Oh, okay. I think that answers my questions in post #19, so feel free to skip them.
I don’t think that. I think we’re playing a significant part in climate change. However I do believe that over the past 150 years, relative warming was going to occur regardless of whether humans were around or not (part of my belief in that regard is the IPCC’s own data which indicates the past 150 years of anthropogenic warming is coincidentally happening during a period of increased solar output–output independent of the normal 11 year solar cycles.) The indicators of that aren’t strong, but I guess my ultimate belief just comes down to me thinking humans are more likely acting as very dangerous multipliers to a natural effect than they are genuine originators of said effect.
Thanks.
Regards,
Shodan
It is true that most of the warming that occurred during the earlier half of the 20th century is understood to be due to natural causes and, in particular, to increased solar output along with a lack of major volcanic eruptions. However, it is worth distinguishing between the causes of the 20th century warming (and even of the 1st half vs. the second half) vs. the warming we are likely to see in the 21st century.
In particular, I think it is in general believed to be quite unlikely that natural effects such as solar variations will continue to act strongly in the warming direction (in fact, I believe some of the solar experts predict that the solar variations will likely be in the cooling direction in the coming decades). And, what we know of past climate variability (on these sorts of timescales) would tend to support this notion.
And, again, just to emphasize: I don’t think your idea of emergence from the general ice age-ish conditions of the last several million years playing any sort of significant role is a very likely scenario due to the difference in the timescale compared to the timescale of interest to us. That difference in timescales means that even if the emergence from ice-ageish conditions could occur extremely rapidly, so that there would be significant warming on the timescale of centuries (and that it could not be predicted from any of the mechanistic things we understand), it would be a very poor statistical bet to bet that such a rare event would actually occur over the next few centuries. Furthermore, I think these major global climate shifts probably did not occur at that sort of rapid geological pace…so that even if such an emergence was happening, it would be a very gradual thing over at least tens of thousand of years if not longer.
If we’re working under the assumption that humans are currently overestimating their importance (imagine that), we do not have the understanding necessary to capably manipulate the global climate.
Thus, mitigation efforts would be necessarily wasting money that could have gone towards survivability and disaster relief preparations. Basically, you end up handicapping the world economy in a fruitless mitigation effort, and then are less able to cope with the damage caused by the climate change.
However, there is no such thing as "long term sustainable growth", so all the energy conservation and environmental neutrality initiatives need to take place whether we’re facing immanent ecological catastrophe or not.
I don’t get this. What is the rationale behind the assumption that “humans are overestimating their importance” when it comes to global climate? Or that humans’ estimation of their importance is somehow determining scientific conclusions about climate change?
I mean, we can pretty much measure quantitatively how much greenhouse gases we’re emitting into the atmosphere by burning fossil fuels, right? That isn’t based on any “overestimation of importance” on our part, AFAICT.
And we can pretty much tell, by things like ice core records and so forth, how much atmospheric concentrations of greenhouse gases have increased due to our emissions, right? That too isn’t based on any “overestimation of importance” on our part, AFAICT.
And we have a fairly well-understood theory of the “greenhouse effect” in basic atmospheric physics, which is where we get our predictions of how much warming will result from the increased atmospheric concentrations of greenhouse gases, right? That also STM to be acceptably objective and evidence-based (although of course we don’t know all the details of how the “greenhouse effect” interacts with other aspects of climate systems), and not dependent on how “important” we consider ourselves.
So where does any “overestimation of human importance” come into it? How would altering our estimation of human importance change any of the main conclusions that are now being drawn about global warming in mainstream climate science?
If the popular thought on the matter was that this was an uncontrollable natural shift in climate to a different equilibrium state, there would be no discussion on greenhouse gas emissions. Raise them, lower them. The global trend continues unbated.
Saying “We produce X million kilograms of CO2, Y million kilograms of methane, etc.” is a statement of fact. I’ve not seen anything showing that these quantities are a significant portion of the total carbon cycle in a given time period, or much attempt to study how emissions effect the network of chemical reactions involved.
