Interview (Part 2)

21 March, 2016

Greg Bernhardt runs an excellent website for discussing physics, math and other topics, called Physics Forums. He recently interviewed me there. Since I used this opportunity to explain a bit about the Azimuth Project and network theory, I thought I’d reprint the interview here. Here is Part 2.


Tell us about your experience with past projects like “This Week’s Finds in Mathematical Physics”.

I was hired by U.C. Riverside back in 1989. I was lonely and bored, since Lisa was back on the other coast. So, I spent a lot of evenings on the computer.

We had the internet back then—this was shortly after stone tools were invented—but the world-wide web hadn’t caught on yet. So, I would read and write posts on “newsgroups” using a program called a “news server”. You have to imagine me sitting in front of an old green­-on­-black cathode ray tube monitor with a large floppy disk drive, firing up the old modem to hook up to the internet.

In 1993, I started writing a series of posts on the papers I’d read. I called it “This Week’s Finds in Mathematical Physics”, which was a big mistake, because I couldn’t really write one every week. After a while I started using it to explain lots of topics in math and physics. I wrote 300 issues. Then I quit in 2010, when I started taking climate change seriously.

Share with us a bit about your current projects like Azimuth and the n­-Café.

The n­-Category Café is a blog I started with Urs Schreiber and the philosopher David Corfield back in 2006, when all three of us realized that n­-categories are the big wave that math is riding right now. We have a bunch more bloggers on the team now. But the n­-Café lost some steam when I quit work in n­-categories and Urs started putting most of his energy into two related projects: a wiki called the nLab and a discussion group called the nForum.

In 2010, when I noticed that global warming was like a huge wave crashing down on our civilization, I started the Azimuth Project. The goal was to create a focal point for scientists and engineers interested in saving the planet. It consists of a team of people, a blog, a wiki and a discussion group. It was very productive for a while: we wrote a lot of educational articles on climate science and energy issues. But lately I’ve realized I’m better at abstract math. So, I’ve been putting more time into working with my grad students.

What about climate change has captured your interest?

That’s like asking: “What about that huge tsunami rushing toward us has captured your interest?”

Around 2004 I started hearing news that sent chills up my spine ­ and what really worried me is how few people were talking about this news, at least in the US.

I’m talking about how we’re pushing the Earth’s climate out of the glacial cycle we’ve been in for over a million years, into brand new territory. I’m talking about things like how it takes hundreds or thousands of years for CO2 to exit the atmosphere after it’s been put in. And I’m talking about how global warming is just part of a bigger phenomenon: the Anthropocene. That’s a new geological epoch, in which the biosphere is rapidly changing due to human influences. It’s not just the temperature:

• About 1/4 of all chemical energy produced by plants is now used by humans.

• The rate of species going extinct is 100­–1000 times the usual background rate.

• Populations of large ocean fish have declined 90% since 1950.

• Humans now take more nitrogen from the atmosphere and convert it into nitrates than all other processes combined.

8­-9 times as much phosphorus is flowing into oceans than the natural background rate.

This doesn’t necessarily spell the end of our civilization, but it is something that we’ll all have to deal with.

So, I felt the need to alert people and try to dream up strategies to do something. That’s why in 2010 I quit work on n­-categories and started the Azimuth Project.

Carbon Dioxide Variations

You have life experience on both US coasts. Which do you prefer and why?

There are some differences between the coasts, but they’re fairly minor. The West Coast is part of the Pacific Rim, so there’s more Asian influence here. The seasons are less pronounced here, because winds in the northern hemisphere blow from west to east, and the oceans serve as a temperature control system. Down south in Riverside it’s a semi­-desert, so we can eat breakfast in our back yard in January! But I live here not because I like the West Coast more. This just happens to be where my wife Lisa and I managed to get a job.

What I really like is getting out of the US and seeing the rest of the world. When you’re at cremation ritual in Bali, or a Hmong festival in Laos, the difference between regions of the US starts seeming pretty small.

But I wasn’t a born traveler. When I spent my first summer in England, I was very apprehensive about making a fool of myself. The British have different manners, and their old universities are full of arcane customs and subtle social distinctions that even the British find terrifying. But after a few summers there I got over it. First, all around the world, being American gives you a license to be clueless. If you behave any better than the worst stereotypes, people are impressed. Second, I spend most of my time with mathematicians, who are incredibly forgiving of bad social behavior as long as you know interesting theorems.

By now I’ve gotten to feel very comfortable in England. The last couple of years I’ve spent time at the quantum computation group at Oxford–the group run by Bob Coecke and Samson Abramsky. I like talking to Jamie Vicary about n­categories and physics, and also my old friend Minhyong Kim, who is a number theorist there.

I was also very apprehensive when I first visited Paris. Everyone talks about how the waiters are rude, and so on. But I think that’s an exaggeration. Yes, if you go to cafés packed with boorish tourists, the waiters will treat you like a boorish tourist—so don’t do that. If you go to quieter places and behave politely, most people are friendly. Luckily Lisa speaks French and has some friends in Paris; that opens up a lot of opportunities. I don’t speak French, so I always feel like a bit of an idiot, but I’ve learned to cope. I’ve spent a few summers there working with Paul­-André Melliès on category theory and logic.

Yau Ma Tei Market - Hong Kong

Yau Ma Tei Market – Hong Kong

I was also intimidated when I first spent a summer in Hong Kong—and even more so when I spent a summer in Shanghai. Lisa speaks Chinese too: she’s more cultured than me, and she drags me to interesting places. My first day walking around Shanghai left me completely exhausted: everything was new! Walking down the street you see people selling frogs in a bucket, strange fungi and herbs, then a little phone shop where telephone numbers with lots of 8’s cost more, and so on: it’s a kind of cognitive assault.

But again, I came to enjoy it. And coming back to California, everything seemed a bit boring. Why is there so much land that’s not being used? Where are all the people? Why is the food so bland?

I’ve spent the most time outside the US in Singapore. Again, that’s because my wife and I both got job offers there, not because it’s the best place in the world. Compared to China it’s rather sterile and manicured. But it’s still a fascinating place. They’ve pulled themselves up from a British colonial port town to a multi­cultural country that’s in some ways more technologically advanced than the US. The food is great: it’s a mix of Chinese, Indian, Malay and pretty much everything else. There’s essentially no crime: you can walk around in the darkest alley in the worst part of town at 3 am and still feel safe. It’s interesting to live in a country where people from very different cultures are learning to live together and prosper. The US considers itself a melting-pot, but in Singapore they have four national languages: English, Mandarin, Malay and Tamil.

