Global Warming: Earth 10,000 AD

Dinwar said:
Not disagreeing with you. Seeing as how Yellowstone's been moving up and down a bit more than I'd like I'm not discounting the idea that it'll go boom, but then again "more than I'd like" translates roughly to "at all" in this case. :)
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Shhhh, you're tempting fate! :covereyes

The particulates (and sulfides [sulfates?]) temporarily cool the planet. The CO2, methane, water vapor, and other chemicals released warm the planet. The cooling lasts for a short time, while the warming lasts substantially longer.
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But (as you point out below) the overall GHG emissions pale in comparison to human emissions, except in the event of a really BIG volcano. But, the likelihood (ie. a particular eruption being a 1/200 or 1/500 etc year event) ,the statistical probability thereof, is very much factored into GCM's

All the models I've seen tend to ignore volcanism, unless they're specifically built to look at the effects of volcanism. With as random as eruptions are it's hard to predict them. I mean, the small ones (Hawaii, the vents in the deep sea, etc--small in terms of property destruction, not necessarily output) are probably factored in as part of the overall CO2 increase in most models, meaning it's dealt with as more or less a constant amount and therefore doesn't change over time. A major eruption--a cauldera or Krakatoa (Mt. St. Helens doesn't count)--would substantially alter our GCMs, one way or another (usually not the direction AGW deniers would like).
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Hansen predicted Pinatubo, don't you know? AFAIK vulcanism is very much factored into GCM's
 
Maybe I've never delved deep enough into the math behind them, but I haven't seen any that specifically deal with volcanism. Got any more examples? (Not that I doubt you--this is something I've never heard of, and it sounds like you know more than me. I'm genuinely interested, not just being a jerk demanding you cite your sources. :) )
 
Nosi said:
Vulcanism can lower tempature by poluting the air with small particulate matter. "The year without a summer" was caused by a big eruption.
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There have been quite a few "years without a summer" in recorded history, each new one tends to eclipse the previous. They're all associated with volcanic eruptions, and the effects last a year or two at most. To have an effect on climate there has to be sustained volcanic activity such as occurred in the 19thCE (or sustained inactivity which we've had for the last century or so, and which occurred around 1000CE). Then the positive feedbacks (which have a pretty sluggish response) have time to kick in.

If the next 10,000 years have similar vulcanism to the last few million at least, it'll average out and have no overall effect.
 
Dinwar said:
Maybe I've never delved deep enough into the math behind them, but I haven't seen any that specifically deal with volcanism. Got any more examples? (Not that I doubt you--this is something I've never heard of, and it sounds like you know more than me. I'm genuinely interested, not just being a jerk demanding you cite your sources. :) )
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Why do you consider it inappropriate to ask people who make assertions or claims in a science forum to support their statements?
 
It's not that I consider it inappropriate. There is, however, a difference between "That's interesting--I'd like to learn more" and "You're wrong, I don't believe you, and I demand you produce your references right now". I wrote that because I'm not the best at transmitting tone in a post, and wanted to be clear which tone I was going for.
 
Dinwar said:
All the models I've seen tend to ignore volcanism, unless they're specifically built to look at the effects of volcanism. With as random as eruptions are it's hard to predict them. I mean, the small ones (Hawaii, the vents in the deep sea, etc--small in terms of property destruction, not necessarily output) are probably factored in as part of the overall CO2 increase in most models, meaning it's dealt with as more or less a constant amount and therefore doesn't change over time. A major eruption--a cauldera or Krakatoa (Mt. St. Helens doesn't count)--would substantially alter our GCMs, one way or another (usually not the direction AGW deniers would like).
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Actually most model runs include volcanic eruptions mimicking normal volcanic activity with Pinatubo or larger eruptions occurring periodically.
 
People have said that, but what I'm asking for is a specific paper/model I can look at to see how they model such things. Without looking at the model I can't agree or disagree with it--it's just a number, or a picture.
 
