Thought, action and social-system models

I was asked by a journalist to comment on a paper. Here is an edited form of part of my response.

Thought evolved over evolutionary time to mediate between sensory perception and muscular action. Models are tools for thought, and help us to mediate between our perceptions and our actions.

Models are like crutches that allow our thinking to advance where it might otherwise be hobbled.

It would seem that recommendations of what sorts of modeling should be done should start with a discussion of what actions we are considering and what tools might be most helpful for informing decisions related to those actions, and then proceed to a discussion of the feasibility and resources needed to construct a model that could usefully inform decisions.

This question is particularly problematic when it comes to models involving social systems.

Clearly, there is some predictability to social systems: We can reliably predict that if political leaders engage in racially or religiously discriminatory speech that there will be an uptick in racial or religious violence within the society.

On the other hand, our primary goal is to inform decisions, not predict those decisions. We do not necessarily want to predict whether political leaders will engage in racially or religiously discriminatory speech, but rather inform the political leaders of the likely outcomes of their actions.

Further, while there is some predictive skill in predicting that increased prices will have a negative influence on demand, for example, the evidence of predictive skill for what we might call “future history” is limited at best.

There remains a major challenge in thinking through what sorts of models of social systems at global scale can usefully improve understanding and decision making at a cost that is commensurate with the value of generated information.

Consumption value and asset value

Much of my work gets done by way of “productive procrastination”, that is, working on things other than what I “should” be working on. This in an example.

There have been differences of opinion about how best to address the question of temporal discounting, especially with respect to intergenerational equity and the climate problem. In its simplest form, this question is often framed:

How should we be valuing the future?

Lately, I have been taking a different tack on addressing this question, asking :

Why do we value the future as much as we do, and not more and not less?

One way of thinking about the discounting question is to ask: What is the relative value of consuming a thing versus owning a thing? How do we compare the consumption value of a thing versus asset value of a thing?

I have been working on a simple mathematical model to explore these issues, as a kind of “fiction science” – a make-believe world that I hope shares properties with the real world, to function as a mathematical metaphor.

From working with this model, I have convinced myself that we value the future as we do because organisms that valued the future (or at least, valued having an asset more than they valued consuming it) increased their evolutionary fitness.

The squirrel that buried the acorn was more likely to survive and successfully reproduce than the squirrel that didn’t bury the acorn.

The psychology of valuing the future is a product of an evolutionary process that tends to increase reproductive success and evolutionary fitness.

Paul Cezanne, Bridge across the Marne at Creteil, 1894

In an earlier version of my model, the agents hoarded assets until they had sufficient assets to achieve reproductive success. This led me to ask a question that I had never thought of before:

Why do we value current consumption as much as we do, and not more and not less?

If we are comparing consumption value versus asset value of a thing, we need to ask not only why we value the asset as much as we do, but also why we value consumption as much as we do.

And I think the understanding of consumption value largely parallels the understanding of asset value. We value consumption because consumption increases our evolutionary fitness.

If that squirrel did not eat acorns today, the squirrel will die and fail to reproduce. Note that the squirrel doesn’t die right now if it does not eat the acorn right now. Eating the acorn right now is another form of investing in the future.

Camille Pissarro, Autumn morning at Eragny, 1897

Consumption value and asset value are two forms of investing in the future, and the balance between consumption value and asset value is the balance that tends to increase reproductive success and evolutionary fitness.

Humans are not squirrels. I doubt squirrels explicitly think very far into the future.

Evolution gives us psychological properties that manifest in unpredictable ways. Evolution, for example, did not select for the ability to play chess, but the ability to play chess is nevertheless a product of our evolutionary past.

One of the properties of human psychology is, when given the opportunity, we tend to consume far in excess of what might be thought to be optimal for maximizing fitness.

Diseases related to obesity and over-eating are rampant in wealthy societies.

Further, people who have enough money, often consume expensive clothing, automobiles, live in large and expensive homes, and so on. They display their consumptive behavior.

What is the explanation for the human tendency to want to consume far in excess of what might be thought sufficient to maximize fitness?

One possible contributing factor is that humans evolved in a resource limited environment, so that we evolved to consume as much as we possibly could, because in most of our evolutionary history, consuming as much as you possibly could directly maximized fitness.

However, one might also imagine that earlier in our past, consuming beyond what was needed to sustain life signaled to potential mates that a potential partner would have the resources to feed and care for offspring – and thus increase reproductive success.

Our drive to consume beyond what is needed to sustain our lives may be in part a consequence of a psychology that improved our evolutionary fitness by signaling our desirability as mates.

Observations indicate that financially successful people tend to be more sought after as mates than people who are living at a subsistence level.

The potential mate that is able to give valuable gifts is likely to be the potential mate that can provide for offspring, increasing reproductive success and evolutionary fitness.

People’s happiness tends to be associated with their amount of consumption relative to their peers, and less so to absolute levels of consumption. This is consistent with the drive to consume being closely tied to social signaling functions that increase evolutionary fitness.

Our drive to excessive consumption might be a bit like the peacock’s tail – something that, absent the signaling value, would decrease our evolutionary fitness; something that is maintained through sexual selection.

One might imagine that, in evolutionary equilibrium in a simple system with perfect information, the marginal benefit to fitness from consumption would equal the marginal benefit to fitness from savings. This, I think, is the conceptual underpinning of determination of the optimal savings rate from the perspective of evolutionary fitness.

Paul Baum, Willows on the brook, 1900

Of course, we are not slaves to evolution.

We have a neo-cortex that not only allows us to play chess, but also allows us to be thoughtful about how we might increase our evolutionary fitness.

