A Note: Global Warming Threads

[iceaura]

The fact that water is produced is wholly irrelevant for two reasons.
1. Water absorption bands are pretty much saturated, so any additional radiative forcing from them is going to be minimal.

As with the CO2, an increase in the absolute concentration of water vapor at high altitudes will create significant greenhouse warming regardless of the "saturation" of the absorption bands - this is so even if the absorption bands were always saturated lower down, which instead varies with the actual concentration of water vapor.

2. The water is Catalytic - the reaction starts when one molecule of Ozone reacts with one molecule of water to produce a hydroxyl radical, and then later a molecule of water is produced as a reaction product.

There is no net production of water in the oxidation process.

The net result of complete methane oxidation is two molecules of water and one of CO2 - says Wiki and everyone else.

According to all sources, methane oxidation is the primary source of water vapor in the upper atmosphere. If there is more of it, increasingly, and the oxidation rate keeps up, it will contribute more water vapor. If the oxidation rate does not keep up, there will be more methane. Either way, an increased greenhouse effect is predicted.

The increased possibility of hydroxyl formation in the sunlight, from the increased water supply, could easily buffer things - but at a higher concentration of water vapor and methane both, in the stable steady state.

"We are, some of us in attempt anyway, discussing the hazards of the anthro CO2 buildup and consequent heat trapping, most recently the possibility of touching off a run of positive feedback in methane release from cold storage.
”
Recently? I've seen reference to Clathrate feedback mechanisms dating back to 1995.

Recently in this thread, last few pages. Now devolving into nsea level increases?

What you seem to be missing is that when you see reports about hundreds of millions being affected, that doesn't mean that they all have to move, just that they have to do something.

You know, for most it will be building seawalls and/or dikes.

Fantasy - few of the people rice farming in low level river delta country will be able to keep salt water out of their water tables and paddies by use of dykes, say - not only poverty, but geography and engineering problems prevent it. They will have to move - and there is no where for such large numbers of people to go, neither is there any replacement for the delta wet-paddy rice farming that is the world's most productive agricultural system at the moment. There are no such deltas and wet-rice setups at higher altitudes.

 

[iceaura]

4.1 Capacity for doomsday
Fortunately, most of the hydrate reservoir seems insolated from the climate of the Earth’s surface, so that any melting response will take place on time scales of millennia or longer.

The conclusion about "any melting response" does not follow.

And the "seems insulated" part is a probability, a presumption based on current appearances based on an admittedly incomplete assessment of possibilities.

4.2 Permafrost deposits
No mechanism has been proposed whereby a significant fraction of the Siberian permafrost hydrates could release their methane catastrophically.

But mechanisms have been proposed by which they could begin to release their methane more and more rapidly, in a feedback process.

4.5 Century-timescale response
On the timescale of the coming century, it appears that most of the hydrate reservoir will be insulated from anthropogenic climate change. The exceptions are hydrate in permafrost soils, especially those coastal areas, and in shallow ocean sediments where methane gas is focused by subsurface migration.

Those are significant exceptions.

The most likely response of these deposits to anthropogenic climate change is an increased background rate of chronic methane release, rather than an abrupt release.

One of the names we have for a sufficiently increased background rate is "disaster".

The question being considered is: what are the odds on disaster, here? Are they long enough to be commensurate with the scale of the possible damages?

 

[adoucette]

Fantasy - few of the people rice farming in low level river delta country will be able to keep salt water out of their water tables and paddies by use of dykes, say - not only poverty, but geography and engineering problems prevent it. They will have to move - and there is no where for such large numbers of people to go, neither is there any replacement for the delta wet-paddy rice farming that is the world's most productive agricultural system at the moment. There are no such deltas and wet-rice setups at higher altitudes.

Clearly, since I'm talking about these huge numbers afra brought up I have to talk in generalities,

when you see reports about hundreds of millions being affected, that doesn't mean that they all have to move, just that they have to do something.