Most of all, it’s great to live in places where the culture and politics is different than where I grew up. But I’m trying to travel less, because it’s bad for the planet.

You’ve gained some fame for your “crackpot index”. What were your motivations for developing it? Any new criteria you’d add?

After the internet first caught on, a bunch of us started using it to talk about physics on the usenet newsgroup sci.physics.

And then, all of a sudden, crackpots around the world started joining in!

Before this, I don’t think anybody realized how many people had their own personal theories of physics. You might have a crazy uncle who spent his time trying to refute special relativity, but you didn’t realize there were actually thousands of these crazy uncles.

As I’m sure you know here at Physics Forums, crackpots naturally tend to drive out more serious conversations. If you have some people talking about the laws of black hole thermodynamics, and some guy jumps in and says that the universe is a black hole, everyone will drop what they’re doing and argue with that guy. It’s irresistible. It reminds me of how when someone brings a baby to a party, everyone will start cooing to the baby. But it’s worse.

When physics crackpots started taking over the usenet newsgroup sci.physics, I discovered that they had a lot of features in common. The Crackpot Index summarizes these common features. Whenever I notice a new pattern, I add it.

For example: if someone starts comparing themselves to Galileo and says the physics establishment is going after them like the Inquisition, I guarantee you that they’re a crackpot. Their theories could be right—but unfortunately, they’ve got delusions of grandeur and a persecution complex.

It’s not being wrong that makes someone a crackpot. Being a full­-fledged crackpot is the endpoint of a tragic syndrome. Someone starts out being a bit too confident that they can revolutionize physics without learning it first. In fact, many young physicists go through this stage! But the good ones react to criticism by upping their game. The ones who become crackpots just brush it off. They come up with an idea that they think is great, and when nobody likes it, they don’t say “okay, I need to learn more.” Instead, they make up excuses: nobody understands me, maybe there’s a conspiracy at work, etc. The excuses get more complicated with each rebuff, and it gets harder and harder for them to back down and say “whoops, I was wrong”.

When I wrote the Crackpot Index, I thought crackpots were funny. Alexander Abian claimed all the world’s ills would be cured if we blew up the Moon. Archimedes Plutonium thinks the Universe is a giant plutonium atom. These ideas are funny. But now I realize how sad it is that someone can start with an passion for physics and end up in this kind of trap. They almost never escape.

Who are some of your math and physics heroes of the past and of today?

Wow, that’s a big question! I think every scientist needs to have heroes. I’ve had a lot.

Marie Curie

Marie Curie

When I was a kid, I was in love with Marie Curie. I wanted to marry a woman like her: someone who really cared about science. She overcame huge obstacles to get a degree in physics, discovered not one but two new elements, often doing experiments in her own kitchen—and won not one but two Nobel prizes. She was a tragic figure in many ways. Her beloved husband Pierre, a great physicist in his own right, slipped and was run over by a horse­-drawn cart, dying instantly when the wheels ran over his skull. She herself probably died from her experiments with radiation. But this made me love her all the more.

Later my big hero was Einstein. How could any physicist not have Einstein as a hero? First he came up with the idea that light comes in discrete quanta: photons. Then, two months later, he used Brownian motion to figure out the size of atoms. One month after that: special relativity, unifying space and time! Three months later, the equivalence between mass and energy. And all this was just a warmup for his truly magnificent theory of general relativity, explaining gravity as the curvature of space and time. He truly transformed our vision of the Universe. And then, in his later years, the noble and unsuccessful search for a unified field theory. As a friend of mine put it, what matters here is not that he failed: what matters is that he set physics a new goal, more ambitious than any goal it had before.

Later it was Feynman. As I mentioned, my uncle gave me Feynman’s Lectures on Physics. This is how I first learned Maxwell’s equations, special relativity, quantum mechanics. His way of explaining things with a minimum of jargon, getting straight to the heart of every issue, is something I really admire. Later I enjoyed his books like Surely You Must Be Joking. Still later I learned enough to be impressed by his work on QED.

But when you read his autobiographical books, you can see that he was a bit too obsessed with pretending to be a fun­-loving ordinary guy. A fun­-loving ordinary guy who just happens to be smarter than everyone else. In short, a self­-absorbed showoff. He could also be pretty mean to women—and in that respect, Einstein was even worse. So our heroes should not be admired uncritically.

Alexander Grothendieck

Alexander Grothendieck

A good example is Alexander Grothendieck. I guess he’s my main math hero these days. To solve concrete problems like the Weil conjectures, he avoided brute force techniques and instead developed revolutionary new concepts that gently dissolved those problems. And these new concepts turned out to be much more important than the problems that motivated him. I’m talking about abelian categories, schemes, topoi, stacks, things like that. Everyone who really wants to understand math at a deep level has got to learn these concepts. They’re beautiful and wonderfully simple—but not easy to master. You have to really change your world view to understand them, just like general relativity or quantum mechanics. You have to rewire your neurons.

At his peak, Grothendieck seemed almost superhuman. It seems he worked almost all day and all night, bouncing his ideas off the other amazing French algebraic geometers. Apparently 20,000 pages of his writings remain unpublished! But he became increasingly alienated from the mathematical establishment and eventually disappeared completely, hiding in a village near the Pyrenees.

Which groundbreaking advances in science and math are you most looking forward to?

I’d really like to see progress in figuring out the fundamental laws of physics. Ideally, I’d like to know the Theory of Everything. Of course, we don’t even know that there is one! There could be an endless succession of deeper and deeper realizations to be had about the laws of physics, with no final answer.

If we ever do discover the Theory of Everything, that won’t be the end of the story. It could be just the beginning. For example, next we could ask why this particular theory governs our Universe. Is it necessary, or contingent? People like to chat about this puzzle already, but I think it’s premature. I think we should find the Theory of Everything first.

Unfortunately, right now fundamental physics is in a phase of being “stuck”. I don’t expect to see the Theory of Everything in my lifetime. I’d be happy to see any progress at all! There are dozens of very basic things we don’t understand.

When it comes to math, I expect that people will have their hands full this century redoing the foundations using ∞-categories, and answering some of the questions that come up when you do this. The crowd working on “homotopy type theory” is making good progress–but so far they’re mainly thinking about ∞-groupoids, which are a very special sort of ∞-category. When we do all of math using ∞-categories, it will be a whole new ballgame.

And then there’s the question of whether humanity will figure out a way to keep from ruining the planet we live on. And the question of whether we’ll succeed in replacing ourselves with something more intelligent—or even wiser.

