Sunday, January 29, 2023

Energy Isn't an End in Itself

Ezra Klein of the New York Times has a recent opinion column advocating for a future in which people everywhere use many times more energy than Americans use today. The column is largely inspired by J. Storrs Hall’s book Where Is My Flying Car?, along with other writers who have been promoting what they call “energy abundance”.

Before I explain how wrongheaded Klein’s column is, let me say what I like about it.

I absolutely agree that “Where’s my flying car?” is a legitimate question. I would even call it a fascinating question—though not, ultimately, a very important question.

I also agree with Klein’s incisive criticisms of Hall’s sociopolitical theories. Rather than review those here, I’ll just refer you to Klein, who’s far better than I am with words.

Finally, I agree that poverty is a huge problem in most parts of the world and that bringing everyone out of poverty will entail a pretty big jump in global energy use.

But by “pretty big” I mean something like a factor of 2, not a factor of 20. The world per-capita energy use rate is currently about 2.5 kilowatts. Ending widespread poverty throughout the world will roughly double that number, bringing it up to the current level in western Europe and Japan, about 4 to 5 kW.

Klein is trying to envision a world in which per-capita energy use doubles three more times, then grows even further by unspecified amounts. The first of these additional doublings would bring the world up to the current per-capita energy use rate in the United States, 9 kW. The next doubling would bring the world up to about 20 kW per capita, the current rate in a few small industry-heavy countries such as Iceland and Qatar. The third doubling would take us to 40 kW per capita, a level of energy use that no country on earth has ever experienced. A recent report from a think tank called The Center for Growth and Opportunity, cited favorably by Klein, defines 40 kW per capita as “energy superabundance” and advocates for such a goal. Yet Klein refers to this goal as “fairly modest”, touting the idea of using still more energy.

So what’s wrong with aspiring to use enormous amounts of energy? Just two things: There’s no known reason to do so, and there’s no known energy source that’s free of unwanted side effects.

Before explaining the first of these points in some detail, let me briefly address the second. The only known energy sources that can conceivably scale up to a significant percentage of 40 kW per capita—that is, 400 terawatts globally—are wind (maybe), solar, and nuclear energy. (Sorry, geothermal resources are too limited to sustainably contribute tens of terawatts.) Wind or solar generation on that scale would take over vast stretches of earth’s surface that many people would prefer to reserve for other uses. Nuclear energy on that scale, whether fission or fusion, would produce enough excess heat to vie with the effects of anthropogenic greenhouse gases on a regional, if not global, scale.

So even “clean” energy sources have unavoidable costs. The question then becomes whether there are benefits that make these costs worthwhile.

Why use more energy?

Merely using more energy provides no intrinsic benefit. I could add massive amounts to my personal energy use just by opening the windows in January and cranking up the thermostat. As Amory Lovins famously said, “People don’t want raw kilowatt-hours or lumps of coal or barrels of sticky black goo. They want hot showers, cold beer, comfort, mobility, illumination.”

Energy is a useful abstraction because we can often substitute one energy source for another: coal for wood, natural gas for coal, wind for natural gas. When we make such a substitution, we can estimate how much of the new source we need by equating its energy content to that of the old source. But real-world complications quickly arise in the actual machinery that captures the energy and transmits it and puts it to use. Energy gets lost as waste heat, in steam turbines and automobile engines and chimneys and incandescent bulbs and open windows. Different technologies can produce the same benefit with vastly different amounts of waste.

So although it pains me, as a physicist, to say this, energy per se is not as fundamental to human needs as Klein and others seem to think.

Klein seems to believe that energy itself is more important than what we use it for. He writes that we can choose among three possible goals as a society: use less energy, or use the same amount, or use more. In fact none of these goals make any sense. It’s wrongheaded to treat energy as an end in itself. The sensible goals are hot showers, cold beer, and so on.

OK, so what about those kinds of goals? Klein lists some particular energy uses that would supposedly become possible if we just had more energy. Much of his list is standard fare among “abundance” advocates: desalination to obtain fresh water; indoor farming with artificial light; capturing carbon dioxide directly from the air. Like his predecessors (at least all those I’m aware of), Klein makes no attempt to do the math to determine whether any of these activities will ever be practical—or desirable—on a scale that would add more than a few percent onto global energy consumption. Desalination, for instance, already provides most of Israel’s municipal water supply, yet adds just 5% to that country’s electricity use.

To this standard list Klein then adds nanotechnology, but here he seems to be misreading Hall. Yes, Hall complains ad nauseam about the slow pace at which nanotechnology has developed in recent decades, supposedly depriving us of all sorts of technological miracles. But nanotechnology isn’t a big energy consumer, and even Hall never suggests that the reason why it hasn’t advanced more rapidly has anything to do with limited energy supplies. Klein implies that it does. Maybe he has some convoluted, unwritten reasoning to back up the claim, but I suspect he’s just confused.

Finally there’s transportation—specifically, aviation and space travel. Hall claims that these technologies have been held back, since the 1970s, by “ergophobia”—fear of using energy. Klein suggests (again without doing any of the math) that if we just had enough energy, virtually everyone on earth would be using it to fly hundreds or thousands of miles a day. Is any of this plausible?

I don’t think so. It’s true that aviation and space travel both require a lot of energy per passenger, but neither is being held back by fuel shortages or even by fuel costs. Less than one percent of the total cost of a Space Shuttle launch was for rocket fuel. For commercial jet flights the fuel cost percentage is higher (typically about 20%), but still not dominant.

The more important role that energy plays in limiting aviation and space travel is indirect. The kinetic and gravitational energies maintained during flight make it intrinsically dangerous—and it’s perfectly rational to be “ergophobic” about that danger. There are ways to mitigate the risks of flying, and the safety record of commercial jet travel is a miracle of the modern world. But risk mitigation comes at a high cost, both in dollars and in convenience: pilot licensing rules, maintenance requirements, air space restrictions, airport security screenings, and so on. People will inevitably disagree over how much risk to accept in exchange for reducing those costs, but let’s not confuse the cost of safety with the cost of fuel.

In summary, it is a logical fallacy to argue that merely supplying the needed energy would give us the world that Klein envisions, in which billions of people commute between continents on a daily basis. Besides the challenges of safety and convenience (and counteracting gravity in the first place), it’s just not clear how many people would voluntarily choose such a lifestyle. Most Americans today could afford to travel more than they actually do, but find life less hectic and more meaningful when they put down roots and spend plenty of time close to home.

Rewriting energy history

Although Klein’s column is ostensibly about the future, his rhetoric relies on comparisons to the past. Such comparisons are all too tempting, because no sane person today wants to go back to the awful living conditions our ancestors had to endure.

