Saturday, May 19, 2018

The Most Powerful Evidence Climate Scientists Have of Global Warming | InsideClimate News

The Most Powerful Evidence Climate Scientists Have of Global Warming | InsideClimate News

The Most Powerful Evidence Climate Scientists Have of Global Warming

The oceans hold the story of a planet warming as fossil fuels are burned. Here is what scientists have discovered, in four charts.

Sea Surface Temperatures. Credit: NOAA

Hurricane forecasters look closely at ocean temperatures. Sea surface temperatures above 78 degrees, shown here in yellow, orange and red, are sufficiently warm to fuel hurricanes. Credit: NOAA

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Earth's temperature is rising, and it isn't just in the air around us. More than 90 percent of the excess heat trapped by greenhouse gas emissions has been absorbed into the oceans that cover two-thirds of the planet's surface. Their temperature is rising, too, and it tells a story of how humans are changing the planet.

This accrued heat is "really the memory of past climate change," said Kevin Trenberth, the head of climate analysis at the National Center for Atmospheric Research and co-author of a new paper on ocean warming.

It's not just the amount of warming that is significant—it's also the pace.

The rate at which the oceans are heating up has nearly doubled since 1992, and that heat is reaching ever deeper waters, according to a recent study. At the same time, concentrations of carbon dioxide in the atmosphere have been rising.

The charts that follow show how the oceans are changing and what they're telling us as a thermometer of global warming.

Oceans Storing More Heat as CO2 Builds Up

Scientists say the accumulation of heat in the oceans is the strongest evidence of how fast Earth is warming due to heat-trapping gases released by the burning of fossil fuels.

Oceans have enormous capacity to hold heat. So ocean temperatures, unlike temperatures on land, are slow to fluctuate from natural forces, such as El Niño/La Niña patterns or volcanic eruptions. Think night and day, said Trenberth. As night falls on land, so do air temperatures. But in the oceans, temperatures vary little.

This makes it easier to tease out the influence of human-caused climate change from other possible causes of surging ocean heat.

Global Warming, at a Glance

How much extra heat are we talking about? And what are the impacts on the climate system? "On a day-to-day a basis, it's really quite small," Trenberth said, but the cumulative effects are not.

According to research by Trenberth and Lijing Cheng, of the Institute for Atmospheric Physics in Beijing, the heat storage in the oceans during 2015 and 2016 amounted to a stunning force: an increase of 30.4 X 1022 joules of energy roiling Earth's systems since 1960. The overload is helping throw off Earth's energy balance, needed for the climate to be relatively stable. Put another way: The excess energy amassed in the oceans since 1992 is roughly equivalent to 2,000 times U.S. electricity generation during the past decade, the researchers explained.

Ocean temperatures have been rising about 0.12 degrees Celsius per decade on average over the past 50 years. The higher temperatures are driving marine life toward the poles in search of livable habitats, bleaching coral reefs, and causing severe impacts on fisheries and aquacultures. They also contribute to more frequent and intense extreme weather events. In the three back-to-back deadly hurricanes of 2017—Harvey, Irma and Maria—warmer waters played a role in worsening the storms.

Ocean Temperatures: Warm and Warmer

Though ocean temperature represents a clear signal of climate change, one challenge for researchers is that the record only goes back so far. Since the early 2000s, an international effort called Argo has launched nearly 4,000 ocean-going sensors that gather important data about the oceans, including temperature.

Meanwhile, as oceans heat up, thermal expansion causes sea levels that are already rising from the melting of land ice (triggered by higher air and sea temperatures) to rise even more. Nearly 50 percent of the sea level rise so far has come from ocean warming, according to new work by Cheng and Trenberth. Much of the rest comes from the melting of ice on Antarctica and Greenland.

Oceans Warm and Expand — and the Seas Rise

Ocean warming can impact sea level rise in another way, too. This year has seen extensive losses from Antarctica's ice shelves. "It's most likely because that ice is being undermined through warmer ocean underneath the ice, which is contributing to the thinning of the ice and weakening of the shelf," Trenberth said. The ice shelves themselves are already floating, but they are attached to land and play a critical role in slowing the ocean-bound ice flow from the massive ice sheets behind them. Scientists say the West Antarctic Ice Sheet alone holds enough ice to raise global sea level by about 11 feet.



_- Steve

Nineteenth Century Philosophy | Five Books with Peter Singer

Nineteenth Century Philosophy | Five Books with Peter Singer

Nineteenth Century Philosophy | Five Books with Peter Singer

You've been actively communicating philosophical ideas to a wider public for many years, through books such as Practical Ethics, and more recently The Life You Can Save, The Most Good You Can Do, and Ethics in the Real World, but also through introductions to the work of past philosophers—I'm thinking particularly of the three Very Short Introductions in the Oxford University Press series you've written or co-written: the ones on Hegel, Marx, and Utilitarianism, all of which relate to your book choices here. How important is it to you to reach a wide audience, to make philosophy accessible to a general reader?

It's very important. That's largely because of the area of philosophy that I work in, which is ethics, and applied ethics in particular. These are areas of philosophy that make a difference to the world and to the lives of individuals. If I were only writing for other colleagues, I would either not be affecting the world, or I would be hoping that somewhere else eventually somebody would convey some of the thoughts and ideas to a broader audience.

To me, it's not just about trying to win arguments with other colleagues that are going to remain in the academic journals, and pretty much inaccessible to anyone else in the world. It's about trying to say something helpful in relation to issues that people are already thinking about, questions such as, 'How should I live? What should my goals be? To what extent should I be working for others rather than thinking only about myself?' And also the broader social questions that we might discuss in the community: 'When is it justifiable to use military force? What should we do about inequality and poverty? Are there limits to freedom of expression?' I think philosophy has things to contribute to all those questions, and if it remains locked away in academia, it's not really contributing in the way that it should be.

Until I asked you to select the five books for this interview, I hadn't realised the extent to which many of your ideas have important precedents in the nineteenth century. Is that a period you were particularly drawn to for some reason, or does it just so happen that the thinkers that influenced you have mostly come from the nineteenth century?

There were wonderful and important thinkers earlier on. I'm particularly thinking of David Hume, for example, in the eighteenth century, who has certainly also been an influence. But I do think the nineteenth century was a particularly fertile period for ideas, and one in which ideas were taken seriously by many people.

Also, it was a transitional period in which academic thinking started to develop. We're going to talk about some utilitarian works. There's a contrast between Jeremy Bentham, at the end of the eighteenth century and early nineteenth century, and what he wrote about utilitarianism, which was tremendously original and important and wide-ranging. But he was certainly not a systematic or careful thinker, like the last of the utilitarians we'll talk about, Henry Sidgwick, who spent almost his whole life at Cambridge, and was an early academic who really wanted to get things right. So, in contrast to Bentham, he was always careful not to overstate his claims. That's a really interesting transition to a more rigorous and scholarly type of argument in fields like ethics.

