In reply to Horace Heffner's message of Sat, 18 Mar 2006 13:21:17 -0900: Hi, [snip] >Given a 30 percent drop in the Atlantic conveyor belt flow rate in 12 >years: > >http://www.timesonline.co.uk/article/0,,2-1898493,00.html > >it may be that there is a powerful but not yet understood biological >feedback occurring in the ocean due to a reduced nutrient flow from >the depths caused by the conveyor belt shutdown.
There are probably lots of them, but I suspect that simple chemical dissolution of CO2 in water outweighs all of them. (It has to dissolve in the water before they can make use of it). According to Wiki, humanity puts about 22E9 tons of CO2 into the air every year (http://en.wikipedia.org/wiki/Global_Warming), which is a rate of increase of about 2.5 ppm / yr. However this assumes that the CO2 is evenly distributed throughout the atmosphere, and it may be more concentrated near the ground because it's heavier than air. It also takes no account of the amount removed by photosynthesis, and other processes. However if the rate of increase of 2.7 ppm/yr previously mentioned were to apply to the whole planet, then we would have to seriously consider the possibility that existing carbon sinks are becoming sources iso sinks, i.e. that they are releasing CO2 iso sequestering it. At least some of our 2.5 is being removed by photosynthesis, and yet the increase is larger than everything we throw in, which would mean that there would have to be a major new non-anthropogenic source (or Wiki is ignoring the clearing/burning of tropical forests?)! I would look to the solubility of CO2 in the oceans as the most likely reason for this. As the average water temperature rises, we may find that CO2 which had already dissolved in the past, is now being released. This would result in a huge positive feedback cycle and rapid warming. Not to mention the additional feedback resulting from the increase in water vapor. (As the air temperature rises, so does the maximum possible partial vapor pressure of water - which is why the tropics are humid and the poles dry). >Polar fresh water >runoff is suggested to be the cause of the conveyor belt slowdown. >The conveyor belt is driven by salinity density changes, and >injection of fresh water in the polar regions disrupts the cycle. >The salinity changes, nutrient changes, and thermal changes brought >about by the slowdown may be affecting both the location of and >population of carbon sequestering organisms, and the carbon >sequestration rate in general. A sudden population change would >occur more like a step function than a logarithmic function. > >"The results, published today in Nature, show that the outward flow >of the Gulf Stream has not changed, but the strength of the cold >water returning from the Arctic has fallen by 30 per cent since 1992. >Over the same period, the flow of warm water branching off towards >Africa has increased by 30 per cent. This suggests that the warm >waters are being diverted away from Europe." Which makes sense, if the flow past Europe were previously being "sucked" North by the falling saline water in the arctic. > >A sudden population change could cause sudden onset long term linear >or non-linear effects. Given the large number of feedback cycles >involved Yes, at least one for every species on Earth, which means 10's of millions of them. Hence this approach to modeling is not feasible. >a non-linear and even exponential parameter change seems >likely but we probably will have to wait until it is too late to find >out. If we ever do. > >Maybe you have a specific underlying model in mind to explain the >regime change Robin? I have already expressed my best guess here above, i.e. that the oceans have changed from being a carbon sink to a carbon source, and that that has probably happened within the last decade. (BTW an increase in sub-marine volcanic activity would also hasten this process). >Attempting curve fitting for extrapolation into >the future is sometimes a lot more meaningful if there is an >underlying physical model to justify the curve family. However, in >this case it looks like there has been an abrupt regime change of >some kind, and we don't even know what family of curve to apply. I tried to show that even an exponential curve doesn't appear to be rising fast enough, so yes I think we are up the proverbial creek without a paddle. Regards, Robin van Spaandonk http://users.bigpond.net.au/rvanspaa/ Competition provides the motivation, Cooperation provides the means.