But Klein mangles the facts about past energy use.

The most eye-popping howler in Klein’s column is his claim that “Across the 18th, 19th and 20th centuries, the energy humanity could harness grew at about 7 percent annually.” He says this in the context of describing Hall’s book, which contains a somewhat similar claim. Hall’s version is exaggerated badly enough. Klein’s version is far worse.

The words “across” and “harness” are somewhat vague, so there’s no unique way to correct Klein’s claim, but no reasonable interpretation of it is anywhere close to true. If we’re talking about the growth in global primary energy use from 1700 through 2000, then the average annual increase was actually about 1.2%, not 7%. With 300 years of compounding, this means the overall increase was by a factor of about 40, whereas Klein’s 7% would imply a growth factor of (brace yourself!) 650,000,000. (The 1.2% annual increase breaks down into a population growth rate of about 0.8% and an energy-per-capita growth rate of about 0.4%.) Even during the 20th century, when energy use grew more rapidly, the average annual growth rate of global energy use was only 2.3% (again about 2/3 from population growth and 1/3 from energy-per-capita growth). There have been shorter time periods over which world energy use grew somewhat more rapidly, but “7 percent annually” over “centuries” is a ridiculous claim.

Hall, for what it’s worth, arrives at his 7% annual growth figure by looking not at all of humanity but only at “our civilization”—by which he seems to mean the United States since 1800, and perhaps Great Britain during the century or so before that. He plots a graph purporting to show a 2% annual growth rate in U.S. per-capita energy use from 1800 through 1979, although it actually shows an average growth rate of less than 1% over that time period. He then compounds the alleged 2% per-capita energy use growth with an alleged population growth rate of 3% (also exaggerated from the actual U.S. value of about 2% over this time period), to obtain a claimed 5% growth rate in “our civilization’s” total energy use. Finally he adds on a 2% “energy efficiency growth rate” (which he obtains by extrapolating from a much narrower data set), to get a purported 7% growth rate in “usable” energy. (Perhaps Klein intends “could harness” to imply the incorporation of some kind of growing efficiency factor. If so he has not made that clear, nor has he incorporated any such factor into his article’s other energy figures.)

In fact the only way to arrive at anything close to a 7% annual energy growth rate over multiple centuries—for the world or any large portion of it—is to arbitrarily define “energy” to exclude the wood and other biomass energy that accounted for nearly all energy use before the Industrial Revolution. That’s what Hall has actually done, as he confesses on his blog. If humanity’s energy use in 1700 was zero by definition, then it has grown since then by a factor of infinity! Does Klein (who calls Hall’s technical analyses “careful”) realize that he’s propagating this foolishness on Hall’s part? We have no way to tell.

But then Klein does it again, this time with a misleading paraphrase from Charles Mann’s book The Wizard and the Prophet:

Without energy, even material splendor has sharp limits. Mann notes that visitors to the Palace of Versailles in February 1695 marveled at the furs worn to dinners with the king and the ice that collected on the glassware. It was freezing in Versailles, and no amount of wealth could fix it. A hundred years later, Thomas Jefferson had a vast wine collection and library in Monticello and the forced labor of hundreds of slaves, but his ink still froze in his inkwells come winter.

Were King Louis XIV and Thomas Jefferson truly “without energy”? Of course not! The Palace of Versailles has 1200 fireplaces, and surely the king could afford to keep them supplied with wood. The fireplace count at the much smaller Monticello is just 8, but they consumed 10 cords of wood per month, which would have provided about 200 million Btu of energy. The same energy in the form of natural gas would now cost you about $3600. Louis XIV and Jefferson weren’t lacking energy. They were lacking efficient central heating systems that capture most of the energy before it goes up the chimney.

Today’s American homes are not merely better heated and better lit than in Thomas Jefferson’s day. We also have refrigerators, air conditioners, hot running water, automatic washers and dryers, electronic entertainment systems, and a cornucopia of other energy-hungry appliances. And our homes have grown, doubling (at least) in square footage per capita. Yet astoundingly, we use less energy per capita in our homes today than Americans used in 1800. How efficiently we use energy can be more important than how much energy we use.

These historical facts about energy use don’t get discussed much, so perhaps we shouldn’t be shocked that Klein could get them so wrong. Still, I would expect someone who writes for such a large audience to consult a knowledgable expert for some basic fact-checking. It’s unfortunate that the New York Times allows its opinion columnists to spread falsehoods that are so easily refuted.

Why promote energy use as a goal?

When smart people misstate facts, even unintentionally, it’s natural to ask why. So I’d like to end this essay by considering some of the possible incentives, motives, and goals of the “energy abundance” movement. Why are so many writers currently pushing the idea that increased energy use is a moral good—a worthy end in itself?

One incentive for virtually every writer these days is to attract readers, generate clicks, and sell subscriptions or books. To do that it helps to say things that are surprising and provocative, not banal and reasonable. Fuel a culture war whenever possible.

It also helps to say things that readers want to hear. Many Americans are understandably tired of being scolded for using too much energy. They’re eager to believe that the scolds were wrong.

But there are plenty of subjects that can arouse readers’ emotions. Why “energy abundance” in particular?

For any intellectual there is a natural urge to understand broad swaths of the world in terms of a few deep principles: to devise a Grand Unified Theory of How the World Works. The so-called “abundance agenda”, as articulated by Klein’s collaborator Derek Thompson (in an article modestly titled “A Simple Plan to Solve All of America’s Problems”), seems to be a proposal for such a theory. We need (Thompson says) an abundance not just of energy but also of housing, infrastructure, immigrants, COVID tests, and admission slots at elite colleges.

As a physicist I’m all too familiar with the temptation to devise Grand Unified Theories. But I also know that virtually all of these theories turn out to be wrong (or sometimes “not even wrong”, that is, too vague to make testable predictions). The world of human affairs is vastly more complex than that of fundamental physics, so we should be even more skeptical of Grand Unified Theories in the social realm. A theory that works beautifully in one situation can still fail badly in another, so we shouldn’t become too attached to any particular Grand Unified Theory. In the language of Archilochus and Isaiah Berlin, we should try to think like foxes, not hedgehogs.

At least that’s my opinion. The “abundance agenda” folks are obviously trying to be hedgehogs.

Of course there’s also a Grand Unified Theory that’s opposite to the abundance agenda: what we could call the “scarcity agenda” of those who preach about limited resources and living within our means. That way of thinking had its heyday when I was growing up during the 1970s, and is still prevalent among environmental activists and many academics. Like the “abundance agenda”, it’s a correct and useful viewpoint in some circumstances but fails badly in others. So a worthwhile motive for the energy abundance tribe would be to counteract the worst excesses of the energy scarcity tribe. I think that probably is part of their motivation, even if they go beyond it to indulge in their own excesses.