Your first book choice is the one that people who know your moral and political philosophy well are likely to be surprised by. That's Hegel's Phenomenology of Spirit (1807). There's not an obvious connection with your thought. I know that you've written an introductory book about Hegel, but with every other book that you've chosen I can see a very direct connection with your thinking. But Hegel is an obscure writer, and incredibly difficult to understand—a real contrast with you who are so lucid in your writing. He seems to be on the Right rather than the Left, in many people's view, very scholastic in his style of thinking about philosophy, and also, in the bits that I understand of his writing, seems to be a historical determinist, which I can't believe you are. So tell me why you chose this book.

You're right that I'm not a historical determinist. The one thing that I wouldn't agree with in what you just said about Hegel is that he's very scholastic. Scholarly writers tend to be very narrow, they tend to focus on some very specific problems and go into great depth. Hegel was incredibly broad: his subject was the entire sweep of human history worldwide. That's not scholastic: you don't find many scholars who say that's what they're going to write about; certainly not many philosophers. That's one of the things that does attract me to him, that he's prepared to look at that.

But another aspect, and the reason why I've included him here, is that we are going to talk about Karl Marx (and that's particularly appropriate in that this very week when we are talking is the two hundredth anniversary of his birth). In order to understand Marx, you really do need to know something about Hegel. It's a mistake to think you could read Marx as a scientist or an economist without understanding the Hegelian framework of his thought. That's why I chose to begin with Hegel.

" I do think the nineteenth century was a particularly fertile period for ideas, and one in which ideas were taken seriously by many people"

Marx himself said of the Phenomenology of Spirit—which does deserve a lot of those adjectives you used like 'obscure' and 'difficult' and is also very long, 750 pages—that it's 'the true birthplace and secret of Hegel's philosophy'. That's why I chose this particular book, rather than some of his other works, to try and see what's going on in Hegel's philosophy and how that links to Marx and his thinking, which of course was tremendously influential in the late 19th and much of the 20th century.

Most people, when they hear the name Hegel, apart from thinking of obscurity, think of his theory of history, his theory of how it all unfolds. Is that the element that you want to draw attention to here?

Yes, absolutely. He has a number of works, he has a History of Philosophy and also a work called The Philosophy of History, in which he presents his views on that. But the work that I've chosen is one in which he is describing all of human history as progress towards the self-consciousness of Mind. That's what I want to talk about.

But already just in mentioning the title, there's one thing that has to be clarified. I used the word 'Mind' just now, to translate the German 'Geist'. That word can be translated that way, in German. Mental illness, for example, is 'Geisteskrankheit.' But we can also translate 'Geist' as 'Spirit'—it's closer etymologically to the English word 'ghost'. So, when Hegel says that all of history is a progress towards self-consciousness or self-awareness, we can understand it as this collective sense of Mind. We might represent that sense by talking about a 'World Spirit' or Weltgeist. Does that mean a single collective mind, or a sort of spirit that animates the world? That's an initial difficulty for any translator of Hegel.

" These are areas of philosophy that make a difference to the world and to the lives of individuals"

The ambivalence between 'mind' and 'spirit' conveys this idea that somehow all of our minds are part of a single mind or spirit, and are drawn in the same direction towards an outcome that will be freedom or liberation for Mind. The fact that Hegel thinks of all our minds as part of a whole means that he is not thinking of freedom in the modern liberal sense, in which we might think of many distinct, individual minds all having political freedom.

I struggle to understand what that means. I know that that moment of self-understanding allegedly occurs in a passage in the book you've chosen. That's the moment when it is supposed to have happened. But what does it mean? Is it that humanity suddenly becomes aware of its own position in relation to everything else?

You're right that here is that immense hubris or, if you like, chutzpah of Hegel because the liberation of Mind occurs when it actually understands itself. You can imagine Mind or Consciousness existing in the world when it doesn't really understand itself, it's just responding to circumstances, and so on. It goes through this long and elaborate process of trying to achieve knowledge, and then self-knowledge. You can see this in 'Know thyself' as a motto of philosophy. You can tell the story of our journey to self-understanding that way. But what's crucial for Hegel is that we are, in a sense, all one, there is a unity of Mind. When we understand that, we are free because now we no longer see ourselves as opposed by and limited by other humans. Instead we see ourselves as all part of this whole, and that, for Hegel, is the achievement of freedom. How does that happen? Well, it happens when Hegel shows it to us by telling us the story of where we've come from and showing us that we are all in this part of a united Mind or Spirit. So, that's the idea, that this is the achievement of freedom, and it is actually brought about by Hegel himself writing The Phenomenology of Spirit, or perhaps thinking the thoughts that constitute it.

I don't accept this idea of the collectiveness of Mind, but it's an interesting thought. And it sets the framework for Marx's transformation of Hegel's thought.

Another famous aspect of this book is Hegel's discussion of the Master/Slave dialectic, as it's usually referred to. Could you give a flavour of that discussion?

It's a good example of the dialectic, the way Hegel thinks history moves forward, which is also something that Marx took over. It's the idea that you have one situation, a thesis, and that somehow is not self-sufficient and it gives rise to its opposite, the antithesis, and that somehow leads to a synthesis that transcends the two. Then, that in turn sets up a new thesis, followed by anti-thesis and synthesis, and so it goes on.

"In order to understand Marx, you really do need to know something about Hegel"

So, in the case of the Master/Slave dialectic, you start with two humans encountering each other. Hegel discusses it in the abstract, but we could imagine them meeting in the jungle somewhere and encountering each other, and each of them sees the other as a limitation on his power (for Hegel, they are men, of course), and perhaps a competitor for resources. Therefore they fight. In this fight one of them is the victor and the other is subdued. So the victor becomes the Master, and the one who is subdued is the Slave. You might think that would be a stable situation, the stronger one has emerged as the Master, the weaker as the Slave, and the Slave will always have to serve the Master. But, no, Hegel says, the Slave is the one who is working on the world, the slave is the one who is developing his powers, because he has to labour, he has to work, he has to transform the world. The Master, let's say, might want him to cut down a tree and shape the wood into a chair for him, but it will be the Slave who develops his skills and powers in doing that, and feels that he can transform the world; whereas the Master, not having to do this work, loses these skills and powers. So, the Slave now becomes more powerful or stronger and eventually rebels against the Master, and overcomes him, and liberates himself, and abolishes slavery. Then, you might think this will now be a stable situation. But it turns out that it's not, because that again is the starting point of the next stage of the dialectic.

That leads very neatly into your second book choice, The Communist Manifesto (1848) by Karl Marx and Friedrich Engels, which is all about transforming society by revolution.

Yes, it is. I chose The Communist Manifesto, rather than, say, Capital because it shows in a much easier-to-read, shorter work something that is central to Marx's vision. Capital is much drier, and a lot of it is focused on economics, although there are some remarkable passages of Capital describing the conditions of industrial workers in England at the time.

The Communist Manifesto is an early work, published in February 1848, the year of revolutions in Europe, when Marx was not quite 30. The Manifesto shows Marx still thinking within the framework of Hegel's ideas about contradiction but transforming them from something that's happening in our consciousness to something that's happening in the material world. Marx agrees with Hegel that history is progress towards freedom or liberation, that humans are in some sense a unity. But he disagrees that this process is all happening in our consciousness. Instead, for Marx, it happens in the way we produce to satisfy our material needs, the way we produce our food or our shelter. That's what gives rise to certain economic relations between humans, and those economic relations in turn give rise to our ideas. Our ideas are supervenient on the underlying economic realities. But, just as with Hegel, progress occurs through the generating and transcending of contradictions, and it leads to liberation.

