|
Post by drkstrong on Oct 31, 2014 23:57:23 GMT
"dk: I agreed with your math etc till you stated 100 meters to 50 meters. I read a lot, and I have never come across that number/statement. Can you back that one up please?"
It is simple radiative transfer: If at 400 ppm the IR mean free path is about 50 M then when the concentration of CO2 was 43% lower, the MFP would be 50/(1-0.43) = 88 meters (or "nearly 100 meters" which is what I said).
|
|
|
Post by drkstrong on Nov 1, 2014 0:17:37 GMT
"Using the estimated 7 years for the average time a CO2 molecule stays in the atmosphere before being reabsorbed by the surface "
Sorry wrong: "The lifetime in the air of CO2, the most significant man-made greenhouse gas, is probably the most difficult to determine, because there are several processes that remove carbon dioxide from the atmosphere. Between 65% and 80% of CO2 released into the air dissolves into the ocean over a period of 20–200 years. The rest is removed by slower processes that take up to several hundreds of thousands of years, including chemical weathering and rock formation. This means that once in the atmosphere, carbon dioxide can continue to affect climate for thousands of years." (source The Guardian)
The problem here is the difference between "turnover time" and "residency time". The turnover time is quite short and is defined as the ratio of the size of the atmospheric reservoir compared to the rate of absorption. If you do that sum the turnover time is 5-7 years.
But that is not what causes global warming, it is how long the excess CO2 remains in the atmosphere. At the moment we are adding 12 GT per year to the atmosphere. So how long will it take for the current excess of about 120 ppm to be absorbed by the land and the ocean (assuming we stop adding to it)? The answer to that is 200 to 2000 years depending on which processes dominate. The thing that is slowing the absorption of the CO2 is transport of the dissolved CO2 into the deep ocean.
|
|
|
Post by sigurdur on Nov 1, 2014 1:23:17 GMT
"dk: I agreed with your math etc till you stated 100 meters to 50 meters. I read a lot, and I have never come across that number/statement. Can you back that one up please?" It is simple radiative transfer: If at 400 ppm the IR mean free path is about 50 M then when the concentration of CO2 was 43% lower, the MFP would be 50/(1-0.43) = 88 meters (or "nearly 100 meters" which is what I said). drkstrong: Your numbers are skewed. 1. CO2 was approx. 27% lower prior to the industrial revolution. That number 292 is subject to question, as stoma proxy data shows a much larger variation in CO2. But for this I will use 27% lower. 2. I don't know what the IR free path is at 400ppmv. Do you have research showing it is only 50M? I do know that the free path will vary with altitude, as over 90% of CO2 is in the lower 5,000ft of atmosphere as measured. When CO2 is present in that lower atmosphere, it is pretty much useless as a GHG. Water vapor trumps any effectiveness in regards to IR transmission.
|
|
|
Post by sigurdur on Nov 1, 2014 1:25:32 GMT
"Using the estimated 7 years for the average time a CO2 molecule stays in the atmosphere before being reabsorbed by the surface " Sorry wrong: "The lifetime in the air of CO2, the most significant man-made greenhouse gas, is probably the most difficult to determine, because there are several processes that remove carbon dioxide from the atmosphere. Between 65% and 80% of CO2 released into the air dissolves into the ocean over a period of 20–200 years. The rest is removed by slower processes that take up to several hundreds of thousands of years, including chemical weathering and rock formation. This means that once in the atmosphere, carbon dioxide can continue to affect climate for thousands of years." (source The Guardian) The problem here is the difference between "turnover time" and "residency time". The turnover time is quite short and is defined as the ratio of the size of the atmospheric reservoir compared to the rate of absorption. If you do that sum the turnover time is 5-7 years. But that is not what causes global warming, it is how long the excess CO2 remains in the atmosphere. At the moment we are adding 12 GT per year to the atmosphere. So how long will it take for the current excess of about 120 ppm to be absorbed by the land and the ocean (assuming we stop adding to it)? The answer to that is 200 to 2000 years depending on which processes dominate. The thing that is slowing the absorption of the CO2 is transport of the dissolved CO2 into the deep ocean. drkstrong: 1st off, the Guardian is totally wrong. That statement about CO2 sounds like something from Nuticelli, who wouldn't know a fact if it hit him squarely between the eyeballs. He makes up more stuff than you can shake a stick at, and it is a very large stick.
