Playing Devil's advocate on climate

Galteeth

It is interesting to me that this board seems to be dominated by those who (assuming the media and government hasn't lied to me) hold a minority position.

sylas

They're all just kidding, of course. You are seeing the consummate example of the whole principle of this thread.

Cheers -- Sylas -- who is of course secretly laughing up his sleeve and has massive investments in a proposed ski resort just out of San Diego.

Andre

So if the numbers make the difference, what, for instance, would be the score on evolution science versus creation believers? And what would that say about scientific merit?

Maybe that the first law of science is not to jump on bandwagons.

Anyway, this thread used to be about the real numbers. However, it seems to be modified a bit.

Skyhunter

Andre you ignore the evidence in your own links and make an on the fly speculation that poisonous chemicals of volcanic origins is as plausible an explanation as the ones offered by the links that you provided! If you want to propose an explanation then provide a link that supports it. Otherwise it is just being contrary for the sake of contrariness.

The second link you provided refutes your claim that there is, "no evidence whatsoever from the paleo records for catastrophes associated with warming".

The Traps were formed over 100's of thousands years by a magma plume. The SO_x caused glaciations while the CO₂ caused long term warming. The climate was on a seesaw.

Vulcanism was the trigger, but the hothouse climate was the primary cause of oceanic anoxia.

Human activity is altering the chemical structure of the atmosphere at a much faster rate than what occurred 250 million years ago. AGW is a radical and unprecedented experiment with the only biosphere we have. I for one am not willing to risk the planet's future and posterity on the off chance that the world's scientific community is wrong.

Galteeth

Wait, what? I understand your point, truth is not determined by consensus, but that example makes no sense to me. Creation "scientists" certainly do not ouitnumber evolutionists, unless you are defining anyone with christian type beliefs as a creationist, which probably isn't an accurate reflection of the number of people.

Andre

Creation believers would probably outnumber scientists that deal with evolution directly and that's what I intended to say. I'm only trying to encourage to take a week or two and try to understand what the core matter is and what the problems are.

Andre

That is speculation. You could just as well argue that the permanent shielding of the sun, due to the volcanic ashes, caused most live to perish. We just don't know, so everybody can project their favorite pet theories. Also because apparantly the climate principles where different then, like in the Ordovician

Skyhunter

Andre,

So you don't actually read the links you post?

You make sweeping absolute statement claiming there is "absolutely no evidence", then provide a link full of the very evidence you declared does not exist!

I would posit that you are simply being contrary for the sake of contrariness.

Saul

There is in paleo record abrupt cyclic cooling events that correlate with solar magnetic cycle changes. Humanity has not in recorded history experience an abrupt cooling event.

As the sun is moving rapidly to an unusual minimum it appears we will be able to observe which hypothesis is correct. Assuming the planet does as it did in the past abruptly cool, I am curious as to how long and what process the scientific change occur.

Based on the solar mechanism there should be an observable difference this winter.

To sylas or skyhunter: Is there any evidence that could disprove the AWG hypothesis?


http://www.sciencemag.org/cgi/conten...20/1367?ck=nck

Solar Forcing of Drought Frequency in the Maya Lowlands
David A. Hodell, Mark Brenner,1 Jason H. Curtis,1 Thomas Guilderson


http://www.essc.psu.edu/essc_web/sem...0al%202001.pdf


Persistent Solar Influence on North Atlantic Climate During the Holocene

Gerard Bond, Bernd Kromer, Juerg Beer, Raimund Muscheler, Michael N. Evans, William Showers, Sharon Hoffmann,Rusty Lotti-Bond,1 Irka Hajdas, Georges Bonani

http://geology.geoscienceworld.org/c...tract/30/5/455

Widespread evidence of 1500 yr climate variability in North America during the past 14 000 yr

vanesch

Might be, but all this has nothing to do with the question of whether (and how much) the earth is going to be warmer with man-made CO2 addition rather than without.

Now that's a funny statement. What could it mean ? On a radiation transport basis, it makes no sense.

You mean during snowball earth events ?