This is sketched out by Marx and Engels, his co-author (though Marx wrote most of it), in The Communist Manifesto. You have an economic system, the economic system of their time, which was capitalism. In that system, you have people who own capital, and you have people who have no capital, and have to sell their labour power because that's all they have. The result of this is that when you work under capitalism you are putting your labour power into making profits for the capitalists. Thus the more the labourer works, the more he enriches his opposite, the capitalist. The capitalist uses the profits to extend the factory, perhaps to put in machines that can do the work of five, ten, fifty people. So the labourer generates profits that work against himself, putting many labourers out of work. In Marx's view, the capitalist class actually shrinks in terms of numbers: instead of many small capitalists you have fewer big ones, and the small capitalists have to become labourers.

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The proletariat, the working class, expands as more and more people are forced into it. The laws of supply and demand keep them at the edge of starvation. Capitalists need workers, and these workers need to eat, they need to reproduce, but the competition for jobs means they will, over the long-term, hover around the bare minimum needed to survive and reproduce. Marx has some moving images, and one of them is of a forest of uplifted arms seeking work, with the forest becoming ever thicker, while the arms themselves become ever thinner.

Marx saw this as a contradiction within capitalism because the small capitalist class, in the end, would inevitably be overthrown by the vastly larger working class. Hegel was a kind of historical determinist, as you pointed out earlier, and so too was Marx. For Marx, the nature of capitalism had this inherent contradiction within it, and that's the vision that's spelled out in The Communist Manifesto.

It's a very powerful piece of writing, especially the first section. As well as spelling out this story of what's going to happen, it does portray capitalism in a way that hadn't been done before. Marx and Engels show how, under capitalism, money becomes the universal solvent. All the older ideas, like feudal ideas about loyalty and the obligations of the lord to his vassals, or for that matter the value of being skilled at a craft like weaving, all of this gets washed away by capitalism which converts everything into cold hard cash. The nexus between man and man ceases to be bonds of loyalty or obligation, or even love, and just becomes one of money.

Now, I can tell from the enthusiasm in your voice that there are aspects of Marx's account that resonate for you. I'd anticipate that, like a lot of ancient Greek philosophers, but not so many contemporary ones, you'd agree with Marx's thought in the "Theses on Feuerbach" that the point of philosophy is not just to interpret the world, but to change it. But presumably you wouldn't describe yourself as a Marxist.

No. I'm certainly not a Marxist. And I'm not a historical determinist either, as you correctly pointed out earlier. Marx's predictions were quite wide of the mark. I think we can see that now, with enough distance between us. For one thing, it's not true that under capitalism the workers remain close to that level of bare survival. In fact, capitalism has produced, even for the working class and despite a great deal of inequality, a situation in which almost everyone is wealthier than the majority were in previous centuries. You could argue that the vast majority of people in the United Kingdom, or the United States, or Australia, or Europe, are much better off than most people were in earlier centuries: they eat better, they live more comfortably, they have electricity and flushing toilets, and so on. So Marx was wrong to think that the working class was going to be constantly struggling to meet their basic needs.

Marx was also wrong to think that capitalism was going to collapse from some inherent contradiction. He thought that capitalism would collapse in the most advanced countries because that's where capitalism had developed most, and the capitalist class would be the smallest and most vulnerable. Because he thought this, he was never troubled by the idea that the communist revolution would need to be defended against more powerful capitalist nations. It would be precisely the most powerful, most advanced nations that would have become communist. But capitalism didn't collapse in the most advanced nations, and the communist revolutions that did break out happened either in less-developed, partially capitalist economies like Russia, or in places that were not really capitalist at all, like China and Cuba.

"There are some ideas in Marx that we now all would accept to some extent"

Marx's materialist theory of history was not wrong in the same sense as the predictions I have just mentioned, but it was often stated too crudely. At one point, Marx suggested that the hand mill—the mill that you use to mill flour by hand—gives you the society with the feudal lord; the steam mill, in contrast, gives you the industrial capitalist. I don't think that was Marx's considered view, but he didn't allow an adequate role for ideas as independent forces, which I believe they can be.

Still, there's a lot to be taken from Marx and his materialist conception of history, as compared to others who treated the realm of ideas as autonomous and independent of material or economic forces. Marx directed our attention to the influence that economic factors have. We developed a capitalist system in which employers needed workers to be free to move where the factories are. So the bonds of feudalism collapsed, people became more mobile, and the power of money prevailed. We developed an ethic that no longer upheld the feudal values of obligation and loyalty to place and instead valued freedom of contract.

Marx got something right here. He has provided us with a framework that we can use to look at our society. Why is it so difficult, for example, to take the action that almost all scientists say we need to take against climate change? Well, at least part of the story is that there are some very powerful people who've made their money from coal and oil, and they have considerable influence on our ideas and on political decisions. You don't have to look very hard in the United States to see that happening. There are some ideas in Marx that we now all would accept to some extent, without going to the extreme of accepting his historical determinism.

The next book you've chosen is John Stuart Mill's On Liberty, published in 1859. Mill was living in London at the same time as Marx, but this is a very different book from The Communist Manifesto. One similarity, though, is that it was written for a popular audience. Could you say something about why you chose this book?

Certainly. They were both written for popular audiences, but whereas Marx was explicitly writing as an advocate for the working class, or for intellectuals who would assist the working class, Mill was writing against conservatives who sought to prevent the expression of ideas they regarded as dangerous. He put forward what he explicitly says is an argument from utility, that is, he's not arguing from the independent value of freedom for its own sake as a principle, but on the basis of the good consequences that freedom of ideas will have for society and the development of individuals as 'progressive beings.'

Like Marx, Mill thinks we're making progress, though I wouldn't say he's a determinist like Marx. I also wouldn't say that he thinks we're going to reach some kind of perfect state at the end. Marx's vision of communism was that this would solve the riddle of history. I don't think Mill had such an idea. But he did think that we make progress through rational inquiry, through free discussion, and through getting rid of dogmas which we believe without sufficient evidence. He puts up several arguments for freedom of expression, but perhaps the most important is that those who want to suppress ideas that they disagree with assume some kind of infallibility. They assume that they cannot be wrong in the things they believe in, and therefore, conversely, can be certain that the ideas they want to suppress are false. Mill points out that very often, throughout history, people have thought that they were certainly right, and then turned out to be quite wrong.

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Mill also says that even if our beliefs are true, if we suppress opposition to them, our beliefs will become a kind of dead dogma. The way for something to be a living truth is for it to be open to challenge and to have to respond to those challenges.

I chose this book particularly because we are having a lively discussion about freedom of expression today. Some of the challenges to freedom of expression today come from the left rather than from the right, although some of them still do come from the right. In this context, Mill's arguments are still relevant and deserve to be more widely known and more widely thought about. If people do think about them, they'll perhaps be more willing to support thinkers with whom they disagree, because they will understand that the value of allowing ideas to be expressed does not depend on whether the ideas are true.