If our drive to excessive consumption is damaging the planet, we can use reason to develop ways to meet our psychological needs while lessening this damage. (An alternative is to deny our psychological desires, but this seems to be a much more difficult path both psychologically and politically.)

Paul Signac, The port at sunset (opus 236, Saint Tropez)

The increase in value from the service sector relative to the manufacturing sector (for example, the value we get from books, movies, music, and so on) points to ways that we can satisfy desires to consume with relatively little impact in the material world.

Rather than asking people to consume less, we can work on dematerialization of value generation. This can be done by expanding the service sector, for example by increasing the value of information and social relationships.

The internet is be a major step forward in human history. We are interacting with each other, often in real time, without the need for transportation. We are consuming music and videos and video games that can be replicated at very low marginal cost.

We may be entering a new era of increasingly dematerialized consumption may allow us to reconcile our evolutionary past with a future that places fewer material demands on our environment.

I thank Harry Saunders and Juan Moreno Cruz for contributing to some of the ideas expressed here.

Aphorisms and over-simplifications


Twitter is interesting because if forces you to try to say things in 280 characters. This tends to lead one to speak in Yoda-like aphorisms or make gross over-simplifications. (And on Twitter, there is no shortage of people to remind you of the myriad ways in which you are over simplifying.)

Also, for those insufficiently disciplined to compose offline and tweet only carefully edited tweets, Twitter is all about rough first drafts, preserved forever, warts and all.

Twitter is odd because it is both ephemeral and eternal — ephemeral in the sense that thoughtful tweets tend to get lost in the sands of time; eternal in the sense that some thoughtless boneheaded comment is there to pursue you for the rest of your life.

That all said, this blog post, which I expect to evolve over time, will be my place to dust the sand off of some old tweets so that they might live on a bit longer.

By the way, my “not-so-professional” Twitter account is @KenCaldeira.
(I meant to write “After decades of R&D and subsidies …”.)

On prescriptive and normative statements in academic research papers

Andrey Lyssenko, pensive artist

A postdoc asked a question about being prescriptive and/or normative in academic papers, noting that some of the people with the most successful scientific careers were scientist/activists who did not shy away from saying in their technical work what we should do or what is good and what is bad.

My response:

It is fine to say “I think we should do XYZ” or “XYZ is good [or bad]” in an opinion piece in academic or informal settings.

But is it OK to make those kinds of statements in regular academic research papers?

A starting point is that there are multiple paths and strategies to success and you have to do something that fits your personal style and also takes account the reality of the job market.

I was trained on Hume’s distinction between empirical and prescriptive/normative statements.

My feeling has always been that we as scientists are trained to generate and disseminate information and our opining on public issues was just our hobby, not our profession.

That said, I am not above language of the sort: “Policy makers should consider doing XYZ” rather than coming right out and saying “Do XYZ”. 

This may seem rhetorical artifice, but there is implicit acknowledgement in that construct that I may be wrong in my recommendation when a broader range of facts is considered.

I am probably near one end of the spectrum of wanting to keep recommendations to a minimum in academic papers (research suggestions, factors for policy consideration).

Others say that the distinction between opinion/informal pieces and scientific/technical reports is artificial and all that is required is transparency.

What should we do? Good or bad?

When something is written in an academic paper, it should be true and you should stand behind it for all time.

Usually the errors are not in what you did, but errors in interpreting the implications of what you did. Often the error is believing your result applies more generally than it does.

When I look back since graduate school, my policy prescriptions have evolved, but I stand by all of the basic findings I have published over the years.

Enough responsibility to go around


To attribute damage to climate change, in principle we would like to fully understand the state of the system with climate change and then subtract out a counterfactual without climate change.

If we wanted to estimate the impact of current climate change on flood damage we could seek to understand current flood damage and then subtract off our best estimate of what would have happened in the absence of climate change.

Obviously, the stochastic nature of weather makes attribution challenging, but here I am after another conceptual issue.

We could have said, “The flood damage would not have been so bad had we not built valuable infrastructure in harm’s way.”

How could we attribute damage to building in harm’s way?

We could adopt a procedure that is similar to climate attribution: We could ascertain the observed damage under current conditions and subtract off what the damages would have been had we not built in harm’s way.

If we assume that damage would occur if and only if there were both climate change and a history of building in harm’s way, then this procedure would attribute the full cost of the damage to each of climate change and building in harm’s way.

The damage would not have occurred had we not changed climate and the damage would not have occurred had we not built in harm’s way.

Is there a truth to the matter in this case what fraction of the flood damage should be attributed to climate change and what fraction to building in harm’s way?

“Responsibility” is a social construct. Bad outcomes are often the consequence of a confluence of a series of unfortunate events, and there is no unique way of partitioning responsibility across the range of events that are jointly sufficient to produce the bad outcome.

We can agree on the empirical facts but disagree on how much responsibility for damage should (or should not) be attributed to climate change.


As a practical matter, as a climate modeler, if I wanted to estimate climate damage I would subtract results from a simulation without climate change from results of a simulation with climate damage, and I would attribute that full difference to climate change.

Also as a practical matter, if I were a coastal hazards investigator and I wanted to estimate the damage caused by inappropriate coastal development, I might compare cases with the same weather but with and without coastal development, and attribute the full difference to coastal development.

If a large number of studies examined damage with and without various factors (e.g., damage from failure to build adequate flood control systems), the sum of all of the attributed amounts could greatly exceed total damage.

There is value in these “all other things equal” studies, but in the real world other things are seldom equal.

