Fractals of Change

One Nation

Almost very article on solar power concludes with the rather obvious fact that the sun doesn’t shine at night (or even on some days). Almost very article on wind energy gives prominence to the fact that the wind doesn’t always blow. Some articles on electrical production point out that there is almost no remaining opportunity for new dams to generate electricity.

Put those three things together and you have the beginning of the end of our dependence on foreign oil.

One of the wonderful things about being a continent-spanning country is that we are not all under the same weather pattern at the same time. We have a variety of climates that create a variety of opportunities. No one region has to be energy independent in order for the country to be energy independent as a whole. We just have to think out of the silo.

According to the US Department of Energy, about 7% of US energy came from hydropower in 2006. The limiting factor on the amount of energy we can get from hydropower is the amount of water flowing into the impoundments behind the dams. During periods of peak demand, the water is drawn down quickly; when demand slackens, the water can build up again. But, in general, we use the total amount of water available over the course of a year except that a minimum downstream flow has to maintained for ecological reasons and water can only be allowed to build to a certain height behind the dams for safety reasons before it must be released.

Suppose that we had a lot of new solar capacity. We would get our maximum output from that capacity during the day which happens to be the time of peak demand. All things being equal, we would then be able to turn the dams down to minimum flow during the day since the solar energy would meet the demand. Then we’d have more water to use for generation at night when the sun isn’t shining. Note that the effect is that we already have a mechanism which is the equivalent of being able to store solar energy.

Same thing goes for wind: if it’s blowing, the water builds up behind the dams; if it’s not blowing, we release the water from the dams. Effectively we’ve bottled the wind.

In fact, we can hold the water until the time when both the sun doesn’t shine and the wind doesn’t blow.

In practice we’d run the dams during the day and avoid burning some natural gas (accounted for 20% of our electricity in 2006) and oil (2%). We’d just hold back enough water to meet nighttime demand because that’s when we’ll all be charging our electric and plug-in electric hybrid vehicles.

All we need is the will to rebuild our national electrical grid so that energy can flow from where it’s currently abundant to where it’s currently needed. We don’t need expensive ways to store solar and wind power to make those technologies practical. Our existing dams are that storage mechanism. Our size and the variability of weather over our expanse are another buffer.

But we need to rebuild the grid and then we need to add regionally appropriate power-generation capability to it. Wind and solar can be done much more quickly than new nuclear capacity (which ought to be built as well for baseline supply).

All of the presidential candidates agree that our dependence on foreign (meaning Middle Eastern) oil is both an economic and a national security danger. To a greater or lesser degree, they think that burning fossil fuels is an environmental threat. One of them should take the bold step of proclaiming that, if he or she is elected president, the nation will be a net exporter of oil in fifteen years. Details to follow – but rebuilding the grid is the immediate first step.

Plug-In Hybrid Vehicles – Readers Add to the Discussion

Lots of good comments from readers that deserve prominence and more discussion.

First from Craig Plunkett:

“PHEV's do exist for the truck market. There is a small company on Long Island producing them. Bucket Trucks and Garbage Trucks are great targets for this technology. The CTO of Odyne at the time came to talk about them to a business group I belong to…”

In his own post about this presentation, Craig points out that PHEV garbage trucks are much quieter than their conventional equivalents. Not only is there not engine roar but the regenerating braking systems don’t make as much noise as truck brakes. I would think that there would also be a market for “pure” electrics in trucks that are heavy anyway (so batteries may not be as much of a problem) and have a predictably short route.

kent beuchert does some useful calculations:

“Actually, if you do the simple math using the DOT's graph of the distribution of commuting trips in the US, you'll find that a 40 mile ranged plug-in like the Volt would achieve 295 MPG in commuting, even without any workplace recharging occurring. This would avoid 93% of gasoline used for commuting. With 1/4 of commuters recharging at work, the fleet's MPG would jump to 397 MPG, avoiding 96% of gasoline usage.”

So why aren’t we (the collective we) doing more to move the world’s ground transportation fleet to PHEV? CJ does point out some practical concerns:

“I almost agree with you on this one. 1) The electric grid is in such poor shape that the added load of charging all these vehicles could put it over the edge. 2) Low temps effect the power output of batteries and 3) Gas electric hybrid's and their massive batteries are dangerous in a crash - both to the occupants and the emergency personnel - because disconnecting the battery no longer eliminates current flowing through the vehicle. As a member of a volunteer fire dept, there is a lot of concern over responding to hybrid's involved in accidents. The special training is just starting to hit small depts such as ours.”

