I agree with Mike. Much of what we know about the geologic past is based on the best possible interpretation of fragmentary evidence. While there are contexts in which the past can serve to illuminate the present, I do not think comparisons of Permian and Holocene oxygen concentrations are very useful.
Regarding phosphate-rock availability, the picture is more nuanced than Bhaskar indicates. I explored this in an article early last year (http://www.igbp.net/news/features/features/phosphorushowmuchisenough.5.1b8ae20512db692f2a680002359.html). Western Sahara is purported to have huge phosphate-rock reserves, but some have questioned the actual figures. Also, mining there brings with it geopolitical baggage and is deemed by some to be problematic on humanitarian grounds. The willingness and capacity to explore and mine phosphate rock depends on technological developments, the demand for fertilisers (triggered by the need to grow more food), the market price of phosphorus, etc. It is conceivable that any increase in production will be commensurate with the increased demand for fertilisers, and not with the need to supply nutrients to the surface ocean. Finally, forrect me if I am mistaken, but 256 million tons is the projected phosphate-rock production for the year 2015, not the figure for today. Ninad R. Bondre On Monday, July 23, 2012 6:10:57 PM UTC+2, Mike MacCracken wrote: > > Bhaskar-- > > Pardon me, but I don't get the sense from the citations you provided me to > justify the finding that the O2 concentration roughly 300M years ago > reached 35% raises this bit of information to “a fact”. I’d note also that > in the plot you reference that the high O2 level is indicated as having > occurred during a time of glaciation, and not warmth. > > I would also note that considerable analysis and inference likely went > into interpreting the geological evidence that makes up the record. There > were no calibrated instruments back then—the inferences usually come from > the types of materials being deposited out of lakes and oceans, the pore > sizes of fossil plants, etc.--all sorts of proxy data, and so there is > clearly analysis, interpretation, and logic involved. > > Mike > > On 7/23/12 11:27 AM, "Bhaskar M V" <bhaskarmv...@gmail.com> wrote: > > Mike > > Historical oxygen levels are a question of fact. > No logic is involved. > > Wikipedia > http://en.wikipedia.org/wiki/Atmosphere_of_Earth > > A good graph of O2 levels > http://www.nap.edu/openbook/0309100615/gifmid/30.gif > > http://www.pnas.org/content/96/20/10955.full > *Oxygen and Paleofires. > *The level of atmospheric oxygen cannot rise indefinitely unless the > frequency of forest fires becomes so excessive that plant life cannot > persist. This has been pointed out by Watson *et al.* (27 < > http://www.pnas.org/content/96/20/10955.full#ref-27> ), who emphasize > that fires serve as strong negative feedback against excessive > O2 variation. Conversely, O2 cannot have dropped to such low values over > Phanerozoic time that fires became impossible. Fossil charcoal, as evidence > of paleofires, has been found for all times that trees have populated the > land, and the lower limit for the production of charcoal has been estimated > to be at about 13% O2 (28 < > http://www.pnas.org/content/96/20/10955.full#ref-28> ). By contrast, the > upper limit for O2 is in dispute. On the basis of experiments on the > ignition of paper strips at different oxygen levels and fuel moisture > contents, Watson *et al.* (27 < > http://www.pnas.org/content/96/20/10955.full#ref-27> ) concluded that > past levels of atmospheric O2 could never have risen above 25%. However, > consideration of actual forest fires and the response of ecological > disturbance to fires led Robinson (29 < > http://www.pnas.org/content/96/20/10955.full#ref-29> ) to conclude that > greater O2 variation might occur and that, at any rate, paper is not a good > surrogate for the biosphere. In fact, Robinson states paleobotanical > evidence for a higher frequency of fire-resistant plants during the > Permo-Carboniferous, supporting the idea of distinctly higher O2levels at > that time." > Apparently there is evidence of more fires, and more fire resistant plants. > Fires would only impact terrestrial life, since more than 50% of life is > in oceans the issue of fires is quite irrelevant. > > While discussing the past, facts should always prevail over logic. > > O2 level today is 20.95%. > CO2 level is 0.039% - desirable level is 0.028%. > > So required increase in O2 level is about 0.01% i.e., from 20.95 % to ~ > 20.96 %. > > In fact the issue may not be an overall increase in photosynthesis at all. > > If share of diatoms increases and share of other phytoplankton decreases > correspondingly the desired result can be achieved. > > Diatoms account for about 40 to 50% of primary production in oceans, if > this is increased to 50 to 60% with corresponding reduction in share of > other phytoplankton, macro algae, weeds, etc., it would be adequate. > > Since diatoms and other phytoplankton consume similar amounts of nutrients > - N and P, there is no need to even discuss whether nutrient availability > is adequate or not. > > If farmers grew weeds instead of grass, we would starve. > In oceans too we should grow grass (Diatoms) instead of weeds > (Cyanobacteria and Dinoflagellates). > > regards > > Bhaskar > > On Mon, Jul 23, 2012 at 8:20 PM, Mike MacCracken <mmacc...