Income Inequality and climate damage: Relative impact on utility


Dog deriving utility by watching a dog on television.

Nordhaus’s DICE model represents utility as population times per capita utility, and it represents per capita utility as increasing with per-capita consumption to the 0.45 power.

A lot of attention has been paid to the issue of temporal discounting in quantifying current value of future costs and benefits. That is, a lot of attention has been paid to assessing how we should value future generations relative to our own, but relatively less attention has been paid to addressing how we should value others living today relative to ourselves.

To address this issue, I thought I would look at the increase in total utility that would be predicted by the DICE utility functions under an assumption of income equality and compare that with the change in utility expected to come from addressing the climate change problem.

That is, what would the predicted change in utility be if everyone were brought to the mean income. (Before people start complaining, I too have read Kahneman and Ariely and understand that real utility is far more complicated than represented in the DICE model.)

Another view of this data is:

Unfortunately, I did not find a location to download this data easily. (I’ll fix up this blog post when I find it.) Therefore, I will just do a very rough-and ready analysis. Since they give us the median and the mean, let’s just assume this is a log-normal distribution with that median and mean.

Luckily, trusty Wikipedia gives us the appropriate formulas for the median and mean of a lognormal distribution:

For a mean income of $5375/year and a median income of $2010/year, this yields mu = 7.6 and sigma = 1.4. (We will forgo pretense to greater accuracy.) Density of people making X $/yr can be estimated by plugging in these numbers into the lognormal function above.

If we now assume that utility goes with income to the 0.45 power, we can calculate that global utility is 78% of what it would be were income distributed evenly. That is, this analysis suggests we are taking a 22% hit on global utility due to income inequality.

This 22% reduction in global utility is of the same order of magnitude as some of the more high-end climate damage estimates and an order of magnitude larger than many climate damage estimates.

This suggests that if we are interested in human welfare, addressing income inequality may be as important as addressing climate challenges.

I know this is just a back-of-envelope calculation and human psychology is a lot more complicated than income raised to the 0.45 power and climate damage is a lot more complicated than temperature squared. No doubt there are complicated relationships between income distributions, capital accumulation, and economic growth. Nevertheless, this analysis suggests that income inequality may be regarded as a challenge to human welfare that is on a scale comparable to that of the climate problem.

Lastly, I would just like to point out that there are two ways of decreasing income inequality: increasing incomes at the lower end of the spectrum and decreasing incomes at the upper end of the spectrum. While some of both strategies may prove useful, it is only by increasing incomes at the lower end of the spectrum that we can increase aggregate utility without decreasing anyone’s individual utility. Thus, while income redistribution may have important roles to play, this suggests that economic development will be the leading player in increasing global aggregate utility.



I am a geoscientist who thinks about energy systems and climate policy, and while I have some general knowledge of energy systems, I do not claim any policy expertise, so this is just me thinking out loud and in public …

WARNING: This blog post is more prescriptive than most things I write.


There are many people who put a lot of faith in the operation of markets who like to see governments do as little as possible.

Often, these people are OK with government action if someone can demonstrate that there is a market failure that government can address.

For the climate challenge, the most well-known market failure is the failure of markets to reflect future costs of climate damage in current prices. Where there is no price signal from future climate damage, markets continue to operate as if the operation of markets will not cause any climate damage — and this is driving us to dangerous climate change.

Economists often conclude that the most efficient way to represent this “unpriced externality” — an external cost that is not represented in market prices — is to have a carbon tax (or fee, if you prefer). A problem with this approach is that taxes are politically unpopular. A basket of policy approaches have been tried instead: carbon-trading markets, subsidies, regulations, etc.

These policies that drive technology deployment are addressing the “cost pricing failure” — the failure to represent costs of future climate damage.

“Unpriced future climate damage” is a market failure that is impeding deployment of clean energy technologies, but there is another market failure that is impeding development and improvement of energy technologies.

Horseshoe crab

Think of all the benefits of technology that we have today. Right now, you are using a computer and staring at a monitor screen. You have a cell phone. You’ve ridden in cars and flown in airplanes.

When these technologies were developed, some proprietary knowledge was generated and patented and this is a mechanism by which investors got rewarded for investing in innovation.

However, such innovative efforts also produced a lot of knowledge of a sort that is not patentable and where the benefits were not privatizable.

People watch each other.

When people see someone try to do something and fail, that gives people ideas on what they could do differently to succeed.

When people see someone try to do something and succeed, that gives people ideas on what they could do even better to out-compete them in the market.

Look around yourself right now: Can you find a single product in your field of view that was not informed by non-privatizable knowledge generated by private investment?

One of the things in my field of view is my DSLR camera.

This is a Canon camera, but the camera looks very similar to a Nikon or a number of other brands. Camera makers have converged on similar designs because there is non-privatizable knowledge about what works, what can be manufactured cost effectively and what can be sold into a market at what price.

Billboard in Wyoming, 2010

Economies and societies benefit from the non-privatizable benefits of private investment.

In most areas, we just accept that investment will be motivated only by privatizable benefits of an investment, and the entirety of non-privatizable benefits will go to other individuals or society-at-large. But the urgency and scale of the climate challenges warrant addressing this market failure specifically in climate tech innovation.

We can accelerate development and deployment of energy technologies that can help us attain net-zero emissions as soon as is practicable.

It is of course important to publicly fund the basic research that is the seed corn for long-term economic growth. But it takes risk-accepting investors to provide resources to develop the best ideas of scientists and engineers to the point where there is a product that can compete in the marketplace.