Although CJ is right about the pathetic state of our electrical grid (like much of our infrastructure), I think the fact that PHEVs would be recharged mainly at night when the grid is way below peak usage mitigates this problem to a large extent (see more on this below). Moreover, having more nighttime usage for the grid improves the economics for capital improvements that need to be made anyway. The more kilowatt hours flow through a given segment, the more quickly investment in the segment can be amortized AND the less each kilowatt hour has to be burdened with depreciation.

Batteries do lose effectiveness in cold weather but the availability of the gasoline backup means that the driver isn’t stranded on a low electric mileage day.

The fire problem is an interesting one and CJ is much more qualified to comment on that than I am. Some work needs to be done here to prepare for a PHEV future.

CJ goes on to recommend fuel cell technology:

“However, there is a slightly different twist on your plugin that should be hitting the market soon from Honda (I believe). A fuel cell vehicle that will power the car without need for batteries and a gas engine, but the big advantage is that when you plug these vehicles in, they generate power. A home owner could supply their home electrical needs, or a portion of it, as well as get long range emission free driving. For businesses that have fleet vehicles, the generating benefits increase greatly. As well, small inputs into the existing grid from home power generation make the whole grid a more efficient system.”

The Honda he is talking about is the FCX Clarity which “Honda plans to lease to a limited number of retail consumers in Southern California with the first deliveries taking place in summer 2008.”  The FCX Clarity is NOT rechargeable; it requires a supply of hydrogen which, in turn, requires a delivery infrastructure which doesn’t yet exist. Moreover, although water is the only tailpipe emission from a fuel cell car; hydrocarbons are usually a by product of producing the hydrogen fuel supply just a some hydrocarbons are a by product of some methods of generating electricity. IMHO, fuel cells will be part of the global answer in time, perhaps the major part – but PHEVs are a quicker fix.

In an offline communication, friend Michael Birnbaum pointed to a post on salon.com by Andrew Leonard which talks about a study published in the March issue of Environmental Research Letters which concludes that the current electrical grid in California could support one million PHEVs without additional capacity assuming that they are not recharged in peak hours of peak days.

The study does say, however:

“Even with gasoline dear at $4.00/gallon and electricity cheap at $0.05/kWh, vehicle purchasers may only find a compact car plug-in hybrid economical if its cost premium relative to an ordinary hybrid vehicle were under $2000 and if its cost premium relative to a conventional vehicle were under $3500. Such price premiums may require battery pack costs (including electronics, etc) under $650/kWh, while current battery pack prices for plug-in hybrids applications may well be in excess of $1000/kWh.”

Gas isn’t $4.00 gallon (yet) and electricity costs $.20/kWh here in the Northeast. Nevertheless, mass production should bring the cost of the battery pack down quickly to an acceptable level. The trick is to jump start the process so the battery cost can come down.

The Answer Is Plug-In Hybrid Electric Vehicles

Whether the question is how to reduce our dependence on foreign oil, how to save money spent on transportation, how to reduce CO2 emissions much more quickly than anyone thought possible, or how to accommodate the transportation demands of the fast-developing developing world, the answer is Plug-In Hybrid Electric Vehicles (PHEV). They’re almost too good to be true; and, in fact, they don’t exist commercially at the moment.

However, late this year Chinese manufacturer BYD plans to start selling its PHEV by the end of 2008; a plug-in Toyota Prius and Chevy’s Volt are scheduled for 2010.

Here’s the trick: theses plug-ins can only go about forty to sixty miles between rechargings. However, the average length of a car trip in the US is less than 10 miles so easily accomplished by even a partially charged car. Sure, we all take long trips at least occasionally; and sometimes we plan a short trip and end up going much further. Not to worry: remember, these are hybrids; they do have gas tanks. Once the battery runs down, the gasoline engine starts up to power the generator as in a conventional hybrid. You keep going; it just costs more per mile than when you’re all-electric but still less than today’s non-hybrid cars.

With current battery technology, the initial cost of an all-electric car with reasonable range for ordinary use is still prohibitive. That’s why these plug-in hybrids are such a good solution. The Chevy Volt is expected to cost about $35,000 and have the pickup and range we are used to in conventional cars.