Show me that human emissions and global atmospheric concentrations track. Temperature and global [GHG] track. I’ve never seen a convincing dataset on the link between external emissions and long term global [GHG]. Volcanic releases, for example, do not cause long term increases in global [GHG].
The assumption is that we’re doing something to significantly disturb [GHG].
The main conclusion affected is that we have the capability to manipulate the global climate. If human emissions do not play an important role in the change in global [GHG], reducing emissions will not affect global warming.
Since global warming will be an ecological catastrophe, we may want to attempt to counteract it even if it is a natural phenomenon. Instead we’re throwing money away on emission controls and industrial carbon credits… which, again, still needs to happen for a whole different set of reasons, but may not be doing anything to avert global warming.
But why should “popular thought” believe that current warming does in fact represent “an uncontrollable natural shift in climate to a different equilibrium state”? The vast majority of climate scientists don’t think it does: they think it’s mostly due to human GHG emissions, and therefore not uncontrollable.
That’s what the second graph on this page indicates, AFAICT. The blue line shows how much carbon we emit through fossil-fuel burning, and the red line shows how much the atmosphere’s CO2 content is increasing.
The two lines don’t exactly coincide, but their general behavior is similar: they’re both essentially flat till about 1850 and then both start to rise, with much more dramatic increases after about 1950. In other words, human carbon emissions and global atmospheric CO2 concentrations do approximately track.
Moreover, AFAIK, no plausible alternative explanation has been proposed for the observed increase in global atmospheric CO2 concentrations. If human GHG emissions aren’t causing the current substantial rise (e.g., about a 30% increase in CO2 levels within the last 300 years) in GHG concentrations, then what is?
Why would we expect them to? Volcanic eruptions aren’t steady massive GHG pumps continuing for decades on end, the way human fossil-fuel burning is. Volcanoes spew comparatively small amounts of CO2, totalling only about 1% of human emissions.
Maybe the reason you have trouble finding information on this is that it is such well-settled science that there is no serious debate about it anymore. In fact, the growth in the amount of CO2 in the atmosphere is quite consistent at a rate of ~50% of what we are emitting from fossil fuels. What this says is that natural sinks are able to absorb about half of what we put into the atmosphere while the other half remains there. It is thus true beyond a shadow of a doubt that the rise in CO2 since the industrial revolution is due to us. [It also, of course, would be a coincidence of remarkable proportions if CO2 just happened to rise to levels well above those seen in the last 750,000 years (over which we have very good data from ice core measurements) and likely the last 10 to 20 million years! 750,000 years, by the way, is a period that spans about 7 glacial – interglacial cycles.]
Furthermore, one can also look at the changing isotopic content of CO2 in the atmosphere as evidence of the CO2 from the burning of fossil fuels. All in all, there is simply no doubt that we are responsible for the current rise in greenhouse gas levels. Where there remains more wiggle room is in exactly how much global temperature increase that will cause…although most scientists think we have a reasonable handle on this now too, or at least enough of one to basically role out the result “very little”.
Just wanted to step back in and say thanks for the replies (as well as the cordial tone). I haven’t posted back because, thus far, every time I’ve thought of a question or comment, someone has beaten me to the punch. This thread has been very informative, so keep on edumakatin’ me.
Sua
The thing is, I’d think it would be fairly easy to demonstrate if that were the case. Instead:
There’s a lot of not particularly well correlated data that supposedly supports the argument for causation. You know the cliche.
Human industry isn’t the only source of carbon emissions.
I blame global warming.
But they do not appear to have the expected step increase effect we would predict from the correlation argument made above… unless the carbon cycle (or nitrogen cycle, for that matter) chooses to reclaim GHG emissions from natural sources while leaving human sources to accumulate in the atmosphere.
Ah. That must explain why the problem with the Ordovician ice age was only put to rest in two years ago.
It’s even more consistent with the rise in temperature. Also, what’s happening to the other 50%?
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Yet natural sinks are apparently able to absorb all of what natural sources put in there. How does it tell the differece?
