Speculation on CO2 and Climate Limits

[JohnB]

Firstly this in Speculations because that is what it is, speculation. While it is an outgrowth of my readings in Climate Science it is not directly involved in the current climate debate and doesn't effect the CO2/AGW argument. (Or at least it isn't intended to.) However I would like to put forward this idea for examination and criticism. I'm also curious if such "limits" occur in other sciences.

 

Background.

 

In this thread I likened the climate to the Drake Equation. I use this comparison to show the many different factors involved in working out the forcings that effect the global temperature. It demonstrates the many factors and could theoretically be used in climate science. By assigning a numerical value (+/- X.X⁰) one could work out the mean global temps from the factors involved. A confounding factor is of course that some factors are dependent on other factors.

 

Thinking along these lines, the global temp could be computed as: A+B+C+D+E......... where each value can be either positive or negative and D might equal 1.26xB and other variables are dependent on D. The example isn't exhaustive, but I hope you get the picture. In the thread I linked to above I said the answer had to equal .72 but it can just as easily be degrees Kelvin for absolute planetary temperature. I've been wondering that an equation, although possibly not a solvable one, might actually exist.

 

Things that are known or can be reasonably assumed.

 

Models based on the more recent paleoclimate data have been converging on around the 2.4⁰ degree mark for the doubling of CO2 and presumably this is correct. This result obviously means that there is a close relationship between CO2 concentrations and global temperatures.

 

The faint sun paradox of a much cooler sun in the distant past, yet there wasn't a snowball Earth.

 

That the Earths climate system is dominated by negative feedbacks. The proof of this is that the planet has neither frozen over or become uninhabitably hot.

 

I would now like you to look at 3 graphics.

 

This one shows global temperatures over 600 million years compared to CO2 concentrations.

 

There are two things that are obvious from this graphic (assuming it is accurate);

1/ There is no long term relationship between CO2 and temperature.

2/ The climate tends to sit at either glacial or interglacial temperatures. Either roughly 22 or 12 degrees.

 

This one shows the movement of the continental plates over the last 225 million years.

 

Comparing it to the one above we can see that there is no relationship between long term temperatures and the distribution of continents. While we can't go back further with the continental distribution, the fact remains that the planet neither froze over nor became uninhabitally hot. Nor does there seem to be a relationship between temperature and whether the oceans and seas are deep or shallow.

 

This third graphic most people have seen showing the temps over the most recent Ice Ages.

 

Note the range.

 

As I said above Climatologists working mainly from the third graphic have concluded that temps increase by 2.4 degrees per doubling of CO2. However the first graphic shows that this is not true.

 

Speculation.

 

That the Climatologists are correct, but the negative feedbacks build up and constrain the temperatures to within a defined range. Going back to the equation idea, this means that when all the temperature effects of all forcings and feedbacks are added up, the answer, the result, must lie between circa 12 and 22 degrees centigrade. Hence the 2.4 degree per doubling is correct but only holds while the temps are within the defined range, after that the relationship breaks down.

 

What I am suggesting is some overarching principle that limits the global temps on Earth to a value between these two figures. It strikes me as impossible that (looking at the third graphic) all the forcings both during the glacial and interglacial periods just happened, by pure chance, to result in temperatures so close to each other. Taking human influence out of the picture, what are the odds that the forcings at 300kBP added up to exactly the same figure as the forcings from 150k BP? And that these are the same as 225million BP? Simply not possible.

 

However, if such an overarching principle does exist then the forcings and feedbacks of 150k BP would equal the forcings and feedbacks of 150million BP. To use a rough analogy from relativity consider two objects moving towards each other. Their relative speeds can be computed (roughly) by adding the two velocities together until the answer is "c", after that the answer is still "c" no matter what the velocities are. In the same fashion all forcings and feedbacks can be added up until the temps go up to 22 degrees or down to 12 degrees.

 

It simply strikes me that either there is some overarching principle limiting the temperature of the planetary climate or all the forcings and feedbacks over the last 600 million years have "just happened" to always equal the same numbers.

 

Are there other areas of science concerning chaotic systems where the results are constrained between certain limits?

 

This constraint to temp limits appears to hold no matter how far back we go. While ever there have been large bodies of water on this planet the temps have been between these limits. Is it possible that this overarching principle is a property of planets that orbit where the triple point of water can exist? (And have above X% of the surface covered by water.) Could this mean that once a planet evolves a hydrosphere, so long as the incoming solar radiation does not vary enough to drop the planet out of the "life zone" it will continue to have a hydrosphere?

 

The next two questions are;

1/ Can the equation actually be written down as an equation? and

2/ Can it be, in reality, solved?

 

Thoughts, arguments and criticisms please.