The Milky Way and Andromeda Nebula after their first collision, 4 billion years from now

The Milky Way and Andromeda Nebula after their first collision, 4 billion years from now

Here’s something cool: red dwarf stars will keep burning for 10 trillion years. If we, or any civilization, can settle down next to one of those, there will be plenty of time to figure things out. That’s what I hope for.

But some of my friends think that life always uses up resources as fast as possible. So one of my big questions is whether intelligent life will develop the patience to sit around and think interesting thoughts, or whether it will burn up red dwarf stars and every other source of energy as fast as it can, as we’re doing now with fossil fuels.

What does the future hold for John Baez? What are your goals?

What the future holds for me, primarily, is death.

That’s true of all of us—or at least most of us. While some hope that technology will bring immortality, or at least a much longer life, I bet most of us are headed for death fairly soon. So I try to make the most of the time I have.

I’m always re­-evaluating what I should do. I used to spend time thinking about quantum gravity and n­-categories. But quantum gravity feels stuck, and n­-category theory is shooting forward so fast that my help is no longer needed.

Climate change is hugely important, and nobody really knows what to do about it. Lots of people are trying lots of different things. Unfortunately I’m no better than the rest when it comes to the most obvious strategies—like politics, or climate science, or safer nuclear reactors, or better batteries and photocells.

The trick is finding things you can do better than other people. Right now for me that means thinking about networks and biology in a very abstract way. I’m inspired by this remark by Patten and Witkamp:

To understand ecosystems, ultimately will be to understand networks.

So that’s my goal for the next five years or so. It’s probably not be the best thing anyone can do to prepare for the Middle Anthropocene. But it may be the best thing I can do: use the math I know to help people understand the biosphere.

It may seem like I keep jumping around: from quantum gravity to n-categories to biology. But I keep wanting to think about networks, and how they change in time.

At some point I hope to retire and become a bit more of a self­-indulgent wastrel. I could write a fun book about group theory in geometry and physics, and a fun book about the octonions. I might even get around to spending more time on music!

John Baez in Namo Gorge, Gansu

John Baez

The Case for Optimism on Climate Change

7 March, 2016


The video here is quite gripping: you should watch it!

Despite the title, Gore starts with a long and terrifying account of what climate change is doing. So what’s his case for optimism? A lot of it concerns solar power, though he also mentions nuclear power:

So the answer to the first question, “Must we change?” is yes, we have to change. Second question, “Can we change?” This is the exciting news! The best projections in the world 16 years ago were that by 2010, the world would be able to install 30 gigawatts of wind capacity. We beat that mark by 14 and a half times over. We see an exponential curve for wind installations now. We see the cost coming down dramatically. Some countries—take Germany, an industrial powerhouse with a climate not that different from Vancouver’s, by the way—one day last December, got 81 percent of all its energy from renewable resources, mainly solar and wind. A lot of countries are getting more than half on an average basis.

More good news: energy storage, from batteries particularly, is now beginning to take off because the cost has been coming down very dramatically to solve the intermittency problem. With solar, the news is even more exciting! The best projections 14 years ago were that we would install one gigawatt per year by 2010. When 2010 came around, we beat that mark by 17 times over. Last year, we beat it by 58 times over. This year, we’re on track to beat it 68 times over.

We’re going to win this. We are going to prevail. The exponential curve on solar is even steeper and more dramatic. When I came to this stage 10 years ago, this is where it was. We have seen a revolutionary breakthrough in the emergence of these exponential curves.

And the cost has come down 10 percent per year for 30 years. And it’s continuing to come down.

Now, the business community has certainly noticed this, because it’s crossing the grid parity point. Cheaper solar penetration rates are beginning to rise. Grid parity is understood as that line, that threshold, below which renewable electricity is cheaper than electricity from burning fossil fuels. That threshold is a little bit like the difference between 32 degrees Fahrenheit and 33 degrees Fahrenheit, or zero and one Celsius. It’s a difference of more than one degree, it’s the difference between ice and water. And it’s the difference between markets that are frozen up, and liquid flows of capital into new opportunities for investment. This is the biggest new business opportunity in the history of the world, and two-thirds of it is in the private sector. We are seeing an explosion of new investment. Starting in 2010, investments globally in renewable electricity generation surpassed fossils. The gap has been growing ever since. The projections for the future are even more dramatic, even though fossil energy is now still subsidized at a rate 40 times larger than renewables. And by the way, if you add the projections for nuclear on here, particularly if you assume that the work many are doing to try to break through to safer and more acceptable, more affordable forms of nuclear, this could change even more dramatically.

So is there any precedent for such a rapid adoption of a new technology? Well, there are many, but let’s look at cell phones. In 1980, AT&T, then Ma Bell, commissioned McKinsey to do a global market survey of those clunky new mobile phones that appeared then. “How many can we sell by the year 2000?” they asked. McKinsey came back and said, “900,000.” And sure enough, when the year 2000 arrived, they did sell 900,000—in the first three days. And for the balance of the year, they sold 120 times more. And now there are more cell connections than there are people in the world.

So, why were they not only wrong, but way wrong? I’ve asked that question myself, “Why?”

And I think the answer is in three parts. First, the cost came down much faster than anybody expected, even as the quality went up. And low-income countries, places that did not have a landline grid—they leap-frogged to the new technology. The big expansion has been in the developing counties. So what about the electricity grids in the developing world? Well, not so hot. And in many areas, they don’t exist. There are more people without any electricity at all in India than the entire population of the United States of America. So now we’re getting this: solar panels on grass huts and new business models that make it affordable. Muhammad Yunus financed this one in Bangladesh with micro-credit. This is a village market. Bangladesh is now the fastest-deploying country in the world: two systems per minute on average, night and day. And we have all we need: enough energy from the Sun comes to the Earth every hour to supply the full world’s energy needs for an entire year. It’s actually a little bit less than an hour. So the answer to the second question, “Can we change?” is clearly “Yes.” And it’s an ever-firmer “yes.”

Some people are much less sanguine about solar power, and they would point out all the things that Gore doesn’t mention here. For example, while Gore claims that “one day last December” Germany “got 81 percent of all its energy from renewable resources, mainly solar and wind”, the picture in general is not so good:

This is from 2014, the most recent I could easily find. At least back then, renewables were only slightly ahead of ‘brown coal’, or lignite—the dirtiest kind of coal. Furthermore, among renewables, burning ‘biomass’ produced about as much power as wind—and more than solar. And what’s ‘biomass’, exactly? A lot of it is wood pellets! Some is even imported:

• John Baez, The EU’s biggest renewable eneergy source, 18 September 2013.

