke actually goes into the upper atmosphere. That’s one example of uncertainty, but yeah, it’s like the Fermi paradox. When you calculate how many civilizations are in our galaxy, some people have come up with zero and some people have come up with millions. There’s this huge uncertainty. At least in this case, I think the uncertainty can be more like two or three orders of magnitude, and so you can actually say something useful when comparing things.

10% global food production shortfall

Robert Wiblin: What about the more moderate cases where there’s a more normal war or an a regional nuclear war. How much would that interfere with the food supply?

Dave Denkenberger: That’s the class of catastrophes that I’ve been labeling the order of magnitude 10% global food production shortfall. Roughly 3% loss to 30% percent loss. In those scenarios, there are a number of catastrophes that could cause that. As you mentioned, regional nuclear war between India and Pakistan, that might only involve 100 total nuclear weapons and actually much smaller nuclear weapons than the US and Russia have, but still they would be targeted at highly populated cities. Some work on this has estimated something like a 10% or 20% global food production shortfall because of it. You can think of smaller versions of the natural catastrophes like asteroid and super volcano, but again, they’re not too likely.

Dave Denkenberger: Another one that’s received some interest recently is called the coincident extreme weather or multiple breadbasket failure. Here, the scenario is you have droughts or floods on multiple continents at once. There was a UK government study on this that estimated right now, it might be around 1% chance per year, but with the slow climate change, that extreme weather probability, so difference between climate and weather actually gets more likely. They were getting more like 80% chance of this century that something like that would happen.

Robert Wiblin: Wow. Okay.

Superweed

Dave Denkenberger: There are other scenarios as well, like the superweed, which is not the savior of medicinal marijuana users but is instead a weed that out competes crops. If this were a natural thing, we could probably contain it or at least slow it down so that it wouldn’t happen too fast. If we have more time in any of these, it makes it less extreme, but it could be an actual coordinated terrorist attack. There have been some examples of people trying to use … I think that was more a crop disease, but that’s another category, something that would kill crops directly could be a coordinated attack as well.

Robert Wiblin: A superweed sounds a bit outlandish because how would a weed spread all around the world really quickly? It seems like wouldn’t a super pathogen like a virus or bacteria be more able to spread to lots of crops quickly enough that it’s hard to respond?

Dave Denkenberger: Yeah, right. It’s hard to have something that can live in many different climates, yet I’m particularly worried about on the crop disease. If something could target the grass family, then you affect not just grass that feeds a lot of our animals, but also wheat, corn, maze, rice and sugar cane. If you add up all of the human calories, it’s something like two-thirds of our calories comes from the grass family. That really could be catastrophic.

Risk of terrorism involving superweeds

Robert Wiblin: You mentioned in the book that a coordinated terrorist attack using superweeds to destroy a lot of crops across a very large region could be a global threat that not that many people are thinking about. Do you have any evidence that a group might actually plan such an attack or has been considering planning such an attack and do you know if anyone else is working on trying to figure out if this is a real risk and what might be done?

Dave Denkenberger: I have not heard of evidence for this particular type of risk, though a related one is crop diseases. These have been used in biological warfare programs, so there is concern that this could be a potentially larger attack. As for the probabilities, I haven’t seen anything quantitative. I just try to quantify what I can and then, say, “Well, we’re not including all these other things, so really the risk is higher.”

Non-nuclear scenarios

Robert Wiblin: Are there any just nonnuclear wars that you think would create the scenario that are plausible? Who could end up fighting without nuclear weapons? If you had a major war, wouldn’t that massively interfere with trade, and so some countries that are currently importing most of their food could well end up starving pretty fast?

Dave Denkenberger: That’s right. The other scenario that could really interfere with trade is a pandemic. If it were a severe one, then it may be rational to close borders to reduce transmission, but you’re right, importing food countries would be in big trouble or it could be a smaller pandemic and just people overreact. It might not be rational, but they still might close the borders.

Dave Denkenberger: There are a couple of other scenarios that could do … similar to this idea of a 10% global shortfall. One of them is called abrupt climate change. This is like Europe going back into the Ice Age, which some people have talked about because of breakdown of the thermohaline circulation, circulation of the ocean that’s driven by salt. That could be a 10% shortfall.

Dave Denkenberger: Another one that people have talked about and some existential risk researchers are looking at is extreme climate change. It’s global but it still happens slowly, like over a century. That’s a little different than the problems I’m mainly focusing on, but I think some of the ideas could be relevant to that.

Robert Wiblin: Yeah. People worry about us just not having enough food over the next century because population is growing quickly and maybe food technology won’t keep up. Do you think just a food shortfall, even setting aside any disasters, is also a serious risk?

Dave Denkenberger: Well, I think it is important to look at, but generally, if the shortfall happened slowly, we have time to react. For the smaller shortfalls, you could always say, well, technically, we feed more than 10% of the food we produce to animals now. Why don’t we just feed it to people? Well, yes, that’s true, but in reality, people in developed countries like to eat meat, many of them. I think the food price would go so high that you could easily have hundreds of millions of people starve. That’s a particular concern if it happens suddenly. If we have more time, I think there are other things we can do.

Robert Wiblin: Let’s say that you had this 10% shortfall of food scenario. How bad do you think that would be? Some people would die but the rest of us would carry on?

Dave Denkenberger: I wrote a paper about this as well. Again, very large uncertainty on what could happen. If we had a massive outpouring of philanthropic work, we could really limit how many people die. On the other end, we could not just have hundreds of millions of people dying, but then tensions could be very high, and you could imagine nuclear war breaking out, even full-scale nuclear war. I think it has a pretty fat tail that the impacts could be really bad.

Robert Wiblin: Why would people start a nuclear war, just because there wasn’t enough food?

Dave Denkenberger: Well, if people are actually starving, if only a certain number of people are going to survive, you want the people in your country to survive. It is actually in your interest to have conflict. This is the lifeboat ethic, and this is exactly what I want to get away from with having alternate food supplies so that we could say, “Well, actually, if we cooperate, we can feed everyone.” We don’t have to have this lifeboat ethic.

Robert Wiblin: The idea is you would be happy to fight a war that resulted in the deaths of other people because then there’ll be more food left for you.

Dave Denkenberger: Yeah, that’s the logic.

Robert Wiblin: Even though the war presumably would interfere with agriculture to an even greater degree.

Dave Denkenberger: Well, if it’s nuclear, yes, potentially. I’m not saying this is what I would recommend, but there’s always the possibility of irrational decisions.

Robert Wiblin: Just to wrap up, we’ve got asteroids and super volcanoes that would create a serious problem. Most people would probably agree with that, but they’re quite unlikely each year. We’ve gotten nuclear winter, which seems a bunch more likely, although a bit … We don’t know exactly how likely it is because we don’t have a long historical record, and there’s a bit of uncertainty about how severe the weather effects would be, but we certainly can’t rule that out. Then, we’ve got a whole lot of other more moderate scenarios that create 10% or something shortfall in food output, which then could cascade into other problems, including superweeds or super pathogens or sudden weather changes or just bad luck with the weather or more moderate size wars. Altogether you think this adds up to a significant risk to humanity as a whole, something that we should be worried about.

Dave Denkenberger: That’s right.

Robert Wiblin: Who’s working on this problem? I guess there’s some people who would try to store up food and presumably some countries have food stored away. How much is that and what else are people trying to do?

Dave Denkenberger: There are certain countries that have done a lot of food stockpiling. One of them is Switzerland. I believe they have around a one-year food supply. I think China does as well, though it’s not public knowledge so you don’t know exactly. On average, it’s more like a few months across the world. You’ll often hear numbers of we have two months of grain supply. That’s actually about right, but for the wrong reasons. It’s at current grain consumption, but of course we feed half of our grain to animals. If we did have one of these catastrophes, hopefully we would be not feeding as much edible food to animals so that helps, but there’s also the fact that most of our stored food is grain because it’s really easy to store, dried, and half of our calories comes from food that is not grain. We have less food storage that is not grain. It works out to just a few months of food storage, and it depends on what time of the year, but that’s the minimum.

Robert Wiblin: Currently we get, you were saying, about two-thirds of our calories from grains of various kinds.

Dave Denkenberger: Yeah. That is when you count direct consumption and food going into animals.

Robert Wiblin: The other third is fruits and vegetables and fish and things like that.

Dave Denkenberger: Right. There’s debate about whether soybean is a grain or not, but it’s a staple. Yeah, basically fruits, vegetables and other things, nuts.

Robert Wiblin: Nuts, okay. Oils maybe.

Dave Denkenberger: Yeah.