There’s one further motivation that I think underlies some, though not all, of the recent literature on “energy abundance”. The Center for Growth and Opportunity, whose “Energy Superabundance” report Klein cites for its energy use rate goal of 40 kW per capita, was established (at Utah State University in 2017) by a $25 million grant from the Charles Koch Foundation. Although the Center denies that its activities are “directed or influenced in any way” by its donors, Charles Koch’s fortune came from oil and he makes no secret of his libertarian political agenda.

After decades of casting doubt on climate science, fossil fuel interests have learned that that tactic is no longer acceptable in polite society. How, then, can they promote continued growth of fossil fuel use? One effective way might be to spread the general message that we should use more energy.

Klein’s essay, of course, includes the perfunctory caveat that the energy we use in our utopian future should be “clean”. He even alludes to the “daunting” task of shifting our energy economy to “nonpolluting sources”. But the thrust of his essay is that energy has brought us wondrous gifts, and promises us new miracles to come, if only we’ll make every effort to use more of it. Seeing that message in the Opinion section of the New York Times surely brought a smile to the face of Charles Koch.

Sunday, November 13, 2022

The Gee-Whiz Energy Graph

In his 1954 book How to Lie with Statistics, Darrell Huff devoted a full chapter to “The Gee-Whiz Graph”—the trick of omitting zero from the vertical axis and stretching what’s left, to make a trend look steeper than it actually is.

We’re currently experiencing an outbreak of people applying this ploy to plots of one particular data set: historical per-capita energy use in the United States. Before this outbreak spreads any further, I’d like to at least document it.

First, here’s a straight plot of the data with a vertical axis that starts at zero (calibrated in two different unit systems for later comparisons):

There’s a lot to notice here! A long plateau at about 4 kilowatts during the 1800s. Dramatic upward spurts between 1897 and 1973, interrupted by temporary plateaus and a deep dip during the Great Depression. A peak at 12 kilowatts in 1979, followed by a gradual downward trend to the present level of about 10 kilowatts. (For comparison, the energy use rate of a typical adult’s food diet is about 0.1 kilowatts.)

If you want to understand this fascinating history, the best place to start is the work of Suits, Matteson, and Moyer, from whom I obtained most of the data.

On the other hand, to quote Huff:

“That is very well if all you want to do is convey information. But suppose you wish to win an argument, shock a reader, move him into action, sell him something. For that, this chart lacks schmaltz. Chop off the bottom.”

Planet Money

In 2013, Jacob Goldstein and Lam Thuy Vo of NPR’s Planet Money did just that, publishing a version of the graph with the bottom chopped off at 50 million Btu/year:

I don’t think these authors were trying to win any arguments, or to sell anything more than an innocent-seeming narrative—that there was a “200-year-long rise in per capita energy use”. But chopping off the bottom of the graph makes the rise appear about twice as dramatic as it actually was.

Besides having a chopped-off bottom, this version of the graph differs in some detailed, substantive ways from my version above. That’s because the Planet Money version uses an older and less complete data set that omits some important energy sources for the years before 1949, as explained here. Including all energy sources raises the 19th century plateau above 110 million Btu per year, and removes the abrupt uptick in 1850, which is an artifact of switching between two different underlying data sources.

To be clear, I don’t blame the Planet Money authors for using an older, incomplete data set, which was the only one conveniently available at the time. But they should have made sure they understood the limitations of their data, and been more suspicious of the 1850 uptick. Without that uptick, essentially all of their “200-year-long rise” occurs over less than 80 years. And by combining incomplete data with a chopped-off bottom, the Planet Money authors made a three-fold increase look superficially like an eight-fold increase. Gee whiz!

Flying Cars

Planet Money’s Gee-Whiz Energy Graph sat dormant, so far as I’m aware, between 2013 and 2020. Meanwhile, in 2018, another plot of the same data appeared. It came from computer scientist and futurist J. Storrs Hall, in his then-self-published book Where Is My Flying Car?. Hall chopped off the graph at 2 kilowatts (60 million Btu/year), again more than doubling the apparent relative increase:

Hall also put a smooth curve on the chart, intended to approximately fit the data up to about 1980. He named this curve after Henry Adams, an American historian who observed in 1907 that the world’s total coal power had been growing exponentially for several decades. Hall’s book says his smooth curve depicts “a 2 percent [annual] growth in actual energy consumed per capita”. To quote Duff again:

“That is impressive, isn’t it? Anyone looking at it can just feel prosperity throbbing in the arteries of the country.”

At first glance, Hall’s “Henry Adams curve” appears to be a pure exponential curve, representing a steady percentage growth rate. But this appearance is an illusion, caused by the graph’s chopped-off bottom. In fact, what Hall has plotted is a 2-percent exponential growth curve shifted upward by an additive constant of 2.5 kilowatts. The book is silent about this sleight of hand, though Hall confesses to it on his blog, where he tries to excuse the trick by arguing that fuel wood—America’s largest energy source until the 1880s—shouldn’t count as a source of energy. When we count all energy sources, the average growth rate from 1897 through 1973 comes to just 1.4 percent—not 2 percent. Over any time period longer than that, the average percentage growth rate was less.

For reference, here is a comparison of the data to some actual exponential growth curves:

No exponential curve fits the data very well, because this is a complex social system—not bacteria growing in a laboratory.

Unlike the Planet Money authors, Hall is definitely trying to sell us something. He says our failure to grow our energy use by 2 percent per year after the 1970s “had real and continuing consequences. There has been a marked drop-off in the technological advances that make a big difference in people’s lives—measured in productivity, health, and, yes, speed and ease of getting around.” Later in the book he writes, “To really reclaim our birthright and an optimistic future, we must get back on the Henry Adams Curve.”

Hall’s book got a publicity boost in November 2020, when Jason Crawford posted an enthusiastic review of it on his Roots of Progress blog. Crawford included Hall’s “Henry Adams curve” graph in his review, and posted the graph again in a follow-up article in February 2021. Crawford is explicitly trying to sell his readers on Hall’s narrative: “We should not seek to merely sustain current per-capita energy usage—we should get back on the Henry Adams Curve and increase it.” Whether we’re talking about energy, population, or technological progress, “Our baseline expectation should be no less than exponential growth.”

