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Post by nautonnier on Sept 28, 2009 12:14:06 GMT
You betcha if you have calculations. If all you have is theory then forget it. There are calculations but it's really the concept that needs to be understood. Think about the pre-industrial period of 'CO2 equilibrium'. At that time CO2 concentrations were ~300ppm (I'm using simple numbers to illustrate a point - don't quote them). A concentration of 300ppm very roughly equates to ~600 GtC. If the carbon cycle meant that 120 GtC were being released annually from the oceans and biosphere then to maintain the 300ppm equilibrium 120GtC would need to be re-absorbed. So we have this cycle where 120GtC is released into the atmosphere and 120 GtC is absorbed by the various sinks. It should be obvious, in this case, that the average lifetime of the CO2 molecule is 5 years. What happens when we add more CO2 by burning fossil fuels? If the natural carbon cycle keeps recycling 120GtC per year then the additional CO2 should accumulate in the atmosphere. But it doesn't - not all of it, anyway. There is an increase in the atmosphere but not as much as might be expected. This means there is increased absorption - an 'extra' sink as it were. What's more this 'extra' sink appears to take up more carbon as the fossil fuel CO2 increases. In other words The amount absorbed by the sink is a function of the total fossil fuel CO2 (C). What happens if we stop all fossil fuel CO2 production. Two things happen: (1) The 'natural' carbon cycle will continue. (2) The extra sink will continue to absorb CO2 until we get back to the 300ppm level. This is where the Maths comes in. As the sink is a function of the CO2 excess, the amount absorbed will reduce over time, i.e. it's a decaying function which can be represented by the following first order differential equation dC/dt = -kC which has the solution C = C 0e -ktwhere C 0 is the intitial value of C and k is the rate of decay. We now need to decide on these values. Currently there are ~750GtC in the atmosphere which means we have ~150GtC more than in the pre-industrial era, so C 0=150. What about k (the rate of decay)? A reasonable current estimate which also gives a nice easy number (this is for illustration purposes remember) is 3 GtC per year. The decay rate is, therefore, 3/150 = 0.02. If we plug these values into the above equation we get C = 150 x e -0.02tIf we want to find out how long it will be before C is half it's initial value (i.e. 75) then the equation becomes 75 = 150 x e -0.02t or 0.5 = e -0.02t i.e. ln(0.5) = -0.02t therefore t =~35 years. From which we can conclude that it will be about 35 years until the CO2 concentration is reduced to 675 GtC. But the important thing to note is that more than 120 GtC (123 GtC at peak) of carbon are being recycled which means that, even with the peak 750 GtC in the atmosphere, the average residence time of a CO2 molecule is still only ~6 years. This shows that the average residence time and the time taken to return to equilibrium are not (closely) related. The numbers used in the above illustration were chosen for simplicity's sake but, as far as I'm aware, they are not a million miles away from the true values. Thanks for the explanation - which is a little more sophisticated than SoCold's water tank and tap. However, you appear to be making the assumption that the sink has a linear relationship to the concentration of CO 2. Can you tell me where the science shows this is the case? |
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Post by baldeagle on Sept 28, 2009 13:32:24 GMT
"What happens when we add more CO2 by burning fossil fuels? "
The trick here is that:
1 - CO2 as a trace gas simply cannot drive the climate. Sure it contributes to our warm atmosphere, but its effectiveness drops off rapidly after the first 20 ppm.
2 - CO2 responds clearly to ocean temperatures, just like a soda, and goes in and out of the seas as it cools and heats, respectively.
3 - CO2 partitions 50/1 between water/air. We would have to add 50 times the CO2 needed to "double" the atmospheric CO2 as we would have to add 50 times the CO2 needed to the seas.
4 - There is not enough available carbon for us to burn to raise the atmospheric CO2 by more than 20% - not much problem there.
5 - The human contribution of 3-4% of the air and the Beers Law effect that doubling CO2 might warm the atmosphere by 0.1 deg C with doubling of CO2, means that we are talking about human effects in the 1/1000ths of a deg C. For this we should cripple our economy?
6 - These considerations and the fact that the Arctic region and the ice are failing to warm and disappear, respectively, as predicted by the AGW computer models (fatally flawed in many ways) and the entire absence of the required (even by the AGW models) upper tropospheric warm region, indicate clearly that CO2 is not what is driving the climate.
I cannot locate the recent post, but one poster mentioned going to realclimate.com and wikipedia to learn about the LIA. Real Climate is a biased defender of the bad model of AGW and Wikipedia's "version" and explanation of the LIA is very erroneous and flawed - being sat upon and moderated by one of Dr James Hansen's colleagues. Heaven forbid that they should accept and explain a temperature record which shows data from truly rural sites - absent the growing effect of the urban heat island effect and the rural monitoring dropout effect.
Who in their right mind would believe that the Medieval Warm Period (MWP) was created by the agriculture of the times and that the LIA was caused by the plagues and the reforestation of the fields due to the decreased population. The site even indicates that indigenous North American farmers of the time contributed to the MWP. There were just plain too few people back then to have a greater effect (the MWP was a lot warmer than now) than is supposed to be happening today, let alone the fact that CO2 then or now cannot do what they say.