Robert Wiblin: Is there anyone else who’s trying to work on feeding the world in these disaster scenarios using something other than just storage?

Dave Denkenberger: I’m not aware of anyone else.

Robert Wiblin: It’s just you.

Dave Denkenberger: Yeah. Well, ALLFED. Luckily I have a team.

Robert Wiblin: Let’s move on to talking about some of the solutions to this problem. If we had a major nuclear winter and people hadn’t really planned ahead, any way of dealing with this, and they start running out of food stores, what things might people start doing? What have they done in the past when they’ve been starving?

Dave Denkenberger: Well, it’s been really terrible. I’ve heard stories of people in the I think Irish potato famine boiling boots because it was made of leather and they could get some calories out of them. I’ve heard of people eating grass straight, but it has so much fiber that you actually don’t get any net calories. It’s like eating 100% celery. The options are really limited.

Dave Denkenberger: Related to eating grass, there has been a technique to extract edible calories out of leaves where you grind up the leaves and squeeze out the liquid so that you get rid of the fiber basically that we can’t digest. You boil that liquid and a protein concentrate comes to the surface. What is left over in the liquid is actually a lot of the toxins that aren’t good for us. This has already been done at the small scale and less developed countries and it’s even been done on the industrial scale in France. That’s a next step of making some of the existing biomass directly editable for people.

Robert Wiblin: That doesn’t get you very far.

Dave Denkenberger: Well, you might only get 10% of the calories total in the leaves as human food.

Robert Wiblin: It sounds like … Wouldn’t there be a lot of actual manual labor that would go into digesting it and extracting it? Is it even clear that you’d come out ahead?

Dave Denkenberger: To back up about these catastrophes, many people will assume that if there’s nuclear war then our entire industrial infrastructure would be collapsed. That may very well be true in the countries that are hit directly by the nuclear weapons, but say it’s a US-Russia exchange. That might be 20% of the global industrial infrastructure. From a global perspective, I would say the majority of infrastructure would still be functioning. I think there is potential to retrofit our industrial infrastructure to producing food. I actually use the analogy from World War II where before the war, US was hardly producing any airplanes, but once it entered the war, it retrofitted its automobile manufacturing plants to produce airplanes and tanks and was able to do that in a very short amount of time.

Dave Denkenberger: I think it’s feasible to look at our chemical processing plants and retrofit them to produce food. One of the ways of doing that would be looking at how we produce biofuels right now. We’re all familiar with first-generation biofuels where we turn corn or soybeans into transport fuel, but the second-generation biofuels or the cellulosic biofuels take the corn stalk and break it into sugar with enzymes and then feed that sugar to a fungus to make ethanol. If our problem is not having enough food, it may be possible to eat that sugar directly.

Robert Wiblin: Interesting. It sounds like you’re more focused on the countries that haven’t been directly affected by the disaster because that’s a somewhat more solvable problem. If there’s a nuclear war in the northern hemisphere or hopefully an asteroid hits the northern hemisphere, then you can think about, what could New Zealand and Australia and Chile and Brazil do that could plausibly save almost everyone in those countries?

Dave Denkenberger: Yeah, it’s certainly easier.

Robert Wiblin: Basically, the unifying idea in this book, Feeding Everyone No Matter What, is that even if the sun goes away, there’s actually just a ton of chemical energy stored on the earth’s surface in the form of wood and soil and other materials. The thing is humans can’t eat those, so we have to find some way of converting all of that chemical energy into something that humans can then digest easily. I guess you’re going through various different options for doing that.

Dave Denkenberger: Right. There are quite a few options for the leaves that we’ve talked about, the cellulose digesting animals like cows, sheep, goats, rabbits can digest. We could also, like we said, turn them into sugar in an industrial process. Wood is actually more difficult, but mushrooms can grow directly on wood. You can get mushrooms from wood, and they can soften the wood, and that leftover from the wood can actually be fed to cows, sheep and goats and bison. That’s actually already been done. You’re right. It’s just a matter of turning this big energy resource into something that’s actually human edible.

Robert Wiblin: Do we know what the denominator there is? How much chemical energy is there in in wood and other things like that?

Dave Denkenberger: It’s very large. In the book, I look at what if we were trying to get all of our food from just one of these food sources, which in reality we’d be getting food from multiple sources but just as a first analysis. The only one that we actually would run out of feedstock or energy source was outdoor mushrooms growing on logs that they’re so inefficient that we would actually run out. Many of these, you really could feed everyone for five years.

Robert Wiblin: Wow. Where is all of this biomass? Is it just in forests that I don’t really see?

Dave Denkenberger: Yeah. Contrary to popular belief, there still are forests left and, yeah, it’s I think hundreds of gigatons of biomass.

Robert Wiblin: Let’s maybe go through the main options that you can within the book. We’ve got mushrooms, which can grow on just plant matter. I guess we’ve already talked about cows, but there’s other potential things that could eat these materials like insects and rats. There’s trying to just digest them with enzymes I guess in big vats and cook them effectively. There’s this other method of growing bacteria on fossil fuels or finding a way to grow something that humans can eat using fossil fuels. Let’s maybe just do mushrooms first. Do you want to describe some more of the details of that?

Dave Denkenberger: You can grow mushrooms just on a log outside, but that’s limited because it’s only in the tropics that would not be freezing. I’m basing my work on climate simulation of nuclear winter where the global temperature reduction is around seven or eight degrees Celsius. So large areas, at least in the tropics, it would actually not freeze. So you could potentially grow mushrooms outdoors. It turns out it would be very difficult to ship hundreds of billions of tons of wood from the mid-latitudes outside the tropics into the tropics, so I don’t actually consider that option.

Dave Denkenberger: But we could do some growing of mushrooms indoors. We would probably do it on the leaves because that can be converted to mushrooms very quickly. And so you can get more mushrooms per growing area, and people could potentially have racks of mushrooms in their basement.

Robert Wiblin: We would go out and harvest wood and plants and things like that, and then grow mushrooms on them. Can the mushrooms grow quickly enough, and how much kind of space would you need to these many … I mean mushrooms aren’t that calorie-dense. So it seems like we would have to convert, basically, what … I guess, eyeballing it, it seems like we have to convert an enormous amount of all of our building space and all of our work into just growing mushrooms.

Dave Denkenberger: I think if we were getting all of our food from mushrooms, I might’ve estimated in the book, it would take a third of our building square footage, which would be a huge impact. But again, we’re going to be getting food from a number of different sources, so it wouldn’t be all from mushrooms in our basements.

Robert Wiblin: So this is just one option?

Dave Denkenberger: Yep.

Robert Wiblin: Hold on, so the problem with mushrooms is that you can’t really grow them outside because it gets too cold.

Dave Denkenberger: Outside of the tropics, right.

Robert Wiblin: So for Australia, this isn’t really going to work. Maybe it would work in Indonesia or something.

Dave Denkenberger: Yeah.

Robert Wiblin: Are there any other weaknesses of the mushroom approach?

Dave Denkenberger: Well, as you said, they’re not very calorie-dense. They’re actually pretty high percent protein by calorie, but there is a lot of water. But it would be feasible to get enough calories if you ate enough mushrooms. But I did write a paper on the nutrition of alternate foods, and I found to meet the United States recommended daily allowance, you would need a mixture of, basically, all 10 of these foods.

Dave Denkenberger: But to do just what people could survive on, like not get scurvy, I think you could have a more limited mixture of foods. I just haven’t done that analysis.

Robert Wiblin: Do you think it would be worth doing an experiment where you get someone to only eat mushrooms for a couple of months and see what happens?

Dave Denkenberger: I think that would be very risky. I think we say in the book that if you ate a variety of alternate foods, but something that might actually be a diet that we could produce if the sun were blocked, and get permission from your doctor and take a multivitamin, then yeah. I think that would be good to know.

Dave Denkenberger: About the vitamins, one way of getting sufficient vitamins is having a variety of foods. But of course, the people who are poorer would typically not get the variety of food, which is what happens today. And so there are backup plans for vitamins like growing bacteria that would have a particular abundance of vitamin, or maybe even [chemical] synthesis. I haven’t analyzed that, because I found that it would be feasible, if you had a variety of food to get enough vitamins.

Robert Wiblin: How do you think people would react to having to eat such a large amount of unpalatable food? Do you think people would just accept it because the alternative is death?

Dave Denkenberger: I think most people would, maybe not the foodies.

Robert Wiblin: Do you know what volume of mushrooms you would have to eat roughly to survive? I mean because it seems like even many of these other foods that you’re suggesting wouldn’t be as calorie-dense as the foods that we normally eat.