The Electric Power Research Institute (funded by power companies mainly) and the National Resources Defense Council (funded by green types, mostly) did a joint study which comes out for very favorable for PHEVs. They say that, even if all the electricity for PHEVs came from coal-fired power plants (the dirtiest way to get electricity in terms of CO2 emissions), there’s still a net reduction in GHG (greenhouse gas) if we switch from inefficient gasoline to more efficient electricity for most of our driving.

In real life that wouldn’t happen. PHEVs presumably get recharged mostly at night; a high greater percentage of our night time electricity comes from hydro and nuclear since total demand is much less then. Moreover, we have lots of options including nuclear, wind, solar, and carbon-sequestration at coal plants for increasing electric power generation while decreasing emissions. Notice that most of these sources are domestic!

An article in Harvard Magazine by Michael B. McElroy commenting on the EPRI study says:

“Replacing 90 percent of gasoline consumption by electricity would be equivalent to raising the fleet’s average fuel efficiency from the present level of about 17 miles per gallon to close to 150 miles per gallon. Were we to accomplish this objective, total oil use would be reduced by 36 percent, cutting the demand for imported oil by as much as 60 percent (a savings of $270 billion per year at current prices for oil). ...”

40% of oil use in the US is to power cars and light trucks, obviously a good target for reduction. No way we’re going to replace a substantial part of this with corny ethanol nor should we try. The Harvard article suggests that, even if (or maybe when) biofuels are developed which don’t compete with food, it’d still be more efficient just to burn them (or the plants they come from) in electric generating facilities than to take all the extra steps needed to make them into transportation fuel.

The operating economics are already right thanks to the rising cost of oil. A gallon of gas is the transportation equivalent of 7.5 kWh of electricity. That mean that even at a pretty high rate of $.20/kWh, using electricity is the equivalent of paying $1.50/gallon. Better yet, it’s reasonable to assume that off-peak electricity can be purchased more cheaply and that there is a per unit savings in MORE use of the electric grid and power plants at night. So that price might at least stay reasonably stable even with escalating demand.

The proof should be in the pudding soon. There is no new technology required although there are some engineering problems: Chevy reports trouble getting the electrical budget of things like in car entertainment, air conditioning, and even windshield wipers down far enough to keep the all-electric range of the Volt high enough. Assuming charging mainly at night, we don’t need to rebuild the electrical grid right away (although we should). We don’t need massive new generating capacity; we just run what we have more hours (but we should be building).

This energy stuff really is more an opportunity than a crisis.

Danger: Biofuels Cause Global Warming

The abstract of an article in a recent edition of Science Magazine says:

“Most prior studies have found that substituting biofuels for gasoline will reduce greenhouse gases because biofuels sequester carbon through the growth of the feedstock. These analyses have failed to count the carbon emissions that occur as farmers worldwide respond to higher prices and convert forest and grassland to new cropland to replace the grain (or cropland) diverted to biofuels. Using a worldwide agricultural model to estimate emissions from land use change, we found that corn-based ethanol, instead of producing a 20% savings, nearly doubles greenhouse emissions over 30 years and increases greenhouse gases for 167 years. Biofuels from switchgrass, if grown on U.S. corn lands, increase emissions by 50%. This result raises concerns about large biofuel mandates and highlights the value of using waste products.^”

Europeans trying to comply with Kyoto mandates have proposed stipulating that biofuels used to meet their alternative fuel mandates cannot come from land that was previously rain forest. However, the study points out that such restrictions are window dressing. Food, like energy, is fungible. If European biofuels come only from existing agricultural land, the food crops formerly grown there will be grown somewhere else; good chance that somewhere else will be newly cleared.

A New York Times article by Elizabeth Rosenthal about the studies published in Science gives this example:

“…Previously, Midwestern farmers had alternated corn with soy in their fields, one year to the next. Now many grow only corn, meaning that soy has to be grown elsewhere.

“Increasingly, that elsewhere, Dr. Fargione said, is Brazil, on land that was previously forest or savanna. ‘Brazilian farmers are planting more of the world’s soybeans — and they’re deforesting the Amazon to do it,’ he said.”

The studies do point out that biofuels made from agricultural waste (technologies for which are being worked on but have not yet been made remotely economical) and that biofuels from sugar – as made in Brazil and, inexplicably to me, not made in any quantity in Hawaii – would and do have a positive carbon impact.

Defenders of the subsidized biofuels industry are quick to point out that biofuels do help energy independence. On a global basis, use of farmland to “grow energy” diversifies energy sources – a good thing – and increases income to farmers in poor as well as wealthy areas – another good thing. On the other hand, diversion of cropland raises food prices.

