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.”
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.
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.
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.
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.
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