Dave Denkenberger: Well, in the case of mushrooms, many of them are around 90% water. The easy calculation, at least for people in the US, is you need about a pound of dry food per day, so half a kilogram. If it were all mushrooms, it would be about five kilograms. But other ones could be significantly less water like if we were eating cow meat, for instance.

Robert Wiblin: Maybe let’s just back up and … Why can’t we use cows and sheep and other animals that eat these plants as the main food source?

Dave Denkenberger: The basic problem is that these large mammals only have about one offspring per year. And so they currently do make up a significant fraction of our total calories, something like 5% globally. But if it can only grow a relatively small percent per year, you just can’t feed everyone on it.

Robert Wiblin: So it could stay at about 5% if we eat half of them [crosstalk 00:33:14].

Dave Denkenberger: Yeah. I think I estimated up to 10% after five years.

Robert Wiblin: So it just doesn’t scale?

Dave Denkenberger: Right.

Robert Wiblin: That’s mushrooms. What’s the next most promising option?

Dave Denkenberger: Well, you mentioned insects. There’ve been quite a bit of interest lately in insects as human food. Of course, many people around the world have eaten them traditionally, but not so much in Western cultures. They’ve been promoted for environmental reasons. They might convert food more efficiently. Though, if you’re concerned about their welfare, that might be a problem.

Dave Denkenberger: And there has been some work on feeding waste products to insects. But I haven’t seen feeding fiber, basically, like wood. And that would be important in one of these scenarios. But there certainly are insects that can eat wood like termites.

Robert Wiblin: Could we live on termites?

Dave Denkenberger: I think they’re pretty nutritious. Again, well, an animal will typically have a lot of protein and lipids or fats but won’t have the carbohydrate. There’s potential if you just have that as your food source, then it might be like being on the Atkins diet where you’re actually losing weight instead of gaining weight. So you need to have some carbohydrates-

Robert Wiblin: Excellent.

Dave Denkenberger: But lots of these other ones would have carbohydrates like the leaf extract and the mushrooms.

Robert Wiblin: How much mileage do you think we might be able to get from insects and rats and things like that, so setting aside any ethical issues?

Dave Denkenberger: Well, the rats one is a little more complicated because they are not as good of a cellulose digester as some of the other animals that we’ve talked about. And so the cue I took is actually from nature where fish will eat partially decomposed leaves, and fish cannot digest fiber. So why are they doing this? Well, they’re doing it to get at the bacteria that are growing on the leaves that the fish can digest.

Dave Denkenberger: And so my thought is we might be able to do the same thing to partially decomposed leaves and feed them to rats or even chickens which, like humans, have very little ability to digest cellulose.

Robert Wiblin: How much mileage do you think we might be able to get out of this category if we tried?

Dave Denkenberger: Well, I produced a graph of how fast we might be able to ramp up the different food sources. Some things could happen very fast like extracting food from leaves. You don’t have to wait for any organism to have offspring. Mushrooms can have a billion spores, so they can grow very rapidly.

Dave Denkenberger: The insects are somewhere in between the large mammals and the mushrooms, so they don’t ramp quite as fast. Chickens are actually quite fast because they can lay an egg a day, and rats are pretty fast too.

Robert Wiblin: So there is decent potential to scale there quickly if we’re organized about it. Let’s move on to things that I think we currently don’t really eat that much, which is growing bacteria with methane and breaking down plant matter with enzymes and bacteria. Let’s maybe do the enzymatic sugar one first. How would that work, and how much food could we get from that?

Dave Denkenberger: Well, we can look at an existing cellulosic biofuel plant and basically interrupt the process, at sugar. But what I’m interested in studying is there are, potentially, some toxins in that. The question is could then we purify that sugar such that people can eat it?

Dave Denkenberger: But once you do that, we eat sugar now. It turns out that there are different types of sugar and some cannot be digested by people, and so we would feed that to animals.

Robert Wiblin: What does that look like? Do we have to have just lots of bioreactors breaking down plant matter and then I guess processing it after that and feeding it to cows? How complicated is this?

Dave Denkenberger: Yeah, that’s right. Right now, we don’t have very many cellulosic biofuel plants. So the bigger question is could we retrofit other chemical plants to do a similar thing? And that’s one area I’d like to do, to work with a chemical engineer to say, “Well, how feasible would it be to retrofit existing plants to do this?”

Robert Wiblin: If you’re getting this broken down [human inedible] sugar coming out of these plants and then we’re feeding it to cows and sheep and so on, then we’re back at square one because you can’t get those animals to reproduce very quickly. But could you get other bacteria to digest it and then eat that bacteria or something like that?

Dave Denkenberger: Yeah.

Robert Wiblin: What are the pros and cons of that?

Dave Denkenberger: Depending on the bacteria, there can be issues with human edibility. But there are certain types of bacteria that are fine for people to eat, and I use the example of Spirulina which is known as a super food. People eat it as a supplement. It’s actually in some health drinks that look very green. It’s not the same type of bacteria. It’s actually cyanobacteria it’s photosynthesizing.

Dave Denkenberger: Many people call it algae, but it technically is bacteria. So people can eat that, and there are many examples of food that have certain amount of bacteria in them like yogurt.

Robert Wiblin: And so you just think that this technology already exists? Do we need many technical breakthroughs to make this practical?

Dave Denkenberger: There’s certainly a lot of research on how to make this cellulosic biofuels competitive with existing gasoline. But it turns out gasoline is relatively inexpensive compared to most food we eat. And in a catastrophe, we’d be willing to pay much more for food. So I think there’s a lot of potential for this to be cost-effective in a catastrophe.

Ever eaten any alternative food substitutes?

Robert Wiblin: Have you actually eaten any of the alternative food substitutes that you’re suggesting, especially the weird ones?

Dave Denkenberger: Yeah, one example is the spirulina. It’s very green and it does taste like spinach. Then, I’ve also eaten a number of different insects and there really isn’t very much of a strong flavor, so you mainly get the spice that’s been put on them.

Robert Wiblin: Well, let’s move on to the next one, which is growing bacteria with methane, which is something that I wouldn’t have guessed was a possible food source. Is that technically hard to do, and can we just then eat the bacteria that manage to grow on methane?

Dave Denkenberger: It is a pretty amazing thing that we have a life form that can not only use methane or natural gas as a food source, as an energy source, but also, it uses the carbon to build its own bodies. Now, you do have to add in some nutrients like nitrogen to make it work. But the basic process is relatively straightforward.

Dave Denkenberger: And there are a few companies around the world that are looking into using stranded natural gas, which means too far away to sell and to market, to produce the bacteria as fish food because it’s high protein.

Robert Wiblin: Is this already done anywhere?

Dave Denkenberger: I believe it has been done. I’m not sure if it’s commercially available. But yeah, they’ve done it at fairly large scale and put tens of millions of dollars into demonstrating pilot plants.

Robert Wiblin: Do you know where we got this bacteria? Are they from hydrothermal vents or deep under the ground where you don’t access to food that comes from sunlight?

Dave Denkenberger: I don’t know the history, but yeah, they are called extremophiles because they can live in an extreme environment, to be able to use methane as a food source.

Robert Wiblin: How much methane or how much natural gas would we need? And would it be conceivable that in a disaster, we could continue getting this much natural gas and spreading it around to everywhere that needs to produce food?

Dave Denkenberger: It would be a lot of natural gas. With the current production of natural gas, I think we could feed about half of the people. But again, we’d probably only be producing 10% of our calories from this or less. So it could be a significant food source. Then as for the catastrophe, again, it comes back to the question, “Is infrastructure still functioning?”

Dave Denkenberger: Then also, I’ve looked at how fast we might be able to scale it up. It takes a certain amount of energy to do your energy production infrastructure. But in the case of fossil fuels, it’s a pretty small percent. So we could technically ramp it up quite quickly.

Robert Wiblin: I guess again, because you’re using bacteria, they can just replicate incredibly quickly. They’ll have some pretty short doubling time.

Dave Denkenberger: It’s not limited by the bacteria. What I was referring to is what’s called embodied energy. So how much energy does it take to produce the drill that is drilling for natural gas?

Robert Wiblin: Oh, I see.

Dave Denkenberger: There’s some physical limit for how fast you could ramp that up. But as long as it’s only a few percent of the energy you produce, you could actually double in less than a year.

Robert Wiblin: With all of these solutions that involve bacteria, do you have an issue with preventing pathogenic bacteria or viruses in invading your vats and taking them over? Or I guess it’s sterility.