That's interesting. You've chosen to focus on chapter two of On Liberty where he talks about free expression. There is much more in the book than that. Some people treat it as a gospel of liberalism, about your freedom to live the life you want to live as long as you don't harm other people in the process. But sticking with the free expression issue, it strikes me that what Mill says about dead dogma encapsulates what's valuable about philosophy. As I understand philosophy, anyway, it's not a matter of acquiring a set of true beliefs, it's about the process you use to investigate the world and your position in it, and your willingness to entertain the possibility that you might be wrong, and to engage with other people in an ongoing conversation which can reveal and enliven your beliefs in various ways. It's the process of being contradicted that allows us to make progress in philosophy. It's not just a matter of learning that utilitarianism is true, as perhaps you might believe, but of examining the arguments on either side, and through the collision of disparate viewpoints you engage in an activity which is incidentally independently satisfying, but is more likely to be robust and yield conclusions which are at least close to the truth.

That's right. Philosophy is exactly the kind of subject that thrives on criticism and discussion. As you say, I do think utilitarianism is the most defensible ethical view, but I don't claim infallibility about that, and I'm always open for people to try to persuade me that I am wrong, and I have changed my mind on some aspects of utilitarianism. In a way, it's particularly ironic when philosophers in the 21st century are not able to express themselves.

Perhaps I'm particularly attracted to chapter two of On Liberty because I have myself had my freedom of expression challenged. In the late '80s and early '90s, in Germany, I was drowned out by protestors. I had invitations to speak that I had accepted cancelled. And even when I went to Princeton in 1999, there were protests against my appointment there. People said that somebody who held my views— these are my views about euthanasia—should not have a Chair at Princeton. Perhaps for that reason I feel this issue in a personal way, as well as thinking about it as a philosopher.

One more thought about this book, before we move on to Darwin. Mill explicitly wrote that it was co-written. Harriet Taylor, who became his wife after her husband died, doesn't get a byline, but Mill does write in the preface and elsewhere about her huge influence on his thinking, particularly in this book.

Mill does make her immense contribution clear. We don't know fully whether it really was co-authored, though it does look like the kind of collaboration that we would now think of as co-authorship.

We should perhaps also mention that Mill wrote "The Subjection of Women," which was an early work on behalf of equality for women. In that he refers to people who have a low opinion of the mental abilities of women, and says that men's views about women may often depend on the woman with whom they're in closest association, namely one's wife in most cases. I'm sure that his appreciation of Harriet Taylor's intellectual abilities was a major contributing factor to his confidence in being able to say that women should have the same rights as men, including the right to vote, which they didn't have at that time. A married woman then didn't even have the right to own property: when she married, all of her property became her husband's property. Mill was briefly a Member of Parliament, and tried hard to change that legislation. It was changed shortly afterwards.

The next book you've chosen isn't The Origin of Species, which was incidentally published in the same year as On Liberty, 1859. Rather, it's a later work by Charles Darwin, The Descent of Man (1871)—not 'descent' in the modern sense of decline or going down, but rather descent as the origins of man.

Yes, in the sense that we are descendants of other animals. I like The Descent of Man better than The Origin of Species because Darwin is prepared to be much bolder in The Descent of Man. In The Origin of Species he was still a little bit timid. He presents the idea of how species develop, and that is what we now refer to as evolution. But he didn't apply it to humans. He really didn't dare to say that we humans developed from other apes just as horses, for example, developed from early proto-horses. He didn't use the term 'evolution' anywhere in the original editions of The Origin of Species. He does use it in later editions, but that's around the time when The Descent of Man is published.

There's something else that I particularly like about The Descent of Man, one that links with another area of my thinking that we haven't talked about. Darwin makes an explicit comparison between humans and other animals in terms of their anatomy and physiology, of course, but also in their mental and moral capacities. He brings up the objection that humans could not have descended from animals because our mental powers are different in kind from animals, and our moral nature is also different in kind from anything we can find in other animals.

"The value of allowing ideas to be expressed does not depend on whether the ideas are true"

Darwin rejects this objection. He draws on many observations of animal behaviour and says that here too we can find evolution. There are differences of course, but they're differences of degree, not of kind. This applies even to morality. He finds the origins of morality in the altruism, or group or kin altruism as we might call it, of social animals. He points out that they do help each other, and will do so even at some risk or cost to themselves, and that this could be a forerunner of morality. Darwin wrote that in 1871, and despite Darwin's prominence, it gets neglected for a hundred years. It's only in the 1970s, with the rise of what was then called socio-biology—what we now refer to as evolutionary psychology—that people really went back to making those sorts of comparisons, and said, 'Look, we can see the origins of human morality in the social mammals in particular.'

It's amazing that there was a century of silence about that. One explanation might be the 20th century history of eugenics, and theories of race that emerged from that and had a terrible effect through the extreme cases of Hitler's eugenic theories and practices, which some have traced back to Darwin and Galton. There's a style of evolutionary thinking which claims that if less-well-adapted members of a species are allowed to breed, then that, in a sense, slows or disrupts evolution. This allegedly happens when a civilization ceases to allow the process of natural selection to weed out the so-called weaker members of society. So perhaps there are dangerous as well as liberating ideas in the book.

There are ideas in The Descent of Man that we would today reject. Darwin refers to 'savages' as an in-between case between animal and human morality, for example. They've progressed beyond the level of non-human animals, in his view, but not up to the level of a nineteenth century Englishman.

That's not unlike Mill, who in On Liberty says that individual freedom is right for people living in a civilised society, but not for those peoples 'in their nonage,' by which he meant more primitive peoples.

That's right. Mill, after all, worked for the East India Company and to that extent was involved in propping up colonialism in India. Both Darwin and Mill were people of their times, and subject to some of those prejudices. What you said about Darwin deploring the idea that we interfere with evolution isn't quite right, though. He did note that we allow the weaker members of our species to survive and reproduce, and suggests that this may be harmful to the human race, but he rejects the idea that we should harden ourselves so as not to help the weak survive. To check our sympathy in this way would, he wrote, lead to 'deterioration in the noblest part of our nature.'

Let's move on to your final choice. You've described Henry Sidgwick's The Methods of Ethics (1907 edition) as 'quite simply the best book on ethics ever written'. Do you still think that? And if so, why?

I said, in my review of Derek Parfit's On What Matters for the Times Literary Supplement, that it was the most significant work on ethics written since The Methods of Ethics. That's consistent with The Methods of Ethics being the greatest work. Parfit himself said that The Methods of Ethics contains more true statements about ethics than any other work: it builds on the work of other great scholars, but it contains more truth than other works. I do think it is a wonderful work, and if it is not the best book written on ethics, I'd like to know what is. Parfit's works come close, Reason and Persons as well as On What Matters.

Neither Sidgwick's nor Parfit's books are particularly accessible to the general reader, unlike some classic books in the history of ethics.

That's right. The Methods of Ethics is a very long book: not quite as long as The Phenomenology of Mind, and not as obscure either—it's reasonably clear. But Sidgwick does write long, carefully-qualified sentences. I said earlier that there is a change between Bentham and Sidgwick, a transition to a more academically careful style of writing. Bentham didn't worry about qualifications, he just put things very bluntly. Sidgwick qualifies what he says, and his honesty and readiness to acknowledge criticisms and weaknesses sometimes makes it difficult to work out what his own view is.