Even then, would you concur that with human-added CO2 to the atmosphere, that hypothetical cooling will be less than it would be without, or not ? Because that would mean that there is (relative) AGW, no ?

vanesch

There is a fundamental difficulty with these kinds of "historic" considerations, in that you only have one go. That's a bit like economic policy: you could ask: "is there any way to disprove that your employment policy has created jobs ?", because you don't have the "two runs" in which you can compare both: or you applied the policy, and, with everything else happening, you have a certain evolution of employment, or you don't apply the policy, and you have another evolution of employment. But you don't have both "at once" to compare them.

So the only way to truly find out, would be to have a very long term experiment, where humans put a lot of CO2 in the atmosphere, then where they cut back their emissions, then when they put again a lot of CO2 in the atmosphere etc... over times of thousands of years, and find out whether there is an observed correlation between the temperature evolutions and the emissions, when there have been a statistically significant number of cycles of emission and no emission, which, moreover must be uncorrelated with other climate events.

The other way is to have a consistent theoretical model based on first principles, where every part is well-checked, which makes accurate climate predictions given all inputs (like solar activity, volcanic activity, relevant human activity...) for hundreds of years, in which we can build confidence. This can be cut short by using paleo climate as test cases, but then we are confronted with the reliability, the accuracy and the completeness of the paleo climate proxies.

So it seems that in any case, we need the experimental record to continue for a few decades / centuries before we can say anything for sure about climate change. In the mean time, it's guessing, based upon one's faith in different theoretical constructions.

Saul

The planet's temperature drops 1C, due to the current solar magnetic cycle change. That will indicate the general climate modeling programs are fundamentally incorrect. The GCM do not model changes in planetary cloud cover. The feedback to an increase in forcing in the GCM is positive. In the physical world it is negative. The feedback is positive to create a knife edge respond to a change in forcing, which is required to create the glacial/interglacial cycle. In reality what is missing in the model is a massive external forcing function which explains why the glacial termination is very abrupt as is the start of glacial phase. The massive external forcing is why there are cyclic abrupt climate changes in the record.

Svensmark estimates the 20th century temperature rise was 75% due to solar. Svensmark's estimate is consistent with Palle's satellite cloud measurement and planetary albedo measurements using earthshine off of the moon to estimate changes in planetary albedo. The solar mechanism which caused the 20th century warming is electroscavenging. Solar wind bursts removed cloud forming ions. There is as noted in the above paper direct correlation of the changes in planetary temperature (up and down) to the Ak which is a measurement of the change in the geomagnetic field.

What you are missing is the magnitude of the temperature change due to AWG and details of the mechanism. The CO2 effect is logarithmic, the first CO2 has the greatest greenhouse effect. CO2 absorbs specific frequency bands. When CO2 has absorb all of the radiation at those frequencies it is saturated. The mechanism is different on Venus as Venus' atmosphere is as at 90 atmospheres. Under high pressure the quantum absorption frequency broaden. That is not true for the earth's atmosphere.

The lower atmosphere is saturated. CO2 absorbs all of the energy it can. Heat is carried higher in the atmosphere by convection and by the latent heat of evaporation of water.

Higher in the atmosphere there are increasing amounts of ions. The CO2 molecules transfer energy to the ions via collisions. The ions mass is different than CO2 hence frequency shifting the emitted photon such that CO2 cannot absorb it.

What is happening physically is not modeled correctly because the upper troposphere is not warming, based on satellite measurements. If additional CO2 did cause warming what would be observed is a steady increase in the trend line with planetary temperature oscillating about the trend line.

Saul

http://www.atmos-chem-phys.org/5/172...1721-2005.html

Analysis of the decrease in the tropical mean outgoing shortwave radiation at the top of atmosphere for the period 1984-2000

vanesch

That is a very elementary misunderstanding of the greenhouse effect, you know. When CO2 absorbs, it also emits thermal radiation. It is unfortunate that the popular explanation of the greenhouse effect concentrates on "absorption" by greenhouse gasses. They absorb, and they re-radiate. However, they re-radiate according to the temperature of the air where they are. A layer of CO2 that is at the same temperature than the surface has strictly no effect on the thermal radiation emanating from that surface, as it will emit exactly as much as it will absorb. It is only because the "last layer" is at a lower temperature than the "emitting surface" that there *seems to be* a net absorption.