Dave Denkenberger: Well, in the case of methane, I don’t think too many random bacteria would be able to live in that environment. But in other cases like leaves and wood, yes, you do have to worry about that. And what we do in the case of mushrooms, we actually often grow them on manure. We first pasteurize the manure, and the cheap way of doing that is having a big pile of manure.

Dave Denkenberger: Then first, the bacteria start growing on it and increase the temperature a little bit. Then high temperature bacteria take over. So the low temperature bacteria actually die off, and then the high temperature bacteria keeps getting it higher and higher. Then it’s only the low temperature bacteria that can actually live in humans, or would be able to live later on.

Dave Denkenberger: And so you’re basically killing off those competing bacteria and then you grow mushrooms on them, and you need to keep it fairly well-sealed so that you don’t get re-contamination. But it’s a commercially mature process.

Robert Wiblin: Interesting. Do you have a problem with mushrooms that humans can’t eat also growing on the manure?

Dave Denkenberger: Well, presumably, they would be killed as well in that pasteurization process.

Robert Wiblin: I see, and then you only spread the spores of the mushroom species that you want.

Dave Denkenberger: That’s right.

Robert Wiblin: All right, so we’ve gone through a bunch of interesting ideas. One that I just remembered is that to my surprise, in a nuclear winter scenario or in a situation where the sun is largely blocked out, we’d actually be able to get more fish probably than we could now. Can you explain that?

Dave Denkenberger: Sure. The logic is that the vast majority of the oceans now are called an ecological desert, obviously, not because of lack of water but because of lack of nutrients. If there were a massive sun blocking scenario, the earth would cool and the upper layer of the ocean would cool and sink, and then deeper layers of the ocean would be brought to the surface, which have more nutrients.

Dave Denkenberger: And so we would have more nutrients available, but we have the disadvantage of less light available, and depending on the scenario, maybe more ultraviolet radiation. It needs more study, but I did do a scenario because I thought it was … in a way, it would be more feasible than relocating plants on earth because you don’t have the issue of different soil type and such.

Dave Denkenberger: Though, I would say in recent work, I have been looking more into whether we’d be able to relocate plants on the ground.

Robert Wiblin: How much would that increase the productivity of the oceans?

Dave Denkenberger: Well, right now, in the open ocean, the productivity is extremely low. Because of that low production, it’s very low density of production of photosynthesis and the phytoplankton, which is just small plants growing basically. Then in order to concentrate that to produce fish, it has to go through many trophic levels.

Dave Denkenberger: So you have the zooplankton that are eating the phytoplankton, and then you have … I don’t know. I’ve heard it can be up to seven different trophic levels. And so you start with low efficiency to start with, and then you go through all these trophic levels and you just produce hardly any fish. But in areas where there’s active upwelling of the ocean, the statistic I saw was .1% of the ocean area, so one thousandth of the total produce 50% of the global fish catch.

Dave Denkenberger: Because there, you have abundant nutrients and you can have a very short food chain. It can be fish that we can catch eating algae directly. So it’s way more efficient.

Robert Wiblin: If the amount of coast that has this updrafting increased a couple of fold, then the productivity of the oceans could increase two or threefold.

Dave Denkenberger: Yeah. It could be a really big increase. Now, there is the issue that once the climate stops cooling down, you’ll stop getting that overturning. Eventually, you consume the nutrients near the surface either because it’s people pulling the nutrients out in the form of fish, though, we might be able to put our waste back there, or material falling out into the deeper ocean.

Dave Denkenberger: So it would only work for a certain amount of time, but then it may be possible to continue that by … If agriculture is not working on land, we’re not using our fertilizers, we might actually just put the fertilizers into the ocean.

Robert Wiblin: Oh, wow. Wouldn’t it be more efficient to eat seaweed or algae directly rather than the fish that eat them, because you don’t lose the energy in the conversion?

Dave Denkenberger: Absolutely. But I have not been able to get the time to run that scenario. But potentially, you could feed a lot more people that way.

Summary of the overall picture

Robert Wiblin: Do you want to summarize the overall picture? You’ve had all of these interesting ideas about how we might feed people that mostly others haven’t investigated. Collectively, how optimistic are you that we’d be able to keep everyone alive?

Dave Denkenberger: From a technical perspective, what we could do … I am quite optimistic because even though some of these solutions might not work out as well as I think they might, we do have quite a bit of redundancy in the system, that is, when I analyzed the food sources individually, many of them could increase up to feeding everyone fairly quickly even in one year.

Dave Denkenberger: Now, in reality, they would be competing for energy sources, so it’s not quite as good. And I did write another paper which actually analyzed them including the interactions but still found that we could feed everyone two times over or three times over. That’s what’s technically possible.

Dave Denkenberger: The other thing is that I’ve come up with another, and some people have given me more ideas based on feedback, that there are other things that just haven’t analyzed yet. One of those is seaweed, like you said, but other things like using energy from fossil fuels to directly synthesize food.

Dave Denkenberger: We’ve already done that at the lab scale. So the question is how fast could we ramp it up? I just haven’t done that analysis yet. Or bacteria that run on electricity. We’ve talked about how we have methane-eating bacteria, but what about nuclear energy? Well, that’s electricity. Well, maybe that could actually grow bacteria, and there are examples of electric bacteria.

Dave Denkenberger: By the way, I would say one other solution that is commonly proposed by people when we talk about this issue is well, why don’t you just grow plants indoors on your electricity? But it turns out it’s extremely inefficient to take electricity and turn it into light, and then do photosynthesis. Even if you have the most efficient algae using all of our electricity, it would only feed, I believe, 5% of the people. So it’s way, way better to use the natural gas directly on natural gas digesting bacteria.

Robert Wiblin: Where are we losing the energy there?

Dave Denkenberger: The biggest loss is actually photosynthesis. So you produce the light and the typical crops in nature might be .3% efficient. If you’re really good, maybe 1%. And then algae, under ideal circumstances, maybe 3%.

Robert Wiblin: So photosynthesis just isn’t that effective?

Dave Denkenberger: Right.

Robert Wiblin: This raises the issue, I imagine that almost none of our calories from any of these methods now. Basically, all of our food comes from the sun fairly directly. Would it be sensible to switch our food supply now so that more of it is produced using these other methods even just because it might be cheaper or these would be just good ways of producing calories for people?

Dave Denkenberger: Yeah, potentially. Of course, you need to make it cheap to compete with current food. But I do think that thinking more about how we can utilize waste … I mentioned how cows used to eat corn stalks. But now in developed countries, agriculture has been disintegrated. That is, we keep our cows separate from our plants and we don’t have that traditional integrated farm.

Dave Denkenberger: We could potentially either reintegrate or ship the corn stocks to the cows and reduce our environmental impact. Even if it’s not cost-effective right now, people may pay a premium just to reduce their environmental impact. Another example is when we log forests. There’s a huge amount of material, woody material that’s left over. It can be higher weight than the actual lumber we take out. But mushrooms can grow on that. I mean why don’t we get some food out of it?

Robert Wiblin: Do you think that, setting aside any disasters, any of these methods would be applied just to feed people for normal reasons within the next 50 or 100 years?

Dave Denkenberger: I think potentially, it all depends on the economics. As you pointed out, if we do have difficulty with conventional food because of, say, slow climate change, population growth, many other problems like loss of soil, soils getting salty, any of these things, they’re not quite the big disasters that I’m working on, but they can add up.

Dave Denkenberger: And if conventional food price increases enough, then I think these other options could come in. The other possibility is local disasters. Generally, if you can just ship outside grain in, that’s going to be the cheapest. But maybe transportation is cut off, and so you might want to know how to grind up your wheat leaves and get some more food out of them.

Robert Wiblin: It surprises me that we haven’t done this before. I guess it’s just that food is currently just so abundant that we don’t have to think very creatively of other ways to get calories.

Dave Denkenberger: And even just in the last 50 years, the long-term trend has been reduction in inflation-adjusted food price. So it’s not thought about too much.

Robert Wiblin: You wrote this book where you discussed all of those options back in 2014. Have you changed your opinion since then about which one of these are most promising and which ones you would like to push the hardest?

Dave Denkenberger: Well, I have done some initial estimates of how much it might cost. Of course, it’s a complicated question for what they might cost in a catastrophe. But I’ve just said, “Well, how much do they cost now?” to give us some idea. The lower cost ones included the natural gas digesting bacteria, the sugar production with enzymes and leaf extract, potentially, low cost fish.

Dave Denkenberger: I didn’t mention that the fish we’d probably be eating in a catastrophe are very small, ones that could algae directly like sardines, and that also breed very frequently. But then another one, as I alluded to, is the potential of relocating crops. That’s something I didn’t include in the book. But I’m actually setting up an experiment now to simulate the conditions of nuclear winter in the tropics to see if plants can grow.