"I do think utilitarianism is the most defensible ethical view, but I don't claim infallibility about that, and I'm always open for people to try to persuade me that I am wrong"

He gives a wonderful analysis of what he calls the morality of common sense: the idea that you can build morality from the intuitions that people have about principles of honesty and gratitude and benevolence, etc etc. He has a critique of that idea: he points out that lurking behind many of these intuitions, when it comes down to difficult cases, is an appeal to utility. He also has an argument that utility can rest on self-evident axioms. This is important because it suggests that there is something objective about morality.

In the sense that morality is claimed to be a human universal that we might be able to investigate scientifically? Morality as emerging from psychology?

No. He would agree with Hume that there is a gap between 'is' and 'ought,' between facts and values: you can't derive morality from a psychological study of human beings. It's an independent normative study. He would compare ethics with mathematics. You don't empirically investigate whether two plus two equals four. Sidgwick thought there were some self-evident axioms that you could build on. For example, the idea that the interests of any one being in the universe are just as significant as the similar interests of any other. One thing that would follow from this is that Sidgwick would have opposed the kind of racism that we were talking about a moment ago. If you had said that the interests of another person are not as important as mine because of some racial characteristic, such as the colour of his skin, Sidgwick would have said, 'No, that's not true'.

" When people think about utilitarianism they think about Jeremy Bentham, they think about John Stuart Mill, but they never think about Henry Sidgwick"

Maybe there would have been some other reasons that would have justified differential treatment for Sidgwick, such as that these people couldn't look after themselves, because he was also part of those Victorian times in which a belief in the superiority of the white race was widespread. But the idea that—just taken on its own—the interests of one person count as much as those of any other, Sidgwick argued was an objective truth that we can see when we reflect carefully on it.

Well, that's how it seems to me. But I'm sure that Ayn Rand thought that two plus two equals four; but I'm also sure she didn't think that everybody's interests are equal. There are many people who are quite happy to accept the truths of mathematics, but don't see that universal respect for other people's moral equality with us at all. They seem to think in terms of moral hierarchies and what's more, they might even see a neo-Darwinist justification for that because it explains why they are at the top, and other people are at the bottom.

Insofar as this involves factual claims about some people having higher capacities, abilities, and so on, than others, I don't suppose Sidgwick would necessarily oppose that: that's something that he'd think needs empirical investigation. But the weighting of the interest is what Sidgwick was making an ethical claim about.

Your suggestion of Ayn Rand as a counterexample is an interesting one because she was an egoist, in the philosophical sense, who thought that we are morally justified in always doing what is in our own interests. Sidgwick was deeply troubled by egoism. At the end of The Methods of Ethics, where he discusses egoism at length, he finds himself unable to refute it. This is what I meant about his intellectual honesty. At the end of 500 pages, he says that perhaps the whole enterprise to put morality on a rational basis has failed because he can't show that egoism is irrational. To that extent, he might have thought that in some sense Ayn Rand had a point, although a lot of the things that Ayn Rand said he would not have agreed with. He acknowledges that perhaps there is some fundamental axiom lying behind egoism that he did not claim to be able to refute decisively. Thus there could be a fundamental contradiction in ethics, because egoism clashes with the idea of everyone's interests counting equally, which he also saw as self-evident.

That's really interesting because it confirms him as a paradigm of a philosopher in that he is not a dogmatic moralist telling you how to live, but rather he's saying, 'Here's my attempt at explaining the issue, and I could be wrong. And what's more, I recognise that I haven't got a complete account in every respect.' That's very different from some systematic thinkers who feel the need to claim that they have solved every possible problem. What's interesting is that you're still having a conversation with him, as it were. I know you've co-authored two books (both with Katarzyna de Lazari-Radek) where you discuss Sidgwick and engage with his ideas.

Yes. The more serious academic study is The Point of View of the Universe which is specifically about Sidgwick; the other is Utilitarianism: A Very Short Introduction in which Sidgwick plays a part. One of the things we want to do in both these books is to make people more aware of Sidgwick's work. When people think about utilitarianism they think about Jeremy Bentham, they think about John Stuart Mill, but they never think about Henry Sidgwick, and that's because The Methods of Ethics is such a difficult, long book to read. But I hope if they read our Utilitarianism: A Very Short Introduction, they'll at least have some idea why he is so significant.

Five Books aims to keep its book recommendations and interviews up to date. If you are the interviewee and would like to update your choice of books (or even just what you say about them) please email us at editor@fivebooks.com



_- Steve

Thursday, May 17, 2018

Key escrow

https://www.schneier.com/academic/paperfiles/paper-keys-under-doormats-CSAIL.pdf





_- Steve

Ancient Rome’s Collapse Is Written Into Arctic Ice - The Atlantic

Ancient Rome's Collapse Is Written Into Arctic Ice - The Atlantic

Ancient Rome's Collapse Is Written Into Arctic Ice

Scientists can finally track the civilization's economic booms and recessions—thanks to the exhaust of its massive coin-making operation, preserved for centuries in Greenland's ice sheet.

Oskari Porkka / Gilmanshin / Shutterstock / Katie Martin / The Atlantic

On March 15, some time ago, several dozen famous politicians—sturdy men, duly elected senators who claimed to love their republic—attacked their chief executive while he walked into the Senate. They stabbed Gaius Julius Caesar 23 times, as he fell to the floor, defenseless, and bled to death, setting off a chain of wars that formally ended the Roman Republic and initiated the Roman Empire.

Some 2,062 years have passed since that day, but we haven't stopped arguing about it. From Central Park productions of Julius Caesar to op-ed accusations of "Caesarism," the Roman dictator—and the world he inhabited—still looms in our political conversation. Even the architecture of Washington, D.C., suggests that it is a kind of New Rome.

But for all those years, the source material for the arguments have remained largely the same. Archaeologists can locate new sites and excavate for coins, plates, or jewelry; scholars can read and reread Roman writers like Cicero, Sallust, and Catullus, who all documented Caesar. These have been the techniques for learning about Rome for centuries, and they are indispensable. But lately, they have been joined by something new.

On Monday, scientists announced the discovery of an entirely new resource that has the potential to remake some of those centuries-old arguments over Roman politics and history. A team of archaeologists, historians, and climate scientists have constructed a history of Rome's lead pollution, which allows them to approximate Mediterranean economic activity from 1,100 B.C. to 800 A.d. They found it hiding thousands of miles from the Roman Forum: deep in the Greenland Ice Sheet, the enormous, miles-thick plate of ice that entombs the North Atlantic island.

In short, they have reconstructed year-by-year economic data documenting the rise and fall of the Roman Republic and Empire. The first news of the record was published Monday afternoon in Proceedings of the National Academy of Sciences.

Why does the amount of lead in the atmosphere tell us something about the Roman economy? "It's a proxy for coin production. That's the biggest thing," said Seth Bernard, a professor of ancient history at the University of Toronto. When the Roman government needed to pay for something, it ordered the creation of new silver coins. These coins were produced, in part, in mines on the Iberian peninsula. But these mines didn't excavate pure silver: Instead, they unearthed an ore of silver, lead, and copper that had to be smelted into silver. This process filled the air with lead pollution.

