Some very interesting videos and links on last weeks weekend sports article. One theme being that running barefoot is much more natural than in shoes, and some interest from folks in making the switch. The latter could be a problem.
Update: Sorry for leaving off the links.
Long video
Journal article
And, a shorter video
If you watch the longer video, you'll see that a person who was used to running in shoes their whole life, when running in shoes, had a big spike in landing forces as you go from the first instant of touching the ground to the first instant of the foot being off the ground. It hits near maximum forces almost immediately on touching down, which is bad news for your body as it means a shock to the systems. Someone who has never run in shoes doesn't have the big spike. There's a smooth rise to the maximum, and then smooth fall to takeoff. Clearly this is a better thing to do, hence the interest in barefoot running.
But there's a third profile -- what happens when someone who has always run in shoes starts to run barefoot. They have exactly the same spikes in forces barefoot as they did when running in shoes. Except that now there's no shoe taking up some of that force for them. This is a recipe for injury -- your body will be experiencing new forces, and be unprepared for them. The one person I know personally who tried the minimalist shoes went promptly to injury (stage one in about a week, stage four in a month). She did an abrupt change to the new shoe, not a transition.
More to the story of course, and it touches on my current rehabilitation.
31 January 2010
23 January 2010
Preemptive rehabilitation
Call it 'prehabilitation' since it seems that having a catchy new word for your idea is important in doing health and fitness writing. This is an idea of mine, about something to do before or concurrently with the start of your aerobic or weight-bearing exercise program. The idea is, most of us live our regular life without exercising our bodies much. Especially, without challenging them much. In my routine work day, for instance, the heaviest thing I life is a book or maybe 2 books. Desk jobs are good for that reason, and they're bad for that reason.
If you don't use muscles, they get weaker. If you're several years past the last time you exercised regularly (and not just some sort of exercise, but exercise that challenged your arms, and legs, and abdominals, and ... on down the list), then I think you are liable to have some areas that are not currently in good shape. What that means, as I've coached beginning runners, is that you're liable to start your exercise program and have some real complaints from your body about it. You can ignore real complaints, for a while. The 'while' is however long it takes your body to make an injury out of the complaint. The easy conclusion -- that you're "just not cut out to run" (or swim, or walk, or ...) -- is the wrong one. The better conclusion is that your shoulders were used to not having to work, so when you made them do so in the pool, for the first time in 15 years, they complained. The swimming itself is not a problem, but having let your arms get used to the idea that they only needed to lift a book or two every so often, and then ask them to pull you through the water, was the problem. Same sort of thing for many other sorts of pains beginners encounter. (There are also many that have nothing to do with this. This is, alas, not a cure-all, even if it does work at what it tries to.)
Hence, prehabilitation. I have had to do rehabilitation, at one time or another in my life, on my knees, shoulders, and back. These seem also to be three major areas where people encounter problems. Since they are such common areas for problems, I suggest that doing rehabilitation style exercises is a good idea -- even before you're injured. Especially before you're injured.
As always, check any exercise advice out with your doctor, or, at the very least, a certified trainer in the sort of exercise you are trying to do. I'm serious about this warning.
If you don't use muscles, they get weaker. If you're several years past the last time you exercised regularly (and not just some sort of exercise, but exercise that challenged your arms, and legs, and abdominals, and ... on down the list), then I think you are liable to have some areas that are not currently in good shape. What that means, as I've coached beginning runners, is that you're liable to start your exercise program and have some real complaints from your body about it. You can ignore real complaints, for a while. The 'while' is however long it takes your body to make an injury out of the complaint. The easy conclusion -- that you're "just not cut out to run" (or swim, or walk, or ...) -- is the wrong one. The better conclusion is that your shoulders were used to not having to work, so when you made them do so in the pool, for the first time in 15 years, they complained. The swimming itself is not a problem, but having let your arms get used to the idea that they only needed to lift a book or two every so often, and then ask them to pull you through the water, was the problem. Same sort of thing for many other sorts of pains beginners encounter. (There are also many that have nothing to do with this. This is, alas, not a cure-all, even if it does work at what it tries to.)
Hence, prehabilitation. I have had to do rehabilitation, at one time or another in my life, on my knees, shoulders, and back. These seem also to be three major areas where people encounter problems. Since they are such common areas for problems, I suggest that doing rehabilitation style exercises is a good idea -- even before you're injured. Especially before you're injured.