Exponential Growth

One quantity that has grown exponentially in recent years is the rate at which the Gee-Whiz Energy Graph keeps popping up. In December 2020, blogger Noah Smith revived the Planet Money version of the chopped-off graph in a Substack post decrying a “stagnation in energy technology” that began in the 1970s (and predicting that cheap wind and solar energy will end this stagnation). Smith doesn’t mention Hall or Crawford or exponential functions, though he does briefly mention flying cars—so the chain of influence isn’t completely clear.

In July 2021, economics journalist Ryan Avent used the same graph in a Substack post. He also mentions flying cars, and his message is similar to that of Hall and Crawford: “Increased energy use is essential to progress.”

Then pundit Matt Yglesias copied the Planet Money graph from Avent into an October 2021 Substack article titled “The case for more energy”. Yglesias doesn’t mention flying cars (or exponential functions) at all, but he does argue that geopolitical and pollution concerns “put us on an energy diet” starting in the 1970s, often preventing us from implementing “cool” inventions such as indoor farming, desalination, and direct removal of carbon dioxide from the air. He expresses the hope that we’ll be able to do all these things in the future, opening up “incredible new vistas”, by deploying zero-carbon energy sources on a massive scale.

In March 2022, Yglesias’s former Vox colleague Cleo Abram released a video based on his “more energy” article. Abram redrew the Planet Money graph, updating it with data through 2020, but continued to use incomplete data from the earlier years and again chose to chop off the bottom:

This graph appears in Abram’s fast-moving video for only a few seconds at a time, so the chance that a typical viewer would notice the chopped-off bottom seems slim. The video’s message is that as long as we can obtain the energy without releasing carbon dioxide, “everyone needs more energy”. As of this writing, the video has over 200,000 views on YouTube.

Over the last year the Gee-Whiz Energy Graph has also proliferated on social media, including tweets from Balaji Srinivasan, Last Contrarian, and Nan Ransohoff. Alec Stapp, co-founder of a new Washington, DC think tank called Institute for Progress, used the Planet Money version of the graph to take a dig at energy efficiency:

What finally provoked me to write this article, though, was the October 2022 special issue of the online publication Works in Progress. That issue, titled “Lost in Stagnation”, consists of six articles that all respond to Hall’s Flying Car book (published by Stripe Press in November 2021) in one way or another. Two of them, by Benjamin Reinhardt and Adam Hunt, feature a replotted version of Hall’s Henry Adams chart:

This version doesn’t even display a 2 kilowatt gridline, so you have to do a mental calculation to realize that the bottom has (yet again) been chopped off.

Both of the Works in Progress articles present this graph without any caveats. Reinhardt’s article, “Making energy too cheap to meter”, echoes Hall’s inaccurate claim in saying “If you plot historical energy use per person over time from the invention of the steam engine, it grew at about two percent per year for hundreds of years.” (This passage originally said the annual growth rate was a preposterous seven percent, as indicated in a “correction” at the bottom of the article.)

So that’s where we stand today: Four separately drawn versions of the Gee-Whiz Energy Graph, all with the bottoms chopped off to make the rise that ended in the 1970s seem bigger than it was. All four versions are being shown and spread to sell us on the idea that energy use goes hand in hand with prosperity, and therefore we should increase Americans’ energy use in the decades ahead.

So What?

I don’t want to exaggerate the harm done by deceptive presentations and interpretations of the Gee-Whiz Energy Graph. Even without the bottom chopped off, the graph shows a striking change during the 1970s, when a pattern of rapid (though lurching) increases in per-capita energy use switched to a pattern of gradual decline. Even though the period of rapid increases lasted less than a century, the changes in Americans’ everyday lives during that period were extraordinary.

But I think it’s notable that making these qualitative points hasn’t been good enough for any of the promulgators of the Gee-Whiz Energy Graph. They’ve all tried to add more quantitative juice to their narrative by displaying the graph in a distorted way.

Here’s my challenge to all such promulgators: Try to rewrite your narrative using an honest version of the U.S. per-capita energy use graph. Start your vertical axis at zero, and use a more complete data set. Acknowledge that the rise in per-capita energy use between 1800 and the 1970s was by a mere factor of 3. Acknowledge that no simple mathematical law can express the rate at which that growth progressed from each decade to the next. Acknowledge that the graph shows multiple time periods when Americans’ material lives improved even while per-capita energy use was not increasing. Then, with all these facts established, ask yourself: Does the rest of your narrative still hold up? If so, great! I’d like to read it. If not, maybe consider whether your worldview is too simplistic.

For what it’s worth, I don’t have my own simple narrative to replace the one I’m challenging. I disagree with a lot of that narrative, but not all of it. I’ll try to organize my thoughts enough to say more in future posts about the complex connections between energy, technology, and prosperity. My point at the moment is just that we can’t have fruitful discussions about these connections if we don’t first agree upon the verifiable facts.

Finally, I’d like to sincerely thank all the “promulgators” I’ve named above for raising fascinating questions and keeping this discussion going. Although I dislike their distortions, at least we agree that the questions are important.

[Revised 8 December 2022 to cite the article by Noah Smith, which I somehow forgot to mention in the original version of this article.]

Friday, August 19, 2022

How Big a Problem Is Siting for U.S. Renewable Energy?

To eliminate fossil fuels, the U.S. will need to build a lot of wind and solar farms, and these are going to cover a lot of real estate. For example, here’s a map of the 100% renewable scenario from the Net-Zero America study (click to enlarge):

And here's a great visualization from Bloomberg, showing how much land those wind and solar farms would cover if you put them all next to each other:

That dark blue region in the middle of Kansas shows the total footprint of the wind turbines themselves. But in this scenario new wind farms (which can be shared with other agriculture) would cover an area equal to all of Kansas, Nebraska, Oklahoma, Arkansas, Illinois, and Kentucky, plus part of Indiana and 15 million acres offshore. Compare that to the area of all existing (as of early 2021) wind farms, indicated by the similarly colored segment of Iowa. Meanwhile, new solar farms would cover an area equal to most of Indiana, with only minor opportunities for shared use of that land.

As another comparison, that big green area that covers all of Missouri and a slice of Iowa represents all the land we’re already using for production of ethanol and other biofuels. (This scenario assumes that the amount of land used for bio-energy production would remain the same, but that the biomass would be used more efficiently to produce hydrogen while sequestering carbon.)

The Net-Zero America study includes other zero-carbon scenarios for 2050 that make somewhat smaller demands on land use, through heavy reliance on nuclear energy and/or fossil fuels with carbon capture and sequestration. On the other hand, demand for wind and solar power could continue to grow beyond the year 2050 due to growth in the U.S. population or in our per-capita energy demand. I find it hard to imagine a future in which U.S. wind and solar farms end up expanding by less than a factor of 10.