@comcast.net> > wrote: > > Bhaskar-- > > With respect to your message, I would very much like to see the evidence > for the oxygen content ever being as high as 35% when life was present as > fire would have run rampant (and since lightning would have been needed to > provide the nitrate source, there would not have been a lack of a natural > match). If that supposedly high oxygen content is what underpins your > assurance that there are plenty of nutrients, then that conclusion would > also seem to come into question. > > It really is not so much whether the full ocean waters contain adequate > nutrients, but how much (or few) make it up to the upper ocean and at what > rate. With warming of surface waters likely to tend to stabilize the oceans > (so reducing the bottom water formation that presumably forces colder, > nutrient rich waters up), it would seem to me much more likely that the > nutrient supply of the upper ocean would be headed down instead of up. Now, > Kerry Emanuel has suggested that the restraint on the thermohaline > circulation may not be the problem of getting cold waters to sink, but of > getting them to come back up, and that tropical cyclones likely play an > important role in this. While the number of tropical cyclones is projected > to decrease, what the net effect (fewer tropical cyclones, perhaps more > powerful, more stable ocean, etc.) on drawing up deeper colder waters > remains, as I understand it, a bit murky, so it seems to me postulating a > lot more nutrients reaching the surface layer is not at all > well-established, and how the marine biological pump would work in the face > of ocean acidification is also unclear—the notion of a great increase seems > to me quite premature, at best. > > Mike MacCracken > > > > On 7/23/12 7:31 AM, "M V Bhaskar" <bhaskarmv...@gmail.com < > http://bhaskarmv...@gmail.com> > wrote: > > Morton > > Iron fertilization is planned to be used in HNLCs, i.e., areas that have > high nutrient levels year after year. > So it appears that there is a abundance of nutrients in the oceans. > > In the past the CO2 levels of atmosphere and oceans were lower due to > natural factors and diatom growth higher, so nutrients to support this were > available. > > O2 levels of atmosphere is today ~ 21 %, peak was ~ 35%. > So nutrients to support more than 50% higher photosynthesis was available > at that point in time. > > P is available only as a solid or dissolved in water, never as gas. > N may exit lakes and oceans as N2 gas but not P. > > So P to support much higher level of photosynthesis was and is available > on land or in water, if it has to be transported it can be done - whether > 100 tankers are required or 1000 tankers are required will be known only if > we experiment. > > Excess carbon in the atmosphere is about 200 billion tons - 390 ppm - 280 > ppm. > At 100 : 1, total P requires is less than 1 billion tons. > > Annual carbon emissions are 10 billion tons of C, P required is about 50 > million tons. > > Global Rock Phosphate production is 256 million tons. > Rock Phosphate reserves in Western Sahara alone are about 50 Billion tons. > > http://minerals.usgs.gov/minerals/pubs/commodity/phosphate_rock/mcs-2012-phosp.pdf > > There seems to be no danger of running out of phosphorus. > > Before you ask how many tankers are required, please read - > > African dust leads to large toxic algal bloom > http://eospso.gsfc.nasa.gov/ftp_docs/African_Dust.pdf > > "Each year, several hundred million tons of African dust are transported > westward over the Atlantic > to the Caribbean, Gulf of Mexico, Central America, and South America." > > "Plant-like bacteria use the iron to set the stage for red tide, a toxic > algal bloom. When iron levels > go up, these bacteria, called Trichodesmium, process the iron and release > nitrogen in the water, > converting it to a form usable by other marine life. The increased > nitrogen in the water makes the > Gulf of Mexico a friendlier environment for toxic algae. The image on the > left shows a red tide > event that was seen by the SeaWiFS sensor on August 26, 2001. A huge bloom > of toxic red algae, > called Karenia brevis (K. brevis), appears on the true-color image as a > black area hugging the > Florida Gulf Coast from the Keys to Tampa Bay." > > The dust contains P, Si and Fe. > N is fixed from atmosphere by cyanobacteria - Trichodesmium. > > The key is to ensure bloom of useful algae and not harmful algae. > We have the key. We can prevent this dust from causing toxic algal bloom > by a very scientific fertilization to cause a controlled bloom of diatoms > instead of dinoflagellates (red tides). > > regards > > Bhaskar > > On Saturday, 21 July 2012 17:31:15 UTC+5:30, O Morton wrote: > > The reported ratio of C:Fe for IEFEX is >10,000:1. The redfield C:P ration > is about 100:1. So you'd need your 100 tankers to be carrying pure > phosphate, not sewage, no? > > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To view this discussion on the web visit https://groups.google.com/d/msg/geoengineering/-/bnxNzNkpJR8J. To post to this group, send email to geoengineering@googlegroups.com. To unsubscribe from this group, send email to geoengineering+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en.