As always, check any exercise advice out with your doctor, or, at the very least, a certified trainer in the sort of exercise you are trying to do. I'm serious about this warning.
21 January 2010
Theory of Climate -- Examples
Now let's move from philosphy of what a Theory of Climate would look like, to some of the components. To repeat yesterday's list:
In climate, some of our principles, or statements of theory, would include:
Conservation of mass:
The water cycle is one of the climate expressions of conservation of mass. If you evaporate water from somewhere, there is less water there. If you condense water from vapor into cloud droplets or ice crystals (make a cloud) then there is less water vapor in that part of the atmosphere. If those cloud droplets or ice crystals fall to earth, then there is less liquid or solid water in the cloud, but more in the patch of ground or ocean that the precipitation fell on. This extends another step -- if some patch of ground experiences more evaporation than precipitation, it will dry out. Or, if it is a lake or inland sea (like the Aral Sea) it will shrink.
Conservation of momentum:
This leads us to learning that winds are largely driven by pressure differences. If something in the climate system changes the pressure differences -- say by warming the poles faster than the equator -- we expect changes to the winds. Getting detailed about this requires paying attention to all the other effects.
Laws of thermodynamics:
This includes both conservation of energy and the entropy law. Conservation of energy tells us that when water condenses from vapor to liquid or solid, it will release energy. It can be quite a lot of energy -- which is what drives hurricanes and typhoons -- if you get enough water to condense. The entropy tells us, for instance, that cloud droplets will form more readily on a nucleus of some kind -- dust or salt particle, for instance -- and something about how much.
General theory of relativity:
I don't need to worry about this in the day job, but it does apply to thinking about climate on periods longer than a few hundred thousand years. On the few thousand to few million year time scale, the earth's orientation and orbit change (Milankovitch theory here). Once you get past a certain point, you need to include general relativity to get an accurate orbit.
Quantum theory:
The absorption of radiation by the atmosphere depends intimately on quantum mechanics (quantum theory). We can pretty much get away with a simple rule for emission from the surface (Stefan-Boltzmann law -- black body emission and absorption). But the atmosphere is nowhere near a black body. It is extremely selective about what colors of light it will absorb, and equally selective about what it will emit. That's why we can largely ignore the major gases in the atmosphere -- nitrogen, oxygen, and argon -- and focus our attention on the rare gases water vapor, carbon dioxide, ozone, methane, and such. Understanding the selectivity is a problem in quantum theory.
Tectonic theory:
Continents move over time, and plate tectonics is our theory for the hows, whys, and how fast. Application of the other components of climate theory tells us that the motion of continents also changes climate. So this is another part of a full climate theory.
Additional theories, laws, principles, ... that would be part of a full Theory of Climate are welcome.
In climate, some of our principles, or statements of theory, would include:
- Conservation of mass applies to the climate system
- Conservation of momentum applies
- The laws of thermodynamics apply
- The general theory of relativity applies
- Quantum theory applies
- Tectonic theory
Conservation of mass:
The water cycle is one of the climate expressions of conservation of mass. If you evaporate water from somewhere, there is less water there. If you condense water from vapor into cloud droplets or ice crystals (make a cloud) then there is less water vapor in that part of the atmosphere. If those cloud droplets or ice crystals fall to earth, then there is less liquid or solid water in the cloud, but more in the patch of ground or ocean that the precipitation fell on. This extends another step -- if some patch of ground experiences more evaporation than precipitation, it will dry out. Or, if it is a lake or inland sea (like the Aral Sea) it will shrink.
Conservation of momentum:
This leads us to learning that winds are largely driven by pressure differences. If something in the climate system changes the pressure differences -- say by warming the poles faster than the equator -- we expect changes to the winds. Getting detailed about this requires paying attention to all the other effects.
Laws of thermodynamics:
This includes both conservation of energy and the entropy law. Conservation of energy tells us that when water condenses from vapor to liquid or solid, it will release energy. It can be quite a lot of energy -- which is what drives hurricanes and typhoons -- if you get enough water to condense. The entropy tells us, for instance, that cloud droplets will form more readily on a nucleus of some kind -- dust or salt particle, for instance -- and something about how much.