Unless, of course, we don’t understand what’s actually happening and are overestimating our own importance.
What are CO2 levels like when not in an ice age? (look further up the thread for clarification on the different between the phases “interglacial period” and “not an ice age”)
Put a funnel under a faucet and adjust flow so you get a constant level in the funnel. Add red food coloring to the water in the funnel. The level does not change, but the water will be tinted red for a while. Partially block the hole out of the funnel or open the valve at the faucet. Add more red food coloring. Level is increasing and the water is red tinted, but the red tint does not indicate that the increase in water level is due to the food coloring.
I don’t believe anyone has disputed the greenhouse effect or that global warming is occurring, so I’m not sure why you’re mentioning them again as if they’re relevant to a discussion of causation.
What if the problem is that pollution of the oceans is interfering with their sink function? That the ability of the carbon cycle to reclaim CO2 is being degraded causing an increase in CO2 levels- it has nothing to do with emissions increases. We could mitigate the problem by cleaning up the oceans, but we’re too busy focusing on sequestering CO2 emissions (and injecting it into the seabed!).
That is just silly! Why would global warming within 100 years suddenly shoot up CO2 to levels not seen in at least 750,000 years, and coincidently at the time we start putting long locked away sources of CO2 into the atmosphere in the right amounts to cause the rise seen? (As noted, we have put in about twice as much as the rise seen accounts for, showing that the carbon cycle is able to remove some of this extra CO2 we are adding but not all of it.) That’s betting on at least a 10,000-to-1 shot.
Also, it is worth noting that, while it is true that previous warmings have led to increases in CO2, the evidence is that the CO2 increase lagged by several hundred years…which corresponds to the sort of timescales that govern the overturning of the ocean. Furthermore, comparing to the glacial – interglacial periods, the amount of warming we have experienced in the last hundred years or so should not have led to nearly the sort of CO2 increases we have seen even ignoring the timescale issue.
That not the right way to look at it. The point is that the carbon cycle was in equilibrium, i.e., there are large exchanges between air and water and air and land/biosphere, but they are basically taken the same carbon and just cycling it around. We, by contrast, are releasing stores of carbon that have long been locked away from the atmosphere. A good analogy is a fountain where the water that goes down the drain is recycled by a pump and comes back up out of the fountain again so that the water level in the basin remains unchanged. If one then starts pouring more water from a hose into the basin, the water level will rise even if the amount of water coming out of the hose is small compared to the amount coming out of the fountain.
See the above discussion. Natural sinks and sources were in equilibrium basically cycling the same carbon back and forth between atmosphere, oceans, and biosphere/land. Then, we came along and opened up a new source that had long been locked away. So far, the oceans and biosphere/land have been able to take up some of this but not all of it.
Well, I don’t really see where the fact that the CO2 levels were higher tens to hundreds of millions of years ago provides much evidence for the idea that the current rise has a natural cause! Yes, on much longer timescales, the CO2 levels can vary significantly but what we are talking about is what has suddenly happened over the last 100 years to shoot the CO2 levels from ~280ppm to 380ppm when they had consistently been between ~180 and 300ppm over the last several glacial - interglacial cycles going back at least 750,000 years.
This is a silly analogy. What has happened over the last 100 years to “partially block the hole out of the funnel or open the valve at the faucet” that hasn’t happened in the last 750,000 years?
Except that we know that the sink function has not decreased over the last 100 years…It has increased. That is why the total rise in CO2 levels is only half of what it would have been if the sink function had been unable to increase at all in response to the elevated CO2 levels that we have produced with our additions of CO2 to the atmosphere. Your hypothesis makes no sense. It is also at odds with what scientists understand about the carbon cycle and I don’t think anyone has proposed a mechanism by which pollution of the oceans could cause a significant decrease in their sink function.
Well, it supports the argument for causation of elevated atmospheric GHG concentrations by human GHG emissions better than it supports any other known explanation for elevated atmospheric GHG concentrations.