Dave Denkenberger: I think it is possible. Of course, there’s uncertainty, but I’m basing it on the simulation where about half of the sun is blocked in about an eight degree Celsius reduction. And so we might be able to grow potatoes, for instance.

Robert Wiblin: How much food do you think we would be able to get from that?

Dave Denkenberger: Well, that’s what I’m going to try to estimate based on this experiment. But even if we can get a quarter of our food from that, then it makes it easier to produce the remainder-

Robert Wiblin: The remainder.

Dave Denkenberger: Of these alternate foods.

Robert Wiblin: It sounds like with a lot of these solutions that you have suggested, there isn’t a lot of existing research. So you’re having to guess quite often, and I think you’re only really claiming, in many of these cases, to be right to the nearest order of magnitude. So it could be three times worse or three times more effective than what you’re suggesting.

Robert Wiblin: What are the pros and cons of having just such a rough view of all of this? I suppose it means you can cover a lot more ground a lot more quickly. But on the other hand, it’s a bit difficult to compare what should be your greatest priorities because there’s just not a lot to go on.

Dave Denkenberger: I think that that’s basically where you have to start. As you say, we don’t have very much data to go by, so there has to be a lot of estimation. There’s some things where we can’t say anything useful, but other places, we can. We have some idea even though there’s uncertainty in how fast we could ramp up different food sources, we can still say mushrooms will ramp a lot faster than cows will.

Dave Denkenberger: I would say also, in the cost-effectiveness, in some cases, you just have to say, “Well, it’s similar cost-effectiveness to something else. But other things, you can actually have reasonable confidence that it’s more cost-effective.”

Robert Wiblin: How did people react to this kind of first cut? Because I guess it seems very good to me that you’ve done this … You’ve put the first brick in the wall here, and you’ve said, “Well, here are the main questions that we need to answer within this field, and no one else has really been working on it.”

Robert Wiblin: But I know sometimes academics don’t really like doing things that … They want to do one thing very precisely rather than cover a lot of ground vaguely. Have you had a negative reaction to the fact that you’re trying to do so much without a lot of existing literature to work with?

Dave Denkenberger: It certainly has been a challenge going through peer review. Many people don’t feel qualified to review it because it covers so many different fields. When I’m writing it, I always get experts to review like a mushroom expert or a rabbit expert. But you can’t have 10 different reviewers on a paper.

Dave Denkenberger: So it certainly has been a challenge. But eventually, we’ve gotten something like seven peer reviewed papers so far, so it is possible. Generally, the way I construct uncertainties like a distribution, is that wide enough such that most people will say, “Yeah. My value is in there somewhere,” and then generally, people are happy.

Dave Denkenberger: Sometimes I’ve been criticized for having too wide of distributions. But I think that’s certainly one of the lessons I’ve learned from the rationality community, is that you should have really wide distributions. And usually, people understand that that’s appropriate.

Robert Wiblin: I’ll just add a note before we go on to the next section, that regular listeners will know that I’m vegetarian and here, we’ve been talking about eating animals. I guess we haven’t even considered the ethical issues here at all. Although, I imagine the ethical calculus would be a bit different if starvation was the alternative.

Robert Wiblin: Though, it does also sound like animals, in most cases, is not going to be the most efficient way to produce food even in a disaster scenario. But I just wanted to bracket that so people don’t email me. Let’s move on to envisaging the world that this would look like. I guess we can have a more concrete idea of actually … to think through how useful would it be to try to prepare to do these things sooner ahead of time.

Robert Wiblin: You said earlier that you thought only some of the world’s infrastructure would be destroyed and only a small fraction of the world’s population would be dead in a nuclear war. Do you mind painting out in any more detail what infrastructure you think would be destroyed and what would still remain? How many people would be injured, say, in this disaster so that we can just try to visualize what a city would look like in this case and what people would be doing day to day?

Dave Denkenberger: Again, there’s uncertainty, and I did actually get into this somewhat in the paper that looked at nuclear winter uncertainty, that basically, if you have the really bad scenario both from killing a lot of people and from the nuclear winter scenario of targeting the population centers, there would still be … Depending on how far away you are from the bomb, there is a criterion of how much pressure the blast wave is, like roughly what the percent of survival is that we’ve gotten from the Japan experience.

Dave Denkenberger: But yes, you could have injuries and then obviously, any healthcare would be overwhelmed, so you’d basically be on your own. But the mortality would not be 100% even in the cities. In the rural areas, yes, there would be radioactive contamination and increased cancer deaths. But it would not kill the majority of people in the rural areas.

Dave Denkenberger: The situation is even less extreme in non-target countries, though many people think, and there’ve been popular movies and such that, “Oh, if we detonated these many nuclear weapons, then everyone in the whole world will die from radiation poisoning.” But that’s not actually the case because the radioactivity generally rains out. Some of it right away but most of it, within a few days.

Dave Denkenberger: Of course, some would travel up into the stratosphere that could stay for years. But at that point, if it’s then only raining out over years, the exposure is just much lower. That’s why we’ve focused on what is the biggest problem, which is the food.

Robert Wiblin: I guess I’ve somewhat ended up, I think, with a distorted picture of what a nuclear apocalypse would look like, because I watched this movie, Threads, which is from the 80s which followed a city in Britain during an all out nuclear war between NATO and Russia. In that case, I think a very large fraction of the population was dead, and most of the remainder died in the coming years of starvation or cold or-

Robert Wiblin: Died in the coming years of starvation of starvation or cold, or just their injuries. And basically all of the infrastructure was down, and basically the government fell apart. And I think that they were trying to be extremely accurate for what would happen in Britain in a situation. But I guess that is a worst-case scenario, because there’ll be so many nuclear weapons at that time targeted at a very small country that’s very densely populated. So the radiation is much worse and the number of cities that are targeted, and the number of people who are hit directly by nuclear weapons would be much worse.

Robert Wiblin: And so I guess you’re saying that I should imagine places where basically almost everything is still functioning except perhaps there is a bit like an uptick in cancer, and trade is, to a significant extent, cut off. But otherwise, things are still running.

Dave Denkenberger: Yeah, yeah, it depends on how we react. The basic assumption in the book of Feeding Everyone No Matter What, assumes that we continue to cooperate. Which means trade of goods, sharing information, etc.

Dave Denkenberger: But I have done some less optimistic scenarios, say, what might be an economic scenario. So you would still have trade, you would not have immigration, seeing just how much trouble we’re having with refugees at this point, that’s probably not gonna be a feasible solution in a disaster. But if you still have trade of goods and sharing of information, and then a world food price, I was able to estimate well, what percent of the population would survive. And if you just have for stored food, it’s only around 10% of the population. I estimate, even now without anymore research and development, if countries just knew about these solutions or were told in time before they resorted to further military action, we could do much better than stored food, maybe 30% or so of people would survive.

Dave Denkenberger: But if we actually got prepared, like some of these alternate foods need more research. Some have already been developed commercially, but we’d need to figure out how to scale it up quickly, say retrofitting factories. And we actually have plans for scale up, and plans for how we would continue trading and things like that. Then survival could easily be 60, 70, 80%.

Dave Denkenberger: So food is gonna cost more if there isn’t charity. But we could still have a much much better scenario than just stored food.

Robert Wiblin: So we’ve mostly talked here about the nuclear apocalypse situation. And I think that makes sense, because if we can deal with that, then that’s the worst case, and we should be able to deal with most asteroids, and super volcanoes, and more modest wars. Is that right?

Dave Denkenberger: That’s right. It is the worst case, especially because it’s longer lived. The black smoke particles from burning of cities would be heated by the sun, and actually lifted up higher, so they would stay there longer. Whereas the super-volcanic eruption, the particles are whiter, and the sun might only be blocked for a couple years.

Robert Wiblin: Are there any other interesting aspects of the other catastrophe scenarios that we should pay attention to?

Dave Denkenberger: Well, certainly some of them don’t involve blocking of the sun. And then you for instance wouldn’t have the overturning of the ocean. You could get a really large asteroid that can completely block the sun, in which case we’re not gonna be growing any potatoes or any seaweed. But generally, the solutions are applicable across a wide variety of catastrophes.

Robert Wiblin: So would the Internet survive this? ‘Cause I was thinking … I mean a very important aspect of the preparation would be that you have to share this information with everyone around the world, so that they know very quickly what they should be doing. But if the Internet’s down, it’s much harder to communicate, then that’s something that you need to prepare for ahead of time.