Once in the air, these lead emissions did not stay in one place. Instead, it wafted with the winds, eventually blowing into squalls and storms over Greenland. When these storms deposited lead-tainted snow or sleet over the Arctic island, the precipitation fused with the ice sheet and became its newest layer. Century upon century of snow and ice fell on the ice sheet, burying but never disturbing that old layer of ice—until 1999, when climate scientists began coring the ice sheet at the NGRIP site. Four-inch tubes, documenting those ancient layers of snow and sleet, were hauled to the surfaces and pristinely preserved.

"There isn't anything close to this detailed" documenting the Roman economy, said Joe McConnell, a professor of hydrology at the Desert Research Institute and one of the authors of the paper. "Our record is dramatically different both in its temporal resolution and in its dating precision."

"The paper speaks for itself," said Seth Bernard, who had early access to its findings but did not work on the research. "It feels sort of like we've discovered the Americas. There was another continent over there, that was always there, that we can see now. And I think that continent is scientific approaches."

The new paper contains findings that Roman historians can already apply to their work. It finds that Rome's economy waxed and waned, following well-documented events in its history, including wars and plagues. In 218 B.C., for instance, when Rome fought with Carthage in the Second Punic War, lead pollution appears to fall—and then it rises, abruptly, as Roman soldiers seized Carthaginian mines in southern Spain and put them to use. It also detects nonviolent events: When Rome debased its currency, reducing the amount of silver in each denarius coin in 64 A.d., lead pollution in the air fell.

And it provides crucial economic context for some of the most pivotal events in Roman history, including the death of Julius Caesar (and the birth of Jesus of Nazareth). The Crisis of the Roman Republic—the series of civil wars and political strife, spanning 134 B.C. to 27 B.C., that brought the Roman Republic to an end— were associated with a broad period of economic stagnation and disintegration, the study finds. And the early Roman Empire—especially the Pax Romana, the 206 years of mostly uninterrupted peace throughout the Mediterranean—were accompanied by an economic boom. When compared with other studies, research suggests that Western Europe may have seen higher lead emissions during the Pax Romana than at any time prior to the Industrial Revolution, nearly 1,800 years later.

This finding reverses a widely cited study from the 1990s that reached almost exactly the opposite finding. That paper, which used a similar but rudimentary technique to pull lead emissions out of the Greenland ice, argued that Roman economic productivity peaked during the late Republic, then stagnated throughout the entire Roman Empire. But that study drew from 18 data points; this new research made 25,000 different measurements of the ice core.


How Lead Emissions Align With Roman and Mediterranean History

There's a lot going on in this chart. It shows the varying amount of lead pollution in the air, as measured from an ice core taken from the NGRIP site in northeastern Greenland. It augments this timeline with major events in Roman history and, after 300 B.C., the silver content of Roman coinage. The letters at the very top signify individual historical events, as follows: A: the Punic Wars, B: the Sertorian War, C: the Civil Wars, D: the final pacification of Gaul and Spain, E: the Antonine plague, F: the Plague of Cyprian, G: the Roman abandonment of Britain, and H: the collapse of the Western Roman Empire. (McConnell, et al. / PNAS)

"Lead pollutants have become enormously important because they give us information that we don't get from literary sources. The one chart that's there—I can already see that chart being produced in 50 articles over the next 10 years," said Bernard about the above graph. "It's great stuff."

Lead emissions are not a perfect record of Roman prosperity, however, because scholars still don't know how Rome thought about its economy. Coins were clearly important: At the height of the Roman Empire, coins were so standardized that the same money could theoretically be used to buy goods, services, and slaves across modern-day Syria, Spain, Italy, and Turkey.

"The size of this integrated monetary zone is unparalleled," said Bernard. "And the volume of coinage seems larger than any time before or afterward—it really shows the integration of the Roman economy and the level of trade that was going on."

Yet for all these coins, it remains unclear how Rome managed its money in a modern sense. "What we'd love to have is a document that says Rome had a state monetary policy," said Bernard. But none have ever been found. So scholars have argued about whether Roman leaders ignored liquidity or inflation, simply ordering a new round of coins whenever the government faced a large expense; or whether leaders managed money more strategically. Nero's order to debase the currency in 64 a.d. suggests that the Empire, eventually, did see some value in increasing the amount of money in circulation.

The study would not have been possible without three methodological advances, researchers told me.

First, computer models of the atmosphere have significantly improved over the last two decades. These simulations allow scientists to estimate how air from the Iberian peninsula—air that, in Roman times, would have been full of lead pollution—wafted up to the Greenland ice sheet. It also allowed them to distinguish between air from the Iberian peninsula specifically and ambient air from farther east in Europe. This has its historical uses, too: The study documents a rise in ambient lead quality starting in 800 B.C., which coincides with the expansion of the wealthy Phoenician civilization into the western Mediterranean.

Second, chemists and hydrologists have become more adept at finding trace amounts of mineral in the ice core. In the 1990s, researchers could only analyze the pollution in ice cores by peeling tiny shavings of ice off of them. Now, labs use highly sensitive mass spectrometers to measure the presence of 35 different elements and chemicals at once.

These techniques are constantly improving. The new study uses more than 25,000 observations of the ice core across 2,000 years of time. Alexander More, a climate scientist and a historian at Harvard University, told me that another team is working on a technique that can generate 2 billion data points across a 2,000-year ice core—and do it without destroying the ice in any way.

A Greenland ice core is analyzed. (PNAS)

Finally, researchers have gotten better at precisely tying each of those observations to a specific year. Over the last decade, scientists have worked together across fields—including climate science, geochemistry, and volcanology—to unify the "dating" of important climate records. Most importantly, they have learned the precise year that every major volcanic eruption in the last 2,500 years occurred and identified these eruptions in a wide set of natural climate records. Ice cores from Greenland and Antarctica, as well as tree rings from around the world, all show a distinct chemical signature left behind by the eruption of the massive Indonesian volcano Samalas in 1257. Using that eruption and others, as well as a number of other anomalies, scientists can "count backward" in ice cores and tie each layer in the ice to a specific year.

"We think the uncertainty in our age scales is about one to two years, even in antiquity," said McConnell, an author of the paper. "And that's pretty good. It's a lot better than what archaeologists are used to, I can tell you that."

This specificity allows them to find precise political events in the ice. For instance, even though Rome took over Iberian mines after the Second Punic War, the peninsula saw revolutions and uprisings for centuries. Only in 19 B.C. did Rome's first emperor, Caesar Augustus, conquer the rest of Gaul and place the entire colony under a new administration.

"The big increase [in lead pollution] corresponds exactly—and I mean exactly—to the pacification of Iberia and Gaul by Caesar Augustus. And [Iberia and Gaul] are where this pollution was coming from, so it all makes sense," said McConnell.