General theory of relativity:
I don't need to worry about this in the day job, but it does apply to thinking about climate on periods longer than a few hundred thousand years. On the few thousand to few million year time scale, the earth's orientation and orbit change (Milankovitch theory here). Once you get past a certain point, you need to include general relativity to get an accurate orbit.
Quantum theory:
The absorption of radiation by the atmosphere depends intimately on quantum mechanics (quantum theory). We can pretty much get away with a simple rule for emission from the surface (Stefan-Boltzmann law -- black body emission and absorption). But the atmosphere is nowhere near a black body. It is extremely selective about what colors of light it will absorb, and equally selective about what it will emit. That's why we can largely ignore the major gases in the atmosphere -- nitrogen, oxygen, and argon -- and focus our attention on the rare gases water vapor, carbon dioxide, ozone, methane, and such. Understanding the selectivity is a problem in quantum theory.
Tectonic theory:
Continents move over time, and plate tectonics is our theory for the hows, whys, and how fast. Application of the other components of climate theory tells us that the motion of continents also changes climate. So this is another part of a full climate theory.
Additional theories, laws, principles, ... that would be part of a full Theory of Climate are welcome.
20 January 2010
Theory of Climate -- Philosophy
Is there a theory of climate, and if so, what is it? That turns out to be a harder question than you might think. It's my slight rephrase of a question asked in this month's question place. The difficulty lies in the fact that 'theory' has several different meanings.
We can dismiss the most common daily life sort of usage -- a theory is something that is false. It's used in comments like 'That may work in theory, but it doesn't work in practice.' If we're talking about what happens in practice, we're talking about what happens in the real world. Scientific theories have to apply to the real world. If your idea makes false predictions about the real world, then the idea is (at least partly) false. And, if your idea consistently makes false statements about the world, then it is not a theory, or even a hypothesis. If there is a scientific theory of climate, it must be making true statements.
We can also dismiss the next most common daily life usage -- a theory is a WAG (wild guess). A common sort of theory of this type is where I, for instance, theorize that since the last time I took my car to the shop, it got good service, that the next time I go, it will as well. There's really very little data behind that thought, and very little analysis. But it seems like a reasonable sort of statement. Or the 'lucky socks' theory sports fans or athletes might have. Their team won the last time they wore a particular pair of socks, so they theorize that the team will win again (or at least have a better chance of winning) if they wear the same socks for today's game. Again, it seems reasonable to the person making the statement, but there's little data behind it and little analysis.
Now to consider the more difficult waters, where I hope that the two philosophers I know sometimes read will comment with appropriate corrections and elaborations.
We can dismiss the most common daily life sort of usage -- a theory is something that is false. It's used in comments like 'That may work in theory, but it doesn't work in practice.' If we're talking about what happens in practice, we're talking about what happens in the real world. Scientific theories have to apply to the real world. If your idea makes false predictions about the real world, then the idea is (at least partly) false. And, if your idea consistently makes false statements about the world, then it is not a theory, or even a hypothesis. If there is a scientific theory of climate, it must be making true statements.
We can also dismiss the next most common daily life usage -- a theory is a WAG (wild guess). A common sort of theory of this type is where I, for instance, theorize that since the last time I took my car to the shop, it got good service, that the next time I go, it will as well. There's really very little data behind that thought, and very little analysis. But it seems like a reasonable sort of statement. Or the 'lucky socks' theory sports fans or athletes might have. Their team won the last time they wore a particular pair of socks, so they theorize that the team will win again (or at least have a better chance of winning) if they wear the same socks for today's game. Again, it seems reasonable to the person making the statement, but there's little data behind it and little analysis.
Now to consider the more difficult waters, where I hope that the two philosophers I know sometimes read will comment with appropriate corrections and elaborations.
18 January 2010
Fingerprinting climate change
I'll take up one of the questions from the question place, how do we 'fingerprint' current climate change as being from CO2, rather than from any of the many other things that affect climate? Same questioner asked several other interesting questions, and they'll be topics for later posts. One thing I've mentioned is that there are indeed many things which affect climate. A few to start with are: CO2 (or, more generally, the non-water vapor greenhouse gases*), solar input, volcanic aerosols, and orbital variations.
I don't really like 'fingerprint' as the description, myself. I think of the process more as the 'duck test' -- if it looks like a duck, walks like a duck, and quacks like a duck, it's probably a duck. We start by finding out what would be true if a given candidate were driving climate change, the more implications the better, and then go look at what is going on in the atmosphere. So I'll approach it that way.