Which brings us to the big question:

  • Can we actually find sites for that many wind and solar farms?

Physically, the answer is an unambiguous yes. Expanding solar farms by a factor of 10 or even 20 wouldn’t eat up any more land than we’re already using for inefficient biofuel production. Expanding wind farms by a similar factor would essentially mean a lot more shared use of agricultural lands.

But there are going to be issues. In fact, there already are issues.

Everyone agrees that industrial-scale wind and solar farms aren’t appropriate in every physically feasible location. Cities and national parks come to mind, for example. So there needs to be a process for deciding whether any particular location is appropriate. In a democracy, everyone gets a chance to participate in that process. By the same token, not everyone will be happy with every outcome.

Indeed, it’s easy to find stories about local opposition (pejoratively, “NIMBYs”) putting the brakes on solar and wind projects. Local opponents killed the Cape Wind offshore farm in Massachusetts and the Battle Born solar farm in Nevada. They’ve delayed the Icebreaker pilot attempt to put wind turbines on Lake Erie. They’ve enacted sweeping bans on utility-scale renewables in Madison County, Iowa, and San Bernardino County, California.

What’s less clear is whether these local efforts to block wind and solar development have made much of a dent in total U.S. renewable energy deployment. There are now more than 5000 utility-scale wind and solar farms operating in the U.S.:

If the number that have been blocked or significantly delayed by local opposition were more than a few percent of 5000, I should think we would have heard more about it. Here’s a study that lists 23 wind projects and 23 solar projects that have run into major local conflicts (though the study doesn’t claim that the list is comprehensive). Here’s a report on local zoning restrictions on renewable energy that gives about a dozen examples (again not claiming to be comprehensive). Until I see evidence to the contrary, my working assumption is that the number of examples of these sorts is still in the dozens, not the hundreds.

Of course, there must also be plenty of potential wind and solar projects that were scrapped on account of anticipated local opposition, before being publicly proposed. Apparently wind developers have given up on the whole state of Vermont, and I’m getting the sense that an awful lot of the desert Southwest, especially in California, is effectively off limits. Local opposition to renewable energy projects has become a very big deal in a few particular regions, but doesn’t yet seem to be a huge obstacle nationally.

So what’s the prospect for the next few decades, as we scale-up wind and solar generation by an order of magnitude? On one hand, siting should get more difficult as the best sites (both physically and in terms of local support) get developed. On the other hand, developers may be learning how to better navigate local siting conflicts, while renewable-friendly officials at the state and federal levels may enact policies that take some legal tactics away from the NIMBYs.

One example of such a policy could be the federal “permitting reform” that Congress has promised to take up in the coming weeks. I don’t doubt that there’s room to improve federal permitting procedures, though I’m not going to endorse a bill I haven’t seen. Whatever ends up in the bill, I’m skeptical that such a move will make as big a difference as its proponents are suggesting, given that most of the legal obstacles to renewable energy projects are being erected at the local—not federal—level.

Naturally I hope that enough reasonably uncontroversial sites can be found for the big buildup of wind and solar that’s in our country’s near future. I’m sure it won’t be easy, yet I remain very unsure of just how difficult it will be. My sense is that the siting of renewable energy projects is a ripe subject for more investigation and reporting, both by academic researchers and by journalists who specialize in energy and climate.

I look forward to reading and learning more.

Thursday, August 4, 2022

One Billion Americans?

One Billion Americans, by pundit Matthew Yglesias, is mostly a book about politics, international relations, and public policy—none of which are a focus of this blog. But as the title indicates, the book is also ostensibly about demographics. Could or should the U.S. try to increase its population to one billion or thereabouts? If so, how long would it take? These are fun questions to think about.

Let’s start with a look at current U.S. demographic trends. Here’s a plot of annual births (green), deaths (red), net migration (blue), and net population change (black, equal to births minus deaths plus net migration):

The left half of the graph shows the past, while the right half, from 2022 on, shows the latest projections of the United Nations Population Division. Notice the spike in deaths and dip in immigration from the Covid pandemic, which have combined to take a sizable bite out of our population growth over the last couple of years.

Looking forward and hoping for no more deadly pandemics, the projection shows our population continuing to grow through 2100, but more and more gradually, approaching 400 million by century’s end. Nowhere near a billion.

If we want to increase this we would need to increase the number of births and/or the number of immigrants. (Let’s assume we won’t have the technology to significantly postpone the deaths.)

Notice that we’re currently at around 4 million births and 3 million deaths each year. But the number of deaths is rising rapidly (as our population ages) and is expected to surpass the number of births about 20 years from now. After that, population rises only because of immigration.

In the book, Yglesias proposes that the U.S. encourage more births by enacting a universal child allowance, guaranteed parental leave, publicly funded child care and preschool, and other pro-family policies. He’s vague about how much difference he thinks all this will make, but others have pointed out that the countries he holds up as good examples for these kinds of policies (Finland, Scotland, Sweden, Germany, Belgium, Japan) tend to have fertility rates that are even lower than ours. (Sweden’s is infinitesimally higher.) In an interview with Kelsey Piper of Vox, Yglesias responded by noting that Americans tend to be more religious than Europeans, and religious people tend to have more children than those who are not religious.

Let’s suppose, then, that through pro-family social programs we can lift the U.S. fertility rate somewhat higher than that of the rich countries in Europe and Asia. Exactly how much higher might that be? Yglesias cites a New York Times summary of data from the General Social Survey, claiming that “The gap between the number of children that women say they want to have (2.7) and the number of children they will probably actually have (1.8) has risen to the highest level in 40 years.” The suggestion, then, seems to be that the social policies listed above might raise the U.S. fertility rate up to something like 2.7.

I think this is a fantasy. For one thing, both the average GSS survey response and the actual fertility rate have dropped somewhat since 2018, when that New York Times article was published. But more importantly, the actual wording of the GSS survey question was not “How many children would you like to have?”, but rather, “What do you think is the ideal number of children for a family to have?”. Some respondents are likely to answer this question from the perspective of a child instead of a parent—especially if they personally have no wish to start their own families—and the number of children in an average child’s family will always be larger than the number of children born to an average adult. The trend in these survey responses over time can still teach us something, but I don’t see how we can use the numerical level of the average response to predict how many children people would have if they could afford them.

Nevertheless, let me err on the side of being overly generous and assume that somehow the U.S. might raise its fertility rate from the current value of 1.66 children per woman back up to the replacement value of 2.1. Then the green curve on the chart above would jump up by about another million, and the U.S. would get a boost of a few tens of millions of births over the next few decades. In the long term, though, the green and red curves would merge, and any further population growth would come entirely from (net) immigration.