That said, the lead record does not seem to mark a few major events in Roman history. The Plague of Justinian, which may have killed half the population of Europe in 541 and 542 a.d., does not seem to feature prominently in the record. Nor does the record encompass the full scope of the Roman coin-minting operation: Many important silver mines sat near Greece and the eastern Mediterranean, and their emissions probably did not make it to Greenland.

Alexander More, the Harvard researcher who was not affiliated with the research, said that even in this study, he remained "interested in knowing how the air [from Iberia] got over to Greenland." His team's own analysis of climate models suggests that air masses tend to travel from Europe's northwest to its southeast, which is the opposite journey that these lead emissions would need to have made. "So there might be input from China here, we don't know," he said. "These are all things that need to be considered."

But above all, he said that he was "very happy" to see the new work. "We are very heartened by the fact that historians and climate scientists and archaeologists are working together to produce interdisciplinary research of this kind," he said.

According to some scientists, lead poisoning played a role in the demise of Rome. So it's ironic that lead provides its own record of what devastated the empire. Starting in 165 a.d., a plague swept out of the east and into the Roman world. The disease, dubbed the Antonine plague, caused fever, diarrhea, and skin pustules. (Some scholars believe it may have been smallpox.) It killed millions of Romans, and it devastated the Roman army in particular.

The Roman economy never recovered. Lead emissions plunged that year, hitting a new baseline that persisted for several centuries. Only in the late fourth century, when a Germanic tribe overthrew the last Western Roman emperor, did emissions fall even lower.

It is a new input in an argument—did plagues doom the Roman empire?—so careworn that even the 18th-century historian Edward Gibbon, who wrote 4,000 pages on Rome's decline, wearied of debating it. And like the rest of the study, it will change how classicists like Seth Bernard go back to the primary sources.

"How we read Cicero, how we read our historical sources of the Gracchi—it does feel like we have new material that we've never had access to before," he told me. "The opportunity lies in taking this new data and rethinking what we have."

And it "all makes sense" that ancient historians would find succor in climate science, he said. "We've known for a very long time that if you're in a world that relies on human power, and calories, and energy—and thus the sun—then what the sun is doing, and what climate is doing, matter a lot," he said.

To that, I would add only: You do not need to return to Catullus and Caesar, Cicero and Catiline, to find a civilization that ran on calories and human power, that relied on the sun and the stable climate. Nor was ancient Rome the only civilization that scattered its exhaust to every corner of the Earth, leaving a record of itself that would have been unimaginable to its own citizens. If you wish to seek out such a civilization, then congratulations: You are living in one right now.



_- Steve

Ancient Rome’s Collapse Is Written Into Arctic Ice - The Atlantic

Ancient Rome's Collapse Is Written Into Arctic Ice - The Atlantic

Ancient Rome's Collapse Is Written Into Arctic Ice

Scientists can finally track the civilization's economic booms and recessions—thanks to the exhaust of its massive coin-making operation, preserved for centuries in Greenland's ice sheet.

The Atlantic

Oskari Porkka / Gilmanshin / Shutterstock / Katie Martin / The Atlantic

On March 15, some time ago, several dozen famous politicians—sturdy men, duly elected senators who claimed to love their republic—attacked their chief executive while he walked into the Senate. They stabbed Gaius Julius Caesar 23 times, as he fell to the floor, defenseless, and bled to death, setting off a chain of wars that formally ended the Roman Republic and initiated the Roman Empire.

Some 2,062 years have passed since that day, but we haven't stopped arguing about it. From Central Park productions of Julius Caesar to op-ed accusations of "Caesarism," the Roman dictator—and the world he inhabited—still looms in our political conversation. Even the architecture of Washington, D.C., suggests that it is a kind of New Rome.

But for all those years, the source material for the arguments have remained largely the same. Archaeologists can locate new sites and excavate for coins, plates, or jewelry; scholars can read and reread Roman writers like Cicero, Sallust, and Catullus, who all documented Caesar. These have been the techniques for learning about Rome for centuries, and they are indispensable. But lately, they have been joined by something new.

On Monday, scientists announced the discovery of an entirely new resource that has the potential to remake some of those centuries-old arguments over Roman politics and history. A team of archaeologists, historians, and climate scientists have constructed a history of Rome's lead pollution, which allows them to approximate Mediterranean economic activity from 1,100 B.C. to 800 A.d. They found it hiding thousands of miles from the Roman Forum: deep in the Greenland Ice Sheet, the enormous, miles-thick plate of ice that entombs the North Atlantic island.

In short, they have reconstructed year-by-year economic data documenting the rise and fall of the Roman Republic and Empire. The first news of the record was published Monday afternoon in Proceedings of the National Academy of Sciences.

Why does the amount of lead in the atmosphere tell us something about the Roman economy? "It's a proxy for coin production. That's the biggest thing," said Seth Bernard, a professor of ancient history at the University of Toronto. When the Roman government needed to pay for something, it ordered the creation of new silver coins. These coins were produced, in part, in mines on the Iberian peninsula. But these mines didn't excavate pure silver: Instead, they unearthed an ore of silver, lead, and copper that had to be smelted into silver. This process filled the air with lead pollution.

Once in the air, these lead emissions did not stay in one place. Instead, it wafted with the winds, eventually blowing into squalls and storms over Greenland. When these storms deposited lead-tainted snow or sleet over the Arctic island, the precipitation fused with the ice sheet and became its newest layer. Century upon century of snow and ice fell on the ice sheet, burying but never disturbing that old layer of ice—until 1999, when climate scientists began coring the ice sheet at the NGRIP site. Four-inch tubes, documenting those ancient layers of snow and sleet, were hauled to the surfaces and pristinely preserved.

"There isn't anything close to this detailed" documenting the Roman economy, said Joe McConnell, a professor of hydrology at the Desert Research Institute and one of the authors of the paper. "Our record is dramatically different both in its temporal resolution and in its dating precision."

"The paper speaks for itself," said Seth Bernard, who had early access to its findings but did not work on the research. "It feels sort of like we've discovered the Americas. There was another continent over there, that was always there, that we can see now. And I think that continent is scientific approaches."

The new paper contains findings that Roman historians can already apply to their work. It finds that Rome's economy waxed and waned, following well-documented events in its history, including wars and plagues. In 218 B.C., for instance, when Rome fought with Carthage in the Second Punic War, lead pollution appears to fall—and then it rises, abruptly, as Roman soldiers seized Carthaginian mines in southern Spain and put them to use. It also detects nonviolent events: When Rome debased its currency, reducing the amount of silver in each denarius coin in 64 A.d., lead pollution in the air fell.

And it provides crucial economic context for some of the most pivotal events in Roman history, including the death of Julius Caesar (and the birth of Jesus of Nazareth). The Crisis of the Roman Republic—the series of civil wars and political strife, spanning 134 B.C. to 27 B.C., that brought the Roman Republic to an end— were associated with a broad period of economic stagnation and disintegration, the study finds. And the early Roman Empire—especially the Pax Romana, the 206 years of mostly uninterrupted peace throughout the Mediterranean—were accompanied by an economic boom. When compared with other studies, research suggests that Western Europe may have seen higher lead emissions during the Pax Romana than at any time prior to the Industrial Revolution, nearly 1,800 years later.