If the main reason we want private investors to invest in clean energy technologies is to benefit society, wouldn’t it make sense for society to provide incentives to generate that societal benefit?

The failure to adequately incentivize people to rapidly generate shared knowledge about better energy systems is a “benefit pricing failure” — a failure to provide a price signal to investors that reflects non-privatizable benefits of energy innovation.

Nearly everyone will benefit from cheaper clean energy technologies, especially-when those technologies can be nearly as cheap or cheaper than their CO2-emitting alternatives .

Ochopee, FL

In addressing climate challenges, one important market failure is the failure of markets to price social costs of future climate damage. Another important market failure is the failure of markets to price the social benefits of future cheaper clean energy technologies.

Policies that address the failure to price widely-shared benefits of energy innovation can be complement policies that address the failure to price widely-shared costs of climate damage. These policies address different market failures but are aimed at achieving the same goal.

And these two sorts of policies are complementary. Whatever the policy is that is aimed at driving deployment, having cheaper technologies will make that deployment-driving policy even more effective. With cheaper technologies, more clean energy technologies can get deployed faster and at lower cost — enabling earlier and deeper reductions in emissions.

We are not in an “either/or world”. The climate challenge is daunting enough that we need to live in an “and/and world”. We need policy drivers that promote deployment of clean energy technologies and we need policy drivers that promote development of better and cheaper technologies that are ready to be deployed.


We do not have to choose between policies that drive deployment of existing technologies and policies that drive development of better technologies.

We can do both and we should do both.

Hydrogen production from curtailed generation


There has been a lot of talk about making electrolytic “Green Hydrogen” using electricity from wind and solar power that would otherwise be curtailed. Less climatically helpful, there is also potential to use electricity from natural gas generators that would otherwise be idled.

Tyler Ruggles set out to answer the questions:

1. How much additional flexible load could we put on electricity systems before we would need to add more generating capacity?
2. In an economically efficient system, how would the fixed generation costs be allocated across fixed and flexible loads?

This study was published in Advances in Applied Energy under the title, “Opportunities for flexible electricity loads such as hydrogen production from curtailed generation”.

Tyler H. Ruggles, Jacqueline A. Dowling, Nathan S. Lewis, Ken Caldeira, Opportunities for flexible electricity loads such as hydrogen production from curtailed generation, Advances in Applied Energy 3, 100051, 2021.

The system considered by Tyler is represented by the following figure:

The system considers several generators, a fixed (i.e. specified and unchangeable) electricity load, and a flexible electricity load, here represented as electrolytic production of hydrogen gas. The dispatchable generator can be thought of as something akin to natural gas, but is left unspecified.

The basic results are summarized in this figure:

The last column (Renew+Storage) is perhaps the most relevant to ongoing discussions of “Green Hydrogen”. In this case, all electricity is produced with wind and solar power. Because of the high cost of storage, with low amounts of flexible load, it is economically efficient to build extra wind and solar generation and then discard some of this potential generation much of the time (curtailment).

However, if we have a lot of excess wind and solar capacity, that means there should be times when there is some excess generation capacity that is going unused. Tyler showed that, with a system sized to meet peak demands, there is some underutilized capacity nearly all the time. Because this underutilized wind and solar capacity has effectively zero variable cost, this excess electricity generation can be offered for free.

Because systems are sized to meet peak demand and there is almost always some underutilized generating capacity, a small amount of flexible load can be added to the system at effectively zero electricity cost and operate at high capacity factors.

The problem is, as additional flexible load is added, there is less and less unclaimed free electricity to go around, and so additional flexible loads need to operate at lower capacity factor, or additional generating capacity would need to be added to the system.

Both of these things cost money.

As can be seen from the above figure, flexible loads can be added to the system with effectively zero additional generating capacity to the point where the flexible load is about 20% of total load.

In other words, if a system is built to satisfy firm loads, it is likely that an additional 25% of that fixed load can be used to satisfy flexible loads with out any additional capacity expansion.

Between about 0.2 and 0.8 (20% and 80% of total load) in the above figures, there is a transition zone, where adding more flexible load would motivate building additional generating capacity, and so the flexible load would need to contribute to this capacity expansion.

When the flexible load is already representing over 80% of the total load, additional flexible load basically requires 1-for-1 expansion of generating capacity and so the flexible load bears the full cost of capacity expansion.

The figure above illustrates this transition. Below a flexible fraction of total load equal to 0.30 in this example, the flexible load draws primarily on capacity that was built to help meet peak electricity demands. Thus the flexible load can largely be a free rider.

But at a flexible fraction of total load equal to 0.40, additional capacity must be added to meet this flexible load. In this case, the flexible load would need to pay for that capacity expansion.

Tyler created this graphical abstract in an attempt to summarize the findings of this study.

As an aside, Tyler has training as a high energy physicist and was working at CERN when I hired him as a postdoctoral research scientist in our group. His most highly cited paper is about Higgs bosons.

My experience is that the most valuable qualities in a scientist include things like creativity, intelligence, work ethic, ability to complete projects, ability to work well with others, writing skills, math skills, etc. These are qualities that Tyler has in abundance.

Our goal is to do simple analyses to highlight fundamental principles. Smart people can learn domain knowledge quickly. This is the kind of analysis for which physicists are well suited.

This study has come to conclusions that are likely to stand the test of time:

  1. In systems designed to meet variable fixed loads, there is almost always some excess generating capacity and so almost always some electricity available to power flexible loads at the variable cost of the generator.
  2. As this excess capacity is increasing utilized, typically when flexible loads exceed 20% of total demand, additional flexible loads will require some additional generating capacity, and in an economically efficient system this cost will be shared between fixed and flexible loads.
  3. When flexible loads exceed about 80% of total demand, nearly every increase in flexible load requires a corresponding increase in generating capacity and so the flexible load would bear the full cost of this capacity expansion.