Moreover, as jshore pointed out, the recent changes in isotopic content in atmospheric CO2 also support the argument that the additional atmospheric CO2 is coming from human emissions.
Again, we’re left with the basic facts that (1) humans over the past several decades have been pumping significant loads of GHGs into the atmosphere, and (2) atmospheric GHG concentrations over the past several decades have significantly increased. (And their changed chemical composition suggests that the increase is coming from the human emissions.)
Therefore, climate scientists have almost unanimously concluded that the recent rise in atmospheric GHG concentrations is due to human GHG emissions. (A much more detailed and technical explanation of what this conclusion is based on is given here.) This is a perfectly reasonable scientific hypothesis to adopt, based on the evidence as we now know it. And if you don’t like it, then you need to come up with (a) a scientific reason why it can’t be true, and/or (b) an alternative explanation that fits the observed evidence better.
So far, no anthropogenic-climate-change skeptic that I know of has successfully managed to do either of those things.
Of course not. However, it is the only significant source of carbon emissions that has been recently added to the total global carbon output. All other known major sources of carbon emissions have been around for many millennia, and have helped form the natural carbon emission/absorption cycle that has kept atmospheric carbon concentrations at approximately constant levels for thousands of years.
Then what’s your explanation for global warming itself? And what’s your explanation of how global warming is causing atmospheric GHG levels to increase? And what’s your explanation of why human GHG emissions are not causing atmospheric GHG levels to increase?
You can’t just arbitrarily select some parts of a complex scientific theory to believe, select others to reject, and then assert that your result constitutes an improvement over the original. If you’re claiming that your explanation is scientifically superior to that proposed by mainstream science, you have to produce a new hypothesis that is at least as consistent and comprehensive as the mainstream one.
Exactly what “step increase effect” would you “expect” to be shown by volcanic emissions? Remember, total volcanic carbon emissions are minuscule compared to human carbon emissions, with the former amounting to not quite 1% of the latter. Exactly what effects from volcanic emissions do you claim are not appearing as predicted in observed climate data? Because AFAICT, mainstream climate scientists seem to think that existing climate models and observed climate data account for volcanic emissions just fine.
You seem to be misunderstanding how carbon absorption works. Prior to major human industrial activity, natural global carbon emissions and natural global carbon absorption had established an equilibrating cycle that kept atmospheric carbon levels roughly constant for thousands of years. Natural processes like volcanoes, vegetation decay, etc., kept emitting carbon into the atmosphere, while other natural processes like plant growth kept taking carbon out of the atmosphere. These inputs and outputs have more or less balanced for the past several thousand years, so the amount of carbon that remained in the atmosphere has stayed roughly constant until recently.
Now that human beings are releasing into the atmosphere large amounts of additional carbon—i.e., carbon that was formerly stored outside the natural carbon cycle, in the form of buried fossil fuels—the natural “carbon sinks” are absorbing more carbon, but they’re not absorbing all of the additional carbon we’re putting in. We’ve started filling the carbon sinks faster than they can drain, so to speak, so the amount of unabsorbed carbon (in the atmosphere) is increasing. The problem is not with the type of our additional carbon emissions, but with the sheer amount of them.
But what is the scientific reasoning, if any, behind your hypothesis that “we don’t understand what’s actually happening and are overestimating our own importance”? Why, scientifically speaking, should we regard this claim as anything but mere wishful thinking coming from somebody who doesn’t want to believe what mainstream science says about anthropogenic climate change?
They tend to be much higher than they are now. But we are in an ice age, so the question of how high CO2 levels would be if we weren’t is essentially irrelevant, AFAICT.
What scientific evidence is there that this is actually happening? In fact, as noted in the cite I linked to above, observations tell us that the “sink function” of the oceans is currently greater, not less, than it used to be. That is, the oceans contain more carbon than they used to in the days before human fossil-fuel burning. (But still the level of atmospheric carbon keeps increasing. If that mysterious extra carbon isn’t coming from formerly-buried fossil fuels, then where is it coming from?)