The world economy isn’t as complex as the environment but it may be as chaotic and hard to model. Food prices and the amount of land under cultivation would both be going up now even without corn-based ethanol production because the huge number of people escaping poverty in India and China are using some of their new income to eat more and better – as well as to buy motorcycles and cars.

In the long term it seems foolish to use plants to convert sunlight to energy for fuel when solar collectors – after a huge capital outlay and with big infrastructure changes – yields one hundred times more energy per acre than growing corn. Moreover, some of the best places for solar generated electricity are not cropland because they are arid.

But now it seems that corny ethanol may not be a good short term solution either. Suppose, for example, we burn more coal even before we have a way to sequester or divert the atmospheric carbon dioxide produced. Even giving full credit to the most alarming predictions of carbon-based global warming, this may be environmentally more friendly than clearing a rain forest. You can stop burning the coal if you can’t sequester the CO2 or whenever replacement energy comes online; you can’t  replant the rain forest. Hmm…

Some will argue reasonably that discrediting ethanol as a panacea is one more reason why conservation (aka less driving in smaller cars) is the only solution to the twin problems of energy independence and global warming. Trouble with that thinking is that the aforementioned newly unpoor aren’t going to forgo the pleasures of personal transportation which we have long enjoyed. We need more energy sources.

The math behind my claim that solar produces 100 times the yield of corn in net energy per acre at 1800 times the capital cost is here.

A Question Which Should Be Asked

Writing in the New York Times on New Years Day, John Tierney repeats a question asked almost a year ago by Roger Pielke Jr. of the University of Colorado on the Prometheus blog:

“What behavior of the climate system could hypothetically be observed over the next 1, 5, 10 years that would be inconsistent with the current consensus on climate change? My focus is on extreme events like floods and hurricanes, so please consider those, but consider any other climate metric or phenomena you think important as well for answering this question. Ideally, a response would focus on more than just sea level rise and global average temperature, but if these are the only metrics that are relevant here that too would be very interesting to know.”

We often hear that warmer temperatures (in some places), rising sea levels, melting ice (in some places), greater weather extremes, and even cold spells are evidence that the “consensus” theory of anthropogenic global warming is correct. It’s a reasonable question – in fact, a very important question from both a scientific and a policy point of view – to ask what would tend to indicate that the theory is incorrect. Note that Pielke is not asking what would “prove” the theory incorrect; in the short term that is as impossible as proving that it is correct; he is asking for indicators which might raise doubts in the same way that many indicators are taken to indicate certainty.

This should be a question which engage climatologists and other scientists. Theories should be challenged; that’s the way we learn more; that’s the way “correct” theories get strengthened and improved; that’s the way errors are uncovered.

Predictably, many of the comments on  Tierney’s column are attacks on both him and Pielke for raising the question. That’s dumb: doesn’t matter what their motives are in asking the question; doesn’t matter whether your own working hypothesis is that the cause of observable recent global warming is anthropogenic or not; the question deserves to be asked.

In a recent comment on a post in which I quoted the skepticism (which is different from disbelief) of John R. Christy, Director of the Earth System Science Center at the University of Alabama at Huntsville and a participant in the IPCC, reader Mark A. York writes:

“It's a pity the top climate scientists on Earth disagree. Why do you think that is? Yeah everyone is crazy but you guys. LOL! Do some homework. www.realclimate.org”

Don’t know why Mark reads Christy out of the ranks of top climate scientists and don’t know who “you guys” is either. I’ve never been given my membership in the secret society of doubters.

Action and skepticism aren’t mutually exclusive. Now that I have that off my chest, I’m gonna go out in the seven degree weather (five below windchill) and brush the snow off my solar collectors (really). It’s sunny and I can’t stand to see them ineffectual.

 

By the time I got there, the sun and wind had done half my job for me (they’re at the winter angle of 80 degrees both to shed snow and to face the low winter sun). When I finished cleaning them off, I had the great pleasure of seeing my electric meter run swiftly backwards.

Cause for Global Warming Discovered

The graphs below from an article by Natural Resources Canada show the movement of the magnetic North Pole. As the article says “The change in velocity of the North Magnetic Pole since the early 1970s has been remarkable – 9 km/yr to 41 km/yr.”