So, for every piece of good news one can find a piece of bad news. But the drop in price of solar power is impressive, and photovoltaic solar power is starting to hit ‘grid parity’: the point at which it’s as cheap as the usual cost of electricity off the grid:

According to this map based on reports put out by Deutsche Bank (here and here), the green countries reached grid parity before 2014. The blue countries reached it after 2014. The olive countries have reached it only for peak grid prices. The orange regions are US states that were ‘poised to reach grid parity’ in 2015.

But of course there are other issues: the intermittency of solar power, the difficulties of storing energy, etc. How optimistic should we be?

Global Temperature Spike

3 March, 2016


GISTEMP - February 2016

Last month Earth’s temperature soared to a record high. This graph, which only goes up to January, shows how much higher the Earth’s surface temperature is than the 1951-1980 average. It’s updated each month by the Goddard Institute of Space Studies, and it’s called GISTEMP. Here is the next month’s graph, which includes February:

GISTEMP 3 2016

As you can see, we’re currently experiencing a huge spike in temperatures! GISTEMP had to change the temperature scale on its graph to handle the new higher temperatures.

GISTEMP relies heavily on meteorological stations. Upper atmosphere temperatures measured by satellites have shown less temperature increase, leading to some interesting controversies. But now, one of the main satellite temperature records, the University of Alabama at Huntsville satellite temperature dataset, is also reporting a big temperature spike.

“The record might have as much to do with an extraordinarily warm month in the Arctic as it does with warming caused by the El Niño,” said John Christy, director of the Earth System Science Center at UAH.

UAH satellite temperature records up to February 2016

It’s also nice to look at a map of temperature anomalies—that is, the temperature in some region minus the average temperature in that region during that time of the year. Here is one from HADCrut4, a data set compiled by the Met Office Hadley Centre in England:


This is from January—that’s the most recent one I could find from them.

This article puts the news quite dramatically:

• Eric Holthaus, Our hemisphere’s temperature just reached a terrifying milestone, Slate, 1 March 2016.

Holthaus, a meteorologist who works for Slate, wrote:

There are dozens of global temperature datasets, and usually I (and my climate journalist colleagues) wait until the official ones are released about the middle of the following month to announce a record-warm month at the global level. But this month’s data is so extraordinary that there’s no need to wait: February obliterated the all-time global temperature record set just last month.

Using unofficial data and adjusting for different base-line temperatures, it appears that February 2016 was likely somewhere between 1.15 and 1.4 degrees warmer than the long-term average, and about 0.2 degrees above last month—good enough for the most above-average month ever measured. (Since the globe had already warmed by about +0.45 degrees above pre-industrial levels during the 1981-2010 base-line meteorologists commonly use, that amount has been added to the data released today.)

Keep in mind that it took from the dawn of the industrial age until last October to reach the first 1.0 degree Celsius, and we’ve come as much as an extra 0.4 degrees further in just the last five months. Even accounting for the margin of error associated with these preliminary datasets, that means it’s virtually certain that February handily beat the record set just last month for the most anomalously warm month ever recorded. That’s stunning.

Then on March 3rd he added this comment:

Since this post was originally published, the heat wave has continued. As of Thursday morning, it appears that average temperatures across the Northern Hemisphere have breached the 2 degrees Celsius above “normal” mark for the first time in recorded history, and likely the first time since human civilization began thousands of years ago. That mark has long been held (somewhat arbitrarily) as the point above which climate change may begin to become “dangerous” to humanity. It’s now arrived—though very briefly—much more quickly than anticipated. This is a milestone moment for our species. Climate change deserves our greatest possible attention.

Arctic Melting — 2016

26 February, 2016

According to this graph on the US National Snow and Ice Data Center’s website, there were 14.2 million square kilometers of Arctic sea ice on 24 February 2016. On an average year over the last three decades, it would take until about 29 April for there to be this little Arctic sea ice.

Since about 10 February, the extent of Arctic sea ice has been noticeably below any of the last 30 years. The Arctic has experienced record-breaking temperatures of about 4° C higher than the 1951–1980 average.

The dashed line is 2012, one of the years with the least Arctic sea ice on record. We may be ready to break that record.

Peter Gleick, a MacArthur ‘genius grant’ winner who founded the Pacific Institute, recently posted this sea ice graph on Twitter, saying:

What is happening in the Arctic now is unprecedented and possibly catastrophic.

In emails to The Independent, he explained:

The current trend is below any previous year. What is alarming is how far below any previous ice extent the current data are [and] how early it is for there to be this little ice. It is certainly possible that the ice extent will track back up if cold enough weather returns, for long enough. It is just very unlikely.

The evidence is very clear that rapid and unprecedented changes are happening in the Arctic. What is much less clear is the complex consequences. We are, effectively, conducting a global experiment on the only planet we have. The interconnections with weather patterns, sea-level, and more are real.

And while there remains uncertainty about the ultimate consequences, there is a good and growing body of research that is pretty scary, and pretty much no evidence that the possible impacts will be good, unless you are a global shipping company hoping to save some money by opening up routes in the Arctic or an oil/gas company hoping to find new cheap fossil fuels.

Here is another chart, from Neven’s Arctic Sea Ice blog:

It shows global sea ice area for Februaries of various years, from 2006 to 2016.

As Neven points out in another article,

Remember, as I said, this measure doesn’t tell us all that much about the health of either Arctic or Antarctic regions, if only because the seasons move in opposite directions (nevertheless, the global sea ice trend is down). It’s just an interesting statistical factoid.

However, climate risk deniers often use the global sea ice metric as an argument that nothing is wrong and AGW is a hoax. In other words, the recent growth in Antarctic sea ice offsets the loss of Arctic sea ice (it doesn’t), even though the poles are literally worlds apart and are pretty much incomparable (except for the sea ice bit).

For more

This post is an update of a previous one which reported very warm temperatures in the Arctic in early January:

Arctic melting—2015, 6 January 2016.

Arctic Melting — 2015

6 January, 2016

With help from global warming and the new El Niño, 2015 was a hot year. In fact it was the hottest since we’ve been keeping records—and it ended with a bang!

• Robinson Myer, The storm that will unfreeze the North Pole, The Atlantic, 29 December 2015.

The sun has not risen above the North Pole since mid-September. The sea ice—flat, landlike, windswept, and stretching as far as the eye can see—has been bathed in darkness for months.

