Answers to physics quiz

[Ike]

BigDog944

No credible method exists to predict long term local climate shifts. Neither can it honestly be said that one will occur at some specific time - even to a decade one way or the other - nor can it be predicted what any such event will be. The best we can get is a guess. The use of computer models are unhelpful in reducing the potential error in such a guess, even when they are constructed to the best present knowledge of systems and how they interact and further are "fed" honest data from the real world, not the output of other GCM computer programs.

These are the basic reasons why that is so. All the various computer models are either: (1) so-called "process models" which are intended to study whether one or another particular model of one factor that is believed to cause long term climate changes has any effect in an artifical system which models one that factor holding all others constant; or, (2) weather forecasting computer models "on steroids" - so to speak - with their ranges enlarged to a global or near-global scope.

Even assuming accurate modeling and plausible real word data is being fed into a "process" model, no prediction or projection can honestly be made from any output from it. It only potentially gives some insight on how the modeled process works. This is the climate science equivalent of what economists do when they say in an econ textbook: "Assuming other variables are unchanged and equal....". This is utterly unhelpful in either guessing the future climate or planning policy for any governmental action.

When you watch the evening local news, please note that the "five-day" forecast for the fourth and fifth days changes sometimes drastically as those particular days approach. How then can we believe the claims made for the climate of the entire globe based upon the output of such a program, when the code and assumptions upon which it's basic code is founded cannot accurately forecast the local weather five days in advance?

I assume your reference to "...the loss of certain plankton species ..." is to say that certain species are now extinct? I refer you to the figures in JasonC's posts about the volume of water in the world's oceans. Now I ask you to consider how it is possible to say that an entire species is extinct, even assuming only the top - say - 10 meters (34 feet) of the vast oceans contains such life. Just as certain species of amphibians, in certain localities, have been observed to have a die-off of about 60% of their populations in recent years were widely touted as being "an extinction", there is a considerable amount of exageration on the part of some of the global warming partisans as well as on the part of the skeptics. In point of fact, a subsequent study or two determined that the frogs in that particular Central American jungle were being killed by a fungal infection imported into the area by American scientists who had been studying that population. Quite unintentionally, I'm sure, but that was the cause; not global warming, as the satellite records showed no significant changes in cloud cover or temperature there during the period of interest. (Sorry; I do go on; don't I?) The point of the frog example is that even the "extinction" where there were actual dead frogs to see was from only a 60% die-off; 40% survived and reproduced. (See if anyone mentions when the population returns to former levels.) Note that there is no mention in any of the literature of any larger animals that we can readily count or at least gain a genuinely useful survey of the numbers for; too easy to refute, I suspect. No evidence of a food chain break caused by species extinction. I'm not entirely certain that such a thing is possible; but assuming it is, no evidence.

Short response: there is no way to determine if another "Dust Bowl" as was in the American Mid and South-West in the 1920's and '30's will recur. (I note that there was no accompanying temperature increase in that period; rather a slight decline.) There is no plausible scientific mechanism to explain how climate change would or could cause another dust bowl anywhere. There is only the bald assertion of causation, without any explanation. Similarly, there is a widely-touted claim of plankton extinctions, but no evidence. Public policy decision-making cannot and should not be based upon fear-mongering. Rather it should be based upon genuine data and scientific theory, openly and honestly debated. Follow the link to realclimate.org and read some of the postings. Notice how often the posters respond to skeptics of man-caused climate change disaster with ad hominem attacks on their integrity because of the source of the skeptics' funding and their ideologies, rather than a response to the skeptics factual or theoretical contentions. Such responses are not the responses of people who believe in a particular theory based on evidence; it is the response of those who are "true believers" in some dogma. This isn't science, only mud-slinging. And, finally, such attacks can be made as easily on those who are advocates of global warming based on their ideologies and their sources of funding. Not science either; likewise only mud-slinging.

But, then, I probably do not count as being among the "thinking people".

[Physim]

I'm by no means knowledgeable on climatology, but a couple layman's observations.

Firstly climate change. There have been many periods of extreme climate change, ice core samples at the poles have shown this as have fossil records. Homo sapiens had not yet even evolved so it wasnt us who caused them.

As for extinctions, these have occurred throughout prehistory, there was the extinction aound 350 million years ago where 95% of species dissappeared, again evidence in fossil records, and of course the dinosaur extinction which was more recent. None of these were due to homo sapiens.