And this graph from the report of the Nobel-sharing International Panel on Climate Change (IPCC) shows an accelerated increase in global warming during exactly the same period (left scale is difference from the 1961-1990 average).

 

Unfortunately the IPCC was distracted by the coincident rise in certain atmospheric gasses and so missed the true cause of global warming. The Director of Natural Resources Canada is precluded from running for President of the US because he wasn’t born here.

OK. This is all junk science. I admit it. Neither Natural Resources Canada nor anyone else I know of has claimed a link between this accelerated movement of the magnetic pole and global temperatures. We could invent a mechanism for cause and effect, however: the location of the magnetic pole affects the shape and poles of the earth’s magnetic field (obviously) which has an effect on incoming cosmic radiation which has an effect on cloud formation which has an effect on reflectivity which has an effect on temperature. It’s a little harder to do the opposite and imagine how warming caused the pole to move but I’m sure some smart reader’ll do that.

All this is just meant as a warning against taking apparent correlations too seriously.

John R. Christy, Director of the Earth System Science Center at the University of Alabama at Huntsville and a participant in the IPCC (he calculates that he is .0001 of a Nobel Laureate) writes in today’s Wall Street Journal:

“I'm sure the majority (but not all) of my IPCC colleagues cringe when I say this, but I see neither the developing catastrophe nor the smoking gun proving that human activity is to blame for most of the warming we see. Rather, I see a reliance on climate models (useful but never "proof") and the coincidence that changes in carbon dioxide and global temperatures have loose similarity over time.

“There are some of us who remain so humbled by the task of measuring and understanding the extraordinarily complex climate system that we are skeptical of our ability to know what it is doing and why. As we build climate data sets from scratch and look into the guts of the climate system, however, we don't find the alarmist theory matching observations….

“It is my turn to cringe when I hear overstated-confidence from those who describe the projected evolution of global weather patterns over the next 100 years, especially when I consider how difficult it is to accurately predict that system's behavior over the next five days.

“Mother Nature simply operates at a level of complexity that is, at this point, beyond the mastery of mere mortals (such as scientists) and the tools available to us. As my high-school physics teacher admonished us in those we-shall-conquer-the-world-with-a-slide-rule days, "Begin all of your scientific pronouncements with 'At our present level of ignorance, we think we know . . .'"”

He’s not saying (and I’m not saying) that anthropogenic activity is NOT causing global warming. He is saying we have less than proof and I’m saying we’ve got to stay skeptical even as we take some obvious actions like reducing our dependence on fossil fuels that we’re running short of anyway. The Oscar for An Inconvenient Truth was deserved since it’s an effective and dramatic polemic; a Nobel Prize for shoddy science seems an inducement to substituting rhetoric for thought in making crucial resource allocation decisions.

Backtested Models – Hot Dogs

Way back in the early 60s I earned my tuition by programming the IBM 7090 in the college computer lab. This monster lived in an air-conditioned space the size of a basketball court and probably had less computing power than your watch, certainly less than your cell phone; but it was awesome for its time. When it was idle, usually in the middle of the night, I could sneak in some projects of my own. Having this unprecedented computing power available, I thought, certainly I can make my fortune at the dog track in Revere. I chose dogs rather than horses because eliminating jockeys made the problem simpler and lessened the possibility of fixed races defeating my algorithms.

What I needed to do was calculate the “actual” odds of each dog winning each race. Then, if the odds at the track just before the end of betting were much worse for a particular dog than I had calculated, betting on that dog was good strategy. Didn’t mean I’d get a payoff in any one race or even any set of races but, over time, should make money. But how to know how to weight all the masses of data available (or the data I had time to keypunch) to come up with the real odds.

That, of course, was where the computer would help. I fed it a mass of data for the past season. I programmed it to try one set of weighting factors after another until it found a strategy that overall made money if bets were placed at the actual track odds at post time. Having found a money-making strategy, the computer then made it better by tweaking the factors in small increments. Eureka! A particular strategy showed an expected 17% on money bet each racing day even given the various ways the track takes a cut. I was off to the races – literally.

Lost 50% of my stake on the first night. Made 5% the second; lost it all the third.

This wasn’t an adequate sample to test the theory; but I was out of money so had to go back to playing on the computer instead of at the track. Of course, could still simulate how I would’ve done if I’d actually been betting. Lousy, was the answer;  but this stimulated a new approach: I tested my method derived from last year’s results against the data from the previous year. That simulation showed a loss of 22% of the stake each racing day. Hmmm….