I don't really like 'fingerprint' as the description, myself. I think of the process more as the 'duck test' -- if it looks like a duck, walks like a duck, and quacks like a duck, it's probably a duck. We start by finding out what would be true if a given candidate were driving climate change, the more implications the better, and then go look at what is going on in the atmosphere. So I'll approach it that way.
16 January 2010
Today, I shall attempt to register a pulse
Pushing 30 years ago, a Garfield cartoon had my subject line as its punchline. Yet, as with many a punchline, there is a good point included. One of the biggest mistakes people make in starting to exercise is to try to start with major activities "I'll run a marathon in 4 months", or even "I'll train every day." The longer it has been since you last exercised regularly, the more sense it makes for you to start with informational things.
Your resting pulse is actually one of the better things to know before you start your exercise program. It isn't a matter that if yours is 44 you don't need to exercise -- you have to do the exercise to get the health benefits. Keeping an eye on your resting pulse is useful in two senses. First, as you get in to better shape, your resting pulse will generally drop. Not talking about going to 44 from 90 in a couple weeks, but you'll see it edge downward over time. What causes this is that as you do aerobic exercise, your heart starts shoving out more blood with each pulse. So you don't need as many pulses to keep plenty of blood moving[1].
Second, one of the biggest errors beginners make is to train too hard, too often. (This also means you even if you used to be in excellent shape, but that time was more than a few months back; sadly it also means me as it's a while since I was really doing the sort of exercising schedule I'd prefer*.) As you make this mistake, you'll see your resting pulse rise over time -- and the time scale for the rise is a matter of days. If your resting pulse has climbed by 10%, it's probably a good idea to go easier on your aerobic work today. If it's up 20%, you definitely want to back off the aerobics and do something else good for your health.
Of course there is more to getting started than that ...
Your resting pulse is actually one of the better things to know before you start your exercise program. It isn't a matter that if yours is 44 you don't need to exercise -- you have to do the exercise to get the health benefits. Keeping an eye on your resting pulse is useful in two senses. First, as you get in to better shape, your resting pulse will generally drop. Not talking about going to 44 from 90 in a couple weeks, but you'll see it edge downward over time. What causes this is that as you do aerobic exercise, your heart starts shoving out more blood with each pulse. So you don't need as many pulses to keep plenty of blood moving[1].
Second, one of the biggest errors beginners make is to train too hard, too often. (This also means you even if you used to be in excellent shape, but that time was more than a few months back; sadly it also means me as it's a while since I was really doing the sort of exercising schedule I'd prefer*.) As you make this mistake, you'll see your resting pulse rise over time -- and the time scale for the rise is a matter of days. If your resting pulse has climbed by 10%, it's probably a good idea to go easier on your aerobic work today. If it's up 20%, you definitely want to back off the aerobics and do something else good for your health.
Of course there is more to getting started than that ...
13 January 2010
Successive approximations
The other title for this would be 'the relativity of wrong', if I were to steal the title that Isaac Asimov used for an essay on a related topic. It's a common issue in science, and successive approximations is both a common and a powerful tool. In the comment section for 800,000 years of CO2 we had a local introduction to the issue. But I'll start with the example that Asimov used, and that I have a number of times myself. (It's entirely possible that I used it because he did -- I've read most of his science and science fiction writing.)
Let's start with the shape of the earth. At some distant time in the past (probably more distant than you're thinking) we start with the thought that the earth is flat. A different version of thinking about this is that the radius of a spheroidal earth would be infinite. Clearly there are local variations, as any runner, hiker, or biker can tell you. But basically a flat surface. Get out to the Great Plains, some of the major deserts, or, especially, the coasts, and it's obvious that the earth is flat. Just look!
Let's start with the shape of the earth. At some distant time in the past (probably more distant than you're thinking) we start with the thought that the earth is flat. A different version of thinking about this is that the radius of a spheroidal earth would be infinite. Clearly there are local variations, as any runner, hiker, or biker can tell you. But basically a flat surface. Get out to the Great Plains, some of the major deserts, or, especially, the coasts, and it's obvious that the earth is flat. Just look!