This finding reverses a widely cited study from the 1990s that reached almost exactly the opposite finding. That paper, which used a similar but rudimentary technique to pull lead emissions out of the Greenland ice, argued that Roman economic productivity peaked during the late Republic, then stagnated throughout the entire Roman Empire. But that study drew from 18 data points; this new research made 25,000 different measurements of the ice core.


How Lead Emissions Align With Roman and Mediterranean History

There's a lot going on in this chart. It shows the varying amount of lead pollution in the air, as measured from an ice core taken from the NGRIP site in northeastern Greenland. It augments this timeline with major events in Roman history and, after 300 B.C., the silver content of Roman coinage. The letters at the very top signify individual historical events, as follows: A: the Punic Wars, B: the Sertorian War, C: the Civil Wars, D: the final pacification of Gaul and Spain, E: the Antonine plague, F: the Plague of Cyprian, G: the Roman abandonment of Britain, and H: the collapse of the Western Roman Empire. (McConnell, et al. / PNAS)

"Lead pollutants have become enormously important because they give us information that we don't get from literary sources. The one chart that's there—I can already see that chart being produced in 50 articles over the next 10 years," said Bernard about the above graph. "It's great stuff."

Lead emissions are not a perfect record of Roman prosperity, however, because scholars still don't know how Rome thought about its economy. Coins were clearly important: At the height of the Roman Empire, coins were so standardized that the same money could theoretically be used to buy goods, services, and slaves across modern-day Syria, Spain, Italy, and Turkey.

"The size of this integrated monetary zone is unparalleled," said Bernard. "And the volume of coinage seems larger than any time before or afterward—it really shows the integration of the Roman economy and the level of trade that was going on."

Yet for all these coins, it remains unclear how Rome managed its money in a modern sense. "What we'd love to have is a document that says Rome had a state monetary policy," said Bernard. But none have ever been found. So scholars have argued about whether Roman leaders ignored liquidity or inflation, simply ordering a new round of coins whenever the government faced a large expense; or whether leaders managed money more strategically. Nero's order to debase the currency in 64 a.d. suggests that the Empire, eventually, did see some value in increasing the amount of money in circulation.

The study would not have been possible without three methodological advances, researchers told me.

First, computer models of the atmosphere have significantly improved over the last two decades. These simulations allow scientists to estimate how air from the Iberian peninsula—air that, in Roman times, would have been full of lead pollution—wafted up to the Greenland ice sheet. It also allowed them to distinguish between air from the Iberian peninsula specifically and ambient air from farther east in Europe. This has its historical uses, too: The study documents a rise in ambient lead quality starting in 800 B.C., which coincides with the expansion of the wealthy Phoenician civilization into the western Mediterranean.

Second, chemists and hydrologists have become more adept at finding trace amounts of mineral in the ice core. In the 1990s, researchers could only analyze the pollution in ice cores by peeling tiny shavings of ice off of them. Now, labs use highly sensitive mass spectrometers to measure the presence of 35 different elements and chemicals at once.

These techniques are constantly improving. The new study uses more than 25,000 observations of the ice core across 2,000 years of time. Alexander More, a climate scientist and a historian at Harvard University, told me that another team is working on a technique that can generate 2 billion data points across a 2,000-year ice core—and do it without destroying the ice in any way.

A Greenland ice core is analyzed. (PNAS)

Finally, researchers have gotten better at precisely tying each of those observations to a specific year. Over the last decade, scientists have worked together across fields—including climate science, geochemistry, and volcanology—to unify the "dating" of important climate records. Most importantly, they have learned the precise year that every major volcanic eruption in the last 2,500 years occurred and identified these eruptions in a wide set of natural climate records. Ice cores from Greenland and Antarctica, as well as tree rings from around the world, all show a distinct chemical signature left behind by the eruption of the massive Indonesian volcano Samalas in 1257. Using that eruption and others, as well as a number of other anomalies, scientists can "count backward" in ice cores and tie each layer in the ice to a specific year.

"We think the uncertainty in our age scales is about one to two years, even in antiquity," said McConnell, an author of the paper. "And that's pretty good. It's a lot better than what archaeologists are used to, I can tell you that."

This specificity allows them to find precise political events in the ice. For instance, even though Rome took over Iberian mines after the Second Punic War, the peninsula saw revolutions and uprisings for centuries. Only in 19 B.C. did Rome's first emperor, Caesar Augustus, conquer the rest of Gaul and place the entire colony under a new administration.

"The big increase [in lead pollution] corresponds exactly—and I mean exactly—to the pacification of Iberia and Gaul by Caesar Augustus. And [Iberia and Gaul] are where this pollution was coming from, so it all makes sense," said McConnell.

That said, the lead record does not seem to mark a few major events in Roman history. The Plague of Justinian, which may have killed half the population of Europe in 541 and 542 a.d., does not seem to feature prominently in the record. Nor does the record encompass the full scope of the Roman coin-minting operation: Many important silver mines sat near Greece and the eastern Mediterranean, and their emissions probably did not make it to Greenland.

Alexander More, the Harvard researcher who was not affiliated with the research, said that even in this study, he remained "interested in knowing how the air [from Iberia] got over to Greenland." His team's own analysis of climate models suggests that air masses tend to travel from Europe's northwest to its southeast, which is the opposite journey that these lead emissions would need to have made. "So there might be input from China here, we don't know," he said. "These are all things that need to be considered."

But above all, he said that he was "very happy" to see the new work. "We are very heartened by the fact that historians and climate scientists and archaeologists are working together to produce interdisciplinary research of this kind," he said.

According to some scientists, lead poisoning played a role in the demise of Rome. So it's ironic that lead provides its own record of what devastated the empire. Starting in 165 a.d., a plague swept out of the east and into the Roman world. The disease, dubbed the Antonine plague, caused fever, diarrhea, and skin pustules. (Some scholars believe it may have been smallpox.) It killed millions of Romans, and it devastated the Roman army in particular.

The Roman economy never recovered. Lead emissions plunged that year, hitting a new baseline that persisted for several centuries. Only in the late fourth century, when a Germanic tribe overthrew the last Western Roman emperor, did emissions fall even lower.

It is a new input in an argument—did plagues doom the Roman empire?—so careworn that even the 18th-century historian Edward Gibbon, who wrote 4,000 pages on Rome's decline, wearied of debating it. And like the rest of the study, it will change how classicists like Seth Bernard go back to the primary sources.

"How we read Cicero, how we read our historical sources of the Gracchi—it does feel like we have new material that we've never had access to before," he told me. "The opportunity lies in taking this new data and rethinking what we have."

And it "all makes sense" that ancient historians would find succor in climate science, he said. "We've known for a very long time that if you're in a world that relies on human power, and calories, and energy—and thus the sun—then what the sun is doing, and what climate is doing, matter a lot," he said.

To that, I would add only: You do not need to return to Catullus and Caesar, Cicero and Catiline, to find a civilization that ran on calories and human power, that relied on the sun and the stable climate. Nor was ancient Rome the only civilization that scattered its exhaust to every corner of the Earth, leaving a record of itself that would have been unimaginable to its own citizens. If you wish to seek out such a civilization, then congratulations: You are living in one right now.



_- Steve