The same poster claims no correlation between temperatures of the LIA and solar activity, but, indeed, the only factor that correlates very well with global temperatures is the solar cycle lengths and overall sunspot numbers. The Maunder Minimum, the coldest period of the LIA, is a minimum of both sunspots and temperatures - the same was true of the Dalton Minimum. The current cooling we have today correlates perfectly with the predicted, cyclical flipping of the PDO to its regular cooling phase and the cooling will probably be accentuated by the current anaemic Solar Cycle 24.
We are also constantly told that CO2 has been low and steady throughout the past until the 19th-20th century. This fallacious idea derives from using indirect and flawed data from ice cores, ignoring totally direct CO2 chemical measurements which clearly show several times in the last 200 years when CO2 was significantly higher than now and nothing unusual happened. Again, who in their right mind believes that indirect data is patently better than direct data - who are they kidding?
Yell and argue all they want, the AGW model fails, CO2 is not a driven, but is driven, and cooling will prevail for quite some time despite CO2 still rising (there is a lag between ocean cooling and CO2 uptake affecting atmospheric levels, ~5-8 years) and the models still predict warming. Just last week Pachauri, Head of the IPCC, jumped on the horn again and claimed that we were warming faster than ever and that the Arctic Ice and Greenland are rapidly disappearing (neither are and the Antarctic is also gaining mass) - he has to yell louder now to drown out the facts and real world.
All of this is based on real material, easily found by one who looks. These are not the opinions and handy bag of science chunks recruited when needed as excuses for arguments from skeptics. Being skeptical is not a bad thing, and going to the real science as well as the real facts is the only way a scientist should function. When they attack the messenger, it mainly means that they cannot attack the message.
Currently the Arctic sea ice is up ~1 million sq km over 2007, besting 2008 which was also larger than 2007. However, the news, being so totally unbiased, reports that 2009's minimum is the 3rd lowest on record, ignoring that we see a fairly decent upward trend and that 2007 was a perfect storm of warming factors, including the fact that much of the sea ice melting was not even in the Arctic - those darn wind patterns!
Do not forget that the North Pole was open water for several years back in the 1950s and it has not done that in these recent years! We thought it was pretty neat back then- nuclear submarines allowed seamen to swim at the North Pole!
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Post by glc on Sept 28, 2009 13:48:47 GMT
Thanks for the explanation - which is a little more sophisticated than SoCold's water tank and tap.
Socold's water tank analogy was fine. I was going to use it myself in order to
However, you appear to be making the assumption that the sink has a linear relationship to the concentration of CO2. Can you tell me where the science shows this is the case?
No it's not actually linear it's exponential. I can see why you think it is. The 'sink' is proportional to the excess. At 150 GtC, the sink is 3Gt C. If the excess increased so would the sink. The science is the observations. That's what appears to have happened over time, i.e. it doesn't matter how much we produce, the sink seems to take about half and half is left to accumulate in the atmosphere. With a total excess of 150 GtC, if we produce 6GtC about 3GtC is removed and 3GtC remains. These are very very rough figures.
If we stopped producing carbon, the sink would remove 3 GtC (or about 2% of the excess) in year1, it would then remove 2% of the remainder (147 GtC) in year 2, then 2% of the remainder in year 3 and so on.....
It should have removed ~75 GtC by year 35.
Each year a smaller amount is removed so the next 75GtC would take quite a bit longer.
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Post by poitsplace on Sept 28, 2009 15:45:35 GMT
And that's why it's virtually impossible for us to hit even 600ppm...its taking ever increasing amounts of CO2 to increase atmospheric levels. At the current needed rates of increase we'll run out of commercially viable natural gas, oil and coal first. I don't even think there are enough known reserves to reach 600.
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Post by glc on Sept 28, 2009 18:08:05 GMT
The same poster claims no correlation between temperatures of the LIA and solar activity, but, indeed, the only factor that correlates very well with global temperatures is the solar cycle lengths and overall sunspot numbers. The Maunder Minimum, the coldest period of the LIA, is a minimum of both sunspots and temperatures - the same was true of the Dalton Minimum. The current cooling we have today correlates perfectly with the predicted, cyclical flipping of the PDO to its regular cooling phase and the cooling will probably be accentuated by the current anaemic Solar Cycle 24.
I just asked for some evidence that a correlation exists. I'm not sure how you know there is one. What is your source for temperature data. What proxies are you using for solar activity. There are problems with some of the earlier solar reconstructions in that the sunspot count was under-estimated and hence the variation in activity has been over-estimated. Any correlation depends on what reconstruction is used and the time period chosen. All climate/solar links appear to have broken down in the past 30 years.
Incidentally I used data from 17 independent records to show that the Dalton Minimum wasn't any colder than several other periods. Do you have anything to show that it was?
There's a quite a bit wrong with the rest of your post as well.
