The Power of Theory In Science

"He who loves practice without theory is like the sailor who boards ship without a rudder and compass and never knows where he may cast." -Leonardo Da Vinci

It's often lonely, these days, as a theorist. As soon as most people hear the word theory, in fact, they start thinking about something like this:

Image credit: F. Steiger.

But if you're scientifically minded, you know just how powerful your theory is. Because your theory - if it's any good - allows you to not only explain what you've already seen, but allows you to predict something new, which you can then go look for.

By the early 1800s, there were two theories about the nature of light. One of them, going back to Newton, is that light is a ray.

Image credit: University of Iowa.

And, of course, it is a ray. But there was another idea - going back even farther (to Christiaan Huygens) - that light might also be a wave. And this gained a lot of support in 1799, when Thomas Young first passed light through two thin, nearby slits.

Image credit: Matthew Parry-Hill and Michael Davidson.

The pattern that comes out of this - the famed double-slit pattern, below - can only be explained if light were, in fact, a wave.

Image credit: Benjamin Crowell.

So this was the leading theory in the 1800s: that light is a wave. So if you're a good theorist, and you're interested in studying light, what do you do?

Well, if you're famed French mathematician and physicist Simeon Poisson, you would think of the most ridiculous configuration you could imagine in the hopes of disproving the light-is-a-wave theory. And that's exactly what he did in 1818.

Image credit: Auburn University.

He imagined that you took a wave source of light, and had it shine on and around a completely black, spherical obstacle, setting up a screen behind it. Obviously, he reasoned, you would see some light on the screen indicating the outside of the sphere, and darkness, or a shadow, on the inside.

But, he calculated, if the wave theory of light were correct, you would get something completely absurd!

Image credit: Robert Vanderbei.

Sure, you'd get light on the outside, and shadow on the inside, but what's that at the very center? Poisson predicted, using the wave theory of light, that you'd actually get a bright spot of light at the very center of this shadow! How absurd was that! And therefore, he reasoned, the wave theory of light was absolutely crazy, and had to be wrong.

Hard to argue with that, isn't it?


Image credit: Alexandre Sixdeniers, from a painting by Henry Scheffer.

Meet Francois Arago, former Prime Minister of France (among many other things). Shortly after Poisson's prediction, Arago decided to put the theory to the test, and actually performed the experiment to look for the "theoretically absurd" spot.

What happens if, in fact, you perform this experiment yourself?

Image credit: Thomas Bauer at Wellesley.

Amazingly, the spot is real! If your theory is any good, scientifically, this is exactly what it will do. It will not only explain what's already been observed, it will allow you to apply it to new situations, and make testable predictions about what you can expect to find. The crazier the prediction, and the more successful the experiment, the more compelling the theory becomes.

And examples abound. In 1927, Georges Lemaitre predicted that the Universe would be expanding, based on his application of Einstein's theory of General Relativity to the Universe. Einstein's initial response was, "Your math is correct, but your physics is abominable."

And yet, two years later, Edwin Hubble discovered, in fact, that the farther away a galaxy is from us, the faster it expands away from us. The only thing that was abominable was Einstein's inability to recognize just how powerful his theory actually was.

In the 1960s, the Big Bang Theory was very much in doubt. But it had a prediction: that there would be a very low-temperature, uniform background of radiation in the Universe, permeating all of space and appearing in every direction.

Image credit: U.S. National Park Service.

But in 1964, exactly that was discovered, by Arno Penzias and Bob Wilson. The Big Bang has - quite justifiably - gone largely unchallenged ever since.

And, although they're outside of my expertise, the same goes for evolution and natural selection in biology, as well as global warming in climate science. They're theories, to be sure, just as sound and compelling as the ones I've described above.

So the next time someone tells you that the Big Bang, Evolution, or Global Warming is just a theory, you'll know what to do.

You'll tell them, yes, it is the best theory. In science, that's as close as we ever get to certainty and the truth. The better we understand and test it, the more compelling, valid, and powerful it gets. And when that happens, we can learn from it, find and identify if there's a problem, and try to deal with it.

But only if you listen to the right theory.

This article first appeared on the Scientific American Guest Blog.



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Your history is a little off. Young was brilliant, but a bad communicator. He did the two-pinhole -- pinhole, not slit -- experiment, providing incedible evidence of the wave nature of light -- and nobody bought it. Eventually he got out of physics and got back to his childhood love of history and languages (and deciphered part of the Rosetta Stone).