|
|
|
Post by sigurdur on Nov 1, 2014 1:28:44 GMT
Stoma proxy data has demonstrated LARGE fluctuations in CO2 levels in the past. I am talking 100's of PPMV over a 100 year period. Ice core data is somewhat useful to describe CO2 concentrations of 1,000's of years, but totally useless in demonstrating CO2 levels over short periods of time. CO2 diffuses in ice, and the rate of diffusion is one of the large problems with definitive levels of CO2 over short periods of time.
|
|
|
Post by drkstrong on Nov 1, 2014 17:53:22 GMT
" CO2 was approx. 27% lower prior to the industrial revolution. That number 292 is subject to question, as stoma proxy data shows a much larger variation in CO2. But for this I will use 27% lower."
The Stoma data has major problems. First they are not a direct measurement as the ice cores are. Second the results from stoma vary wildly from author to author for the same period of time. Some show values higher than the ice cores, some lower. You have chosen just the higher ones. Thirdly experiments show that the stoma values are not just dependent on the CO2 level but also soil moisture levels so unless you can somehow reconstruct the soil moisture levels at the time it introduces a huge uncertainty in their measurement of atmospheric CO2. This accounts particularly for the sudden changes in the stoma values. When you put those error bars (~30%) on the stoma data they are consistent with the ice core results.
How can 290 increasing to 400 be 27% ... even if I were to accept your figures, it represents a 37% increase!
"When CO2 is present in that lower atmosphere, it is pretty much useless as a GHG. Water vapor trumps any effectiveness in regards to IR transmission."
CO2 is present throughout the atmosphere. WV is highly variable as a function of altitude, location, and time. The same is not so true of CO2 because it remains around for so long it gets thoroughly mixed. What you don't seem to be getting is that with out CO2 and the other GHGs there would be no water vapour in the atmosphere. The amount of WV is dependent on the temperature. Remove CO2 et al. and the temperature falls. The WV content falls and the temperature drops a lot more. In a few days you end up with an ice planet. The role of WV is to magnify the increases or decreases in temperature caused by the changes in atmospheric composition.
The other experiment is to remove all the WV. What happens? The temperature drops but with the GHGs still in place the WV levels return in a few days.
|
|
|
Post by sigurdur on Nov 1, 2014 19:00:05 GMT
drkstrong: You are making a common error in using percentages. You take the percentage of the final value, which in this case we will use 400ppmv. 27% of 400=108. Subtract that from the 400 and you will get 292. The percentage increase from 292 to 400 is 27%. Remember, you can never go over 100% when accurately using percentages. Don't feel bad, it is a very common mistake. 200% of a number, any number would result in a negative value.
drk: NO...NO....NO....CO2 is NOT well mixed. The predominance of current CO2 is in the 1st 5,000 ft of the atmosphere. And when CO2 and H20 are side by side, which they are in the lower atmosphere, H2O totally trumps any radiative function of CO2. This is another common mistake by those who have not read the actual measurements via drone/plane etc.
The planetary boundary layer holds over 1/2 of the total CO2 in the atmosphere.