But later this week, something extraordinary will happen: Air temperatures at the Earth’s most northernly region, in the middle of winter, will rise above freezing for only the second time on record.

On Wednesday, the same storm system that last week spun up deadly tornadoes in the American southeast will burst into the far north, centering over Iceland. It will bring strong winds and pressure as low as is typically seen during hurricanes.

That low pressure will suck air out of the planet’s middle latitudes and send it rushing to the Arctic. And so on Wednesday, the North Pole will likely see temperatures of about 35 degrees Fahrenheit, or 2 degrees Celsius. That’s 50 degrees hotter than average: it’s usually 20 degrees Fahrenheit below zero there at this time of year.

Here’s a temperature map from a couple days later—the last day of the year, 31 December 2015:

(Click on these images to enlarge them.)

And here, more revealing, is a map of the temperature anomaly: the difference between the temperature and the usual temperature at that place at that time of the year:

I think the temperature anomaly is off the scale at certain places in the Arctic—it should have been about 30 °C hotter than normal, or 55 °F.

These maps are from a great website that will show you a variety of weather maps for any day of the year:

Climate Reanalyzer.

How about the year as a whole?

You can learn a lot about Arctic sea ice here:

• National Snow and Ice Data Center, Arctic Sea Ice News.

Here’s one graph of theirs, which shows that the extent of Arctic sea ice in 2015 was very low. It was 2 standard deviations lower than the 2000–2012 average, though not as low as the record-breaking year of 2012:

Here’s another good source of data:

• Polar Science Center, PIOMAS arctic sea ice volume reanalysis.

PIOMAS stands for the Pan-Arctic Ice Ocean Modeling and Assimilation System. Here is their estimate of the Arctic sea ice volume over the course of 2015, compared to other years:

The annual cycle is very visible here.

It’s easier to see the overall trend in this graph:

This shows, for each day, the Arctic sea ice volume minus its average over 1979–2014 for that day of the year. This is a way to remove the annual cycle and focus on the big picture, including the strange events after 2012.

What to do?

The Arctic is melting.

What does that matter to us down here? We’ll probably get strange new weather patterns. It may already be happening. I hope it’s clear by now: the first visible impact of global warming is ‘wild weather’.

But what can we do about it? Of course we should stop burning carbon. But even if we stopped completely, that wouldn’t reverse the effects of the warming so far. Someday people may want to reverse its effects—at least for the Arctic.

So, it might be good to reread part of my interview with Gregory Benford. He has a plan to cool the Arctic, which he claims is quite affordable. He’s mainly famous as a science fiction author, but he’s also an astrophysicist at U. C. Irvine.

Geoengineering the Arctic

JB: I want to spend a bit more time on your proposal to screen the Arctic. There’s a good summary here:

• Gregory Benford, Climate controls, Reason Magazine, November 1997.

But in brief, it sounds like you want to test the results of spraying a lot of micron-sized dust into the atmosphere above the Arctic Sea during the summer. You suggest diatomaceous earth as an option, because it’s chemically inert: just silica. How would the test work, exactly, and what would you hope to learn?

GB: The US has inflight refueling aircraft such as the KC-10 Extender that with minor changes spread aerosols at relevant altitudes, and pilots who know how to fly big sausages filled with fluids.

Rather than diatomaceous earth, I now think ordinary SO2 or H2S will work, if there’s enough water at the relevant altitudes. Turns out the pollutant issue is minor, since it would be only a percent or so of the SO2 already in the Arctic troposphere. The point is to spread aerosols to diminish sunlight and look for signals of less sunlight on the ground, changes in sea ice loss rates in summer, etc. It’s hard to do a weak experiment and be sure you see a signal. Doing regional experiments helps, so you can see a signal before the aerosols spread much. It’s a first step, an in-principle experiment.

Simulations show it can stop the sea ice retreat. Many fear if we lose the sea ice in summer ocean currents may alter; nobody really knows. We do know that the tundra is softening as it thaws, making roads impassible and shifting many wildlife patterns, with unforeseen long term effects. Cooling the Arctic back to, say, the 1950 summer temperature range would cost maybe $300 million/year, i.e., nothing. Simulations show to do this globally, offsetting say CO2 at 500 ppm, might cost a few billion dollars per year. That doesn’t help ocean acidification, but it’s a start on the temperature problem.

JB: There’s an interesting blog on Arctic political, military and business developments:

• Anatoly Karlin, Arctic Progress.

Here’s the overview:

Today, global warming is kick-starting Arctic history. The accelerating melting of Arctic sea ice promises to open up circumpolar shipping routes, halving the time needed for container ships and tankers to travel between Europe and East Asia. As the ice and permafrost retreat, the physical infrastructure of industrial civilization will overspread the region […]. The four major populated regions encircling the Arctic Ocean—Alaska, Russia, Canada, Scandinavia (ARCS)—are all set for massive economic expansion in the decades ahead. But the flowering of industrial civilization’s fruit in the thawing Far North carries within it the seeds of its perils. The opening of the Arctic is making border disputes more serious and spurring Russian and Canadian military buildups in the region. The warming of the Arctic could also accelerate global warming—and not just through the increased economic activity and hydrocarbons production. One disturbing possibility is that the melting of the Siberian permafrost will release vast amounts of methane, a greenhouse gas that is far more potent than CO2, into the atmosphere, and tip the world into runaway climate change.

But anyway, unlike many people, I’m not mentioning risks associated with geoengineering in order to instantly foreclose discussion of it, because I know there are also risks associated with not doing it. If we rule out doing anything really new because it’s too expensive or too risky, we might wind up locking ourselves in a "business as usual" scenario. And that could be even more risky—and perhaps ultimately more expensive as well.

GB: Yes, no end of problems. Most impressive is how they look like a descending spiral, self-reinforcing.

Certainly countries now scramble for Arctic resources, trade routes opened by thawing—all likely to become hotly contested strategic assets. So too melting Himalayan glaciers can perhaps trigger "water wars" in Asia—especially India and China, two vast lands of very different cultures. Then, coming on later, come rising sea levels. Florida starts to go away. The list is endless and therefore uninteresting. We all saturate.

So droughts, floods, desertification, hammering weather events—they draw ever less attention as they grow more common. Maybe Darfur is the first "climate war." It’s plausible.