A retired French engineer, with the awfully familiar name of Fresnel, realized you could get more light (no lasers in those days so coherent light sources were WEAK, typically you passed the sun though a preceding pinhole or slit as in your figure) by using a slit. Et voila!

So, Young's double PINHOLE experiment, FRESNEL'S double-slit experiment.

Cool stuff. I always imagine this response to it's only a theory (IOAT) -
Hold a pen out to my side
Me: If I let this go, will it head towards the floor or the ceiling?
IOAT: It will fall to the floor
Me: Why?
IOAT: Gravity
Me: How do scientists explain gravity??

Anyway - 2 questions on your discussion above:
1. What is a "ray" specifically?
2. What does the particle nature of light predict about the absurd spot?


When I'm forced to deal with the rabidly religious, I tell them that theories in science are built the same way a circumstantial case is built in a court of law. The prosecutor collects the evidence and builds his case (his theory) of what happened. He has to account for all the evidence or his case will fall apart with a single counterexample or data point that doesn't fit.

Unfortunately, it doesn't work that well because the rabidly religious are also dumb enough to "think" that defendants should be guilty until proven innocent (unless it's themselves on trial, of course). It's a decade after 9/11 and the majority are still too dumb to look past knee jerk reactions.


Poster number 2 (Walt's Garage) raises a good question about what a ray is. I've always heard this debate was about whether light was made of particles or if it was waves. How does a ray relate to particles?

"Unfortunately, it doesn't work that well because the rabidly religious are also dumb enough to "think" that defendants should be guilty until proven innocent"

Well of course, it would be unfair to try an innocent man. ;)

The Big Bang Theory has two problems.

1) If it did create everything; this requires that everything that does now exist consists of that which preceded the Big Bang. And according to the Big Bang Theory that is nothing. In other words: According to the Big Bang Theory everything consists of nothing. That is a fundamental contradiction. The Big Bang Theory cannot be correct.

2) If the Big Bang Theory created the universe then where did it occur? It had to have occurred no where at all. There must have been a no-place prior to the Big Bang. In other words: No-place must have existed in the place occupiedpied by someplace all places and every-place.

The big issue with "theory" is that it has a different meaning in the common vernacular than it does in science. "Theory" would translate as "hypothesis" in the world of science.

When someone claims "it is only a theory" they don't understand that in science, "theory" is the highest level that can be obtained.

UncleJim!! How obvious when you point it out. You are going to cosmology and high energy physics on its ass, my boy. Are you prepared for fame, because as soon as you publish, you are going to get it!
Oh, hold on, oh fuck. Seems that you are ascribing a 'prediction' made using the theory to be paradoxical. Shit, your very first word is "If" as in, "I don't know exactly, but what if"
I just read the big bang theory at coffee, and I am also sorry to inform your lame ass that 'the theory' says fuck all about what was before, why, where, how, it says fuck all because, as every scientifically literate peon knows, the laws of physics break down well before you reach the point of singularity and there is no way it can possibly apply to any situation before or at the beginning of expansion. It has never, fucking ever, predicted anything before, let alone the concrete conclusion that there was nothing.
Where did you get such a lame-assed idea, anyways? Moving on:
2) If the Big Bang Theory created the universe then where did it occur?

The theory created the universe?!? The big bangâuniverse didn't happen before 1929 then, because there was no big bang theory yet.
Sheesh ;)

Doesn't this mean we should see a nice spot at the center of the eclipsed moon, on those occasions when it does pass through the center of earth's shadow?

By Nathan Myers (not verified) on 16 Jun 2011 #permalink

I've never really understood why Penzias and Wilson were deemed worthy for the Nobel prize for their accidental discovery of the background relic noise of the Big Bang.

They were not looking for what they found.

They stumbled onto a discrepancy that they mistook for unwelcome noise and interference and, to make it worse, they needed to have the whole thing explained to them by scientists who were actively looking for what they had inadvertantly blundered upon.

The people who did the final analysis are the ones who deserved the trip to Stockholm and the medals.