Edited December 11, 2010 by JohnB

[granpa]

good post

 

interglacials are too short to register on a graph like that.

it is common knowledge that during most of the earths history

the poles have been not only ice free but positively balmy.

 

therefore a 3 tier system seems more likely to me.

1. glacials

2. interglacials

3. something even warmer.

 

while you are looking at feedback mechanisms

you might also ask why the atmosphere is maintained at 1 bar.

I suspect that lightening might have something to do with it.

too much atmosphere leads to too much lightening which

ionizes the air, which is then washed into the ocean and becomes locked up in rock.

 

http://en.wikipedia.org/wiki/Water_vapor#Water_vapor_and_dry_air_density_calculations_at_0.C2.B0C

 

 

http://www.angelfire.com/nj2/weatherfacts/evaporation.html

 

The capacity of air for holding water vapor depends on the temperature of the air. The warmer the air, the more water vapor it can hold. The amount of water vapor actually present in the air is called specific humidity. It is the number of grams of water vapor in one kilogram of air...The air’s capacity for holding water vapor roughly doubles for every rise in temperature of about 11 degrees Celsius. For example, a kilogram of air at 15.5 degrees Celsius can hold about 11 grams of water vapor. A kilogram of air at 26.5 degrees Celsius can hold about 22 grams. A regression equation for finding water vapor capacity of a kilogram of air in terms of its temperature is roughly .02066*X2 + .1322*X + 3.9865

 

Edited December 11, 2010 by granpa

[cypress]

Thinking along these lines, the global temp could be computed as: A+B+C+D+E......... where each value can be either positive or negative and D might equal 1.26xB and other variables are dependent on D. The example isn't exhaustive, but I hope you get the picture. In the thread I linked to above I said the answer had to equal .72 but it can just as easily be degrees Kelvin for absolute planetary temperature. I've been wondering that an equation, although possibly not a solvable one, might actually exist.

 

It does not seem to be too much of a stretch to suppose that there may be a formula of causal drivers that could describe global average temperature, though I doubt it would be as simple a form as you have proposed.

 

This one shows global temperatures over 600 million years compared to CO2 concentrations.

 

There are two things that are obvious from this graphic (assuming it is accurate);

1/ There is no long term relationship between CO2 and temperature.

2/ The climate tends to sit at either glacial or interglacial temperatures. Either roughly 22 or 12 degrees.

 

Interesting observation.

 

This third graphic most people have seen showing the temps over the most recent Ice Ages.

 

Note the range.

 

As I said above Climatologists working mainly from the third graphic have concluded that temps increase by 2.4 degrees per doubling of CO2. However the first graphic shows that this is not true.

 

Yes, One limitation of Ice core data though is that while they provide a low frequency average CO2 level over long periods of time, they greatly underestimate (by nearly 100%) variability for shorter periods of time according to Van Hoof in "Atmospheric CO2 during the 13th century AD: reconciliation of data from ice core measurements and stomatal frequency analysis." Tellus (2005). One reason may be due to diffusion of CO2 because of localized concentration gradients. This would tend to diminish the apparent magnitude of CO2 variation over time and would account for disagreement you mention.

 

 

It simply strikes me that either there is some overarching principle limiting the temperature of the planetary climate or all the forcings and feedbacks over the last 600 million years have "just happened" to always equal the same numbers.

 

It seems like an odd coincidence. Building on what you have presented thus far, one factor that could contribute the most to this proposed pinciple would be cloud cover. 100% cloud cover has the ability to cool an overheated earth very quickly while near 0% cloud cover would warm the earth very quickly (relative to geologic time). If 12 degrees centigrade represented a practical lower limit to substantial cloud formation and 22 represented the point where cloud cover increases dramatically, this might be one area of possible investigation.

 

Are there other areas of science concerning chaotic systems where the results are constrained between certain limits?

 

Yes. Flow systems that involve scaling due to pressure drop are constrained this way. Likewise systems that include phase changes are as well.

 

This constraint to temp limits appears to hold no matter how far back we go. While ever there have been large bodies of water on this planet the temps have been between these limits. Is it possible that this overarching principle is a property of planets that orbit where the triple point of water can exist? (And have above X% of the surface covered by water.) Could this mean that once a planet evolves a hydrosphere, so long as the incoming solar radiation does not vary enough to drop the planet out of the "life zone" it will continue to have a hydrosphere?

 

The fact that our weather is predicated on a system involving two phase changes and that these sorts of practical limits show up in systems involving phase changes is interesting to say the least. It seems like an area worthy of more investigation.

 

The next two questions are;

1/ Can the equation actually be written down as an equation? and

2/ Can it be, in reality, solved?

 

This is the part that I have an issue. Your form of equation seems overly simplistic and there is no good reason to chose this form just yet. I think you are onto something here but the form of your equation seems to have the weakest support.

Edited December 26, 2010 by cypress