Replenishing the wind


People sometimes presume that when scientists set out to test a hypothesis, they are engaged in motivated reasoning and want to show that the hypothesis is correct.

While there might be some merit in that presumption, it is also the case that there are few things more pleasurable to the working scientist than being presented with evidence that your beliefs are false.

Working with Enrico Antonini, I recently had just such a pleasurable experience.

Like many other energy system researchers, I thought kinetic energy removed by wind turbines in large wind farms was replenished primarily by downward transport of kinetic energy from the overlying free troposphere.

For the first row of wind turbines, most of the kinetic energy transport is horizontal with the winds. However, each wind turbine can remove more than half the kinetic energy that passes through the disk swept by its rotors. The wind does not have to pass through many wind turbines before horizontal transport of kinetic energy is largely depleted. A source of kinetic energy is therefore needed to explain why wind turbines can still generate energy even when they are not in the first several rows of wind turbines.

Many energy researchers, including me, thought the wind energy was maintained by downward transport of kinetic energy from the overlying free troposphere. For example, in a 2017 paper published in PNAS, with Anna Possner as lead author, we wrote:

However, it remains unclear whether these open ocean wind speeds are higher because of lack of surface drag or whether a greater downward transport of kinetic energy may be sustained in open ocean environments.”

I believe many people held this view. For example, a paper was published in Geoscientific Model Development with a nice illustration of this mental model, showing a downward flux of kinetic energy


Enrico Antonini did some nice work in a paper published in PNAS this week that expands on a paper published in Applied Energy earlier this year. The Applied Energy paper showed how maximum power densities in regional scale wind farms are limited to a few watts per square meter, and are related to the Coriolis parameter times the pressure gradient.

In these papers, Enrico provides compelling evidence that the kinetic energy removed by wind turbines is replenished primarily by acceleration of air masses within the boundary layer by large-scale pressure forces (which are no longer balanced by apparent Coriolis forces due to the slowing of winds caused by the wind turbines).

Below is a schematic diagram of how things seem to work. Normally, large-scale pressure forces are balanced by apparent Coriolis forces resulting in what is known as “geostrophic flow”. However, as wind turbines remove kinetic energy from the winds, the apparent Coriolis forces weaken, and the unbalanced pressure gradient forces accelerate the air within the boundary layer.

Very little of the replenishment of wind energy is associated with downward transport of kinetic energy from the overlying free troposphere. The dichotomy we presented in our 2017 paper was a false dichotomy. Open ocean wind speeds are higher, but not primarily because there is less drag and not because there is substantially more downward transport of kinetic energy. The explanation for higher wind speeds over the ocean has to do with higher horizontal pressure gradients.

In the supporting material to the 2017 paper, Anna and I showed how wind power potential was closely related to heat fluxes at the planetary surface (blue are ocean areas, green is land; top to bottom is northern latitudes, tropics, and southern latitudes).

We presented this result without firm theoretical foundation. But now it seems that wind speeds over the ocean are high largely because ocean heat fluxes are high, and they can produce large temperature gradients, and these large temperature gradients can produce large pressure gradients, and large pressure gradients can drive strong winds.

Additionally, the theoretical understanding that Enrico developed predicts a length scale for recovery of winds downstream from a regional-scale wind farm. This length scale is the product of a time scale related to the Coriolis parameter times the geostrophic wind speed. The theoretical prediction of a length scale of several tens of kilometers is nicely supported by a recent study of wind speeds near large wind farms in the North Sea that which found a similar length scale in detailed simulations.

It is a real pleasure to be able to work with nice, smart, and productive people like Enrico Antonini. It is a privilege to be able to hire a bright early-career scientist who can show me my beliefs were wrong. And it is really nice to be working in a community where there is no great stigma to being wrong, if you are willing to adjust your beliefs in the light of new evidence.

On a final note, Enrico is on the job market. For his Master’s work, he worked at the scale of the turbine blade. For his PhD work, he worked at the scale of optimizing wind turbine positions within a wind farm. For the first part of his postdoc work, he worked at the transition between wind farm scale and what we might call the mesoscale. Now, he is engaged with a study on placement of wind farms in the context of continental-scale optimization.

Very few postdocs develop a fundamental theoretical understanding that makes testable predictions and has real world implications for energy system transition. (Enrico’s understanding can help people make a quick estimate of how closely wind farms can be spaced without them interfering with each other too much.)

If your department is would benefit from hiring somebody who understands scale-transition issues related with wind power development, you need look no further than Enrico.

High Energy Planet: Interview transcript

This is an edited transcript of an interview I did with Katie Auth and Rose Mituso for their High Energy Planet podcast. They were kind enough to allow me to reprint the transcript of our discussion here. Originally distributed on 7 June 2021.

I did some copy editing to improve infelicities of verbal expression, but tried not to change meaning. [Bracketed clauses were appended to two sentences a little too unqualified for my liking.] You can go to the High Energy Planet podcast for a more literal transcript.

I thank everyone at Energy for Growth Hub who helped make this a productive and enjoyable experience.


KATIE:  Ken, welcome to High Energy Planet.  It’s so wonderful to have you here.

KEN:  Thanks for inviting me.

KATIE:  So we’re just going to dive in with a pretty big question, which is a couple of years ago you tweeted, “Imagine it’s the year 2100 and the poorest parts of the world are prosperous and carbon-free.  What had to be true to make that happen?”  And I’m curious how you yourself would answer that question.