12 January 2010
Sharing source
What do my gentle readers think would be the best way for me to share some source code? I was doing some cleaning up of my files over the weekend, focusing on things from graduate school days. I'd like to put the codes out in 'public', and if people find them worth making improvements to, I'd be happy to have those come back in. Or at least, I'd like to put them out there so that people who'd like to check my work could come pull down my source and compile and go. For the barebones later part, I could always put it up on my personal web site as a tar file. But I'm thinking that something like sourceforge would be a good idea for more general use. The codes I'm particularly thinking of are those for harmonic analysis of time series, and some lightweight statistics. It's more by way of a library than any free-standing programs.
What say you?
What say you?
11 January 2010
Fitness blogging
ERV (Abbie Smith) has suggested blogging about our fitness activities, and with it being the new year and folks having made resolutions about health and fitness, it seems like a good idea.
This is distinctly aimed at the adults and parents, rather than the middle school or jr. high students I try to write to. Of course, parents, it's an excellent thing for your kids to be active starting yesterday, if not sooner. Doesn't make a lot of difference what it is they do. If it's pick up soccer/football, that's fine. Basketball is great. Running around the yard/track/field is also just fine. If the kids run fast for a little, then walk, then run fast again, that's great, too. No need for the under 13s to worry about extending how long they run at one time.
But, parents, you do really need to be getting activity yourself, and you need to be more particular about what you do. As many of the beginning runners I've coached over the years have said, they want to be running around with their children and grandchildren -- not essentially stuck in a chair for the last 30 years of their life as some of their parents had been. The books* Younger Next Year by Chris Crowley and Henry S. Lodge, M.D. illustrate the point nicely. Imagine a curve representing your fitness/health/capacity for doing stuff, versus your age. It climbs rapidly in your childhood and then works more slowly towards a peak in your 20s or 30s. What happens next is very much in your hands. You can do no exercise, and see a steady decline from that peak towards death over the rest of your life -- spending your last 30 years perhaps below the level at which you could go for walks with your children or grandchildren. Or you can exercise routinely and spend almost the entire rest of your life up at a high level, able to walk with your grandchildren and even run with them. Age does have its say -- you won't be able to run the 20 minute 5k of your 20s and 30s when you're 60. But you'll be able to go cover that 5k in comfort into your 70s.
This is distinctly aimed at the adults and parents, rather than the middle school or jr. high students I try to write to. Of course, parents, it's an excellent thing for your kids to be active starting yesterday, if not sooner. Doesn't make a lot of difference what it is they do. If it's pick up soccer/football, that's fine. Basketball is great. Running around the yard/track/field is also just fine. If the kids run fast for a little, then walk, then run fast again, that's great, too. No need for the under 13s to worry about extending how long they run at one time.
But, parents, you do really need to be getting activity yourself, and you need to be more particular about what you do. As many of the beginning runners I've coached over the years have said, they want to be running around with their children and grandchildren -- not essentially stuck in a chair for the last 30 years of their life as some of their parents had been. The books* Younger Next Year by Chris Crowley and Henry S. Lodge, M.D. illustrate the point nicely. Imagine a curve representing your fitness/health/capacity for doing stuff, versus your age. It climbs rapidly in your childhood and then works more slowly towards a peak in your 20s or 30s. What happens next is very much in your hands. You can do no exercise, and see a steady decline from that peak towards death over the rest of your life -- spending your last 30 years perhaps below the level at which you could go for walks with your children or grandchildren. Or you can exercise routinely and spend almost the entire rest of your life up at a high level, able to walk with your grandchildren and even run with them. Age does have its say -- you won't be able to run the 20 minute 5k of your 20s and 30s when you're 60. But you'll be able to go cover that 5k in comfort into your 70s.
New Year, New Question Place
Time for a new place for people to leave their questions. I don't forget about the older questions, don't worry about that. Some just take some time to answer -- sometimes I have to go learn something myself. I like doing so, but it takes time. Sometimes, fortunately, some readers already know an answer, so you don't have to wait for me. Of course, other times, I do know the answer and can let you know more quickly.
This is also a place for suggestions of topics to cover. Those, too, may take a while. I really do, for instance, want to get hold of the biofilm article that Hank mentioned in the last question place. Not the easiest thing for me to get. But it should happen.
This is also a place for suggestions of topics to cover. Those, too, may take a while. I really do, for instance, want to get hold of the biofilm article that Hank mentioned in the last question place. Not the easiest thing for me to get. But it should happen.