The Arctic is the canary in the climate coalmine. Cutting CO2 emissions will take far too long to significantly affect the sea ice. Permafrost melts there, giving additional positive feedback. Methane release from the not-so-perma-frost is the most dangerous amplifying feedback in the entire carbon cycle. As John Nissen has repeatedly called attention to, the permafrost permamelt holds a staggering 1.5 trillion tons of frozen carbon, about twice as much carbon as is in the atmosphere. Much would emerge as methane. Methane is 25 times as potent a heat-trapping gas as CO2 over a century, and 72 times as potent over the first 20 years! The carbon is locked in a freezer. Yet that’s the part of the planet warming up the fastest. Really bad news:

• Kevin Schaefer, Tingjun Zhang, Lori Bruhwiler and Andrew P. Barrett, Amount and timing of permafrost carbon release in response to climate warming, Tellus, 15 February 2011.

Particularly interesting is the slowing of thermohaline circulation. In John Nissen’s "two scenarios" work there’s an uncomfortably cool future—if the Gulf Stream were to be diverted by meltwater flowing into NW Atlantic. There’s also an unbearably hot future, if the methane from not-so-permafrost and causes global warming to spiral out of control. So we have a terrifying menu.

JB: I recently interviewed Nathan Urban here. He explained a paper where he estimated the chance that the Atlantic current you’re talking about could collapse. (Technically, it’s the Atlantic meridional overturning circulation, not quite the same as the Gulf Stream.) They got a 10% chance of it happening in two centuries, assuming a business as usual scenario. But there are a lot of uncertainties in the modeling here.

Back to geoengineering. I want to talk about some ways it could go wrong, how soon we’d find out if it did, and what we could do then.

For example, you say we’ll put sulfur dioxide in the atmosphere below 15 kilometers, and most of the ozone is above 20 kilometers. That’s good, but then I wonder how much sulfur dioxide will diffuse upwards. As the name suggests, the stratosphere is "stratified" —there’s not much turbulence. That’s reassuring. But I guess one reason to do experiments is to see exactly what really happens.

GB: It’s really the only way to go forward. I fear we are now in the Decade of Dithering that will end with the deadly 2020s. Only then will experiments get done and issues engaged. All else, as tempting as ideas and simulations are, spell delay if they do not couple with real field experiments—from nozzle sizes on up to albedo measures —which finally decide.

JB: Okay. But what are some other things that could go wrong with this sulfur dioxide scheme? I know you’re not eager to focus on the dangers, but you must be able to imagine some plausible ones: you’re an SF writer, after all. If you say you can’t think of any, I won’t believe you! And part of good design is looking for possible failure modes.

GB: Plenty an go wrong with so vast an idea. But we can learn from volcanoes, that give us useful experiments, though sloppy and noisy ones, about putting aerosols into the air. Monitoring those can teach us a lot with little expense.

We can fail to get the aerosols to avoid clumping, so they fall out too fast. Or we can somehow trigger a big shift in rainfall patterns—a special danger in a system already loaded with surplus energy, as is already displaying anomalies like the bitter winters in Europe, floods in Pakistan, drought in Darfur. Indeed, some of Alan Robock’s simulations of Arctic aerosol use show a several percent decline in monsoon rain—though that may be a plus, since flooding is the #1 cause of death and destruction during the Indian monsoon.

Mostly, it might just plain fail to work. Guessing outcomes is useless, though. Here’s where experiment rules, not simulations. This is engineering, which learns from mistakes. Consider the early days of aviation. Having more time to develop and test a system gives more time to learn how to avoid unwanted impacts. Of course, having a system ready also increases the probability of premature deployment; life is about choices and dangers.

More important right now than developing capability, is understanding the consequences of deployment of that capability by doing field experiments. One thing we know: both science and engineering advance most quickly by using the dance of theory with experiment. Neglecting this, preferring only experiment, is a fundamental mistake.

The Paris Agreement

23 December, 2015

The world has come together and agreed to do something significant about climate change:

• UN Framework Convention on Climate Change, Adoption of the Paris Agreement, 12 December 2015.

Not as much as I’d like: it’s estimated that if we do just what’s been agreed to so far, we can expect 2.7 °C of warming, and more pessimistic estimates range up to 3.5 °C. But still, something significant. Furthermore, the Paris Agreement set up a system that encourages nations to ‘ratchet up’ their actions over time. Even better, it helped strengthen a kind of worldwide social network of organizations devoted to tackling climate change!

This is a nice article summarizing what the Paris Agreement actually means:

• William Sweet, A surprising success at Paris, Bulletin of Atomic Scientists, 21 December 2015.

Since it would take quite a bit of work to analyze this agreement and its implications, and I’m just starting to do this work, I’ll just quote a large chunk of this article.

Hollande, in his welcoming remarks, asked what would enable us to say the Paris agreement is good, even “great.” First, regular review and assessment of commitments, to get the world on a credible path to keep global warming in the range of 1.5–2.0 degrees Celsius. Second, solidarity of response, so that no state does nothing and yet none is “left alone.” Third, evidence of a comprehensive change in human consciousness, allowing eventually for introduction of much stronger measures, such as a global carbon tax.

UN Secretary-General Ban Ki-moon articulated similar but somewhat more detailed criteria: The agreement must be lasting, dynamic, respectful of the balance between industrial and developing countries, and enforceable, with critical reviews of pledges even before 2020. Ban noted that 180 countries had now submitted climate action pledges, an unprecedented achievement, but stressed that those pledges need to be progressively strengthened over time.

Remarkably, not only the major conveners of the conference were speaking in essentially the same terms, but civil society as well. Starting with its first press conference on opening day and at every subsequent one, representatives of the Climate Action Network, representing 900 nongovernment organizations, confined themselves to making detailed and constructive suggestions about how key provisions of the agreement might be strengthened. Though CAN could not possibly speak for every single one of its member organizations, the mainstream within the network clearly saw it was the group’s goal to obtain the best possible agreement, not to advocate for a radically different kind of agreement. The mainstream would not be taking to the streets.

This was the main thing that made Paris different, not just from Copenhagen, but from every previous climate meeting: Before, there always had been deep philosophical differences between the United States and Europe, between the advanced industrial countries and the developing countries, and between the official diplomats and civil society. At Paris, it was immediately obvious that everybody, NGOs included, was reading from the same book. So it was obvious from day one that an important agreement would be reached. National delegations would stake out tough positions, and there would be some hard bargaining. But at every briefing and in every interview, no matter how emphatic the stand, it was made clear that compromises would be made and nothing would be allowed to stand in the way of agreement being reached.