Summary: You can’t just pull unsubstantiated speculations out of your ass like this and expect us to regard them as serious criticisms of mainstream scientific theories on anthropogenic climate change.
If you’re suggesting that we shouldn’t believe a particular part of the anthropogenic-climate-change hypothesis, you need to provide scientifically valid reasons why we should believe something else instead. Not just offer up half-baked “what ifs” with no supporting evidence as though they somehow constitute a viable alternative theory.
[In preview: Curse you jshore and your fast-typing fingers. 
No really, thanks for the good points.]
The level of industrialization has increased dramatically in the past century which would interfere with natural sink operations (deforestation) while at the same time adding to emissions. Yet the carbon cycle has somehow increased capacity to consistently absorb approximately half of the emissions? That’s not what I would expect if we’re artificially overloading the system. I would expect the relative coping ability of the system to decrease as the overload has grown larger and larger. By your argument, this hasn’t happened, the increased emissions are countered by increased reclamation maintaining an apparent 50% track. How?
Considering the suggested climate shift is the end of the ice age, referring to glacial/interglacial shifts within the ice age would not be relevant.
So how does the fountain keep pumping faster and faster as we turn up the flowrate from the hose? Why doesn’t level increase when a bucket of water is dumped in the fountain?
Normal climate/atmospheric behaviour during the previous several hundred thousand years of the present ice age is not relevant if the change that is occuring is the ending of the present ice age.
This is a silly analogy. What has happened over the last 100 years to “partially block the hole out of the funnel or open the valve at the faucet” that hasn’t happened in the last 750,000 years?
Except that we know that the sink function has not decreased over the last 100 years…It has increased. That is why the total rise in CO2 levels is only half of what it would have been if the sink function had been unable to increase at all in response to the elevated CO2 levels that we have produced with our additions of CO2 to the atmosphere. Your hypothesis makes no sense. It is also at odds with what scientists understand about the carbon cycle and I don’t think anyone has proposed a mechanism by which pollution of the oceans could cause a significant decrease in their sink function.
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The level of industrialization has increased dramatically in the past century which would interfere with natural sink operations (deforestation) while at the same time adding to emissions. Yet the carbon cycle has somehow increased capacity to consistently absorb approximately half of the emissions? That’s not what I would expect if we’re artificially overloading the system. I would expect the relative coping ability of the system to decrease as the overload has grown larger and larger. By your argument, this hasn’t happened, the increased emissions are countered by increased reclamation maintaining an apparent 50% track. How?
Considering the suggested climate shift is the end of the ice age, referring to glacial/interglacial shifts within the ice age would not be relevant.
So how does the fountain keep pumping faster and faster as we turn up the flowrate from the hose? Why doesn’t level increase when a bucket of water is dumped in the fountain?
Normal climate/atmospheric behaviour during the previous several hundred thousand years of the present ice age is not relevant if the change that is occuring is the ending of the present ice age.
Wouldn’t it be nice to get some funding to look into it? Or to look into mechanisms by which sink function has been increased, as you suggest below?
Or it could be that the rise in atmospheric CO2 levels is a change in carbon cycle equilibrium caused by something other than human emissions. Global warming, for example.
A detailed explanation of how natural carbon absorption is thought to have increased due to excess anthropogenic carbon is given in chapter 3 of the 2001 IPCC report. Some highlights:
But what plausible scientific reason is there to think that we are currently seeing a sudden and unexpected end of the current ice age?
I gotta say, 1010011010 (or do you mind if I just call you by your decimal equivalent 666? much easier to type), your standards for scientific credibility seem extremely… variable.
On the one hand, you’re complaining about the almost universally-accepted hypothesis that human emissions have caused the recent climb in atmospheric GHG levels, because you personally don’t feel scientists have adequately accounted for the increase in carbon absorption during the period of human industrial activity.
In practically the next breath, though, you’re willing to blithely hypothesize that the cause of the observed warming trend is that we’re now seeing a completely unexpected and unaccountably sudden end to the current ice age, despite the utter lack of any known physical mechanism or statistical pattern that we could use to justify any such occurrence at the present time!