KEN:  I’m not an energy-systems engineer, and so I’m a little reluctant to make very specific predictions about future trajectories of energy systems.  But to my mind, while wind and solar and a lot of these other technologies have a lot of nice properties, they require a real transformation of how our whole electricity grid works.  It’s much simpler to have centralized power generation and distributed consumption. 

There are very few energy sources that can provide huge amounts of power in concentrated forms with proven technologies without emitting carbon dioxide into the atmosphere.  Nuclear power is one of the very few technologies that could potentially meet those requirements.  And so if you would ask me, like, what’s the most likely way we can have a prosperous future with low carbon emissions I would guess it’s going to depend a lot on nuclear power.  That’s not to say over the course of the rest of the century a lot of other technologies could be invented and developed.  So I’m not making a prediction.  But if you’re asking for my sense of what’s the most likely path to be successful given what we know today I would guess a heavy reliance on nuclear power.

KATIE:  Not an uncontroversial position to take at the moment.

KEN:  One of the things – and this is actually in many different contexts – I’ve found that often it’s better to argue for good process than to argue for specific outcomes.  And so I don’t pretend I know what’s going to be the best technology mix in 2100. 

But I do know that if we prematurely push things off the table and don’t subject various technologies to a fairly objective analysis that we might end up building some things that aren’t so good and overlooking things that could be very helpful.  My focus is on trying to get good process and open, transparent, inclusive processes with obviously democratic and local determination for people [i.e., respect national sovereignty].

ROSE:  So Ken, continuing this theme of prosperity and climate and balancing those two things, you authored a paper last year that found that if poor countries waited to decarbonize until they reached about $10,000 per capita GDP, it would cause less than .3 degrees Celsius’ additional warming.  And that suggests that we should just leave poor countries to develop and kind of take down the climate pressure on that side.  But on the other hand you’ve also returned a paper finding that less-wealthy countries shouldn’t be allowed to get locked into long-term fossil-fuel infrastructure.  So how do we reconcile those two things?

KEN:  Well, first of all to push back a little bit on your language, I probably wouldn’t have said “shouldn’t be allowed,” because I don’t think it’s my responsibility to tell others what they can and can’t do.  And so…

ROSE:  Very fair point.  [CROSSTALK] You pass the Energy for Growth Hub Climate Justice Test.

KEN:  [LAUGHTER] And so, the question is: How can we help make it in everyone’s self-interest to behave in ways that are also good globally? 

If you look historically, the amount of emissions that have come out of sub-Saharan Africa is climatically negligible.  It’s a little odd for the West, who’ve developed based on fossil-fuel emissions, to say to other countries, “Well, you can’t develop the same way we did.” 

If you’re developing on a fossil-fueled economy what could we do to make it an easier transition off of that?  And this is, again, coming back to this nuclear issue. 

Let’s say you build a natural gas plant and it’s centralized.  Maybe later you’ll replace that with a nuclear power plant and you still have a hub and spoke kind of electricity system.  But if you think the future’s going to be wind and solar then you might want to build a different kind of electricity grid now even if it’s fossil fuel, in anticipation of this distributed system later.

ROSE:  I think then this for me naturally leads to this question of, well, the people who are actually locked in are the rich people.  How do we square that circle?  You know, you’ve advocated for hard zero-emissions targets and you’ve likened this kind of hilariously to we need to seek to fully eliminate muggings of older ladies, rather than setting a rate for muggings that we can live with, you know?  So basically we can’t live with old ladies being mugged, and we shouldn’t live with old ladies being mugged, and we shouldn’t live with more carbon in the air.  But then you’ve also expressed a lot of skepticism about the viability of (coupled removal) at scale, which is central to many of our climate models and to this world that we live in that is fossil-based now and into the foreseeable future.  So how do you reconcile these two positions if, okay, putting poor countries to one side you have some breathing room?  What do we say to the rest of the world?

KEN:  I’ve been a climate scientist, biogeochemist and climate physicist and so on, for my whole career.  And then over the last years – more recently switched to trying to focus more on energy systems and solutions.  With that was the recognition that most people most of the time operate in what they perceive to be their self-interest, and that you’re going to solve this problem when you align people’s self-interest with a more global interest.  One of the ways you do that is by making the better energy sources even better and cheaper so that it’s the least cost approach. 

In the same way that there is a portfolio of energy technologies that will be used, there’s a portfolio of political strategies.  I find this somewhat disturbing, that…  Some people should be working to pass legislation through Congress.  And that means you need to – for the way the Senate is now that you need to get Republican votes.  And so you have to be very careful.  And there’s other people who should be saying, “oh, we need zero emissions today, and we should be sending boatloads of money to poor countries to pay their cost differential.”  I see these different political strategies as supporting each other.

I wish that people could appreciate that there’s value in political disagreement.

ROSE:  It’s an ecosystem.

KEN:  Yeah, and that – and it really bothers me to go on Twitter and see people badmouthing each other who are working towards the same goal through different strategies.  Because these strategies are complementary, if people would focus a little more on advancing their positive vision and a little less time expressing their negative energy about somebody else’s vision, we’d all be better off.

KATIE:  So the political strategy of climate alarmism really didn’t work particularly well for about three decades.  But now terms like “climate emergency” and “climate crisis” are part of policy lingua franca, and climate action is at the forefront of many policy agendas, at least rhetorically.  So what do you think was the tipping point?  And does using a framework of urgency change the way we think about or react to climate change?