And indeed, for most of those hundreds of millions it will be building seawalls and/or dikes, and yet you ignore that and focus on one place where the general solution won't work and use that exception to call my response a Fantasy.

But you claim you have been following the discussion and so you know that I've discussed Bangladesh quite a few times.

Indeed, I posted a topographic map of Bangladesh and I used that map to point out how little elevation there was even far from the coast, and I suggested that the people there were some of the worst off from rising waters:

Bangladesh is probably one of the places on the globe where the extent of the problem and the lack of funds to deal with it are at the greatest odds, and the world does need to help them out,

I also posted the IPCC data to put the number of people and the timeframes in perspective (compared to the claim of hundreds of millions)

This analysis showed that much of the population of these 40 deltas is at risk through coastal erosion and land loss, primarily as a result of decreased sediment delivery by the rivers, but also through accentuated rates of sea-level rise. They estimate, using a coarse digital terrain model and global population distribution data, that more than 1 million people will be directly affected by 2050 in three megadeltas: the Ganges-Brahmaputra delta in Bangladesh, the Mekong delta in Vietnam and the Nile delta in Egypt. More than 50,000 people are likely to be directly impacted in each of a further 9 deltas, and more than 5,000 in each of a further 12 deltas

So realistic data, no fantasy at all.

Arthur

 

[Trippy]

As with the CO2, an increase in the absolute concentration of water vapor at high altitudes will create significant greenhouse warming regardless of the "saturation" of the absorption bands - this is so even if the absorption bands were always saturated lower down, which instead varies with the actual concentration of water vapor.

1. The source of radiation is below the greatest densities of water vapour, not above it - hence predictions of Mesopheric cooling and the current interest in noctilucent clouds.
2. The concentration of water in the atmosphere is governed by the Clapeyron-Clausius equation - at a given temperature there's only so much water vapor the atmosphere can hold, the rest precipitates out.

Saturated means precisely that, saturated. You can't consider parts of the atmosphere independently, you need to consider the whole column. If the absorption bands are saturated near ground level, then that means that the radiations simply isn't there to absorbed at higher altitudes - hence predictions of Mesopheric cooling.

Global warming is bottom up, not top down.

Again, keep track of what I'm actually saying - I'm not claiming that there will be no increases in absoprtion, only that those increases will be small.

According to all sources, methane oxidation is the primary source of water vapor in the upper atmosphere. If there is more of it, increasingly, and the oxidation rate keeps up, it will contribute more water vapor. If the oxidation rate does not keep up, there will be more methane. Either way, an increased greenhouse effect is predicted.

Water absorption bands are in the region of non-linear response - the degree of saturation of the water absorption bands means that any further absorption can only be achieved through spectral band broadening, and there's only so much of that that can occur. With the amount of water vapor that's in the lower atmosphere, an increase of orders of magnitude is virtually required to produce a linear increas in long wave absorption due to water.

This is why Methane is rated as such a highly potent GHG - its spectral bands are in the right part of the spectrum, and are nowhere near saturation.

The increased possibility of hydroxyl formation in the sunlight, from the increased water supply, could easily buffer things - but at a higher concentration of water vapor and methane both, in the stable steady state.

Show me again where I claimed otherwise?
You're familiar with buffer solutions right?
Large additions of acid result in small movements, not no movement of pH.
I didn't claim that there would be no net change in Methane, only that if buffering occurs then we should expect any net changes to be small until some critical value is exceeded.

I'm not sure why you seem to object to this idea as it (as I've already pointed out) provides a natural causal mechanism for the observed flatness in the methane graphs that Arthur has been posting.

Recently in this thread, last few pages. Now devolving into nsea level increases?

That was something in response to Billy.
He stated that positive feedback, and increased halflife was something that had only recently been considered.
I responded by saying that they had been considered since at least 1995.

 

[adoucette]

The conclusion about "any melting response" does not follow.