Dinwar said:
It's not that I consider it inappropriate. There is, however, a difference between "That's interesting--I'd like to learn more" and "You're wrong, I don't believe you, and I demand you produce your references right now". I wrote that because I'm not the best at transmitting tone in a post, and wanted to be clear which tone I was going for.
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Understandable, but, many on this forum are probably more sensitive to those who act offended or somehow put out by being asked for support (links, references, etc.,) than by being asked to support their statements. Motivations (congenial or oppositional) for asking are largely irrelevent. Of course, that is not par for the course across the internet, so it is understandable you may not have realized this.

So, what are you looking for with regards to volcanism and climate models, just general statements and accountings which indicate that such are accounted for, or something more detailed and specific?
 
Dinwar said:
People have said that, but what I'm asking for is a specific paper/model I can look at to see how they model such things. Without looking at the model I can't agree or disagree with it--it's just a number, or a picture.
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And how will you judge whether or not any given method of accounting for volcanism in a given climate model is accurate and sufficient?
 
Here's a good article on Hansen's famous 1988 projections (which I had in mind when I replied)

http://www.realclimate.org/index.php/archives/2007/05/hansens-1988-projections/

In the original 1988 paper, three different scenarios were used A, B, and C. They consisted of hypothesised future concentrations of the main greenhouse gases – CO2, CH4, CFCs etc. together with a few scattered volcanic eruptions. The details varied for each scenario, but the net effect of all the changes was that Scenario A assumed exponential growth in forcings, Scenario B was roughly a linear increase in forcings, and Scenario C was similar to B, but had close to constant forcings from 2000 onwards. Scenario B and C had an ‘El Chichon’ sized volcanic eruption in 1995. Essentially, a high, middle and low estimate were chosen to bracket the set of possibilities. Hansen specifically stated that he thought the middle scenario (B) the “most plausible”.

These experiments were started from a control run with 1959 conditions and used observed greenhouse gas forcings up until 1984, and projections subsequently (NB. Scenario A had a slightly larger ‘observed’ forcing change to account for a small uncertainty in the minor CFCs). It should also be noted that these experiments were single realisations. Nowadays we would use an ensemble of runs with slightly perturbed initial conditions (usually a different ocean state) in order to average over ‘weather noise’ and extract the ‘forced’ signal. In the absence of an ensemble, this forced signal will be clearest in the long term trend.
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And how will you judge whether or not any given method of accounting for volcanism in a given climate model is accurate and sufficient?
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Considering I have a background in geology and paleontology, and have taken several paleoclimetology classes, oceanography classes, etc., I'm pretty confident that my own view of the thing would suffice, particularly considering I'm not intending to publish anything or use these models for anything, but rather to educate myself about how these models work. Because people who use GCMs sometimes test their data using paleoclimetological records (and most of that data comes from fossils) I thought it would be a good idea to educate myself about paleoclimetology, and by extension GCMs. Not to belabor the point, but I'm familiar with the general concepts behind the models. This is new data, which always interests me.

However, if there are tricky bits that I don't understand I have several options. I can 1) look into the subject more deeply (through peer reviewed research, asking people I know with far more experience in models in general than I have (for example, my wife has a background in physics and geology)), 2) ask people here who are far more knowledgeable than I about such models and about volcanology, 3) talk to old professors and friends who study climetology and volcanology (one of the benefits of my background--I actually have those friends), or if all else fails 4) ask the author for a brief explanation (doubt they'll respond, but it'd be worth a shot).

In all, I'm pretty confident that I can accurately asses how well the models model global climate, and how well they handle factors such as volcanism.

So, what are you looking for with regards to volcanism and climate models, just general statements and accountings which indicate that such are accounted for, or something more detailed and specific?
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Not sure yet. First and foremost I'd want to see one that's been ground-truthed--that is, one that's been applied to some previous events and can yield a reasonably close proximity to what actually happened. If I can't get that, I'd want to see how they deal with volcanism. Do they state that it produces X tons of CO2 per year? Do they say that it can vary between X and Y tons/year? Do those numbers make sense? How do they handle the sulfur compounds? How do they handle the dust? Do they take into account the possibility of a large eruption? If so, how? If not, why not? Do they account for the differences in response to equatorial volcanism vs. temperate volcanism?