UncleJim, the BBT does expect 'nothing' to remain as nothing, a total energy amount in the universe of zero, in other words. Surprisingly and un-intuitively, this is what we actually see. When doing the maths to tot up the total amount of energy in the universe, gravity acts as a negative energy (the mathematics explained in detail here: )

As for what came 'before' the BBT, this is irrelevent when discussing the theory itself as it is outside the theory's 'remit' In the same way if I say that a dropped ball will fall to the ground at a rate of 9.81m/s because of gravitational attraction to the centre of the Earth, I don't need to be able to explain where the ball came from for my theory to stand up.

P.S> anybody feel welcome to correct any mistakes or misunderstandings in my comment.

By Chrissetti (not verified) on 17 Jun 2011 #permalink

These Global Warmist "Climate Researchers" are not scientists, and what they are doing is not science. The notion that their computer climate models have anything to do with science, or even the real world, is unproven. What they do may have the trappings of science, i.e. measuring tree rings, etc. But they have only a hypothesis which remains unproven, and which increasingly is indicated to be incorrect and false.

Your article makes the point perfectly for why global warming alarmists are not scientists. They almost never make accurate predictions, instead they look at what has already happened and conjure up an explanation for why it is "consistent." Meanwhile the few predictions they do make don't seem to come true, but they always have a new explanation ready.

Actually the Penzias and Wilson experiment was interesting in that it's primary objective wasn't to confirm the cosmic background radiation but to identify a noise source on the microwave bands that was giving The Bell System and their engineers some serious fits.

I call it an accidental discovery. But one that proved the big bang in an elegant manner.

Doesn't this mean we should see a nice spot at the center of the eclipsed moon, on those occasions when it does pass through the center of earth's shadow?
Posted by: Nathan Myers | June 17, 2011 2:24 AM

Mind = blown

Aside from the factual errors already pointed out above, there is the problem on the global warming argument in that there has never been a grand experiment or result to convince all scientific minded people that global warming is real.

There is only some slight and statistically weak warming that is claimed to have been caused by an increase in CO2 levels. That is far from a grand experiment that proves a theory should be taken seriously.

Correlation is not equal to causation. Milankovitch remains the superior theory to objective scientists. That is why they try to work in Milankovitch while also stating it isn't enough by itself. Your article discredits itself and science by comparing true experiments to weak correlations.

Uncle Jim:
1) If the BB created everything [FALSE: BB describes conditions in the early universe; it did not 'create' anything] this requires that everything that does now exist consists of that which preceded the Big Bang [google up 'inflation', which is as early in the universe we have been able to probe; hint: no singularity, no 'nothingness']. And according to the Big Bang Theory that is nothing [FALSE. Still lots of 'something' there, in fact everyting, in the inflation period which set up conditions for the BB; nowhere does BB theory make claims about it coming from nothingness...gotta even dig deeper into reality for that one.] In other words: According to the Big Bang Theory everything consists of nothing. That is a fundamental contradiction. The Big Bang Theory cannot be correct. [No, it is only your conclusion, based on faulty assumptions, that is incorrect.]

2) If the Big Bang Theory created the universe then where did it occur? It had to have occurred no where at all. There must have been a no-place prior to the Big Bang. In other words: No-place must have existed in the place occupiedpied by someplace all places and every-place. [BB did not 'create' the universe; it is a description of conditions at a very young stage of the unuverse. And It happened EVERYWHERE. You are perseverating in the incorrect assumption that the BB was the beginning/origin, and it simply is not. So far, we can look back to the BB, and the preceding inflationary period, but that's as far back as we can look. Origins of the universe is still pretty far out there, but as previously stated, 'nothingness' is unstable.]


You make a common error of assuming that Global Warming is a single agreed-upon clearly-stated theory, which any rudimentary review of the literature will show is simply not true. It is this point that causes all the brouhaha.

What nearly everyone accepts is that increasing atmospheric C02 will increase atmospheric temperatures --> 'warm the earth'. Some people think this is a good thing, some people think this is a bad thing.

The theory that is not universally accepted is what is better described as Catastrophic Anthropogenic Global Warming ( CAGW )- which posits that the human-caused rise in atmospheric CO2 will cause catastrophes of various kinds over widely differing time spans. Both the specific catastrophes and the timing depend on the flavor of your CAGW theorist. It is in reality made up of a number of related hypotheses about the relationship between earth's climate and various proposed ideas about the climate's future response to increasing CO2 and the earth's climatic response to any resulting increasing in temperatures.