I don't think we have enough data on our climate, most is no more than 100 years which is a blink of an eye in climatology, to make any predictions.

The last ice age finished about 10 000 years ago, we could just be going through the normal warming cycle. Who knows?

Just my 2c worth I claim no expert knowledge in this area.

[BigDog944]

I agree Physim, we don't really know, and that has largely turned the issue into an emotional one.

However, it is getting a lot of press time down in the US at the moment, with some heavy weight media outlets coming down on the side of "We need to do something" I think. I'm not American, but it seems CNN is running a week long focus on it in the "Anderson Cooper 360" show. Could just be more wood on the fire against Bush/Chenny/Rumsfield et al., or it could be a general swaying of American public opinion on the topic.

Time will tell.

[c3k]

Egads!!

BigDog944, a LARGE body of opinion holds that the American media does NOT represent American public opinion. Rather, it (the media) represents the radical ideology of the liberal (American political usage) wing. As such, it leads opinion, shaping it, rather than reflecting it. CNN is an egregious example (as is "60 Minutes".). The Fox News Network would be the counterpoint which proves the generality.

Now, I don't want this thread to dissolve into a liberal versus conservative debate. The point of my paragraph, above, is to wave a large red "Danger" flag to highlight the vast gap between U.S. media outlets and accepted science.

Regards,

Ken

[c3k]

An on-topic question: JasonC has expostulated a model using a uniform column of water 2km in height (depth?) to represent the heat absorption dynamics of the earth. What about land mass?

Ignoring 30% (plus or minus) of the surface area of a sphere (most of which is nearer the equator than the poles, granting a larger relative proportion of the irradiated zones) is a large assumption. The land mass would create many localized hot-zones or, in the case of the polar caps, cold-zones. (Is the Sahara expanding? Does biomass have an effect? Do biological cycles extract heat? Polar albedo? Etc.)

Additionally, since the focus is on trace gas reflectivity in the atmosphere, how does the atmosphere act? Is it a heat-sink? What of the water vapor cycle? How much energy would it take to create complete cloud cover? Etc, etc.

Thanks,

Ken

[c3k]

Finally, one more thought on this. JasonC's model uses energy input and output to model temperature changes and highlight the overall robustness of the planet's heat balance. I submit the following question to perform a rough check on the model's assumptions.

What is the energy input to the system (planetary heating) of a meteorite which impacts the earth? Assume typical asteroidal body velocity, density, and a size of a few miles diameter.

My point being that the energy of that body relative to the overall energy inputs to the earth may be quite small. (I don't know. Would someone kindly do the maths? Thank you.) Yet, a widely accepted theory holds that a body such as that could have severe climatalogicol repercussions.

If the energy comparison shows the impact to be negligable - purely from a relative analysis - that would show that severe localized phenomena may have a larger impact than a generalized uniform body model would show.

(This would be the appropriate point for someone to mention chaos theory...)

Regards,

Ken

[JasonC]

Land is not going to appreciably change the temperature to any significant depth. It is hotter deep than the surface is, due to pressure etc. That creates an inner to outer temperature gradient that generally keeps net energy flowing upward. The core is very gradually cooling off, but on a scale that is well below the contribution even from radioactive elements in the crust (themselves a significant power source, actually), and much lower than solar radiation. There is also essentially no physical circulation of land bound matter into the rest of the system, which is not remotely true for the water system.

As for the atmosphere, since it is a tenuous gas at low pressure, it has vastly lower mass and therefore heat capacity than the oceans. It can't act as a heat sink of any significance.

As for the meteor example, the raw kinetic energy of a largish body moving at orbital speeds is quite high, but the pure energetics won't matter at all for a different reason. That energy is on-off, purely transient. Equilibrium temperatures are set by the power term - energy per unit time - not stock energy.

The basic physical fact is that energy wants to spread out, and light enables it to do so. To keep anything warmer than its surroundings therefore takes an ongoing input of energy continually pumping into that warmer thing, not just a one-off energy blip.

The kinetic energy of any large body - kms in diameter - moving at orbital speeds, is up in the millions to billions of megatons. Not all of it would be turned into heat energy on an impact, though - a lot of it would remain kinetic, slightly altering the earth's orbital velocity etc. But in a matter of years, any heat energy is did generate would radiate away again, since it is not a power term and can't keep adding energy per unit time.