OK, scientific method says a theory is no good unless it predicts something that can be tested. I shouldn’t have trusted my model just because it fit the past. So I modified my technique to generate algorithms using last year’s data and then “predict” the first half of this year which had already happened. Aha..  That eliminated a lot of methods but one survived with flying colors. Meanwhile, I was working overtime at my regular night job so I had a new stake to take back to the track and make my fortune.

This time it took five nights to go broke. But, by the fifth night, the people who always stood in the same place I always stood, had noticed my green-and-white sprocket-punched fanfold computer paper. I explained my theory to them and boasted about my access to a computer (remember, rare and almost mystical in those days). They offered to buy printouts from me. I warned them that I hadn’t done very well yet but the authority of the fanfold paper was unimpeachable; they suspected I was holding back on them.

On the sixth night I had only enough money for subway fare and admission to the track but also had a sheaf of my computer-generated tip sheets. Sold out in almost no time and, as luck would have it, the tip sheet tips did pretty well so my circle of prospects grew rapidly.  Next night I brought a whole box to the track.

That’s when my first career in information processing ended. A very small and intense man with a very large but vague companion told me that I didn’t have a permit to sell tip sheets at the track. “Where do I get one,” I asked. “You don’t” is a polite rendition of what he told me. The large companion kindly disposed of the rest of my box of printout. I was escorted outside the track

But the lesson is really about backtested models. You can always find a correlation between two sets of data if you have a computer look hard enough. Trouble is, you can as easily find a correlation between unrelated datasets as you can between datasets where there may be some causal relationship (astrology, anyone?). If your algorithm (model) can’t make predictions, it’s worthless. If it can make predictions, you test the predictions. Testing can easily falsify your model but can’t actually prove it (a black swan could always show up in the next test). However, the more successful predictions a model makes, the more it makes sense to rely on it provided that you know that the stuff you don’t put into your model is going to be the same in the future as it was in the past (a big if).

As you may have suspected, this has a lot to do with predicting global warming. Stay tuned.

BTW, my predicting the unknown past was not equivalent to predicting the future. It was just another way of doing backtesting.

Answers to Probability Puzzle

As usual, smart readers knocked the cover off the ball almost immediately. Some day I’ll stump you.

First question taken from Randomness by Deborah J Bennett:

“If a test to detect a disease whose prevalence is one in a thousand has a false positive rate of 5%, what is the chance that a person found to have a positive result actually has the disease, assuming you know nothing about the person’s symptoms or signs?”

First to answer correctly was Matt Crawford:

“Assume that the test is performed on everyone regardless of symptoms of the disease. Then out of every thousand people who receive the test, one has the disease and 999 do not. Further, assume that the test has no false negatives: anyone who actually has the disease gets a positive result. Then 1 out of every thousand tests are true positives. The remaining 999 should be negative results, but the 5% false positive rate means that 49.95 (so round to 50) of these people will receive false positive results. Then out of our 1000 tests, 51 return positive results. But only one of these is a true positive, so the chance that a positive test identified someone who actually has the disease is 1/51 or about 2%.”

You might quibble that 5% false positives means 50 false positive out of a population of 1000 (plus one correct positive) but this is close enough. It’s fair to make the assumption that there are no false negatives since this isn’t stated in the question (and otherwise you’d be unable to answer) but Aswath is right to point out this should have been specified.

Second question: “what percentage of the physicians, residents, and fourth year medical students at a prominent medical school who were asked this question got it right?”

jb guessed that 80% of those tested would give the tempting wrong answer of 95%. Actually, only 19% gave the right answer but only 50% said 95%. jb, you would’ve nailed it if you hadn’t given more detail in your answer than called for. Rob’s an optimist and hoped that 80% would get it right because their care is so important and getting into medical school requires critical thinking. He’s dead right that it’s scary that so many get it wrong.

Interesting answers to third question: “why is it critically important that doctors be able to get this one right? Give one example.” Most not about doctors, though. This type of bad thinking does cover lots of ground.

Matt Crawford cites the Red Cross using an HIV test on donated blood which is known to have a high incidence of false positives and speculates that many donors are probably panicked by the result. “However, the Red Cross continues to use the same test, probably because it combines low cost with very low false negative rate. In this case it may be justified to trade a high false positive rate for a low false negative rate, because a false positive merely requires a second test but a false negative would spread HIV through transfusions.”