It is the CAGW theory that is generally under discussion when refuted and which is most often called 'just a theory'. It would be more correct referred to as 'a collection of as-yet-unproven hypotheses'.

By Kip Hansen (not verified) on 17 Jun 2011 #permalink

Global warming alarmist abandoned the scientific method a long time ago. Your analogy is amusing, and your logic is faulty. Please read Hawkings 'The Grand Design' and you might see the joke. There are so many problems with your statement, on so many different levels, (as you can read in the comments above) that I wouldn't know where to begin. Your statement reads like propaganda rather than a thoughtful article.

"You'll tell them, yes, it is the best theory. In science, that's as close as we ever get to certainty and the truth. The better we understand and test it, the more compelling, valid, and powerful it gets. And when that happens, we can learn from it, find and identify if there's a problem, and try to deal with it. "

This definitely works for Evolution and natural selection.
There are holes in darwin's theory, but so far it is the best theory around.

It is not quite so good with Global Warming.
You see, you are not allowed to try to DISPROVE global warming.
And that is the primary requirement of a theory.
It must be disprovable!

If you are not allowed to TRY to disprove it. It is no longer a theory, or science.

Evolution's defenders sometimes cross that line ( read the Pennsylvania decision -- seriously the judge said any attempt to disprove Evolution was by definiton illegal ) but not always, not even usually.

Global Warming's proponents do not just cross the line they jump two feet over.
remember Mr. mann's reasoning for not showing the "hockey stick" data?
( paraphrased )
"All that would do is give people who want to tear down this work information to do so. There is no need for independent verification and replication of my work by anyone who agrees with me."
( We also know now that ANY random set of data put into Dr. mann's algorithm produces a hockey stick -- thus the hockey stick is no longer even mentioned in polite society ).

Simple test -- if the author were to say he has doubts about climate change science, but that those doubts could be used to IMPROVE the theory.
Would he get nods of approval?
Or fired?

My bet?
Fired. Even if he has tenure.

By chromehawk (not verified) on 17 Jun 2011 #permalink

Doesn't this mean we should see a nice spot at the center of the eclipsed moon, on those occasions when it does pass through the center of earth's shadow?
Posted by: Nathan Myers

wow â the science ignorati are plenty in this post. Big Bang denial, global warming denial - all without any sign they can do anything past spell the topics (par for their course).

As velocity (distance/time) approaches infinity distance approaches infinity and/or time approaches zero. An assumed ultimate velocity implies an assumed maximum distance over an assumed minimal time. Our observed velocity for the speed of light in a vacuum (the fastest thing we observe) is commonly expressed as 186,000 miles per second.

Our convention is that units of distance are fixed entities while Einstein has taught us that units of time are not fixed entities but are variable depending upon gravity and velocity. As velocity increases, it is usual to assume that some distance has changed over some time, however, it may just as well be true that velocity is generated by time that decreases regardless of any change in distance. Well, that's the theory anyway... perhaps a shifty one.

Uncle Jim:

To ask what happened before the beginning of the universe is a meaningless question, akin to asking what is South of the South Pole.

So Global Warming is a theory that makes predictions. How have those predictions panned out?

Let's see, in 1965 the Warmists told us that temps would be 7 degrees higher by the year 2000 and New York and DC would be under water. In 1988, James Hansen predicted 3 different temperature scenarios, and temps have most closely followed his "null hypothesis" curve. In 2005 Al Gore told us that we would see more frequent and more powerful hurricane slamming into the US. Instead, cyclonic energy has plummeted to 30+ year lows.

Theories are only useful when the predictions they make actually happen. For the 5 examples you make here, there were hundreds more theories that were proposed, but failed to predict reality, so they were discarded. Global Warming doesn't fit into this definition, and is actually more of a religious faith than anything.


You use a lot of passive sentence structure to avoid identifying who precisely disallows counter arguments against Global Climate Change. A sure sign of conspiratorial paranoia.

The reality is that many HAVE challenged Global Climate Change, and those challenges have been refuted. But since the deniers dislike that outcome, it becomes a conspiracy to silence them. It is functionally the same to Lunar Landing Denialists...when shown evidence to refute their claims, they invoke conspiracy and retreat into victim mode as misunderstood geniuses.

"It is not quite so good with Global Warming.
You see, you are not allowed to try to DISPROVE global warming.
And that is the primary requirement of a theory.
It must be disprovable!"