What it might do is throw up so much dust in altered the sunlight hitting the earth, changed the planet's effective albedo, etc. Those all act not from the one-off energy deposited by the hit itself, but by altering the ongoing power terms.

In geological time scales, all the transient stuff is gone in a flash, and even the few hundred year lags represented by ocean heat sink coupling are such a flash. Geological climate deals in tens of thousands of years, to millions of years. There are important cycles at 40,000 and 100,000 year periods (whose "beats" can reinforce or offset each other) - probably do to orbital variations.

Over multiple hundred million year time scales, where the largest climatic changes are inferred from fossile records etc, practically nothing about the power terms of the system can be reliably known at present. Take the period since the Permian boundary extinction at 250 million years before present. Since then, the sun has orbited the milky way twice and gone from maximum deflection above the galactic plane to below it, and back, 4 times. Nobody has any idea how Jupiter etc has pertubed orbits over 20 million revolutions. We can't solve an n-body problem with real gravity without approximations, let alone say whether the mean orbital distance of the earth to the sun was 93 million miles with a low eccentricity for all of the past 250 million years. We have no idea of the variation in the sun's output over such time scales, either.

Over the last 100,000 years we can be a little more confident that such huge scale causes are not acting, but projecting back to time figures with 4 more zeros on them is blind guesswork. The power input could be anything, practically, and we have no idea whether any change inferred in the total power term is due to climatic factors or orbital ones or solar ones, any of it really.

On the 100,000 year time scale we see ice ages. The leading explanation for them traces the periods involved to orbital variation, especially changes to the eccentricity of the earth's orbit. Even with no net change in the gravitational potential energy of the earth over its whole orbit, you can get higher or lower integrated solar input over a year, from a more nearly circular or more elongated ellipse.

The reason is the farther portions of the orbit have lower kinetic, higher potential energy, therefore the orbital speed is lower, and in effect you "linger" at the farther points. You pick up more per unit time at the closer distances and less at the farther ones, but if you spend more time in the farther regions the net energy over the whole orbit is lower overall.

Other factors undoubtedly contribute to ice ages, including albedo changes from large continental ice sheets well down into the temperate zone, and from atmospheric composition changes, cloud cover changes, etc. There may be meaningful solar variation as well. How much each of these factors contributes is not obvious.

The standard physics can still tell us, to get 5C drops in global mean temperature you have to find changes in power terms that add up to around 20 watts per square meter. Known changes to CO2 in ice ages might contribute a tenth of that, maybe 2 tenths (pushing it and frankly unlikely), but they don't cause all of it, remotely. More likely you get 5-10 watts from solar or orbital factors and albedo changes those set off get your 5 W more, with atmospheric stuff contributing some remainder.

The original theory that ice ages were caused by changes in CO2 alone came out within 10 years of Boltzmann's founding work on radiative transfer physics. The sign was right and the idea plausible. They had no way of measuring the scale. That was about 110 years ago. Bizarrely, the central predicted change in temps has remained essentially unchanged from that time (see below for exceptions), despite much greater understanding of the physics and much more accurate measurements and data. And the error bars on the predictions haven't gotten smaller. They've grown.

In the 60s when modern climate research got off the ground, the recent data suggested cooling and people predicted new ice ages. They had no workable power budgets. It is easy enough to make fun of them, but they thought they had located the cause of ice ages and that they would still be operating. Then in the mid 70s we got vastly improved theories of long time scale orbital dynamics, and with it much more plausible explanations of 40,000 and 100,000 year periodic changes in global climate. Which tracked more minor wiggles more recently (but still on multi-century time scales - things like medieval maximum and little ice age in the early 17th century etc), as well.

As a theory of the cause of ice ages, CO2 alone was pretty well dead at that point. We then got much more accurate measurements of the actual power it could apply, which put the scale at 2 to 4 watts per square meter. Since revised by still better measurements to more like 1.5-2 watts, with 2 more likely. And that is clearly just way too small to account for 5C changes alone.

So the hunt for additional power terms was on. Albedo changes could clearly contribute on ice age time scales. More modest changes than giant continental ice sheets, though, were not going to make more than a watt or so of difference. Next clouds were the hot topic - maybe cloud cover changed by significant amounts in response to other forcings, effectively amplifying them. Physicists went and looked. The found 1% cloud cover changes with a dampening not amplifying sign.

