1942Fairbanks, AK, USAJoined Apr 2015


Dr. David Denkenberger co-founded and directs the Alliance to Feed the Earth in Disasters ( and donates half his income to it. He received his B.S. from Penn State in Engineering Science, his masters from Princeton in Mechanical and Aerospace Engineering, and his Ph.D. from the University of Colorado at Boulder in the Building Systems Program. His dissertation was on his patented expanded microchannel heat exchanger. He is an assistant professor at University of Alaska Fairbanks in joint in mechanical engineering and Alaska Center for Energy and Power. He received the National Merit Scholarship, the Barry Goldwater Scholarship, the National Science Foundation Graduate Research Fellowship, is a Penn State distinguished alumnus, and is a registered professional engineer. He has authored or co-authored 124 publications (>3000 citations, >50,000 downloads, h-index = 28, third most prolific author in the existential/global catastrophic risk field (, including the book Feeding Everyone no Matter What: Managing Food Security after Global Catastrophe. His food work has been featured in over 25 countries, over 200 articles, including Science, Vox, Business Insider, Wikipedia, Deutchlandfunk (German Public Radio online), Discovery Channel Online News, Gizmodo,, and Science Daily. He has given interviews on 80,000 Hours podcast twice ( and ) and Estonian Public Radio, WGBH Radio, Boston, and WCAI Radio on Cape Cod, USA. He has given over 80 external presentations, including ones on food at Harvard University, MIT, Princeton University, University of Cambridge, University of Oxford, Cornell University, University of California Los Angeles, Lawrence Berkeley National Lab, Sandia National Labs, Los Alamos National Lab, Imperial College, and University College London.


I think this is important work. The survey of inclusion of GCRs in national risk assessments was very helpful. Related is Alexey’s and my paper on a global catastrophic and existential risk communication scale and its probability-impact risk matrix.

I agree that much more GCR mitigation could be funded through CBA.

There are suites of existential-risk-reducing interventions that governments could implement only at extreme cost to those alive today. … Governments could also build extensive, self-sustaining colonies (in remote locations or perhaps far underground) in which residents are permanently cut off from the rest of the world and trained to rebuild civilization in the event of a catastrophe....More generally, governments could heavily subsidise investment, research, and development in ways that incentivise the present generation to increase civilization’s resilience and decrease existential risk.

Though I agree that refuges would not pass a CBA, I don't think they are an example of something that would be extreme cost to those alive today-I suspect significant value could be obtained with $1 billion. And while storing up food for the US population for a five year nuclear winter might cost around $1 trillion, preparing to scale resilient foods quickly in a catastrophe is more like hundreds of millions of dollars and passes a CBA.

kill at least 5 billion people and hence qualify as a global catastrophe

This is higher than other thresholds for GCR I've seen - can you explain why?

And the Biden administration already includes costs to non-U.S. citizens in its social cost of carbon (SCC): its estimate of the harm caused by carbon dioxide emissions (The White House 2022a). The SCC is a key input to the U.S. government’s climate policy, and counting costs to non-U.S. citizens in the SCC changes the cost-benefit balance of important decisions like regulating power plant emissions, setting standards for vehicle fuel efficiency, and signing on to international climate agreements.

I'm pretty sure this includes effects on future generations, which you appear to be against for GCR mitigation. Interestingly, energy efficiency rules calculate the benefits of saved SCC, but they are forbidden to actually take this information into account in deciding what efficiency level to choose at this point.

It's probably too late, but I would mention the Global Catastrophic Risk Management Act that recently became law in the US. This provides hope that the US will do more on GCR.

You might want to check out this book on on the analogies between a personal relationship and the relationships between countries (focusing on nuclear war) by a husband and wife team.


Even though it is very unlikely that all of the three countries would dramatically reduce their arsenals if it is uncorrelated, if they are correlated, but I think it would become more likely. Also, if you could just get one country to reduce arsenals, this would reduce the expected damage of the nuclear war significantly, so then I think it would be competitive cost effectiveness.

As a simple example, if one thinks there is a 1% chance of settling the galaxy (lots of X risk, but then X security) with Dyson spheres that last 1 billion years, then I think this is around 10^33 expected future biological human lives. With digital minds, it would be far higher.