The mere possibility of being called a poopy-head in polite company is enough to cower even the greatest of conservative minds. Is this what you are trying to say?

By gocart mozart (not verified) on 18 Jun 2011 #permalink

In simple terms:

A "fact" = a measurement.

A "hypothesis" = a prediction about the outcome of one or more measurements.

Hypotheses are not "proven." They are either "supported" by facts, or they are "falsified" by facts. "Proof" = always true, as in logical proofs in mathematics. You can collect plenty of facts to support a hypothesis, but unless you are doing math or logic, you can't say with absolute (100.00%) certainty that no one will ever find a contrary fact. You can quantify your degree of certainty statistically, to conclude for example that there is only 1 chance in (some large number) that your hypothesis is incorrect. In any case, it only takes one verifiable fact that contradicts your hypothesis to "falsify" it, demonstrating that it is not correct.

A "theory" = a statement about the outcome of a number of hypotheses. Usually but not always, theories develop from supported hypotheses. They give rise to more hypotheses that can be tested. The more of the latter hypotheses that are supported, the stronger the support for the overall theory. The most powerful theories in science are those that provide the most comprehensive explanations for observed results, and those that generate the largest numbers of hypotheses that are subsequently supported.


Now about climate change.

Either the climate is changing or it is not. Either human activity changes the climate or it does not. In addition to the question of science is the question of policy: what do we do about this?

The key question to ask is, "what if you're wrong?"

If climate change proponents are right, we need to build a new energy infrastructure, and doing so will avert disaster.

If climate change proponents are wrong, we build it and it turns out to have been unnecessary. However it will also have produced an enormous amount of new business activity, jobs, and prosperity.

If climate change deniers are right, we don't need to do anything in particular, just keep going along with business as usual, because there is no disaster to avert.

If climate change deniers are wrong, we do nothing and get hit by disasters of large magnitude.

So: where's the upside and where's the downside? Build something that in the end we don't need? Or fail to build something that would have averted disaster?

And shall we apply the same reasoning to fire escapes and storm cellars?

"If climate change proponents are right, we need to build a new energy infrastructure, and doing so will avert disaster.

If climate change proponents are wrong, we build it and it turns out to have been unnecessary. However it will also have produced an enormous amount of new business activity, jobs, and prosperity."

Or, we slaughter a bunch of camels, dump a few trillion into third world countries for "carbon credits" which Al Gore takes a healthy slice of, we spend literally decades doing this nonsense while we all "wait and see" if the hypothesis pans out.

Is that science? It sure doesn't sound like it. Try suggesting a multi-trillion dollar experiment that takes decades to reach an uncertain outcome, which may turn out to be of absolutely no benefit to humanity, and see how soon it gets funded.

It actually sounds a lot more like those billboards telling us the Rapture is upon us. If they're right and you sent a few thousand dollars to the right preacher you go to heaven. If not, you're out a few thousand dollars but life goes on.

kc, your comments are stupid all the way through, but the comment about Al Gore is pure crank gold.

A question for the climate naysayers in this thread:

What evidence would it take to convince you that human activity is causing the climate to change?

By Journalmalist (not verified) on 19 Jun 2011 #permalink

Nice article, shame about the linkage to global warming at the end.

It is ironic that you follow this up with a nice post about Heisenberg and uncertainty. There is a limit to our ability to understand climate as well, due to two well understood and evidenced scientific issues. These are: (1) that any prediction of climate is an initial condition problem (i.e., it exhibits exponential divergence with respect to initial conditions), and (2) the Hurst-Kolmogorov dynamics within the system, which fundamentally limits our ability to interpret climatic changes on a range of different scales.

Unfortunately, when you account for these two factors, you find out that what many scientists thought they knew about climate just ain't so. As Al would be quick to remind us.

Hopefully, this also answers Journalmalists' question. Evidence of climate change must be tested against the true uncertainty of climate system behaviour, which is governed by the limits described above. If compelling evidence (as opposed to hand-waving or incompetently applied statistics) can be found either showing a way around the limits above, or that a change exceeds the limits above, then that would constitute evidence I would accept. Of course, on this issue, I speak for myself only, not others.

"Human activity"???

That is a loaded term. Do you even understand WHY the Warmists use the term "human activity"?

It's because they have NOT been able to link CO2 emissions to any rise in temperatures. If they did, they would just say carbon emissions, but they can't.