The only place in our atmosphere that CO2 truly has a blanket effect is above approx. 55,000'. There is a slight effect in the strat, but part of the strat is warm and has H2O vapor in it. Hence the 55,000' and above notation.
|
|
|
Post by sigurdur on Nov 1, 2014 19:16:04 GMT
|
|
|
Post by sigurdur on Nov 1, 2014 19:17:30 GMT
drk: Yes, soil moisture etc has an effect on stoma. But the single largest effect over time is the level of CO2 in the atmosphere.
|
|
|
Post by nautonnier on Nov 2, 2014 7:48:22 GMT
"Using the estimated 7 years for the average time a CO2 molecule stays in the atmosphere before being reabsorbed by the surface " Sorry wrong: "The lifetime in the air of CO2, the most significant man-made greenhouse gas, is probably the most difficult to determine, because there are several processes that remove carbon dioxide from the atmosphere. Between 65% and 80% of CO2 released into the air dissolves into the ocean over a period of 20–200 years. The rest is removed by slower processes that take up to several hundreds of thousands of years, including chemical weathering and rock formation. This means that once in the atmosphere, carbon dioxide can continue to affect climate for thousands of years." (source The Guardian) The problem here is the difference between "turnover time" and "residency time". The turnover time is quite short and is defined as the ratio of the size of the atmospheric reservoir compared to the rate of absorption. If you do that sum the turnover time is 5-7 years. But that is not what causes global warming, it is how long the excess CO2 remains in the atmosphere. At the moment we are adding 12 GT per year to the atmosphere. So how long will it take for the current excess of about 120 ppm to be absorbed by the land and the ocean (assuming we stop adding to it)? The answer to that is 200 to 2000 years depending on which processes dominate. The thing that is slowing the absorption of the CO2 is transport of the dissolved CO2 into the deep ocean. You are making the surprisingly common error of assuming a finite and fixed CO2 absorption rate. So saying we are adding 12GT per year how long will it take to disappear is meaningless if the absorption rate can vary by far more than that amount, which it does. If you look at graphs of CO2 concentration you will see huge variances during a year. This shows the variance in absorption over a year is more than all sources of CO2 outputas the PPM drops. There is a background increase which is more than human caused emissions, and is due to outgassing from the oceans due Henry's Law. As the oceans cool the rate of rise of CO2 will eventually reduce. Not that it matters anyway as CO2 has historically not shown any causal relationship to atmospheric temperature. Indeed, over geological time periods, rises in CO2 have show a centuries long lag to warming temperatures which is what one would expect with outgassing from upwelling thermohaline currents.
|
|
|
Post by drkstrong on Nov 2, 2014 15:06:56 GMT
"This shows the variance in absorption over a year is more than all sources of CO2 outputs the PPM drops. There is a background increase which is more than human caused emissions, and is due to outgassing from the oceans due Henry's Law. As the oceans cool the rate of rise of CO2 will eventually reduce."
The variation you see here is the planet breathing - as the northern hemisphere has more land than the south so there are more plants and animals to absorb CO2 during the N. summer months so the global level of CO2 drops. As they die and return CO2 to the atmosphere the level goes back up. The overall trend is the additional CO2 we are adding.
The oceans cannot be "outgassing" to cause the trend as they are absorbing more CO2 then they release at the moment that is why the pH of the oceans is decreasing (i.e., acidifying).
I think you need to look up and try to understand Henry's law (and not the interpretation of it in WUWT or the like). It states that the amount of gas absorbed in a liquid IN EQUALIBRIUM and AT CONSTANT TEMPARTURE is proportional to the partial pressure of the gas above that liquid. I.e. the more say CO2 above the oceans the more they will absorb at a given temperature.
But neither of those provisos are true. The oceans are not in equilibrium nor are they at constant temperature. They would only out gas (and not because of Henry's law) if the water is saturated with dissolved CO2 and then temperature goes up. The oceans are nowhere near saturated with CO2.
|
|
|
Post by drkstrong on Nov 2, 2014 15:30:15 GMT
"You are making a common error in using percentages. You take the percentage of the final value, which in this case we will use 400ppmv. 27% of 400=108. Subtract that from the 400 and you will get 292. The percentage increase from 292 to 400 is 27%. Remember, you can never go over 100% when accurately using percentages. Don't feel bad, it is a very common mistake. 200% of a number, any number would result in a negative value."