Like I said, none of the models I've seen deal with volcanism at all, or at least that part has never been discussed in ANY detail. At most, I may have seen a line saying "This model assumes volcanic activity will remain constant, contributing X tons of CO2/year", or something similar. Considering the complexity of the issue involved, I'm curious to see what's going on under the hood.

bit_pattern: Thanks. I'll look into that. :)
 
refamat said:
some geologists believe the term glacial period means that there are glaciers in existence, when they are gone, you have the interglacial period.
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As far as I understand, time is split into epochs of 'greenhouse', 'icehouse', and 'snowball Earth'. We are currently in an icehouse epoch and even during the interglacials we still have significant glacial coverage.
 
And other geologists think that the term "glacial period" means when ice expanded down into the lower latitudes (remember, "glacial period" and "icehouse earth" aren't the same thing). More specifically, glacial and interglacial periods are recognized by temperature, CO2 levels, delta-C13, delta-O18, and a few other things.

Either way, the presence/absence of glaciers as such isn't and cannot be the main factor. For example, we are currently in an interglacial period. However, there are substantial glaciers in Antarctica and Greenland, as well as substantial alpine glaciers on a number of mountain ranges. We have evidence of alpine glaciation in periods not considered ice ages (some morains from the Mesozoic, I don't remember which off hand). So no geologist has ever said that a glacial period is simply when glaciers are present.
 
Dinwar said:
bit_pattern: Thanks. I'll look into that. :)
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Dunno if you're familiar with RC or not but they have a lot of layman's info on GCM's, there is a lengthy GCM FAQ there somewhere that might go into more details on volcanism.
 
Dinwar said:
Like I said, none of the models I've seen deal with volcanism at all, or at least that part has never been discussed in ANY detail. At most, I may have seen a line saying "This model assumes volcanic activity will remain constant, contributing X tons of CO2/year", or something similar. Considering the complexity of the issue involved, I'm curious to see what's going on under the hood.
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Volcanism isn’t part of the model it’s an input to the model just like CO2. Levels of volcanic activity come from the scenario being looked at. When Pinatubo erupted for example, it was used extensively as a test platform for models of the day. It wasn’t built into the model, instead it was entered into the models to predict what it would do to the climate, something they did quite well
 
Volcanism isn’t part of the model it’s an input to the model just like CO2.
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Which makes how they deal with it even more interesting.

What I'd love to see is a range--models that have been run 1000 times or so (going off PAST's standard bootstrap/jack knife tests) using various levels of volcanic activity, ranging from none to a full-scale basalt trap cutting loose, and from the equatorial areas to the higher latitudes. That'd be the best way to demonstrate the effects of volcanism. We could probably cut down on the options using the most probable eruption locations, and eruption sizes.

Baring that I'd like to see 1000 papers on the topic, each covering a different section. :)

I know I won't GET it (supercomputers aren't cheap), but that's my wish list! :D
 
Dinwar said:
Which makes how they deal with it even more interesting.

What I'd love to see is a range--models that have been run 1000 times or so (going off PAST's standard bootstrap/jack knife tests) using various levels of volcanic activity, ranging from none to a full-scale basalt trap cutting loose, and from the equatorial areas to the higher latitudes. That'd be the best way to demonstrate the effects of volcanism. We could probably cut down on the options using the most probable eruption locations, and eruption sizes.

Baring that I'd like to see 1000 papers on the topic, each covering a different section. :)

I know I won't GET it (supercomputers aren't cheap), but that's my wish list! :D
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The issue, however, is how much of this is necessary to characterize the volcanism as a well accounted for factor in general climate modelling, while acknowledging that enhancing our understanding and incorporating such detailed understandings more intimately into these general models will undoubtably make such models more robust, the question is more practically, whether or not the currently modelling is sufficient to yield reasonably reliable information and actionable projections.
 
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