Curtis Carmack says: “the medical profession as a whole has given insufficient thought to how to address the false positive issue with patients, leading to much more angst than is necessary when patients receive a positive test result -- invariably late on Friday -- and have to wait at least a couple of days to ask questions about it. ;-)”

Dennis Shanley posts: “This directly effects the overall cost of health care in a huge way. Assume that it costs $10,000 to cure a patient who presents positive. Not an unlikely assumption. Assume further that the 50 false positive patients do not exhibit negative effects as a result of their treatment that require further medical treatment and they do not litigate as a result of the unnecessary treatment. This is a highly improbable assumption made for the sake of simplicity.

“The true cost to cure 1 patient is $10,000.

“The cost to cure that one patient and treat the 50 false positives is $510,000.”

Aswath writes: “Suppose now we are told that the false positive predominantly affects a biological group - gender or a racial group. Will that decision stand reason? Let us assume that the situation is internment during WWII in US. A nation has to live with the effects of a callous operation decision to accept a large false positive.”

Otmar: “There is another interesting application for this kind of statistics: The beloved war on terror. The chance of a random person to be a terrorist is hopefully less than 1/1000. Imagine you manage to build some automated system which somehow claims to spot suspicious behavior, known faces, or miscreants by some other clever scheme.

These systems all have a non-negligible error-rate. If you're really lucky, you might push that one down to less than 1%.

“Now do the math again, assuming a 1/100000 terrorist-rate and 1% false positives. No wonder I read that one trial for such a system got terminated.”

The point is that you must weight the costs of being right and the costs of being wrong both for the positive and the negative case. Back to medicine, suppose your doctor is one of the benighted 81%. He or she tests you using the test in the first question and you come up positive. Let’s suppose that the disease is always fatal if not treated and there’s a treatment available but it has a 25% chance of killing you itself. If the doctor believes that there’s a 95% chance you have the disease, the dangerous treatment is clearly justified; but, since the true likelihood is less than 2%, the treatment is more dangerous than your untreated prognosis. Always a good idea to get a second opinion AND check your doctor’s math.

A Turkey Connects the Wrong Dots and Finds a Black Swan

The Black Swan by Nassim Nicholas Taleb is simply a great book. Not flawless, sometimes annoying, always stimulating, but overall great. Here’s an example about connecting the wrong dots:

“Consider a turkey that is fed every day, Every single feeding will firm up the bird’s belief that it is the general rule of life to be fed every day by friendly members of the human race ‘looking out for its best interests,’ as a politician would say. On the afternoon of the Wednesday before Thanksgiving, something unexpected will happen to the turkey. It will incur a revision of belief.”

Back to the title: doesn’t matter how many white swans you see in a row; they don’t prove the non-existence of black swans. On the other hand, you only need to see one black swan to DISPROVE the proposition that all swans are white. That’s why good thinkers in general and good scientists in particular set out to DISPROVE rather than affirm their own hypothesis. You don’t add much credibility to the “all swans are white” theory by finding yet one more white swan; you learn a lot about the truth of the theory by finding one black swan.

Black swans are, according to Taleb, unexpected and unpredictable rare events. By their nature, we can’t know which black swans are about to reverse an orderly flow of dots and shatter our complacency; but, by the nature of the universe, we can be sure that sooner or later one will come along. Black swans can be good or bad: a book becoming a hit (unpredictable), suddenly becoming rich (or poor), the Internet, the rise to dominance of Google – all examples given by Taleb.

If you think that each day that a stock or a class of stocks goes up makes it more likely that owning those stocks will make you rich, you’re making the same mistake as the turkey. Actually, it’s statistically true that a stock is slightly more likely to go up than down on the day following an up day, but the odds of losing rather then making money on the stock go up rather than down following a rise. That’s because a decline, even though it is less likely than an advance for a stock with “up momentum”, is more likely to be big. A stock or a market which has been rising quickly is more and more vulnerable to a black swan event.

Taleb honed his skill as a trader but applies the black swan (and Fooled by Randomness) lessons to much more:

“The turkey problem can be generalized to any situation where the same hand that feeds you can be the one that wrings your neck. Consider the case of the increasingly integrated German Jews in the 1930s – or my description in Chapter 1 of how the population of Lebanon got lulled into a false sense of security by the appearance of mutual friendliness and tolerance.”

Being a Jew born during WWII, I was brought up on the first example. Taleb is Lebanese and grew up there as the country went from peace and prosperity to a chaos which still hasn’t ended.