At this point the predictions were fixed in policy pronouncements and the idea was to find the power. Skeptics said maybe it is solar variation. It was checked, not big enough. Might account for 0.5C changes in the first half of the 20th century, and can account for some periodic swings after that, but no net movement on recent time scales.

Next it was aerosols. It was known that particulates and dust e.g. from volcanic eruptions could have year-long effects, maybe there were longer ones. All classes of industrial gases were thrown in for good measure - see if other "pollutants" besides CO2 were culprits. They found after prolonged debate that aerosols recent contribution was net cooling, scale perhaps a half a watt, perhaps a watt. No power there.

This string of hunts and misses created an amusing game that I call the thermonuclear CO2 molecule theory. Whenever more power was found from some secondary cause the handwaving explanations had appealed to, naturally just chalk it up as a follow on consequence of CO2 changes supposedly "driving" that other factor. But what about when the power term found was negative, what then? Should the temperature change predictions be lowered?

Instead, the modelers reasoned as follows. Well, we have only 2W from CO2. If aerosols are contributing -1, then the net driving power is only 1W. Now here is the beauty. If the past temperature change we have observed is still +0.7C (a linear fit in noise over ~100 years), then each watt of driving power must cause 0.7C warming - "climate sensitivity" is the magic phrase for that empirical and physics-free projection. Since not all of it has probably shown up yet, make that 1.4C. And since the future new added power will be 2-4 watts, without new masking by extra aerosols, we can predict 2-4 x 1.4 = 2.8 to 5.6 C changes ahead. Ta da! Half the power, four times the prediction.

Now, I call this the thermonuclear CO2 molecule theory because if you continue the same logic, and find another -1W in the next proposed driver, wackiness ensues. The net power driving the system will then be said to be zero, up until now. The 0.7C supposedly observed change won't move. So 0 power input will produce 0.7C changes, ergo the "climate sensitity" which is their quotient must be 0.7/0, which is infinity. Ergo, the next CO2 molecule added to the atmosphere, must create an infinite temperature response. The world will explode like a supernova, because zero net power has been found to explain past warming.

It suffices to project the reasoning that way to expose the fallacy. If you can find the power for a big change in temperature, it is sensible to predict a big change in temperature. If you can't find the power, don't conclude the system is even more sensitive than you thought, but reduce the prediction. And conclude the past warming is probably smaller than you thought, or has other past drivers you are not aware of, or both.

There is another game played with allegations of scientific consensus on this matter, which plays on people's basic ignorance of the real scientific debate. Real scientists agree that warming is happening and disagree about its scale. Popular accounts report the agreement as a consensus, do not report the disagreement about its scale (or pretend that is minor or a quibble, when it is the substance), and then give the predicted scale of only one side of the scientific debate. And then pretend anyone not agreeing with that scale prediction, is some non-scientitic luddite or something.

I believe the earth is warming slightly from human causes, that CO2 is rising, that the rise is caused by human activities, that it has already had measurable effects on global mean temperature, that future CO2 changes are in the cards and will bring further increases. Every one of them items the consensus is correctly said to agree with. But I also think the past changes caused that way are scale a quarter to a half a degree C, and likely future ones are half to 1 degree C, depending on likely future CO2 concentration trajectories. And I think the chances of 3-5C warming from CO2 alone are beyond "low", I think they are at "physically impossible".

I think it possible, though not likely, that faster warming is already happening from other causes as yet unidentified, and that is a fine reason to keeping looking and to measure everything. But I am not remotely worried about 5C changes from mystery terms that nobody can even name a power source for, let alone one that has been checked and actually checked out as predicted. And I frankly think it is gross superstition of a Pascal's Wager variety to worry about it, like thinking you have to obey whoever says "boo" loudest.

But I recognize the hypothesis that larger scale warming may be happening with other as yet unlocated causes as a serious scientific position worthy of investigation. That is what the best warming advocates effectively say, because they do not dispute that CO2 greenhouse alone lacks sufficient power to cause the headline sized predictions of future temperature changes. They just think it isn't alone. I want them to show me the power, but that is a reasonable scientific discussion.