Dave Denkenberger: Yes, that is extremely important. But fortunately, the Internet was actually designed to survive a nuclear war-

Robert Wiblin: Oh, wow, okay.

Dave Denkenberger: … back in the 60s or so.

Robert Wiblin: So everything can just be rerouted through different parts.

Dave Denkenberger: That was the idea, yeah. And so that was even trying to keep connectivity within the US, and of course it’s much easier in the non-affected countries or non-target countries.

Robert Wiblin: What about other issues like people dying because it’s really cold, or they don’t have access to water, have you considered those, or is that just someone else’s job?

Dave Denkenberger: I did do a quick survey in the book of the different problems. My background is actually in energy. So I was interested in that part of it. So there’s a question; can the buildings be heated adequately? There may be some circumstances where we can’t do that and we need to relocate some people, or people would do makeshift stoves and burn wood. So it seems to be not too hard.

Dave Denkenberger: Now, the water issue is particularly interesting, because if the earth cools, you get less evaporation from the ocean, and that ends up in less precipitation on the land, something like only half as much, which sounds really bad. But it turns out, more than half of our water is actually used for growing food. So if we’re not growing food, we could use the water for other things.

Robert Wiblin: Okay. So I guess drinking water is the last thing that you would stop using. So if you cut back on showers, then you’re not going to die of thirst.

Dave Denkenberger: Yeah, and it turns out the major uses of water are agriculture and cooling power plants, even showers is relatively small, and the actual drinking water is minuscule compared to those other things.

Robert Wiblin: All right. I guess that it’s the first benefit of most agriculture being gone.

Dave Denkenberger: Yeah, yes.

Robert Wiblin: So a critique that I’ve seen in some comments on your work is that in this scenario, with a nuclear winter or an asteroid, once that happens, kind of so many people’s attention is gonna be turned to how do we continue feeding ourselves, ’cause that’s just going to be obviously a huge potential threat to society? And given that you might then have hundreds of millions of people, thinking about this question after the fact, how much value do we really get from preparing, having a few dozen people prepare for it ahead of time?

Dave Denkenberger: Yeah, it’s a good question. There are some historical analogies, the siege of Leningrad, I believe, was a case where the city was cut off for years, and many people just starved. I mean you could argue now that we have better technology, and better educated people, so we should have a better chance. Certainly if we do have free flow of information, that makes it easier, they might find the work that ALLFED has done so far just on the Internet, or yeah, people could invent it independently. So there’s certainly that possibility.

Dave Denkenberger: One concern I have is just that leaders react quickly before the information gets out, and chose the military route, and then you can easily have a downward spiral.

Dave Denkenberger: The other thing is that … I mean I do think that further dissemination of the research we’ve done so far would be beneficial. But we would certainly have a better chance of success if we did more work, like studying long-lived animals, you can’t do that overnight. Or figuring out what plants might actually grow in the tropics. Well, it takes a long time to grow plants. And we can do things in the greenhouse, but then we have to wait three months. So it would be hugely advantageous to actually have figured that out ahead of time. And then have a plan, so that we could start implementing it right away. Because every delay you have, means fewer people are gonna survive.

Robert Wiblin: Okay, so just the first one is that you think it’s very important that people be made aware very quickly that it will be possible to feed everyone, and so they don’t need to go out and fend for themselves, and we see kind of a breakdown of the legal system, or of security.

Dave Denkenberger: Right. Either within countries or between countries.

Robert Wiblin: Yeah, how confident are you that that’s a big effect that for example if we promoted this message, that we would be able to persuade people of that, and that it would make the difference between the legal system continuing and kind of a bigger breakdown of security?

Dave Denkenberger: Not very confident, and basically we’ll talk about later about the actual cost effectiveness modeling. But there’s some probability that it will work out well based on our current preparation. If we prepare more, that probability increases. And you could certainly imagine spending trillions of dollars, like storing up food, and then we would be extremely confident that it would work, because we wouldn’t have to have any new technology work. We would just have the stored food.

Robert Wiblin: So I suppose it then becomes important to be able to persuade people that these technologies will work, which I guess is another reason why you wanna be able to demonstrate them on a smaller scale first.

Dave Denkenberger: That’s right. So that’s one of our priorities now, is to demonstrate technologies on a small scale. And it has a number of advantages. One of course, doing a small-scale experiment is less expensive. But then the other thing is that depending on the scenario, if we do have breakdown in cooperation, then we may not be cooperating well enough to retrofit factories. But if we could have something that grows food in people’s basements, then that could still save more lives. And I’ve been focusing on saving lives, but the primary motivation for me is the long-term impact. And so I just think there’s a very strong correlation between saving lives and actually retaining a functioning civilization.

Robert Wiblin: And you’re saying that, I guess, the thing that can’t be done after the fact very quickly is just many rounds of testing to figure out how to do this, right?

Dave Denkenberger: Right.

Robert Wiblin: Because you can’t parallelize that, if you have a 100 million people doing it, it takes a month to test it out, and then you gotta go back to the drawing board and rework the prototype. So that, you have to do ahead of time.

Dave Denkenberger: Mm-hmm (affirmative).

Keeping the peace in GCR scenarios

Robert Wiblin: In terms of us being able to keep the peace in a disaster scenario, so long as the government tells people that it has a plan for feeding everyone and so they need not turn to violence, do you think that people would believe the government if they said that? Is there kind of going to be an issue of credibility that people might think, “Well, of course, they’re saying that. They just like want to trick us into going along with them.”

Dave Denkenberger: Yeah that was something that came out of EA Global San Francisco Workshop I did in 2016, where the general thought was that of course the government is going to say, they have a plan, but unless they could credibly back that up with what they had done ahead of time, then many people would not believe them. I think that’s a good reason to do at least some planning ahead of time.

Dave’s additional point about post GCR scenarios

Dave Denkenberger: Another concern I have is that in the immediate response to the catastrophe, there may be lots of suggestions of ways of handling the catastrophe. The best ones technically might not win out, depending on the charisma of the advocates. One example we give is the dependence on using all our fossil fuel energy or electricity to make artificial light and grow plants that way. Because that’s an extremely inefficient way of producing food, we could use literally all our energy for that and not feed very many people. The fact that we’ve tried to think ahead about how we could allocate resources efficiently, I think would help in the catastrophe time when not everyone will probably be thinking rationally.

ALLFED’s plan

Robert Wiblin: Okay. So what is ALLFED’s plan? If it had a million dollars, or $10 million or $100 million, what kinds of levers would you be pushing?

Dave Denkenberger: Well, I see it as a two-pronged strategy. One, as I’ve said, I think that greater awareness of what we’ve done so far would make it more likely that we have a good outcome. But of course it’s expensive to get the message out [ahead of time]. But we could be prepared to get it out very quickly.

Dave Denkenberger: So one strategy would be to have a panel of experts, and this could actually apply to even beyond agricultural catastrophes. But have people trained in the media, and aware of how to react, and then say to the media, “Well, we don’t need a lot of your time now, but if some of this happens, call us and we’ll actually have a message that’s not just everything’s going to hell and panic.” Which the media tend to like to say.

Dave Denkenberger: Similarly, maybe instead of the mass media, it could be on social media. It’s very difficult to figure out what goes viral now. But if people are of the sudden interested in feeding themselves, we could be prepared with a message that could potentially go viral at that time.

Dave Denkenberger: And then a third way is to find influential people who it would be very advantageous for them to know ahead of time. And one example I give is Tim Benton who was the UK government food security champion. And even though he’s not the Prime Minister, that’s his [Benton’s] job of food security, so you would think he might be able to get the message [to the Prime Minister] in a catastrophe.

Robert Wiblin: Okay, so this kind of the advocacy and message spreading thing, is there also … I mean how much infrastructure should be built ahead of time? Should we have appropriate mushrooms spread out all over the place so that we can very quickly start growing them?

Dave Denkenberger: Yeah, so I guess I’m just saying the information sharing, why that’s the first prong is one of these catastrophes could happen this year. And so I think we should spend some of our efforts to say what would we do if that happened. But of course then we should further develop the technologies to have a better message to spread if the catastrophe happened later.

Dave Denkenberger: As for the preparation beyond the research, development and planning, there are many solutions that we could do that would cost a lot of money, other than food storage. We could, ahead of time, retrofit plants, or build new plants, chemical plants, so that they could be very easily switched. That would be great, but it might cost billions of dollars. So I wouldn’t do it first.

Dave Denkenberger: So basically there’s a big supply curve, basically, of risk mitigation. And what I wanna identify is the ones that could give us the biggest bang for the buck. That’s what we should do first.

Media

Robert Wiblin: Is ALLFED doing very much media at the moment in order to kind of spread the word about how we could feed everyone in a disaster, so that people will stay more calm after the fact?