Next question: How high might we raise the annual U.S. immigration numbers? Yglesias doesn’t say. The average over the last two decades has been about a million a year, and that’s what the U.N. projections assume going forward. At that rate it would take us 600 years to add another 600 million Americans. (The exact time required would depend on how many children the immigrants have after they arrive, which in turn would depend on their distribution in age, sex, and education level.)

But immigration has been higher at times in the past. In the 1990s the annual rate reached almost 2 million a year. That was the all-time high in absolute terms, and immigration rates were much lower throughout most of the 20th century. But before World War I immigration rates were fairly high, especially relative to the population at the time.

Here is a plot (data here) of the annual number of people obtaining lawful permanent resident status in the U.S., as a fraction of the population at the time, since 1820:

In the heyday of U.S. immigration, from 1847 through 1914, we were taking in nearly 1% of our population each year, on average. If we wanted to do that today, we’d need to triple our recent legal immigration rate.

Before continuing that thought, I should point out that U.S. fertility rates were also much higher in the past. So even when immigration rates were in the vicinity of 1% of our population each year, the high birth rate meant that the fraction of U.S. residents who were born in other countries never exceeded 15%. Today that fraction is about 14%, despite our much lower immigration rate (as a percentage of population), because our birth rate is also much lower. If we were to raise our immigration rate to 1% of population over a sustained period, our foreign-born fraction would rise to a level never before seen in the U.S. as a whole, though familiar in places like California and Australia.

So in today’s political climate, increasing the immigration rate may be another fantasy. But let’s forget politics and suppose that the U.S. were to admit 1% of our population as immigrants every year. That would be 3.3 million immigrants per year initially, rising over time as our population increases. If we could sustain it, this immigration rate would bring our population up to one billion in about 100 years. (Again the exact time would depend on the demographics of the immigrant pool.)

Is this close to what Yglesias has in mind? We can only speculate. He devotes considerable space in his book to arguing that the U.S. can hold a billion people, while neglecting to say how long he thinks it might take us to reach that level. But putting a specific time scale on the target adds clarity to some issues the book raises, while inviting us to ponder some further questions.

For instance, a hundred years is considerably longer than the time scale—just a few decades—over which the world needs to transition away from fossil fuels. So we needn’t let the prospect of a much higher population clutter our thinking about how to carry out that transition here in the U.S. Then, after a few decades, we’ll have a much clearer picture of what it might take to scale up the fossil-free energy system to meet the needs of the hypothetical one billion Americans.

On the other hand, a hundred years is about the same time scale over which the world as a whole will (probably) transition from rapid population growth to likely decline. Projections suggest that this transition will be especially dramatic in Asia and Latin America, the origins of most U.S. immigrants in recent years. Meanwhile, a century of further economic development is likely to bring the wealth level of much of the world closer to that of the U.S.

So although there seems to be no shortage of people who would like to migrate to the U.S. today, we shouldn’t assume that this will be the case a full century into the future, as we (hypothetically) seek the hundreds of millions of immigrants we would need to reach the one billion level. Already we compete with places like Europe, Canada, and Australia to attract many of the world’s migrants. In a hundred years the list of other rich countries that are eager to attract migrants could be much longer.

Of course there’s nothing sacred about a 1% annual immigration rate. Could we raise it significantly higher still? That would shorten the time needed to reach one billion, but would also bring us into truly uncharted cultural territory, with immigrants arriving so fast that they could soon outnumber native-born Americans. And although I said I’d forget politics, I have to draw the line somewhere on such politically far-fetched speculations.

Wednesday, July 27, 2022

Limits to Growth, 50 Years Later

I’ve just finished rereading The Limits to Growth (LtG), a book that the Malthusian pessimists love and the technological optimists hate. Here I’d like to offer a few thoughts that are more nuanced.

(Many volumes have been written in response to LtG, and I have nothing original to add; I just think certain points deserve a little more attention.)

Let’s first be clear on what LtG is and is not.

Unlike some other books about population and growth that appeared in the 1960s and 70s, LtG did not breathlessly scream that our planet was already overpopulated, or that widespread famines or other disasters resulting from overpopulation would occur within mere decades. Nor was it concerned about a very distant future, when unforeseeable technologies might be at humanity’s disposal.

Instead, LtG looked at a century-long time scale, and used abstract mathematical projections to argue that the growth rates prevailing in 1970 couldn’t be sustained on that kind of time scale. Here are the book’s conclusions, quoted directly from pages 23-24:

1. If the present growth trends in world population, industrialization, pollution, food production, and resource depletion continue unchanged, the limits to growth on this planet will be reached sometime within the next one hundred years. The most probable result will be a rather sudden and uncontrollable decline in both population and industrial capacity.

2. It is possible to alter these growth trends and to establish a condition of ecological and economic stability that is sustainable far into the future. The state of global equilibrium could be designed so that the basic material needs of each person on earth are satisfied and each person has an equal opportunity to realize his individual human potential.

3. If the world's people decide to strive for this second outcome rather than the first, the sooner they begin working to attain it, the greater will be their chances of success.

To make their projections, the LtG authors (Donella Meadows, Dennis Meadows, Jørgen Randers, and William Behrens) used a computer simulation code (called World3), which modeled the interrelated behavior of the quantities they listed in conclusion 1 above: global population, industrial output, pollution, food production, and resources (raw materials and energy). They fit the simulation parameters to data from 1900 through 1970, then ran the simulation forward to the year 2100. Acknowledging that many of the model parameters were uncertain, they carried out a variety of model runs using different parameters. The book emphasizes that these model runs are not quantitative predictions. Rather, they are scenarios used to explore what general types of behavior are possible and how the various parameters tend to affect that behavior.

Over a wide range of parameter choices, these modeling runs produced behavior that the authors call “overshoot and collapse”: population and industrial output would rise for a time, reach a peak, and then fall rapidly. Here is their first example (Figure 35, page 124):

After pausing to admire the advanced computer graphics of 1972, notice what’s happening here: growth continues into the early 21st century, but then dwindling resources cause industrial output and food production to turn sharply downward. Population keeps rising for a few decades (“overshoot”), because the time scale of these downturns is much shorter than a human life span. But the death rate (which I’ve highlighted in pink) soon skyrockets due to shortages of food and medical services, causing population to peak and then decline. By 2100 the industrial era has ended, leaving humanity in a state of widespread hunger and short life expectancy (“collapse”).