What isn't, is preying on people's physical ignorance to suggest to them that tiny changes in atmospheric composition can and will necessarily lead to massive changes in global mean temperature, and to pretend everyone who knows the subject agrees with that proposition. Or to use the fact that I agree to prior propositions - CO2 warms, is happening, human caused etc - but not that one, to pretend there is consensus about 5C rather 0.5C. There isn't. There can't be, when those saying 5C can't name the power source supposedly responsible.

When and if they do, finding a measureable and measured net new power term with sign positive and scale 20 watts, I'll be happy to stand corrected. And I'd then be happy to entertain ways to intervene in whatever that 20W power term system is, to try to regulate it and moderate large scale changes in climate.

But they haven't named it, or more accurately, the last 3-4 so named have been checked and do not produce the required power. The honest thing to do in such circumstances, it seems to me, is to revise the predictions and keep investigating.

And if I can inform even a tiny number of people about these factors, I consider it a disgrace that real scientists in the debate, regardless of their hypotheses, can't do likewise, and make clear where the debate really is. And drop the straw men about no changes or not human caused or consensus on things besides the scale, and talk about the real subject, the scale of likely temperature change and what is actually known of its sources.

One man's opinions.

[BigDog944]

Excellent essay, Jason. Thanks for sharing.

[c3k]

Ahh, allow me to poke. (Hey, it's fun...)

JasonC, where is the temperature rise being measured? It seems to me (and I could very well be misinterpreting your postings) that you keep on using the earth's oceans as the only possible heat sink. Is this so?

My earlier posting questioned a model which ignores all the land mass. Obviously, there is little land mass circulation. But the land does absorb heat. How much and how deeply and how it radiates it seems to be a non-trivial part of any model. Likewise the gaseous envelope.

My use of the meteorite impact was to show that a localized energetic event could have a much greater impact (pun!) than would seem likely. Assume every bit of a meteorite's energy is transferred as heat (no momentum transfer). How much energy is that? How does that compare to a year's worth of solar energy? Yet, that relatively minor event (my assumption, not having worked out the energy comparison) is believed to have caused a drastic climactic change.

Comments?

Regards,

Ken

[Corvidae]

How much wood could a wood chuck chuck

If wood chuck could chuck wood ,,,,,,

[JasonC]

Um, if it all converted into heat, the energy from a 10 km wide asteroid (assume earth's density, a typical orbital velocity) hit would be about like 52 days worth of the sun's energy absorbed in a short period of time.

The math - 4/3 Pi (5000 m) ^3 volume, time 5.5 density of earth gives a mass of 2.9x10^12 kg. Orbital velocity might be 40 km/sec, gives a kinetic energy of 2.3x10^21 joules. Divide that by square meters of earth surface and you get 4.5 million joules per square meter. Rather a lot, really. Divide that by seconds in a year and you get about 1/7th, or 52 days worth of sunlight. Of course, it wouldn't exactly take 52 days to be absorbed, and would instead vaporize much of what it hit.

But a few months later, the only effect would be any change in power caused by more particulate matter in the atmosphere, whiter areas covered with soot, changes to cloud formation etc.

As for land mattering, asked and answered. The net flow of heat from the land portion is upward, not downward. If there were a larger heat sink it would just slow the response, not change the equilibrium level, anyway.

As for where temperatures are measured, lots of series are used in practice. Most are land surface weather station data. Some are ocean surface measurements from bouys and the like. Some are satellite measurements of average ground temperature over wide areas of earth or ocean. There are some taken of deeper ocean. And some specifically target upper atmosphere. They all are noisy and give different results. The deep ocean stuff gives a very slight uptrend. The satellite stuff has mostly recorded no signal.

The earth ground stations report warming over the past century of 0.4 to 0.7C, depending on which series you look at. And that one has curious timing - upward well before the CO2 rise, then a plateau to slight cooling through middle years of the 20th century, then up again, with plenty of year to year variation.

Anybody who has seen the actual graphs will understand the slope of a least squares line through such bouncy data is decidely loose as a measure of what is happening. Change two or three points in the data set and the slope changes. Still positive, though some dispute even that (I don't).

[JasonC]

Finally a CM tie in! The 4.5 million joule figure (per square meter) in the previous asteroid hit calculation, is approximately the energy of a Russian 76mm or US short 75mm AP round. Does the earth have StuG front armor? (lol).

[Physim]

Very interesting posts, I dont pretend to understand everything you have written but it is food for thought and seems to back up my layman's observation that human activity does not support the level of increase postulated by doomsayers.

Thanks for an enlightening read