Impressive analysis on an important topic!

Philosophically, we take the more conservative person-affecting view, in looking specifically at the welfare of actual people, whether present or future – as opposed to contingent/merely potential people that would not exist if not for our intervention (or lack thereof).

  • Under the totalist view, this cause area would naturally be even more cost-effective – roughly 6.4x more, insofar as any person saved now will have children, who will go on to have children too and so on, such that (given expected future birth and death rates, plus relevant discount rates) counterfactually 6.4 lives are created/maintained by the averting of one death.

You only have a small ratio due to the totalist view because you have a constant exponential discounting for existential risk. Most people think that if we make it through a few centuries and start settling the galaxy, existential risk will fall dramatically, and so the expected number of human (or digital) lives becomes many orders of magnitude greater.

Using a person affecting view, we found for spending a few hundred million dollars on research, development and planning (you don't have to change the food system ahead of time to increase the chance of a good outcome significantly), the cost per life saved was $0.20 to $400, which is 1 to 4 orders of magnitude more cost-effective than GiveWell charities, so your number is near our most optimistic number.

If I understand you correctly:

This yields a probability of advocacy success of 17% [outside view]...

Multiplying these rates together yields the probability of persuading the United States, Russia and China to limit the size of their nuclear arsenals: 0.0000021% [inside view]...

Consequently, I end up weighing the far more conservative inside view more than the comparatively optimistic outside view – yielding a probability of advocacy success of 1.5%.

This could make sense if you started with an arithmetic mean. But with very large variation in size of numbers, the more appropriate mean is the geometric mean, which would be 0.006%. So then weighting the inside view similarly in logarithmic space as you have done in linear space could mean 0.00001% chance of success, which I think would then result in significantly worse cost-effectiveness than GiveWell.

Answer by DenkenbergerFeb 15, 2023156

I think that working out how resilient food technologies could be scaled up in a catastrophe such as nuclear winter is legible and concrete, including natural gas (methane) protein, hydrogen protein, greenhouses, seaweed, leaf protein concentrate, fat from petroleum, relocating cool tolerant crops, etc. Indeed, a survey and a poll have indicated that this work has reduced existential risk.

Nice piece and great visualization! It's an interesting framework to classify left and right of boom. Another way is prevention, response, and resilience. I would argue that much of the work on the impacts of nuclear war is motivated by prevention, so if you look at how much money has been spent on each of response and resilience, it might be 100 times lower than prevention. As you say, just because response and resilience are neglected does not prove that if they are highly cost-effective. So then I think actual cost-effectiveness models are useful, such as this, this, and this.

You covered a lot in only 20 hours!

I think Dave was referring to this report, but I haven’t cross-checked.


I think part of the explanation of some people's estimate of a greater long-term impact given nuclear war/winter is how AGI could lock in worse values. Will MacAskill talked about that in his most recent 80k podcast.

Thanks for mentioning ALLFED! We touched on this in one of our papers:

The importance, tractability, neglectedness (ITN) framework [45] is useful for prioritizing cause areas. The importance is the expected impact on the long-term future of the risk. Tractability measures the ease of making progress. Neglectedness quantifies how much effort is being directed toward reducing the risk. Unfortunately, this framework cannot be applied to interventions straightforwardly. This is because addressing a risk could have many potential interventions. Nevertheless, some semi-quantitative insights can be gleaned. The importance of AGI is larger than industry loss catastrophes, but industry loss interventions are far more neglected.

Or another way of saying this is that different solutions could solve different parts or percentages of the problem. So really I think we should be doing more actual cost-effectiveness analyses, and only using ITN for initial screening.

Transition to renewables require huge amounts of minerals, including copper, lithium, graphite and rare earth metals. Some studies suggest that the amount of minerals for a full transition to renewables may be beyond the Earth's reserves. If correct, this means that a full transition is physically impossible to accomplish.

Reserves are the amount of a mineral that can be extracted at a profit with current prices and technology. Even if technology does not improve, higher prices means much more mineral can be extracted profitably.

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