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Post by nautonnier on Sept 28, 2009 19:45:19 GMT
What you said in your initial post was that a CO 2 molecule had a life of 5 years in the atmosphere. What you are NOW saying is I am still saying a co2 molecule has a lifetime of about 5 years in the atmosphere. OOOOK so now lets assume an extra peta-tonne of CO 2 enters the atmosphere - 5years later - its all left the atmosphere. Where does the 1000 years life suddenly come from? |
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Post by socold on Sept 28, 2009 20:14:46 GMT
I am still saying a co2 molecule has a lifetime of about 5 years in the atmosphere. OOOOK so now lets assume an extra peta-tonne of CO 2 enters the atmosphere - 5years later - its all left the atmosphere. Where does the 1000 years life suddenly come from? Average lifetime of 5 years doesn't mean all co2 leaves the atmosphere after 5 years. Or else there wouldn't be any co2 in the atmosphere today. A co2 molecule being replaced by another co2 molecule on average every 5 years would be a lifetime of 5 years without causing a change in co2 level for example. |
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Post by poitsplace on Sept 28, 2009 21:23:22 GMT
OOOOK so now lets assume an extra peta-tonne of CO 2 enters the atmosphere - 5years later - its all left the atmosphere. Where does the 1000 years life suddenly come from? Average lifetime of 5 years doesn't mean all co2 leaves the atmosphere after 5 years. Or else there wouldn't be any co2 in the atmosphere today. A co2 molecule being replaced by another co2 molecule on average every 5 years would be a lifetime of 5 years without causing a change in co2 level for example. Yeah, I agree with you on this. CO2 will probably begin by going down almost as fast as it ramped up (assuming we just suddenly stopped) and slowly decrease. Assuming temperatures stayed the same (which they won't) the temperatures would probably take around 1000 years to level off. Most of the CO2 would probably be absorbed within a few hundred though. |
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Post by nautonnier on Sept 28, 2009 21:51:42 GMT
I think that SoCold and glc need to get their acts together  |
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Post by sentient on Sept 29, 2009 2:15:45 GMT
bump for baldeagle, welcome to the forum.
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Post by glc on Sept 29, 2009 8:27:21 GMT
Poitsplace says:
Yeah, I agree with you on this. CO2 will probably begin by going down almost as fast as it ramped up (assuming we just suddenly stopped) and slowly decrease. Assuming temperatures stayed the same (which they won't) the temperatures would probably take around 1000 years to level off. Most of the CO2 would probably be absorbed within a few hundred though.
Nautonnier says
I think that SoCold and glc need to get their acts together
In theory, we could actually remain above the pre-industrial level forever. Remember if we stopped CO2 production the amount removed from the atmosphere will reduce year on year.
Have you heard of the "frog" problem. This describes a frog which sits in the middle of a large pond. The frog wants to get to the edge of the pond. On the first day he jumps half the distance, on the 2nd day he jumps half the remaining distance (so he's now 3/4 of the way) ...on the 3rd day he jumps half the remainder again...and so on. The question is when will he get to the end. The answer is, of course, never - because he will always be a half way from whatever distance is remaining.
Poitsplace has it about right, though. For all practical purposes the vast majority will be gone (of the excess 100ppm) will be gone in a couple of hundred years. As I suggested above, half of it (~50 ppm) will be gone within 35-40 years. Around 63% will be gone after ~50 years. By then we'll be down to ~310ppm and the "problem" will be over.
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Post by icefisher on Sept 29, 2009 16:06:28 GMT
For all practical purposes the vast majority will be gone (of the excess 100ppm) will be gone in a couple of hundred years. As I suggested above, half of it (~50 ppm) will be gone within 35-40 years. Around 63% will be gone after ~50 years. By then we'll be down to ~310ppm and the "problem" will be over. What problem? I would suggest your model does not provide for natural variation. Put together as if all other forces on the planet are static and forever in balance. Such assumptions simply are irrational when dealing with natural systems. Its kind of a deterministic view that eventually humbles all natural scientists. |
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Post by steve on Sept 29, 2009 16:31:18 GMT
glc:
Where does the 3GtC value come from?
Can you be sure that the absolute amount of uptake each year continues to be the same. What if there is a short term sink that fills up quickly as a function of atmospheric CO2 levels, but empties elsewhere slowly?
Eg. for illustration of my meaning only, suppose the top few metres of the ocean quickly reach equilibrium with the atmosphere as it absorbs the bulk of the 3GtC. This means that even if emissions cease, the ocean cannot absorb any more until either the atmosphere concentration starts to rise again or the top layers have a net loss of "dissolved CO2" to the deeper ocean through ocean circulation and/or biological activity.
If this were the case, the subsequent rate of absorption could be much lower.
Given that CO2 levels have been sustained at much higher levels in the past, other people's suggestions that it could be so easily constrained now seems optimistic.
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Post by thingychambers69 on Sept 29, 2009 17:16:28 GMT
So does that mean a 1000 years of carbon taxes?
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Post by thingychambers69 on Sept 29, 2009 17:20:34 GMT
Why does every climate model I come across assume that CO2 is the driving force?
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