The Paris outcome

The two-part agreement formally adopted in Paris on December 12 represents the culmination of a 25-year process that began with the negotiations in 1990–91 that led to the adoption in 1992 of the Rio Framework Convention. That treaty, which would be ratified by all the world’s nations, called upon every country to take action to prevent “dangerous climate change” on the basis of common but differentiated responsibilities. Having enunciated those principles, nations were unable to agree in the next decades about just what they meant in practice. An attempt at Kyoto in 1997 foundered on the opposition of the United States to an agreement that required no action on the part of the major emitters among the developing countries. A second attempt at agreement in Copenhagen also failed.

Only with the Paris accords, for the first time, have all the world’s nations agreed on a common approach that rebalances and redefines respective responsibilities, while further specifying what exactly is meant by dangerous climate change. Paragraph 17 of the “Decision” (or preamble) notes that national pledges will have to be strengthened in the next decades to keep global warming below 2 degrees Celsius or close to 1.5 degrees, while Article 2 of the more legally binding “Agreement” says warming should be held “well below” 2 degrees and if possible limited to 1.5 degrees. Article 4 of the Agreement calls upon those countries whose emissions are still rising to have them peak “as soon as possible,” so “as to achieve a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of this century”—a formulation that replaced a reference in Article 3 of the next-to-last draft calling for “carbon neutrality” by the second half of the century.

“The wheel of climate action turns slowly, but in Paris it has turned. This deal puts the fossil fuel industry on the wrong side of history,” commented Kumi Naidoo, executive director of Greenpeace International.

The Climate Action Network, in which Greenpeace is a leading member, along with organizations like the Union of Concerned Scientists, Friends of the Earth, the World Wildlife Fund, and Oxfam, would have preferred language that flatly adopted the 1.5 degree goal and that called for complete “decarbonization”— an end to all reliance on fossil fuels. But to the extent the network can be said have common positions, it would be able to live with the Paris formulations, to judge from many statements made by leading members in CAN’s twice- or thrice-daily press briefings, and statements made by network leaders embracing the agreement.

Speaking for scientists, at an event anticipating the final accords, H. J. Schellnhuber, leader of the Potsdam Institute for Climate Impact Research, said with a shrug that the formulation calling for net carbon neutrality by mid-century would be acceptable. His opinion carried more than the usual weight because he is sometimes credited in the German press as the father of the 2-degree standard. (Schellnhuber told me that a Potsdam team had indeed developed the idea of limiting global warming to 2 degrees in total and 0.2 degrees per decade; and that while others were working along similar lines, he personally drew the Potsdam work to the attention of future German chancellor Angela Merkel in 1994, when she was serving as environment minister.)

As for the tighter 1.5-degree standard, this is a complicated issue that the Paris accords fudge a bit. The difference between impacts expected from a 1.5-degree world and a 2-degree world are not trivial. The Greenland ice sheet, for example, is expected to melt in its entirely in the 2-degree scenario, while in a 1.5-degree world the odds of a complete melt are only 70 percent, points out climatologist Niklas Höhne, of the Cologne-based NewClimate Institute, with a distinct trace of irony. But at the same time the scientific consensus is that it would be virtually impossible to meet the 1.5-degree goal because on top of the 0.8–0.9 degrees of warming that already has occurred, another half-degree is already in the pipeline, “hidden away in the oceans,” as Schellnhuber put it. At best we might be able to work our ways back to 1.5 degrees in the 2030s or 2040s, after first overshooting it. Thus, though organizations like and scientists like James Hansen continue to insist that 1.5 degrees should be our objective, pure and simple, the scientific community and the Climate Action mainstream are reasonably comfortable with the Paris accords’ “close as possible” language.

‘Decision’ and ‘Agreement’

The main reason why the Paris accords consist of two parts, a long preamble called the “Decision,” and a legally binding part called the “Agreement,” is to satisfy the Obama administration’s concerns about having to take anything really sticky to Congress. The general idea, which was developed by the administration with a lot of expert legal advice from organizations like the Virginia-based Center for Climate and Energy Solutions, was to put really substantive matters, like how much the United States will actually do in the next decades to cut its greenhouse gas emissions, into the preamble, and to confine the treaty-like Agreement as much as possible to procedural issues like when in the future countries will talk about what.

Nevertheless, the distinction between the Decision and the Agreement is far from clear-cut. All the major issues that had to be balanced in the negotiations—not just the 1.5–2.0 degree target and the decarbonization language, but financial aid, adaptation and resilience, differentiation between rich and poor countries, reporting requirements, and review—are addressed in both parts. There is nothing unusual as such about an international agreement having two parts, a preamble and main text. What is a little odd about Paris, however, is that the preamble, at 19 pages, is considerably longer than the 11-page Agreement, as Chee Yoke Ling of the Third World Network, who is based in Beijing, pointed out. The length of the Decision, she explained, reflects not only US concerns about obtaining Senate ratification. It also arose from anxieties shared by developing countries about agreeing to legally binding provisions that might be hard to implement and politically dangerous.

In what are arguably the Paris accords’ most important provisions, the national pledges are to be collectively reassessed beginning in 2018–19, and then every five years after 2020. The general idea is to systematically exert peer group pressure on regularly scheduled occasions, so that everybody will ratchet up carbon-cutting ambitions. Those key requirements, which are very close to what CAN advocated and what diplomatic members of the so-called “high ambition” group wanted, are in the preamble, not the Agreement.

But an almost equally important provision, found in the Agreement, called for a global “stocktake” to be conducted in 2023, covering all aspects of the Agreement’s implementation, including its very contested provisions about financial aid and “loss and damage”—the question of support and compensation for countries and regions that may face extinction as a result of global warming. Not only carbon cutting efforts but obligations of the rich countries to the poor will be subject to the world’s scrutiny in 2023.

Rich and poor countries

On the critical issue of financial aid for developing countries struggling to reduce emissions and adapt to climate change, Paris affirms the Copenhagen promise of $100 billion by 2020 in the Decision (Paragraph 115) but not in the more binding Agreement—to the displeasure of the developing countries, no doubt. In the three previous draft versions of the accords, the $100 billion pledge was contained in the Agreement as well.

Somewhat similarly, the loss-and-damage language contained in the preamble does not include any reference to liability on the part of the advanced industrial countries that are primarily responsible for the climate change that has occurred up until now. This was a disappointment to representatives of the nations and regions most severely and imminently threatened by global warming, but any mention of liability would have been an absolute show-stopper for the US delegation. Still, the fact that loss and damage is broached at all represents a victory for the developing world and its advocates, who have been complaining for decades about the complete absence of the subject from the Rio convention and Kyoto Protocol.