Dave Denkenberger: We have done some of that though we have been updating recently based on EA feedback on the potential downsides for mass media outreach now. Our thought more now is to be ready for a catastrophe that is have relationships with journalists, so that they would contact us in a catastrophe and then, hopefully, we would get this more positive, cooperative information out rather than the typical doom and gloom in a catastrophe.

Robert Wiblin: Yes, do you need to build up an experience with media? I suppose you’re doing that now to some extent.

Dave Denkenberger: We have had some experience with interviewing, though we do want to do more training. Ideally that we work with other organizations, so that they could react well in a catastrophe. It doesn’t have to be necessarily just agricultural catastrophes.

Experiments

Robert Wiblin: Earlier you mentioned doing an experiment to figure out how much food you could grow in the tropics in a nuclear winter scenario. Are there any other experiments or trials that you’re thinking of running?

Dave Denkenberger: Yeah, lots of them. So I’ve talked about the methane-digesting bacteria being done at commercial scale, it’s potentially possible even at household scale, assuming natural gas still flows. So I’d like to try that out, see how efficient it might be.

Dave Denkenberger: It’s also been suggested that … UK listeners might be familiar with Quorn, with a Q, which is fungus-based protein source, often as a meat substitute. And that is grown more like industrial, like in vats. So that might be a cheaper way of converting cellulose into food than growing mushrooms. So that would be great to investigate small and large scale.

Robert Wiblin: Yeah, that makes me think. It sounded like some of the options you’re considering could have commercial applications today, and potentially even if it’s not exactly what you would do to prepare for a disaster, if you could build a business that figures out a way to grow mushrooms on wood in a way that’s profitable now, then it could be at a much larger scale, should one of these disasters happen. You wouldn’t need donations, ’cause you could fund it just by selling the product.

Dave Denkenberger: Yes, and we’re certainly open to that. And I’ve heard one critic say, “Well, but then if it becomes mainstream, then you don’t have the ability to ramp it up quickly.” But that would only if it were very large. So still I think it would be of benefit to commercially develop more of these technologies.

Robert Wiblin: Sorry, I don’t understand that. Let’s say that we were getting 50% of our food through Quorn hypothetically, this vat-grown mushroom stuff, then doesn’t that just mean that we’re not so dependent on sunlight anymore, even if we can’t scale it up that much more?

Dave Denkenberger: Yeah, I guess that is true. You still need to have a supply of the energy source. But yeah, if it’s using wood, then we would have lots of wood.

Robert Wiblin: Okay. So let’s switch now to talking about the cost effectiveness analysis that you’ve recently got published. And actually, it looks like you’ve got two different papers published; one cost effectiveness for interventions for alternative food to address global catastrophes globally. And the another one doing, I guess, a similar analysis just for the United States. Do you wanna describe how you did that cost effectiveness analysis, and what you found?

Dave Denkenberger: Sure. So in the case of the United States, it gets back to what I talked about before, the modeling of nuclear winter, because really that’s the only catastrophe that could cause starvation in the United States. There of course could be other bad consequences, even if there’s not starvation in the United States, like a refugee crisis, or a conflict abroad that spreads. But the easiest model is starvation in the US. And for that, the cost effectiveness turns out to be very large, even though it’s only just from one country selfishly to prepare for these alternate foods.

Dave Denkenberger: And it’s partly because the alternatives for saving American lives are extremely expensive. Like healthcare or environmental regulation or traffic safety.

Dave Denkenberger: But what is probably more interesting to your listeners is looking at the global case. And for that, I actually did the 10% shortfalls that we’ve been talking about. Because those can cause mass starvation globally, as I said, not because there is technically not enough food, but because of price increases and the poor of the world not being able to afford it. And as I said, there is tremendous uncertainty in what our response would be, the mortality could be as low as millions, or it could even be billions if it goes very poorly. But the expected value is in the hundreds of millions if one of these catastrophes happened.

Dave Denkenberger: And in this case, we’re comparing to actual GiveWell estimates of saving lives of saving lives with mosquito bed nets. And that, the cost to save a life is in the thousands of dollars.

Dave Denkenberger: As you mentioned earlier, my analysis indicated it was more like tens of cents to hundreds of dollars to save an expected life. And this is not … Assuming the catastrophe will definitely happen, this takes into account some probability that the catastrophe will not happen, and actually only looks out a couple decades, because things could change dramatically. For people in a general audience, the research we do now could get out of date, or planning we do now could get out of date. If you’re worried about risk from artificial intelligence, then something much more dramatic could occur, and then these things would no longer be relevant.

Robert Wiblin: So do wanna kind of map out what the key parameters were? And one thing that I really like about the cost effectiveness analysis that you’ve done is that you’ve put it into this Internet talk or Guesstimate, where you map out ranges or probability distributions for all of the different parameters that are feeding into the ultimate life saved per dollar figure. Which makes it a lot easier to kinda scrutinize and figure out where you agree or disagree.

Robert Wiblin: But maybe what are kinda the key numbers that you had to estimate to figure out how many lives you might save per dollar?

Dave Denkenberger: Well, in this case, these papers were actually written before Guesstimate existed, so I was using the software Analytica, but it’s still possible that you could view it for free and modify assumptions if you’re interested in doing that.

Dave Denkenberger: But there are a number of assumptions that go into this, we’ve already talked about some of them. But some other important variables are … In this case we’re talking about saving lives, so the probability of feeding everyone if we don’t do anything more, versus if we do these interventions, and I actually broke out three different, actually four different interventions. One was this planning, one was more research, especially on the technologies that have not been researched very much. One was on development to actually commercially develop the more promising technologies.

Dave Denkenberger: Those all cost something around $100 million. I also consider a more expensive options which is training. So here, you can easily spend billions of dollars, because it involves lots of people, and it’s actually maybe even periodically or every year or something, running drills. Obviously the military is very good at this. So then they know exactly … They are fully trained, they know how to respond. That would provide more value. It would increase the probability of success, but it would cost billions of dollars. And so it’s not the first thing I would do.

Dave Denkenberger: So then you put all this together in a Monte Carlo model, which a probabilistic model to give you outputs, and they are, as we said, they vary orders of magnitude. But in the case of cost per life saved, even though the variation was four orders of magnitude, it still really didn’t overlap with the estimates of saving lives with mosquito bed nets. So you can actually say with some confidence, if you believe in the inputs, that this would be better.

Robert Wiblin: So the high end in this paper, it looks like it was $400 per life saved, which I guess compares pretty favorably to the few thousand dollars that give all things that takes to save a life with bed nets.

Dave Denkenberger: That’s right. That’s for the three relatively inexpensive interventions.

Robert Wiblin: So in this paper, you’re estimating just a very low cost per life saved, do you wanna kind of justify? Is there any way of kind of intuitively justifying that to a listener who might be skeptical that that’s plausible?

Dave Denkenberger: Yeah, I would say that I think that there are clear things that we can do to increase the probability of feeding everyone. I think we would, as we said, be much better prepared with a plan, and with more research and development.

Dave Denkenberger: And then of course, you have to believe there is a significant chance of one of these catastrophes happening, which I think there is reasonable evidence for. But then the big picture is just that no one has worked on it before. So you could say that unintentionally, people have developed this methane-digesting bacteria, which is great for us that’s already been commercially developed. But they haven’t thought about how it would be done in a disaster. So we can just be much better off if we actually think that through.

Dave Denkenberger: And then there are other things that just haven’t been researched. And so I think we’re just at the very early stage where we can be highly cost-effective. We can pick that low-hanging fruit.

Robert Wiblin: All right, so in addition to that paper, you’ve also done an analysis where you looked at how likely this is to make a difference to kind of the long-term future of humanity, and lowering existential risk, do you wanna kind of talk about what’s different about that model? What gets added?

Dave Denkenberger: Sure. So we still have the probability of a catastrophe happening, and so we’re using the probability of nuclear war for one part of the model, for the sun-blocking catastrophes. But now, here, we’re not asking how many people would die, but we’re asking what is the impact on the far future? And my initial work, actually on a EA forum post, was considering one of impacting the far future, and that was a collapse of civilization, and then not recovering that civilization.

Dave Denkenberger: And so by some definitions you would say, “Oh, that’s not an existential risk, because people have not gone extinct.” But if you actually look back at Nick Bostrom’s original paper, there are several different types of existential risk. And he defines existential risk as something that prevents humanity from achieving its potential. And so if we lose civilization, and we continue on earth as hunter-gatherers with a few million population, maybe we would go extinct, because of the next asteroid. But even if we didn’t, we certainly are not achieving humanity’s potential. And so that does qualify, by that definition, as one existential risk.