Again, the point here is not this projection's specific dates or numerical values. It’s easy to change these details by making different assumptions about resource levels, crop yields, and/or pollution controls. The problem is that both population and industrial activity are growing exponentially as long as there are no physical constraints, and the authors found no way for earth’s bounty to outrun that exponential growth.

Many criticisms of LtG have focused on the constraints. These critics argue that energy and mineral resources are vastly greater than the LtG authors assumed, even in their most optimistic model runs; that pollution can be controlled much more effectively; and that crop yields can grow even more in the future than they have in the past. I think it’s now apparent—thanks to 50 more years of data—that all these things are true. But I don’t see how any of these factors, or even all of them together, could do more than delay the overshoot and collapse behavior into the 22nd century. It’s really hard to outrun exponential growth!

So to get at the heart of the LtG argument, I think we need to focus on the exponential growth itself. Is it really true that both population and industrial production will, if left unconstrained, grow exponentially?


In 1972 it was natural to answer yes. Population growth during the preceding decades was actually super-exponential, with a rising annual percentage increase that by then had reached 2%. I’m too lazy to dig into the World3 code, so I don’t know exactly what assumptions about unconstrained population growth it makes, but the authors must have tuned it to match this 2% growth rate in 1970, and their results seem consistent with the assumption that the rate doesn’t change much until the constraints kick in.

Let’s look at what would have happened if population had continued to grow at 2% per year from 1970 onward:

As the red curve shows, population would have risen from 3.7 billion in 1970 to 10 billion in 2021, and would continue rising to 18 billion in 2050, 27 billion in 2070, and 48 billion in 2100. That’s the type of exponential growth the LtG authors were so concerned about.

Yet as you can see, that’s not what is happening. Although population has continued to grow, we were still below 8 billion in 2021. The annual percentage growth rate has dropped to less than 1%. Fertility rates are now below replacement level in the Americas, Europe, and Asia, and are falling steadily in Africa. The United Nations projects that world population growth will continue to slow over the coming decades and will probably end late in the present century, with a peak slightly above 10 billion. (Other researchers project a somewhat earlier and lower peak.)

Now a Malthusian might argue that this slowed growth is a sign of resource constraints already taking their toll, as in the LtG model run shown above. That sounds plausible at first, but it’s not consistent with the facts. Resource shortages are not causing industrial output to plummet. Per-capita global food production is higher than ever. Population growth has slowed due to falling birth rates, not rising death rates. And it has slowed the most in wealthy and middle-income countries, where any hypothetical global resource shortages would be felt the least.

So what’s causing birth rates to fall? The main factors are now pretty well understood. Economic development, urbanization, education, integrating women into the labor market, and decreased child mortality have all contributed to reducing the desired number of children per family. The Limits to Growth doesn’t enumerate these factors, though it does seem to suggest that the model incorporates them collectively, to some degree:

A changing industrial output per capita also has an observable effect (though typically after a long delay) on many social factors that influence fertility. (page 101)

The LtG model also incorporates a further factor—access to contraceptives—that can close the gap between desired and actual family sizes. But it seems clear today, in hindsight, that the model greatly underestimated the impact of “social factors” on birth rates, and/or overestimated the delay of this impact.

More prominent in LtG is the suggestion that lowering the birth rate would require “deliberate” society-wide efforts:

All of the “natural” constraints to population growth operate [by raising] the death rate. Any society wishing to avoid that result must take deliberate action to control the positive feedback loop—to reduce the birth rate. (page 159)

In fact, since the 1960s many societies have taken deliberate action to reduce birth rates. These deliberate actions have emphasized public education campaigns, including the 1972 U.S. stamp that was my first exposure, at age 10, to the term “family planning”. But the actions of some governments went further, to include coercion. And near the end of the book, the LtG authors implied that some amount of coercion would be needed:

Equilibrium would require trading certain human freedoms, such as producing unlimited numbers of children or consuming uncontrolled amounts of resources, for other freedoms, such as relief from pollution and crowding and the threat of collapse of the world system. (pages 179-180)

Again with the benefit of hindsight, it seems clear today that coercion was not necessary—let alone morally acceptable—for lowering birth rates. Where it was used, it probably had little long-term effect. Non-coercive public education campaigns, whether coming from governments or from private-sector book authors, probably have played a role in lowering birth rates—although it seems likely that this role has been small compared to the more “natural” effects of modernization, listed above.

Whatever the precise mix of causes, global population is now on track to stop growing before the end of this century.

Industrial Production

Let me briefly address a second source of exponential growth in the LtG model, besides population. The authors argued that the industrial system (energy, mining, and manufacturing) tends to grow exponentially even in the absence of population growth, because it puts some of its production into infrastructure that enables increased production (a “positive feedback”). To support this claim they provided a chart (on page 38) showing that per-capita industrial production rose steeply between 1950 and 1968.

I think the authors would agree that we should use caution when basing a 130-year future projection on less than two decades of empirical evidence. As for the theoretical positive-feedback argument, I see the point but I should also think that growth in industrial production would be limited by consumer demand, and I doubt that per-capita consumer demand for energy or manufactured goods tends to grow exponentially without limit. Once people have achieved a reasonable level of physical safety and comfort, they tend to shift their spending from energy and material goods into services. Today (again with 50 years of hindsight) we can see that per-capita energy use is no longer growing in rich countries, even while it continues to grow in many middle-income countries. This is not the pattern we would expect if the overall slowdown in the growth of per-capita energy use were due to resource constraints.

I suspect that a similar pattern holds for industrial production overall, but I can’t seem to find a convenient data source for global industrial production trends. In the U.S., per-capita industrial production has been essentially flat for the last 20 years:

This behavior is consistent with the hypothesis that industrial production, like energy use, is something that grows rapidly only until a society crosses a certain standard-of-living threshold.

In Summary

The Limits to Growth was a groundbreaking and reasonable attempt to extrapolate the rapid growth of the post-war decades into the 21st century. But it was very much a product of its time, and times have changed. Today, with 50 years of hindsight, it’s not hard to look back and find serious flaws in the LtG model’s assumptions. Positive feedbacks do not drive fast exponential growth under as wide a range of conditions as LtG assumes.

It seems likely that widespread concern about run-away exponential growth during the 1960s and 70s was partly responsible for the slowdown in population and industrial growth that has occurred since. Perhaps the publication of LtG played a small role in steering the world away from the catastrophe it predicted. Mostly, though, the slowdown has resulted from “natural” social factors that LtG underestimated or overlooked.