The so-called Group of 77, which actually represents 134 developing countries plus China, appears to have played a shrewd and tough game here at Le Bourget. Its very able and engaging chairperson, South Africa’s Nozipho Mxakato-Diseko, sent a sharp shot across the prow of the rich countries on the third day of the conference, with a 17-point memorandum she e-mailed enumerating her group’s complaints.

“The G77 and China stresses that nothing under the [1992 Framework Convention] can be achieved without the provision of means of implementation to enable developing countries to play their part to address climate change,” she said, alluding to the fact that if developing countries are to do more to cut emissions growth, they need help. “However, clarity on the complete picture of the financial arrangements for the enhanced implementation of the Convention keeps on eluding us. … We hope that by elevating the importance of the finance discussions under the different bodies, we can ensure that the outcome meets Parties’ expectations and delivers what is required.”

Though the developing countries wanted stronger and more specific financial commitments and “loss-and-damage” provisions that would have included legal liability, there is evidence throughout the Paris Decision and Agreement of the industrial countries’ giving considerable ground to them. During the formal opening of the conference, President Obama met with leaders of AOSIS—the Alliance of Small Island States—and told them he understood their concerns as he, too, is “an island boy.” (Evidently that went over well.) The reference to the $100 billion floor for financial aid surely was removed from the Agreement partly because the White House at present cannot get Congress to appropriate money for any climate-related aid. But at least the commitment remained in the preamble, which was not a foregone conclusion.

Reporting and review

The one area in which the developing countries gave a lot of ground in Paris was in measuring, reporting, and verification. Under the terms of the Rio convention and Kyoto Protocol, only the advanced industrial countries—the so-called Annex 1 countries—were required to report their greenhouse gas emissions to the UN’s climate secretariat in Bonn. Extensive provisions in the Paris agreement call upon all countries to now report emissions, according to standardized procedures that are to be developed.

The climate pledges that almost all countries submitted to the UN in preparation for Paris, known as “Intended Nationally Determined Contributions,” provided a preview of what this will mean. The previous UN climate gathering, last year in Lima, had called for all the INDCs to be submitted by the summer and for the climate secretariat to do a net assessment of them by October 31, which seemed ridiculously late in the game. But when the results of that assessment were released, the secretariat’s head, Christiana Figueres, cited independent estimates that together the national declarations might put the world on a path to 2.7-degree warming. That result was a great deal better than most specialists following the procedure would have expected, this writer included. Though other estimates suggested the path might be more like 3.5 degrees, even this was a very great deal better than the business-as-usual path, which would be at least 4–5 degrees and probably higher than that by century’s end.

The formalized universal reporting requirements put into place by the Paris accords will lend a lot of rigor to the process of preparing, critiquing, and revising INDCs in the future. In effect the secretariat will be keeping score for the whole world, not just the Annex 1 countries. That kind of score-keeping can have a lot of bite, as we have witnessed in the secretariat’s assessment of Kyoto compliance.

Under the Kyoto Protocol, which the US government not only agreed to but virtually wrote, the United States was required to cut its emissions 7 percent by 2008–12, and Europe by 8 percent. From 1990, the baseline year established in the Rio treaty and its 1997 Kyoto Protocol, to 2012 (the final year in which initial Kyoto commitments applied), emissions of the 15 European countries that were party to the treaty decreased 17 percent—more than double what the protocol required of them. Emissions of the 28 countries that are now members of the EU decreased 21 percent. British emissions were down 27 percent in 2012 from 1990, and Germany’s were down 23 percent.

In the United States, which repudiated the protocol, emissions continued to rise until 2005, when they began to decrease, initially for reasons that had little or nothing to do with policy. That year, US emissions were about 15 percent above their 1990 level, while emissions of the 28 EU countries were down more than 9 percent and of the 15 European party countries more than 2 percent.

Regime Shift?

25 November, 2015

There’s no reason that the climate needs to change gradually. Recently scientists have become interested in regime shifts, which are abrupt, substantial and lasting changes in the state of a complex system.

Rasha Kamel of the Azimuth Project pointed us to a report in Science Daily which says:

Planet Earth experienced a global climate shift in the late 1980s on an unprecedented scale, fueled by anthropogenic warming and a volcanic eruption, according to new research. Scientists say that a major step change, or ‘regime shift,’ in Earth’s biophysical systems, from the upper atmosphere to the depths of the ocean and from the Arctic to Antarctica, was centered around 1987, and was sparked by the El Chichón volcanic eruption in Mexico five years earlier.

As always, it’s good to drill down through the science reporters’ summaries to the actual papers.  So I read this one:

• Philip C. Reid et al, Global impacts of the 1980s regime shift on the Earth’s climate and systems, Global Change Biology, 2015.

The authors of this paper analyzed 72 time series of climate and ecological data to search for such a regime shift, and found one around 1987. If such a thing really happened, this could be very important.

Here are some of the data they looked at:

Click to enlarge them—they’re pretty interesting! Vertical lines denote regime shift years, colored in different ways: 1984 blue, 1985 green, 1986 orange, 1987 red, 1988 brown, 1989 purple and so on. You can see that lots are red.

The paper has a lot of interesting and informed speculations about the cause of this shift—so give it a look.  For now I just want to tackle an important question of a more technical nature: how did they search for regime shifts?

They used the ‘STARS’ method, which stands for Sequential t-Test Analysis of Regime Shifts. They explain:

The STARS method (Rodionov, 2004; Rodionov & Overland, 2005) tests whether the end of one period (regime) of a certain length is different from a subsequent period (new regime). The cumulative sum of normalized deviations from the hypothetical mean level of the new regime is calculated, and then compared with the mean level of the preceding regime. A shift year is detected if the difference in the mean levels is statistically significant according to a Student’s t-test.

In his third paper, Rodionov (2006) shows how autocorrelation can be accounted for. From each year of the time series (except edge years), the rules are applied backwards and forwards to test that year as a potential shift year. The method is, therefore, a running procedure applied on sequences of years within the time series. The multiple STARS method used here repeats the procedure for 20 test-period lengths ranging from 6 to 25 years that are, for simplicity (after testing many variations), of the same length on either side of the regime shift.

Elsewhere I read that the STARS method is ‘too sensitive’. Could it be due to limitations of the ‘statistical significance’ idea involved in Student’s t-test?

You can download software that implements the STARS method here. The method is explained in the papers by Rodionov.

Do you know about this stuff?  If so, I’d like to hear your views on this paper and the STARS method.