Dave Denkenberger: Then after that work, partly based on feedback on it and also based on my reading of 80,000 Hours work, I shifted to a different perspective, which is well, there are many routes how these catastrophes could reduce our long-term potential. It doesn’t have to be just losing civilization and not recovering.

Dave Denkenberger: So one example this catastrophe if it goes poorly, many people die, lots of conflict, that could be a scar on the human psyche, and we could become nastier now. And I would say that would make it more likely that that nastiness gets put into artificial intelligence that we develop that then may determine our long-term future. And I think there are several other possible routes to having our long-term impact from these catastrophes.

Robert Wiblin: So it’s kind of there’s two different flows of value here. One is thinking about just like lives saves in a more normal sense, and then you are thinking about what’s the likelihood of it reducing an existential catastrophe which could put humanity on a worse trajectory, such that we never manage to achieve our full potential, whatever that is.

Dave Denkenberger: Right.

Robert Wiblin: There’s two different kinda cost effectiveness analyses that you could do. And I suppose there’s also two different scenarios. There’s the like an all-out sun is massively blocked case, and then also thinking about the 10% reduction in agriculture scenario. Out of those two, which one is generating the most value in the analysis?

Dave Denkenberger: Perhaps surprisingly, they are similar. And of course I say similar because that means the very large uncertainties are overlapping each other. So the 10% shortfalls are more likely to happen. But of course if they do happen, it would be less likely to have a far-future impact. So for this particular work, implemented on Guesstimate, which was developed by an EA, and it’s great that it’s very easy, like basically spreadsheet-based, that you can modify the assumptions if you disagree with them.

Dave Denkenberger: But what I try to do instead of just coming up with the distributions myself, I thought I would survey other existential risk research to try to get estimates of what is the far future impact likely to happen with current preparation, and how much would spending $100 million actually improve the outcome, both for the sun-blocking scenarios and the 10% shortfalls.

Robert Wiblin: So it seemed to me looking over this guesstimate sheet, I mean I wasn’t able to fully understand it, it’s pretty scrutable for a Monte Carlo simulation, but it does take some thinking through. And I definitely encourage people to go and take a look at it, ’cause it’s fascinating. And I think that it’s an approach to modeling that should be used a much more.

Robert Wiblin: So there was kind of four key numbers that you needed to estimate. One is the likelihood of a big food shortfall. Then there’s kind of the likelihood that that flows on and wrecks the long-term future, and then there’s the likelihood that kind of preparations that ALLFED might do would make the difference between it being really bad for long-term future, versus we recover from it and things go okay.

Robert Wiblin: And then I suppose you had to estimate how much that would cost. And if you can multiply those three, then divide by the cost, then that gives an idea of the benefit to cost ratio. Is that kind of right?

Dave Denkenberger: That’s right.

Robert Wiblin: So maybe let’s go through each of these in turn. So it looks like you estimated, or you had like a median of 1.9 [percent] risk of a full-scale nuclear war each year. Where did you get that number from? ‘Cause it seems quite a bit higher than figures I’ve heard from other sources.

Dave Denkenberger: Right, so I should clarify that in Guesstimate, the single value that is reported is the mean not the median.

Robert Wiblin: Oh, okay.

Dave Denkenberger: And this is a huge difference in the case very large distributions. But the background is that two of my colleagues at the Global Catastrophic Risk Institute, Seth Baum and Tony Barrett, looked back at the close calls for nuclear war. And on this podcast, you’ve gone into some of those. And many of them are very scary how close we might have come to nuclear war. And they built what’s called a fault tree analysis where you have to go through a certain number of steps for it to actually turn into nuclear war. So then they were able to actually put a quantitative estimate on nuclear war. And it’s very large range. The 95% confidence interval is something like 0.1% to 10% per year. But because of that large range, partly, but the mean turns out to be around 1 or 2%.

Dave Denkenberger: And that does sound pretty high, that is higher than most people’s estimates. And from one perspective, you should say that maybe we should update based on the fact that we have not had a nuclear war in the last 72 years. However, you could say we have had a nuclear war in the last 73 years. Now, of course the circumstance in World War II was different than now, but if you were to say that, then the annual probability would about 1.4%, which is in the ballpark.

Dave Denkenberger: Now, because it’s not the same, I do think we should be doing some updating downward based on the evidence. However, this model actually only considered inadvertent nuclear war, which means one side thinks they’re being attacked, and therefore quotes retaliates, and then the expectation is that there would be an actual retaliation afterwards.

Dave Denkenberger: But there are other scenarios that could lead to full-scale nuclear war such as an actual intentional attack, or there could be an accidental detonation of a nuclear weapon that could be misinterpreted and then escalate. So from that perspective, you could actually argue the probability should be even higher.

Robert Wiblin: Yeah, I think I still think that this number is too high. So what are some of the reasons? I guess it doesn’t seem right to say that we had kind of one … It’s true that nuclear weapons have been used once in a war in the last 73 years, but the situation was so different, just to use it over a single city, and the risk of that precipitating an all-out nuclear were so … Well, I mean obviously it can happen, ’cause they’re the only ones with nuclear weapons. That doesn’t really seem like it’s in the same reference class, ’cause everyone knows that if they used the nuclear weapons now, it would kind of be the end of their country in effect. And that wasn’t the case when it was used against Japan in World War II.

Robert Wiblin: So if you do the calculation where you say you had a 1.8% chance of a nuclear war per year, then over 70 years there should be a 72% chance of an all-out nuclear war over that period. So it seems like we get like a pretty big update against that having been the probability at least in the past, right?

Robert Wiblin: And in addition, that paper with Seth Baum where they did that [inaudible 01:26:45] analysis, it’s got … So the 90% confidence interval is between, I guess, 0.33% per year and 16% per year, which is … I mean ’cause that’s over like three or four orders of magnitude. It seems that they’re basically saying that they just have no idea. And then just to take kind of mean of people, giving this such a wide range.

Robert Wiblin: Yeah and then just to take the mean of people, given there’s such a wide range. It just seems like a lot of weight to put on something that’s basically saying we have no clue. What do you think of those ideas?

Dave Denkenberger: Well, I think that it’s good that it’s actually quantitative because so much of people’s guesses are not based on an actual quantitative model. So I would trust it more because of that reason. I would also say that we can’t just multiply the probabilities using the mean because there’s … And actually, I do this at the bottom of the guesstimate model, that if this were true, the 1.8% per year, what’s the probability remaining in the 21st century? If you use the means, it’s very high when you actually multiply out the distributions, which is what the accurate way of doing it, then you get 38% chance, but it’s still high.

Robert Wiblin: Yeah, okay. So what does that come to if you just had to pick one number then? I guess that’s like .5% chance a year, .6% chance a year?

Dave Denkenberger: Yeah, around there.

Robert Wiblin: Okay, so that’s less far off the estimates people give. I think Anders Sandberg wrote a paper where he said it was closer to .1%. Maybe that seems a bit on the low side because we have model uncertainty.

Dave Denkenberger: Yeah, I think he was saying that the .1% was the median, and the mean was closer to 1%.

Robert Wiblin: Oh, interesting.

Dave Denkenberger: So it would be fairly close. But yeah, you could certainly argue that it should be half as much or a third as much as this. It turns out that the conclusions don’t change very much.

Robert Wiblin: I suppose it’s also true that you haven’t considered any scenarios other than the nuclear war, although that probably is the biggest one.

Dave Denkenberger: It does dominate the asteroid and the super volcano, yeah.

Robert Wiblin: If you had to critique this number and say it as a lot lower, what kind of argument would you make?

Dave Denkenberger: Well, I would say the arguments you have made to basically how much should we update based on the evidence. If the evidence is no war in the last 72 years, then there’s a pretty strong update.

Robert Wiblin: I think Anders also claimed in my podcast with him that the fact that we’ve had so many near misses and haven’t had use of nuclear weapons could actually point in the other direction that this final step from a false alarm to actually using nuclear weapons is in fact extremely implausible. Because otherwise, we wouldn’t have as many, we wouldn’t be able to see as many near misses, because we would be dead if it was a near miss. Have you heard that line of reasoning?

Dave Denkenberger: I did listen to that good podcast, and that was an interesting point. But I think the counterpoint is we could’ve also been lucky.

Robert Wiblin: Yeah, so you just have to weigh those out. I’ve got to admit; I did find that a bit counterintuitive. Maybe you and Anders should talk and see how much you should update that number. I suppose another argument for being lower is maybe just that people find this implausible on