The Black Swan is a book of contradictions. Taleb warns us against our predilection for making up stories to explain events yet he is a master story teller himself; his books work better because we learn through well-told stories like the fate of the turkey.

Taleb warns us against the fallacy of thinking that a trader who is rich is necessarily smart; very likely that she or he is just lucky. After all, if hundreds of thousands of people start out as apprentice traders – and if all trading were governed by pure luck, at the end of a year randomness would assure that there were some who were extremely successful as well as a whole bunch of losers. But Taleb’s credibility comes partly from HIS success as a trader. He’s even written a book on his techniques called Dynamic Hedging, which I’ve ordered. I’ll let you know if it makes me rich – maybe.

Taleb loves to puncture arrogance and does so fiercely and effectively – Nobel laureates in Economics are a particular target; but Taleb is quite arrogant himself, says he has no intent or reading random reviews and please don’t send him notes about typos or how to make his website better (it’s a mess).

But read The Black Swan if you haven’t.

Random thought: Hansel DIDN’T make the turkey’s mistake. He figured out why the witch was fattening him up and, every day, gave her a skinny stick rather than his fat finger to test for plumpness. Skepticism is a good but not infallible weapon against black swans.

The Ice-Free Arctic – Excellent Coverage in the NY Times

Kudos to New York Times reporter Andrew C. Revkin for today’s article Arctic Melt Unnerves the Experts: Revkin clearly explains how this may be evidence of global warming - or not, may be evidence of anthropogenic causes for global warming – or not. More of this type of reporting would certainly reduce the heat and increase the light of the global warming debate.

Note that by the second paragraph the facts in the first paragraph are put in perspective:

“The Arctic ice cap shrank so much this summer that waves briefly lapped along two long-imagined Arctic shipping routes, the Northwest Passage over Canada and the Northern Sea Route over Russia.

“Over all, the floating ice dwindled to an extent unparalleled in a century or more, by several estimates.”

In other words: this is a big deal with lots of implications – some of them positive like easier shipping – but the conditions are a repeat of what may well have happened relatively recently and BEFORE anthropogenic global warming could have been a factor. This doesn’t prove, of course, that increased CO2 concentrations had nothing to do with this warming episode – it just makes clear that there could be other causes.

Another very good paragraph:

“The pace of change has far exceeded what had been estimated by almost all the simulations used to envision how the Arctic will respond to rising concentrations of greenhouse gases linked to global warming. But that disconnect can cut two ways. Are the models overly conservative? Or are they missing natural influences that can cause wide swings in ice and temperature, thereby dwarfing the slow background warming?”

Much faith has been put in the many models which predict dramatic future warming based on the last few years and some assumptions and correlations between CO2 levels and average global temperature. But are they connecting the wrong dots? The test of a model is not how well it fits the past; it’s how well it predicts the future. If the model-driven estimates of ice melt are badly off in either direction, it suggests that the models are broken. If we really want to be alarmed, let’s think about the possibility that the earth is getting warmer faster than we think it is for reasons that have nothing to do with our activities. Could be that we’re not in control at all.

Interestingly the Arctic ice deficit may not be directly temperature related at all. The article also gives lots of space to alternative or contributing causes including wind patterns which have been pushing ice out of the Northwest Passage into the open ocean. Sound bites will leave alternative possibilities out, of course.

Some more balance:

“Proponents of cuts in greenhouse gases cited the meltdown as proof that human activities are propelling a slide toward climate calamity.

“Arctic experts say things are not that simple. More than a dozen experts said in interviews that the extreme summer ice retreat had revealed at least as much about what remains unknown in the Arctic as what is clear. Still, many of those scientists said they were becoming convinced that the system is heading toward a new, more watery state, and that human-caused global warming is playing a significant role.”

Evidence is important. What happens in the Arctic is evidence. The best use of evidence is to try to DISPROVE existing theories (more on that in a future post). The Times article gives sufficient space to using the evidence as challenge rather than confirmation.

The closing quote from Dr. Hajo Eicken, a geophysicist at the University of Alaska, suggests a lack of imagination (although it may be out of context): “The Arctic may have another ace up her sleeve to help the ice grow back. But from all we can tell right now, the means for that are quite limited.”

Seems it would be a very good idea to study both why the ice melted a century or so ago and how it happened to grow back. Maybe the conditions from then apply now, maybe they don’t. But the last warming (and cooling) is certainly relevant.