And the "seems insulated" part is a probability, a presumption based on current appearances based on an admittedly incomplete assessment of possibilities.

But mechanisms have been proposed by which they could begin to release their methane more and more rapidly, in a feedback process.

Those are significant exceptions.
One of the names we have for a sufficiently increased background rate is "disaster".

You need to take those up with the author, find some science to back up your assertions though.

The question being considered is: what are the odds on disaster, here? Are they long enough to be commensurate with the scale of the possible damages?

Well I think the author makes this general point that we aren't looking at a disaster:

Hydrates are releasing methane to the atmosphere today in response to anthropogenic warming, for example along the Arctic coastline of Siberia. However most of the hydrates are located at depths in soils and ocean sediments where anthropogenic warming and any possible methane release will take place over time scales of millennia. Individual catastrophic releases like landslides and pockmark explosions are too small to reach a sizable fraction of the hydrates

(Bolding mine).

And then in the Risk section each risk is looked at and as shown before, none are labeled a disaster and they DO discuss the WORST CASE scenario, and they say that would occur over THOUSANDS of years and releases what we have doing with fossil fuels over HUNDREDS of years.

In a worst-case scenario, after thousands or hundreds of thousands of years, the methane hydrate reservoir could release as much carbon as fossil fuel emissions

Arthur

 

[arfa brane]

This analysis showed that much of the population of these 40 deltas is at risk through coastal erosion and land loss, primarily as a result of decreased sediment delivery by the rivers, but also through accentuated rates of sea-level rise. They estimate, using a coarse digital terrain model and global population distribution data, that more than 1 million people will be directly affected by 2050 in three megadeltas: the Ganges-Brahmaputra delta in Bangladesh, the Mekong delta in Vietnam and the Nile delta in Egypt. More than 50,000 people are likely to be directly impacted in each of a further 9 deltas, and more than 5,000 in each of a further 12 deltas

This doesn't seem to compare that closely with:

... there will be problems of global warming. Due largely to sea-level rise and flooding of coastal-zone communities, but also to increased droughts and disruptions of rainfall regimes, such as monsoonal systems, global warming could threaten large numbers of people, with displacement by 2050 or earlier. Preliminary estimates indicate that the total number of people at risk of sea-level rise in Bangladesh could be 26 million, in Egypt 12 million, in China 73 million, in India 20 million, and elsewhere, including small island states, 31 million, making a total of 162 million. At the same time, at least 50 million people could be at severe risk through increased droughts and other climate dislocations (Myers 1996; see, also, Watson et al. 1998).

All in all, the issue of environmental refugees promises to rank as one of the foremost human crises of our times. So far, however, it has been viewed as a peripheral concern, a kind of aberration from the normal order of things—even though it is an outward manifestation of profound deprivation and despair. Although it derives primarily from environmental problems, it generates problems of political, social and economic sorts. As such, it could readily become a cause of turmoil and confrontation, leading to conflict and violence. Yet as the problem becomes more pressing, our policy responses fall further short of measuring up to the challenge. To repeat a key point: environmental refugees have still to be officially recognized as a problem at all.

--http://webcache.googleusercontent.c...+of+the+21st+century&cd=1&hl=en&ct=clnk&gl=us

Is there a problem? I mean, the AR4 appears to have a significantly downgraded number of affected people than the earlier analysis by Myers et al. And yet, there are more recent estimates with potential numbers in the hundreds of millions. Either the IPCC is being seriously conservative or the other authors are being seriously pessimistic. Who to believe?

 

[Trippy]

Show me again where I claimed otherwise?
You're familiar with buffer solutions right?
Large additions of acid result in small movements, not no movement of pH.
I didn't claim that there would be no net change in Methane, only that if buffering occurs then we should expect any net changes to be small until some critical value is exceeded.

I'm not sure why you seem to object to this idea as it (as I've already pointed out) provides a natural causal mechanism for the observed flatness in the methane graphs that Arthur has been posting.