KEN:  One of the things that was important for changing the political landscape is the reduction in costs in wind and solar power, that in large part was brought about by Germany’s Energiewende program.  The idea that it might actually be feasible to deploy some of this stuff, it might not cost that much, moved a lot of people to see the energy system transition as something that might be done realistically. 

This shows the importance of cost, in that wind and solar got cheaper, making it feasible to deploy. This made people take energy system transition more seriously.  That’s one component.  A more thorough-going energy system transition will depend on making other technologies cheaper as well. 

With regard to rhetoric, that’s a tougher question.  The social dynamic encourages a ratcheting up of rhetoric, so that, okay, we have two degrees.  Well, I’m going to say we should stabilize at 1.5 degrees.  Well, I’m going to say 1.25.  I’m going to – you know?  You can always get some social credit by saying something slightly more extreme than what the mainstream view is now. 

I used to say things like, “oh, we shouldn’t research adaptation because that will make people acknowledge that there’s going to be climate change, and that – just make it more likely, so we should just work on climate-change avoidance and not on adaptation.”  And I used to be somebody who was taking the more extreme positions and saying negative things about people who are taking more compromising positions. 

I don’t think any of my beliefs about, like, if I were the benevolent dictator of the world what would be the good thing to do is, have shifted.  What has shifted is my sense of how change happens in the world. 

Change happens by making more people see it in their self-interest.

ROSE:  You sound like a man who’s briefed Congress, Ken [LAUGHTER].  You know, out of the lab and into Congress.

KEN:  Well, one of the most depressing things for Congress was – this was on ocean acidification – I testified in a hearing for some legislation for money to fund research into ocean acidification.  At the end of it, after the formal testimony was over, the staffer walked up to me and said, “Okay, so what part of ocean science’s budget shall we take this money from?”

ROSE:  Oh no.

KEN:  “Because of course we’re not going to expand funding for marine sciences.”  And I felt, like, oh man, I did all this work just to shift…

ROSE:  Oh Ken.

KEN:  …(how) that marine science (inaudible) was.

ROSE:  There’s some species of jellyfish or octopus or something that’s dead because of you [LAUGHTER], unstudied.


ROSE:  Coming up, we ask Ken about his mixed feelings about geoengineering and his new approach to Twitter.

KATIE:  And we play Rant or Rave to find out about his checkered past as a bassist and a pumper of crocodile stomachs.


KATIE:  So Ken, you’ve been advising Bill Gates for about 15 years I think on climate change, arranging learning sessions for him with climate scientists and thinkers from around the world.  I’m actually curious, how did you go about designing that curriculum when you’re dealing with one of the most complex and multidimensional issues on the planet?  Where do you start?

KEN:  What I really liked about these sessions is that I could get these world’s leading experts in whatever – hydrogen, cement, battery technologies, whatever – and I could be there asking the stupid questions and being the student.  And being willing to expose my own ignorance all the time – I think me feeling comfortable with that also let me play this role well. 

I figure if I have a question there’s probably other people in the room with the same question. 

I used to feel like I knew what to do politically and that I also felt like I knew a lot of things.  And as time has gone on I’ve become less sure I know the right things to do politically and more accepting of a diversity of political strategies.

My awareness of what I don’t know has grown faster than my knowledge. 

This has put me in a good position to be in these kind of helpful and advisory roles.  Because – and I also have a commitment to process – let’s have an open, inclusive, and fact-based process.  And so all of these qualities put me in a good position to be in roles where I’m trying to help develop a good process, and bring in good information, and help facilitate others to make good decisions.

ROSE:  That’s really great, Ken.  I wonder how much this kind of softening of your posture has equipped you for Twitter fights.  But that’s – we’ll discuss that later.  Where, you know, it’s very absolutist now, like, where you have to know and speak with so much confidence.

KEN:  I’ve actually changed my Twitter strategy substantially and with very positive outcomes. 

Basically I’ve decided to try to not say anything negative on Twitter, and not to respond to negative comments to me, and try to be entirely positive on Twitter. 

And I see this in my own family relations or spousal relations as well.  Often we say negative things and it’s more about us releasing our negative emotions, and it’s not really about trying to effect positive change in the world. 

It’s very rare that a negative statement produces a positive outcome. 

I see this even with my postdocs and students, where if I’m not very careful, even if I’m trying to make a positive suggestion, people can hear that as a criticism of what they did wasn’t good enough.

People get hurt very easily.  We’re just not aware of how much our negative statements hurt people. 

Unless you’re really sure that a negative statement will produce a positive outcome, you shouldn’t do it. It’s more about yourself trying to get attention or releasing emotions, and not really about trying to help anybody.  And so, yeah, I think just being a little thoughtful – am I helping somebody by doing this?

KATIE:  So we wanted to talk a little bit about geoengineering.  In the past you’ve called yourself a [quote] “reluctant advocate” of researching solar geoengineering.  And as of 2014 you thought there was maybe something like a 20% chance that somebody would ultimately try it.  And, you know, now we’re in 2021–would you bet on different odds today?

KEN:  All the model simulations of solar geoengineering suggest that it would basically work to offset most climate change for most people, most of the time. 

Now, it doesn’t save you the need to do an energy-system transition, because everybody acknowledges that if greenhouse gases continue to accumulate in the atmosphere and you continue engineering the planet to mask that, that eventually that’s going to lead to some pretty nasty outcomes. 

On the other hand, if we get to mid-century or beyond and there’s massive crop failures throughout the tropics and widespread suffering, and richer countries aren’t really doing anything to alleviate that suffering, solar geoengineering is basically the only way known to cause the planet to cool within years to decades.