So instead they use "human activity". It's a nonsensical term. The science equivalent of "God did it". Why is the sky blue? God did it. Why is the globe warming? Human activity. In both cases the person offering the explanation doesn't understand the REAL explanation, so they make up a catch-all term that's not refutable.

Again, it's more religion than science at this point. And by the way, you're asking exactly the WRONG question. Nothing in science can be proven, which is why a true scientist tries to refute their hypothesis. If global warming were truly a scientific endeavor, its adherents would be asking what it would take to change their minds and refute their own hypothesis, not make up irrefutable nonsensical terms then demand others refute them.

I would beg to differ, when you suggest that Human activity is (in effect)a straw-man/not interlinked.

From what I have studied there are lots of ways we change our climate (for good or ill)as a little known example, for three days after the 911 tragedy, a no fly zone was instituted across North America, during these three days the pan evaporation rate significantly increased, this increase was blatantly due to lack of air traffic byproducts in the atmosphere, whether that is good or bad is not the issue, the issue is, we do have an effect on our environment.

We live in a system that changes all by itself, though just like any other system our actions are relevant, there are a lot of us and we all strive to produce in one way or another, surly you can see that the Earth system is a dynamic system with lots of inputs and lots of outputs.

By Sphere Coupler (not verified) on 19 Jun 2011 #permalink

Of course we're affecting the environment. But to say that "human activity" is the problem means that NON-activity is the solution. Do Warmists want to throw us back to the stone age, just in case?

No, they don't say that. They just want CARBON taxes. If carbon was the problem, carbon taxes might be part of the solution. But if carbon is not and cannot be linked to global warming, why bother taxing it unless you have an ulterior motive?

It's a shell game. They know their goal, and they're trying to massage the science to get there. Since that has failed, they are now changing strategy by telling everyone that the science is settled so they don't look at it too closely, then they move the goalposts. No link between carbon and temperature? Call it "human activity". No warming in the last 10 years, call it "climate change" or "global weirding" or whatever other non-refutable term they pull out of their rectum.

No thanks.

@Spence, Re "Hopefully, this also answers Journalmalists' question."

I gather that your answer is that issue is too complex to adequately make testable predictions? To say that the evidence needs to be "compelling" as opposed to "hand-waving" is itself a form of hand-waving, innit? More accurately, it is a tautology, since I'm asking what the compelling evidence could be. You seem to think it is unattainable. Shall we give up on trying to know whether anthropogenic activity is driving climate change?

@KC : I could be wrong, but this doesn't seem like the right blog for you. However, I persevere. Since in your view I've asked "exactly the WRONG question", perhaps I can reword it just for you: What evidence would it take for you to falsify your hypothesis, that the tens of thousands of climate scientists are in on a global conspiracy to instill CARBON taxes?

P.S. The plural of hypothesis is "hypotheses," and "global warming" (sic) is not a "scientific endeavor."

By Journalmalist (not verified) on 20 Jun 2011 #permalink

So, kc, what is your scientific/mathematical/statistical backgound? I want to know what training you've had that gives you the ability to understand the studies and conclude that they are bogus.

I gather that your answer is that issue is too complex to adequately make testable predictions?

Ermm... no, you gather wrongly. I did not intend to say that, although blog comments are often written quickly and may contain errors, so I double checked my comment to make sure it was reasonably clear and what I intended to say.

On re-reading, I can safely say that nobody reasonably knowledgeable about data analysis would conclude what you wrote from my comment.

If you want to make up arguments yourself, and then argue against them, be my guest. It's a free internet. I would be most grateful if you did not attribute claims to me that I clearly did not make.

You then ask a more relevant question about what constitutes compelling evidence. It is true that required levels of evidence are, to some degree, subjective and vary from discipline to discipline, and from person to person. For example, in particle physics, a 2-sigma result is generally considered poor, a 3-sigma result as interesting (perhaps "evidence") and 5-sigma is the standard for declaring a discovery (perhaps compelling evidence). Comparatively, double-blinded clinical trials may consider 2-sigma or 3-sigma to be sufficient to declare a result.

As another example, a homeopathic practitioner may present a range of anecdotal examples of people who got better under their care as a form of "evidence". This evidence is very weak and not compelling, because the individuals are not objectively sampled, and many people can recovery from illness without any intervention; without a proper control and significance test, the evidence is not compelling. You could use other words as well (e.g. the evidence is not credible).