I'm going to elaborate on this a little further - why I think it's so important.

At this point, regarding Methane, on the one hand we have the argument forwarded (including by me) that Tundra and Siberian shelf methane emissions are increasing, and going to become increasingly important in the future, seemingly backed up by insitu observations.

On the other hand we have the observation that the amount of Methane in the atmosphere has flatlined.

The idea that as a result of the chemistry involved, the atmosphere provides a degree of buffering to Methane levels provides a means of reconcilling these two seemingly conflicting observations without the need to invoke anthropogenic changes - the reality is it's probably a combination of both.

And as, I believe, I have stated repeatedly buffers have limits, they can only be pushed so far - hence my comments regarding thresholds.

 

[Trippy]

And then in the Risk section each risk is looked at and as shown before, none are labeled a disaster and they DO discuss the WORST CASE scenario, and they say that would occur over THOUSANDS of years and releases what we have doing with fossil fuels over HUNDREDS of years.

Arthur

In fact, one scenario examined (it might be Archer 2005) is the effects of release of the entire (estimated) store in timescales as short as 1000 years.

 

[adoucette]

In fact, one scenario examined (it might be Archer 2005) is the effects of release of the entire (estimated) store in timescales as short as 1000 years.

By any mechanism related to AGW?

 

[Trippy]

By any mechanism related to AGW?

I don't recall.

I have an inkling they treated them as two seperate issues.

First the examined releases of various amounts over various timeframes.
Then they examined various release scenarios, the likelyhood of those scenarios, and the quantities of methane involved.

I have to be honest though - it's been longer than I'd care to admit since I read either of them in depth.

 

[iceaura]

Again, keep track of what I'm actually saying - I'm not claiming that there will be no increases in absoprtion, only that those increases will be small.

So we are agreed that they could easily be significant - as with the CO2, despite "saturation".

1. The source of radiation is below the greatest densities of water vapour, not above it

Mostly. And those densities vary a lot.

- hence predictions of Mesopheric cooling and the current interest in noctilucent clouds.

Which are above regions of methane influence, including water vapor contribution.

2. The concentration of water in the atmosphere is governed by the Clapeyron-Clausius equation - at a given temperature there's only so much water vapor the atmosphere can hold, the rest precipitates out.

That governs the maximum. What we are talking about is contribution to the actual - and that only in the event that the methane is oxidized as fast as it is produced, that the buffering is not overpowered.

You need to take those up with the author, find some science to back up your assertions though.

I have no serious quarrel with the author, as far as I can tell. He's the one carefully specifying "presumably" and so forth - a bit slippery, but the situation is visible in his descriptions.

Well I think the author makes this general point that we aren't looking at a disaster:

“
Hydrates are releasing methane to the atmosphere today in response to anthropogenic warming, for example along the Arctic coastline of Siberia. However most of the hydrates are located at depths in soils and ocean sediments where anthropogenic warming and any possible methane release will take place over time scales of millennia. Individual catastrophic releases like landslides and pockmark explosions are too small to reach a sizable fraction of the hydrates
”
(Bolding mine).

So? How does that description eliminate disaster from the possibilities?

The only form of disaster the author concludes from evidence is reasonably unlikely to the point of impossibility is an immediate and very quick onset Venusian catastrophe. Other than that, lots of possibilities are admitted.

And if we bring our own info to the table - such as by noticing that his presumption of no thresholds or break points in the factors governing methane release from any source, is not a sure thing - these possibilities gain likelihood to some degree.

 

[Trippy]

So we are agreed that they could easily be significant - as with the CO2, despite "saturation".

No, because I am unconvinced that any scenario posited could lead to a large enough increase in water vapor concentration.

And remember, I've explicitly argued against CO2 being saturated, and argued that ppCO2 is in the region resulting in linear responses.

Mostly.