Sorry you are completely wrong on this. We are talking the percentage increase over preindustrial levels. Thus you divide by the starting value.
Simple example: I have $100 in my bank account. I win $100 in the lottery and put it in the bank. So now it has $200 in it. That is a 100% increase in my bank assets. According to your approach it is only a 50% increase which is nonsense.
"drk: NO...NO....NO....CO2 is NOT well mixed. The predominance of current CO2 is in the 1st 5,000 ft of the atmosphere. "
In a 2011 paper by Foucher et al they measured the concentration of CO2 at 10Km (30000 ft) in 2008. It was 388 ppm. The surface measurement at the same time was 391 pmm so a less than 1% difference and within the stated uncertainty of the measurements. That is just one example, there are many more. So, yes, well mixed.
|
|
|
Post by hrizzo on Nov 2, 2014 16:41:55 GMT
drkstrong wrote: "The oceans cannot be "outgassing" to cause the trend as they are absorbing more CO2 then they release at the moment that is why the pH of the oceans is decreasing (i.e., acidifying)."New paper finds the oceans are a net source of CO2 to the atmospherehockeyschtick.blogspot.com.es/2013/09/new-paper-finds-oceans-are-net-source.html A new paper published in Global Biogeochemical Cycles proposes large revisions to the ocean carbon cycle based upon observations and models, finding the global oceans act as a net source of CO2 to the atmosphere. … The authors find middle-layer carbon flux toward the ocean surface exceeds flux to the ocean depths ["subduction"] by 11 Petagrams of carbon per year, which by comparison is significantly more carbon than generated by all man-made activities [8.8 Petagrams of carbon per year]. In other words, the deep oceans naturally contribute more carbon to the middle ocean layers [between 25-150 meters deep] than produced by all of man's activities combined.
|
|
|
Post by sigurdur on Nov 2, 2014 16:48:50 GMT
"You are making a common error in using percentages. You take the percentage of the final value, which in this case we will use 400ppmv. 27% of 400=108. Subtract that from the 400 and you will get 292. The percentage increase from 292 to 400 is 27%. Remember, you can never go over 100% when accurately using percentages. Don't feel bad, it is a very common mistake. 200% of a number, any number would result in a negative value." Sorry you are completely wrong on this. We are talking the percentage increase over preindustrial levels. Thus you divide by the starting value. Simple example: I have $100 in my bank account. I win $100 in the lottery and put it in the bank. So now it has $200 in it. That is a 100% increase in my bank assets. According to your approach it is only a 50% increase which is nonsense. "drk: NO...NO....NO....CO2 is NOT well mixed. The predominance of current CO2 is in the 1st 5,000 ft of the atmosphere. " In a 2011 paper by Foucher et al they measured the concentration of CO2 at 10Km (30000 ft) in 2008. It was 388 ppm. The surface measurement at the same time was 391 pmm so a less than 1% difference and within the stated uncertainty of the measurements. That is just one example, there are many more. So, yes, well mixed. DRK: follow the link. This is the correct way to show percent change. One of the large flaws that I observe in published papers and even discussions about AGW etc is that most folks have forgotten basic stats and math and the correct utilization of such. I have always felt that before actual publication, the main author should run his papers by an educated math person so that some of these errors are corrected. A person can't be an expert in everything, and it is very worthwhile to use experts so that the output is actually a qualified output and understood by all. math.about.com/od/prealgebr1/a/percent.htm
|
|
|
Post by sigurdur on Nov 2, 2014 16:52:18 GMT
drk wrote: "The oceans cannot be "outgassing" to cause the trend as they are absorbing more CO2 then they release at the moment that is why the pH of the oceans is decreasing (i.e., acidifying)."
There is no acidifying of the oceans. The oceans are becoming closer to base, but are not in any way, shape, or form becoming acidic. You have to get below a PH of 7 to be considered acidic. Another common mistake by some folks who have forgotten basic chemistry.
|
|