This is not to say that Malthusian pessimists are happy with the current situation. Many of them, including Dennis Meadows himself, believe that human population and industry are already in a state of overshoot, with unsustainable levels of industrial activity. It’s certainly true that present levels of fossil fuel combustion are not sustainable, but of course that isn’t the same thing. In any case, this view is more pessimistic than the conclusions expressed in The Limits to Growth, where the authors carefully avoided claiming the world would hit any limits within 50 years.

Meanwhile, the technological optimists are not happy either. Many of them would like to see human population grow well beyond 10 billion, with per-capita industrial production and energy use rising well beyond the levels now prevalent in rich countries. Perhaps that will happen some day. But it doesn’t seem to be where we’re headed during the current century, and I think that’s for the best until we make more progress toward weaning ourselves off fossil fuels.

Like it or not, humanity may have to wait a rather long time before getting a clear view of the ultimate limits to growth.

Monday, July 18, 2022

Nineteenth Century Americans Used a Lot of Energy

Americans are notorious for using a lot of energy, even compared to people in other rich countries. Over the last two centuries our energy consumption has increased enormously:

What seems to be less well known is that most of that breathtaking rise in U.S. energy consumption was merely due to population growth. If we plot the same data on a per-capita basis, it looks like this:

According to this data, the 200-fold increase in energy use between 1800 and 2000 breaks down into a roughly 50-fold increase in population, combined with just a four-fold increase in energy use per capita. Considering that we didn’t have electricity, cars, or even trains in 1800, I find it astonishing that we used so much energy even then.

Of course the early data in these charts isn’t as reliable as the more recent data. Everything before 1949 comes from Table D1 of the Energy Information Administration’s Monthly Energy Review, which in turn cites a 1960 treatise for data between 1850 and 1945, and cites a 1942 Department of Agriculture study for data before 1850. These early studies were careful, but they were incomplete. They omit the energy content of feed for draft animals, as well as wind energy that propelled sailing ships and water energy that powered mechanical water wheels. The pre-1850 data is for fuel wood only, even omitting coal.

But there’s good news! We now have better data, from a new study by Suits, Matteson, and Moyer (2020). These authors have carefully estimated all the forms of energy I’ve just listed, all the way back to 1800. Here is how their bottom-line results compare to the EIA data for the period from 1800 through 1920:

According to Suits et al., Americans’ energy consumption during the early 1800s was higher than the EIA/DOA numbers by about a third. About half of the difference comes from including feed for draft animals, with smaller additions from including coal, wind, and water, and from revisions to fuel wood estimates.

[Technical comment on wind and water: There’s no single correct way to compare these mechanical forms of energy to fuels that we burn (or feed to animals). Suits et al. quantify wind and water energy by the amount of frictional heating that the motion (of a sailing ship or water wheel) can produce; the dashed blue line in the chart above adheres to this methodology. EIA, on the other hand, counts non-thermal sources of electrical energy according to the amount of fossil fuel that would be needed, in power plants of average efficiency, to generate the same amount of electrical energy. Even today, that average efficiency is less than 40%, while in 1920 it was only around 10%. The solid blue line in the chart shows the result of applying this 10% efficiency factor to wind and water throughout the time period shown—that is, multiplying the wind and water numbers by 10 to give what I consider a fairer comparison to biomass and coal that fueled inefficient engines. This factor of 10 is probably too low, because engines before 1920 were even less efficient than in 1920. In any case, as you can see, this ambiguity doesn’t have a huge effect on the results (because wind and water were never a huge fraction of total energy use).]

The Suits et al. data strengthen the point I made above: Although U.S. population and energy consumption grew enormously from the early 1800s to the late 1900s, per-capita energy consumption grew by only about a factor of 3. Our standard of living has improved considerably as a result of using more energy per person, but vastly more because we now use that energy so much more effectively.

Whichever data set we use, the big picture is the same: 19th century Americans used enormous quantities of fuel wood. They could do that because wood was abundant and free for the taking, after measles, smallpox, and genocidal warfare had so thoroughly depopulated the continent. Most of the wood was burned to heat homes in the winter, using inefficient open-hearth fireplaces before the widespread adoption of more efficient stoves.

For a detailed look at how Americans have used energy since 1800, I highly recommend the Suits et al. paper, as well as its supplement and the accompanying web site. I especially appreciate how both the paper and the web site illuminate the data with the insights of a professional historian. For even more insights, see this write-up in The Atlantic.

For improved versions of the first two charts above, using the Suits et al. data instead of EIA for the earlier years, I've created this interactive chart.

And how has U.S. energy consumption compared to other parts of the world? There is a wealth of recent statistics at Our World in Data, but numbers from before 1965 are harder to come by. The most complete data set I know of that goes back to the 19th century is the one compiled by Paulo Malanima, which begins in 1820. Here is a plot of Malanima’s data comparing per-capita energy use in North America (defined as the U.S. and Canada only), western Europe, and the world as a whole:

Today, North Americans use about twice as much energy each as western Europeans, and nearly four times as much as the world average. But in the early 1800s we were even more of an outlier, using about five times as much as western Europeans and seven times the world average. North Americans have a very long history of high energy use, but the energy gap between us and the rest of the world has been gradually closing. I suspect it will close further during the coming decades, as we find ways to be more efficient while the standard of living in poorer countries continues to improve.

Tuesday, August 31, 2021

Review of Murphy's Energy Book

I’ve written a formal review of the new book Energy and Human Ambitions on a Finite Planet by physicist Tom Murphy. You can read the review at its American Journal of Physics home, or find a thoroughly annotated version here.

The book covers much of the same material as Murphy’s Do the Math blog, except that it’s a textbook, written mainly for college students who are not majoring in physical science but are taking a course to satisfy a science breadth requirement.

I was a big fan of Murphy’s blog back in its heyday a decade ago. It was one of my inspirations for eventually starting this blog. Murphy is a first-rate physicist, and his blog is full of great examples of how to think like a physicist about energy.

But as you’ll see if you read my review, my opinion of this textbook is more mixed.

A blog is a great place for trying out ideas and getting feedback on them from whoever might be interested in reading. It’s inherently informal, and readers generally assume that any conclusions might be tentative and/or controversial. Alternative viewpoints are always just a click away.

A textbook is different. Here we’re imparting knowledge and wisdom to the next generation. Students reading the book may be a captive audience, taking the course to satisfy a school requirement. This setting obligates us, I think, to be much more balanced and authoritative.

As I explain in the review, I think Murphy’s book falls short of this standard in several places. But it’s still a major accomplishment, full of food for thought, and I recommend downloading it (it’s free!) and taking a look. Leave a comment below to share your own thoughts on the book.

I’ll have more to say about some particular parts of Murphy’s book (and blog) in later posts.