I have already laid out in my above post the issues I feel need to be addressed for me personally to be convinced. This is inevitably subjective and varies from person to person, but this is what you asked for, and I answered. My expectations are reasonable, and such analyses are tractable (although not trivial).

The rest of your post then continues the straw man you started from the beginning and requires no further response from me.

Why is this thread? My guess is because the thought that what science says should drive policy is interesting. But what parts of policy? Perhaps if that were discussed it would all be clearer, whether evolution (a well-validated set of explanations for facts, but as far as I know NOT viewed as a source of compelling reasons for major economic decisions), or climate change is the topic.

I'm pretty sure that climate does vary and that many human activities including combustion have some causal affect on what changes, in what direction, when, and how quickly. I'm not persuaded that what is really going on or likely to go on is as yet particularly well understood. But I am convinced that we are doing some things likely to produce noticeable affects and not necessarily pleasant ones.

When and if climate is better understood we may have a better idea of what affects might occur and with what severity. And surely there will be some progress on what we might do to mitigate either the effects themselves or the suspected human activities, and that improved mitigation would entail decreasing levels of uncertainty inconvenience and cost, as knowledge is gained.

Now what about policy. Since the issues involve pervasive activities its clear change might entail considerable inconvenience uncertainty and cost. If we can learn how better to gauge and compare what we think we know of the costs and benefits of current policy with those of alternatives, perhaps we can better decide whether any alternative is preferable, and if so, which one(s).

There doesnât seem to be much discussion about this.
Partisans of change argue that possibly dramatic projections justify dramatic action, and stop there. Opponents of change argue that possible dramatic costs of change justify doing nothing and risking unknown but arguably significant consequences, and stop there. Some say Bangladesh or New York City might be destroyed, which would be noticeable at best if true, and call for anything that can be imagined to be imposed. Others say that commanding the entire world to change its economy and to redistribute its wealth and power is being proposed, a scary thought at best, and call for the whole subject to be ignored.

Few provide any reasonable analysis of causes, affects, benefits, costs, and the choices to be traded off. Iâm not sure science can speak to what choices should be made, but I would hope that those interested in the issue would work to lay out the facts as they see them about these costs and benefits.

By john werneken (not verified) on 20 Jun 2011 #permalink

I always love the Global Warming Pascal's Wager.

"In re-reading, I can safely say that nobody reasonably knowledgeable about data analysis would conclude what you wrote from my comment."

My goodness Spence but you are a blowhard. You write like a high school student who is not nearly as precocious as he pretends to be, and then you whine like a child when you're misunderstood by native speakers of English.

Meanwhile, upon rereading your idiotic drivel, I find your "answer" to my question is exactly what I thought it was the first time. Do you really fool your teachers with this word salad?

By Journalmalist (not verified) on 22 Jun 2011 #permalink

So... I'm discussing sensitivity to initial conditions and Hurst-Kolmogorov dynamics, your otherwise content-free post refers to mine as "idiotic drivel", and you think I'm the blowhard!?!?

Sure. When you're finished throwing your toys out of the pram, let me know when you're ready to talk science.

Spence, quick question;

Regarding the Hurst-Kolmogorov dynamics in generating a model, do you consider Human activity forced or emergent, or does it depend on the individual circumstance?...just wondering.

By Sphere Coupler (not verified) on 22 Jun 2011 #permalink

Let me give my 3 cents

1 cent
Focus on slinging insults; means out of focus on new understanding.

2 cent
The prehistoric oxygen levels rose to 35% due to the first plants.

The emergence of land animals reduced the oxygen level to the 21% of today.

The Earth (land, sea and atmosphere) is vastly different due to human activity. But does that changed atmosphere mean global warming this 21st century?

3 cents
Yes, global warming is a best working scientific hypothesis. But humans self interest until a crisis is at hand (financial or environmental) is also a best working hypothesis.

Thus, the global warming political debate will continue until the Colorado River runs dry; New York City is surrounded by dikes; and the Everglades is reclaimed by the sea.

But the scientific world is very open to a well reasoned alternative hypothesis.

By AngelGabriel (not verified) on 22 Jun 2011 #permalink

Meanwhile, James Hansen is now in hot water for having accepted millions of dollars in cash and "pro-bono" legal advice from the environmentalists and George Soros.