Unless you want to get into a discussion of (significant) Topography, entirely.

And those densities vary a lot.

I made no claim to the contrary - only the implication that I'm discussing the bulk composition of the atmosphere.

However, the regions that have low methane concentrations tend to have low water vapor concentrations, the Methane being generally biogenic.

Which are above regions of methane influence, including water vapor contribution.

No.

Also consider - Polar Mesopheric Clouds.

That governs the maximum. What we are talking about is contribution to the actual - and that only in the event that the methane is oxidized as fast as it is produced, that the buffering is not overpowered.

As this is phrased, it's virtually meaningless. The buffering effects on Methane concentrations have nothing to do with the Clapeyron Clausius equation.

I have no serious quarrel with the author, as far as I can tell. He's the one carefully specifying "presumably" and so forth - a bit slippery, but the situation is visible in his descriptions.

Nothing slippery about it. He's not using weasel words, he's simply using cautious language.

 

[iceaura]

That governs the maximum. What we are talking about is contribution to the actual - and that only in the event that the methane is oxidized as fast as it is produced, that the buffering is not overpowered.
”
As this is phrased, it's virtually meaningless.

? Simply that the maximum possible water vapor concentration is not involved, in general - we are talking about the commonly found or generally obtained concentration, and the possible increasing contribution to it of methane oxidation - which requires the methane oxidation be increasing, which requires that the buffering be keeping pace more or less (otherwise you have increasing methane but not increasing water vapor).

Which are above regions of methane influence, including water vapor contribution.
”
No.

? According to your entire discussion here, mesospheric cooling and so forth, as well as the rest of the evidence, the methane contribution to water vapor is in the stratosphere and troposphere - in some fairly dry layers of the atmosphere, in particular.

 

[Trippy]

? Simply that the maximum possible water vapor concentration is not involved, in general - we are talking about the commonly found or generally obtained concentration, and the possible increasing contribution to it of methane oxidation - which requires the methane oxidation be increasing, which requires that the buffering be keeping pace more or less (otherwise you have increasing methane but not increasing water vapor).

It's absolutely involved, because it places a cap on the maximum column density of water vapor in the atmosphere, and a cap on the maximum amount of radiative forcing water vapor can contribute.

Especially when one considers in conjunction with it where in the stratosphere the Methane actually is.

 

[iceaura]

It's absolutely involved, because it places a cap on the maximum column density of water vapor in the atmosphere, and a cap on the maximum amount of radiative forcing water vapor can contribute.

Why are we worried about a cap so seldom approached?

 

[Trippy]

Why are we worried about a cap so seldom approached?

Seldom approached?
You understand the concept of relative humidity, right?

 

[Trippy]

? According to your entire discussion here, mesospheric cooling and so forth, as well as the rest of the evidence, the methane contribution to water vapor is in the stratosphere and troposphere - in some fairly dry layers of the atmosphere, in particular.

Ummm, not really, no.

 

[iceaura]

Seldom approached?
You understand the concept of relative humidity, right?

I have never seen it at 100% over even one entire continent at ground level - let alone the entire atmospheric column on a global scale.

? According to your entire discussion here, mesospheric cooling and so forth, as well as the rest of the evidence, the methane contribution to water vapor is in the stratosphere and troposphere - in some fairly dry layers of the atmosphere, in particular.
”
Ummm, not really, no.

Not really what?

 

[Trippy]

I have never seen it at 100% over even one entire continent at ground level - let alone the entire atmospheric column on a global scale.

Irrelevant.
Not the claim I made.
Not implied by anything I said.

Having said that:

Now you have.
(data for 10-14km)

 

[iceaura]

Irrelevant.
Not the claim I made.
Not implied by anything I said.

So we can shelve the Clausius - Clapyeron equation, and get back to the mroe relevant issues.

Now you have.

Uh, no, not in that picture.

Tropical latitudes, 10-14 km up, seems about half saturated. Maybe less.