Basically if you zero out emissions the planet even continues to warm; it doesn’t start cooling for centuries.  And I don’t know what the likelihood of some kind of crop failure throughout the tropics is.  But, if that should happen… 

Well, first of all I’d also like to say that I don’t think there’s any reason why anybody, even in that situation, anybody would need to go hungry in the world.  Because there’s enough food produced, if you look at all the waste of food going on in the United States and Europe and so on.  I think if there ever is geoengineering it’s going to be multiple failures.  First of all, the failure of the social system to prevent the CO2 emissions.  But, then the direct climate crisis.  But then it’ll also need to be a social failure that the global community doesn’t mobilize to address issues.  But, the global community hasn’t been very good at mobilizing to address important issues to date. 

I don’t know what the likelihood that there’ll be something perceived as an acute climate crisis that needs to be dealt with right now.  But if that’s felt the only – solar geoengineering is really the only thing that could cool the planet [within the politician’s political career].  And, if you were the leader of a country and people were starving to death, and you felt that you could save lives by solar geoengineering, you would be remiss not to give it serious consideration.  And so I don’t know what the chances are of having widespread famines or something like that, but if that happens the possibility of solar geoengineering could be quite high.

KATIE:  Do you worry that the prospect of geoengineering, kind of having this as a last-resort solution, kind of impedes action now?

KEN:  I don’t think it really does.  There are different metaphors, but I would look at solar geoengineering as like morphine for the cancer patient, in that it provides some symptomatic relief but it’s not addressing the root causes.  If you have cancer, morphine can be extremely valuable.  So symptomatic relief shouldn’t be scoffed at. 

But I don’t think that the prospect of solar geoengineering is preventing action on climate change.  There was some rhetoric in that direction maybe a decade or so ago.  But I think now everyone understands that even if you’re doing solar geoengineering you still need to stop emitting CO2.  It’s doesn’t work to do both at the same time.

KATIE:  Yeah.


ROSE:  Okay Ken, now it’s time to play Rant or Rave.  So this is a quick-fire game where we say a word or a term and you go on a short – very short rant or rave about it.  Are you ready?

KEN:  Okay, I’ll give it a go [LAUGHTER].

ROSE:  All right, rant or rave: hallucinogenic drugs?

KEN:  I enjoyed them when I was in high school.  I would be afraid to take them now.

KATIE:  Rant or rave: pumping crocodile stomachs?

KEN:  Not pleasant, a little bit similar to (inaudible), but a very interesting experience.  Before I went to graduate school I was a software developer in the financial district in New York.  And between software development projects I did other kinds of projects.  And one of the things I did was go to Mexico and work as a field assistant to some herpetologists in the Mexican rainforest, the Selva Lacandona.  And one of the things that they were doing was ecological study of the crocodiles there and looking at both their population and what they were eating.  And so we were out there trying to catch crocodiles, and tag them, and pump their stomachs and see what they’re eating.  And so a crocodile sits with its mouth open and basically waits for a fish or something to swim past it, and then it closes its mouth.  And even a grownup crocodile will eat little bugs and little tiny fish.  And they might just get, like, one fish a month.  And that was actually the experience that made me go back to graduate school and get a PhD.  Because I thought, oh, if I don’t get a PhD I’m always going to be somebody’s field assistant.  If I want to lead expeditions I have to get a PhD.  And it was a really fun and interesting thing, and really my motivation for going back to – to going to graduate school was to try to lead field expeditions in the rainforest, which I never did.  But I did finally get to go to coral reefs so that’s pretty good.

ROSE:  Climate purity tests?

KEN:  I don’t like them so much.

KATIE:  Okay, this is a throwback.  Punk-funk and Fists of Facts.

KEN:  I like playing bass guitar, and I still – I played last night, but just by myself.    I went to Rutgers College in New Jersey and a bunch of my friends and I all moved into New York City when we graduated.  And all my friends were artists and musicians in fairly reasonably-successful bands.  And I went and did computer programming work on Wall Street, which was, like, the boring thing to do. But I still played music with my friends, and we had a band and we called it “Fist of Facts,” an idea – even then it was the idea that facts did have this political import.  Even before graduate school I was still on that kind of thread [CROSSTALK]…

KATIE:  Science fights back.

KEN:  Yeah.  So – and we played – we were basically fans of Fela Kuti and had our downtown New York version of Afrobeat I guess and reggae kind of stuff.  So that was our [CROSSTALK].

ROSE:  That’s awesome. [LAUGHTER]

KATIE:  We have to look you up after this.

ROSE:  Definitely on (Spotify).

KEN:  [CROSSTALK] We’re not so good.  But we’re on Spotify, so… [LAUGHTER]

ROSE:  That is so great.

KATIE:  All right, final one.  Bets with Ted Nordaus?

KEN:  Oh yeah.  So we’ve had about whether…

ROSE:  The (peaking) emissions.

KEN:  …[CROSSTALK] have CO2 emissions already peaked?  And I think I’m going to be winning a bet very soon.

ROSE:  All right, good one.

KATIE:  Unfortunately yeah.

KEN:  And this was actually even symbolic on this bet, because we had to say what charity we wanted to give it to.  And I said I want to give to the Doctors without Borders to say, look, it’s not all climate change.

ROSE:  All right Ken, thanks so much for being with us on High Energy Planet.  We’ve really enjoyed this discussion; it’s been a lot of fun.

KATIE:  Thanks Ken.

KEN:  Thank you.

Environmental science of climate, carbon, and energy