Climate change science is now "too big to fail". It's crumbling due to an utter lack of foundation, but the political and environmental classes are propping it up at all costs.

The feral camel slaughter for carbon credits is still planned, and Chairman Mao, er I mean Al Gore is telling women to have fewer kids.

Again, as I said in my very first post here, the Theory is only as good as the predictions. In this case, it's hogwash because none of the predictions have panned out. Any self-respecting scientist would have abandoned it long ago. But because there is an ulterior motive, post-hoc hand waving is used to try to whitewash the failures. Nobody has attempted to address that, as usual.

Sphere Coupler - thanks for the thoughtful question. I will offer a slightly rambling response - being a blog comment, I haven't spent to much time drafting it, so my apologies if the answer is not as clear as it could be.

In terms of the modelling, I would say we need to set up the modelling to answer the exam question. My assumption is that the exam question would be posed something like this: "Are humans having a discernable effect on the earth's climate?"

What is a discernable effect? Well, it could mean a number of things. But to get us started, how about we define it as a change in the population mean of the global average temperature.

To test this, I would propose the Hurst-Kolmogorov (H-K)dynamics be used to capture the natural variability of the climate only. Any exogenous components (e.g. human activity) would need to be represented as a forcing, rather than an emergent property.

In this example, we would seek to determine whether (1) the consequence of the human forcing would be expected to exceed the natural variability* and (2) whether such a change in the population mean would be detectable against a background of H-K natural variability.

Incidentally, detecting a change in the population mean (equilibrium value, if you like) is just one way of detecting change; there are others. Furthermore, for a complex system such as climate, particularly a system which exhibits H-K dynamics, it may not be the best approach for detecting change.

So, with that background, I'd like to return to your question. Human activity is not an emergent property of H-K dynamics. (H-K dynamics could be an emergent property of human activity... but that is a whole other question!). In testing what we understand about climate using a model containing H-K dynamics, I believe at present this is best achieved using human activity as an exogenous forcing.

I hope the above makes some sense!

* For this, we could use other models, whether it be a simple Arrhenius-like model for radiative effect of CO2, a more complex model such as a GCM, or perhaps even regional model to assess the consequences of regional climate influences, such as irrigation schemes, deforestation etc. This would effectively form the model under test.

Again kc, other than the ability to read a press release, what actual knowledge do you have in any of the relevant areas?

Nathan Myers wrote: Doesn't this mean we should see a nice spot at the center of the eclipsed moon, on those occasions when it does pass through the center of earth's shadow?

Answer: Yes, if the Sun were a point source we would see Poisson's spot. But, it is an extended source. Hence, there is a continuum of Poisson spots at slightly different locations and therefore the spot gets lost in the blur.

Regarding climate change, any mathematically/statistically literate person can grab unedited daily temperature data from the NOAA website and do there own analysis. I did. I grabbed 55 years of data from a single weather station here in NJ. I made a regression model that accounts for three things: (1) seasonal variations, (2) variations due to the solar cycle, and (3) a linear trend. My model correctly detected the period and the phase (i.e, date of minimum) of the solar cycle. It also gave a linear trend of +3.6 degrees Fahrenheit per century. I then repeated the analysis for about 2000 sites distributed all over the world. Details can be found here...

I invite everyone here to do the computations yourselves. You can then come to your own conclusions.

According to NASA and other sources, CO2 accounts for 20% of the direct greenhouse effect, but controls (like a thermostat dial) up to 80% of total radiative forcing. Even though its concentration (0.04%) in the atmosphere seems small to laymen, it's a major greenhouse gas.

So, why would any sane, rational person claim that a species capable of raising CO2 from 280 ppm to 400 ppm (a huge relative increase since 1850) is somehow incapable of causing that gas to trap even more heat?

Also, those who insist CO2 is merely a "trace gas" need to ask themselves if the absence of CO2 (i.e. 0.00%) would not turn the Earth into a refrigerator, incapable of supporting most species. Studies have shown it would do exactly that. The point is, you can't have it both ways with the "CO2 is benign" argument. It either trap heat or it doesn't.

And it doesn't matter, in today's context, whether CO2 increased for non-anthropogenic reasons in ancient epochs. We are here and it is NOW. Dump your Creationist tax-paranoia ideology and deal with the evidence.