07 January 2010
CO2 and temperature for 800,000 years
First, the figure gives the answer on CO2 and temperature over the last 800,000 years:
Here we have each value of CO2 plotted against the temperature deviation from reference values -- with the temperature being for 1000 years before the corresponding CO2 value. The correlation for this is about 0.89 (R), meaning that you could explain 79 percent (0.89*0.89) of the variation (R^2) in CO2 by looking at the temperature. As is mentioned in my post Does CO2 correlate with temperatures, where we saw equally high correlation between temperature and CO2 (even higher if you give CO2 a 20-30 year lead on temperature), and quite a few times in the comments, correlation is not causation. Could be that both temperature and CO2 are pushed around by something else. More about that in a moment.
It's common to see the claim that temperature 'leads' CO2. Loosely speaking, this means that temperatures generally change before CO2 does, and that there is a consistent pattern to the connection -- if temperature rises, CO2 does as well. This is true; it leads by about 800 years [Caillon and others, 2003]. The amount of lead also seems to depend on whether you're in a glacial period or (as we are now) an interglacial. The correlation between temperature and CO2 is lower (by a very small amount) if you take their values for the same time (drops to 0.88). And it drops by more if we take the temperatures for 2000 years before the CO2 value, to 0.87, indicating from this very simple approach that the lead is between 0 and 1000 years, probably closer to 1000 -- as is found from the more serious approach in the reference.
So there's some interesting science to do, to understand why that lead exists, why it is many hundred years (rather than a few dozen years, or a few thousand), and why the lead time depends on whether you're in a glacial period or an interglacial period. Oddly, to me, most of the time that people mention this lead relationship, they are not referring to any of this.
Here we have each value of CO2 plotted against the temperature deviation from reference values -- with the temperature being for 1000 years before the corresponding CO2 value. The correlation for this is about 0.89 (R), meaning that you could explain 79 percent (0.89*0.89) of the variation (R^2) in CO2 by looking at the temperature. As is mentioned in my post Does CO2 correlate with temperatures, where we saw equally high correlation between temperature and CO2 (even higher if you give CO2 a 20-30 year lead on temperature), and quite a few times in the comments, correlation is not causation. Could be that both temperature and CO2 are pushed around by something else. More about that in a moment.
It's common to see the claim that temperature 'leads' CO2. Loosely speaking, this means that temperatures generally change before CO2 does, and that there is a consistent pattern to the connection -- if temperature rises, CO2 does as well. This is true; it leads by about 800 years [Caillon and others, 2003]. The amount of lead also seems to depend on whether you're in a glacial period or (as we are now) an interglacial. The correlation between temperature and CO2 is lower (by a very small amount) if you take their values for the same time (drops to 0.88). And it drops by more if we take the temperatures for 2000 years before the CO2 value, to 0.87, indicating from this very simple approach that the lead is between 0 and 1000 years, probably closer to 1000 -- as is found from the more serious approach in the reference.
So there's some interesting science to do, to understand why that lead exists, why it is many hundred years (rather than a few dozen years, or a few thousand), and why the lead time depends on whether you're in a glacial period or an interglacial period. Oddly, to me, most of the time that people mention this lead relationship, they are not referring to any of this.
05 January 2010
The Biggest Control Knob
I've mentioned Richard Alley before, with good reason. You can get a flavor of the reason by looking at his Bjerkenes lecture The Biggest Control Knob: Carbon Dioxide in Earth's Climate History.
It's about 50 minutes, and you can skip the introduction to save a little time. One thing not to miss from the introduction, so I'll mention it here, is the title of Richard's popular book The Two Mile Time Machine. In it, he discusses how we (he) figures out what climate was like from examining ice cores. First hand discussion.
Digressing to the personal a second, I do know him personally. I was a guest lecturer in the 1991 edition of the class he mentions. My thing at the time being deep ocean circulation, with some concern about how that affected atmospheric CO2 levels.
It's about 50 minutes, and you can skip the introduction to save a little time. One thing not to miss from the introduction, so I'll mention it here, is the title of Richard's popular book The Two Mile Time Machine. In it, he discusses how we (he) figures out what climate was like from examining ice cores. First hand discussion.
Digressing to the personal a second, I do know him personally. I was a guest lecturer in the 1991 edition of the class he mentions. My thing at the time being deep ocean circulation, with some concern about how that affected atmospheric CO2 levels.
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