Indeed, but what counts is what is re-emitted, and hence, at what altitude (and hence at what temperature) that "last emitting layer" is. As such, the fact that there is total absorption (several times over) of certain lines doesn't matter, because it also means that there is re-emission. More (evenly distributed) absorption gas simply means that the "last emitting layer" is higher up, and hence colder.

If you would have a thick layer of totally black gas, 50 meters thick, hovering over the earth's surface, that wouldn't cause any greenhouse effect at all, because that layer of gas (at the same temperature as the surface) would absorb all of the surface's radiation, but would also emit exactly the same radiation upward.

vanesch

This is possible. I hope - I have no idea - that the feedback for clouds is NOT based upon paleo climate data. In fact, I hope that none of the climate modeling uses paleo climate data AT ALL, but have models based upon observed behavior, or preferentially first principles. Maybe someone knowledgeable about this could comment here, whether paleo data are actually USED in the setup of climate models.

In the case that no paleo data are used to model any climate, it might be, or it might not be, that some external forcing is missing. I can't comment on that. But it would *still* mean that, in as much as the model is correct, the temperature with the forcing is higher with extra CO2 than without (even if the external forcing makes temperatures go down).

In other words, if the external forcing imposes, say, a 6 C decrease of temperature "as is", it would mean that with human CO2, this will then be a decrease of, say, only 4 or 5 C. That's still AGW. It is in that case just not the dominant forcing. But it is then still there.

sylas

Climate models are used in paleoclimate studies, both as a way of checking the model and as a way of testing hypotheses about causes and effect in climate in the past.

The best actual checks for a model are (IMO) with historical climate events; but checks of earlier times have value as well.

There a quite a large number of projects in which different climate models are compared to each other and to data for some time period or region, and there are lengthy reports available in the literature. See, for example, the Program for Climate Model Diagnosis and Intercomparison (PCMDI). This is mainly using comparisons over the last century.

With respect to paleoclimate studies, see the Paleoclimate Modelling Intercomparison Project (PMIP) and Paleoclimate Modelling Intercomparison Project Phase II (PMIP2).

I don't know what you mean by a climate model "using paleo climate data". Models don't use climate data for the model itself. The model is basically a representation of the physics of energy flow and so on. You use data as input to a model.

It is always the case the there may be external forcings that are overlooked. It gets pretty implausible in the present that there's a monster forcing no-one has noticed, but hey.

You don't need climate models to show that CO2 has a significant effect in the present. The thread Estimating the impact of CO2 on global mean temperature explains how this is done. The forcing from CO2 is not based on climate models.

Of course knowing that carbon dioxide is significant says nothing at all about the magnitude of contributions from other less well understood forcings. Also, even assuming a particular set of forcings, the magnitude of the climate response is still uncertain. This depends on climate sensitivity and feedback processes for which there remains considerably uncertainty.

I'm not proposing to get into debates in this thread; the irony of that would be too overwhelming. I'm just giving the links for climate model intercomparisons with each other and with climate data past and present; and a pointer to the thread where the specifics of the CO2 impact is discussed in more detail.

Cheers -- sylas

vanesch

The question was the other way around: are paleo climate data used in the models themselves, to set them up ? For instance, are paleo climate data used to estimate feedback coefficients which are then plugged into climate models ;
or is it rather the other way around (as you seem to say): are paleo data used as independent TEST SET against which to test a particular model ?
The latter would be great, the former, rather risky.

Yes, that's my question. Does one *need* paleo data, say, in some kind of neural network fit, to establish a certain kind of response, or are these models "first principles" models, using physics, chemistry and knowledge from specific fields to calculate responses ?

Because it seems that certain people here think that climate models are *inspired* by paleo data in order to predict certain quantities. If that's the case, I would find that indeed somewhat dubious.

I agree. That's what I wanted to point out: if one or other other forcing pushes us in a cooling, that by itself doesn't say anything about any AGW.