One difference is that nonanthropogenic climate change is usually a whole lot slower, and the ecosystem has more time to adapt. As does the human economy.
The short version seems to be: Le Chatelier’s principle. Which brings us back to the question: how does global warming affect the chemical equilibrium of the network of reactions that make of the oceanic portion of the carbon cycle? Warming the seas should reduce solubility, right? Resulting in net increase in atmospheric CO2, right? Thus we would expect CO2 and Temperature to closely track, right? There’s ten times more carbon tied up in the oceans than the entire estimated fossil fuel reserves, seems like this might be something that deserves considerable attention. Instead we’re looking at the dwarfed fraction of the fuel reserves we manage to burn each year.
We’re seeing climatic changes significantly different from what we’ve seen over the past several hundred thousand years?
It’s more a matter of being unsatisfied with the scale of action being proposed compared with the inadequacy of the knowledge presented to justify the actions. It really does seem to boil down to a “correlation is causation” argument with a bunch of very nice graphs.
jstone’s fountain analogy is a good example. That seems like the basic argument being made all the way to the very top… but that’s not what’s actually happening. When you add water to a fountain, the level doesn’t go up by 50% of the water you add. When you add a bucket of water to a fountain, the level doesn’t go up temporarily and then rapidly return to the previous level. What’s actually happening? “It’s poorly understood, but have you seen all our very pretty graphs?”
Kyoto inexplicably ignores large controllable sources of GHG emissions from things like coal seam fires. It lines them out of a nation’s carbon debt as “natural” and it’s like they magically stop contributing to global warming. It doesn’t say that they’re a shared responsibility which we should all work together at eliminating.
I agree that the “greenhouse” atmospheric model is basically correct.
I agree that global temperatures have been increasing lately.
I agree there are a number of factors that show varying degrees of correlation.
I do not agree that the causative relationships between those factors have been adequately explored to warrant the level of attention applied to anthropogenic GHG emissions to the exclusion of all other possible causes.
My lack of agreement at that last point is due to the inadequacy of the information I’ve encountered to this point… not hostility or willful ignorance. It seems like most of the explanatory information is tailored to people who deny global warming in general OR people who accept anthropogenic global warming. The main subject I’m stuck on is glossed over in both cases.
You have two effects: First, the increase in CO2 in the atmosphere itself causes the equilibrium to change such that the upper oceans start to absorb more CO2. A secondary effect is, as you say, that as the oceans warm, they can’t hold as much CO2. However, the first effect is the more important…although the second will help to limit how much the oceans can help get rid of the excess CO2 that we emit.
Well, people have thought about it. And, while there may be a lot of carbon in the oceans, the part of the oceans that warm and the amount that they warm is not such that what it releases dwarfs the amount of CO2 we are releasing from fossil fuels. In fact the opposite is true and because of the effect of increased CO2 concentration in the atmosphere, measurements show that the amount of CO2 in the oceans is increasing…making the oceans more acidic.
Okay, so let me get this straight. Since industrialization, over the period of about a century, we are seeing these climatic shifts and you want to conclude that it is not due to the well-understood mechanism by which we have increase levels of greenhouse gases but instead just so happens by coincidence to correspond to the century in which the earth’s climate system on its own decided it was bored with the climate it has been in for the last several million years and will switch to a new one that we haven’t seen for millions of years? Doesn’t that sound a tad bit unlikely? Add to that I don’t think there is any evidence that such global climate shifts in the past occurred on such a rapid timescale (except, e.g., from a major asteroid impact) and with no discernable cause.
You explained it yourself…Le Chatelier’s principle. With increasing atmospheric CO2 concentrations, the equilibrium with the upper oceans shifts and they are able to take up some of the excess CO2.
You are making the mistake of believing that because scientists don’t understand absolutely everything about the carbon cycle, they understand essentially nothing about it. You is seem to be making the mistake of believing because you don’t understand something, the scientists don’t either.