New estimate of effect of methane on climate

[pattylou]

I need to read through this a few more times before I really "get it" but it will be of general interest. After one read-through, it looks like the effects of methane on climate have been underestimated in the past because this gas was measured in the atmosphere after it has mixed with other GHG. It looks like if you separate out the components at the source of emission you end up with a different contributory effect of methane (twice that thought previously).

This may ultimately affect policy on climate change.

http://www.nasa.gov/centers/goddard/news/topstory/2005/methane.html

 

[Garlic Bread?]

Without looking it up, I think you'll find that natural additions of methane are twice as much as anthropogenic ones. Why would this effect our policy on CC? So what? If our methane effects it twice as much then natural emissions does to!

 

[Garlic Bread?]

Yeah. Pre-industrial baseline was 848 ppb. Natural additions have been 577 and man-made just 320.

 

[pattylou]

Of course. I am sure you understand that our society is working hard to understand the inputs into climate regardless of whether they are man made or not?

If we can cut methane emissions by reducing man-made methane, it help lower GHG in the atmosphere.

Also, any present policy that shifts us from reducing CO2 --- by increasing methane - may need to be revisited in light of this report.

Finally, natural sources of methane could at least theoretically be addressed as well, if necessary - although that is a risky proposition. For example, some microorganisms utilise methane. Swamps and bogs are natural sources of methane, but it may be possible to increase the methane-users there, I am not sure the end result of such a proposition. Alternatively, policy could entail capturing naturl methane. I am sure there are plenty of useful applications for it, although I don't know the "cost" of any of those applications.

 

[Andre]

For example, the amount of methane in the atmosphere is affected by pollutants that change methane's chemistry,

Am I missing something? Isn’t chemistry about changing compounds. If methane is changed chemically, it’s not methane anymore. isn’t it?

Molecule for molecule, Methane is 20 times more potent than carbon dioxide as a greenhouse gas,

This is a very misleading statement and it’s not true. CO2 is more than triple as strong as CH4 as greenhouse gas. But the logarithmic relation makes the first few ppbv and ppmv the most effective. If the CO2 was in the same very low concentrations as methane then the effect would have been about triple. This can be easily seen when playing a bit with the http://geosci.uchicago.edu/~archer/cgimodels/radiation.html Just enter
CO2 = 0, ch4 = 0 output:

W / m2 = 250.352

The basic value.

Then CO2=1, ch4=0,

W / m2 = 246.93

Hence a difference of some 3.4 W/m2 with the basic value

Then CO2=0, CH4=1

W / m2 = 249.442

Hence only some 0.9 W / m2 difference.

Since the decay time of CH4 in the atmosphere is about 12 years, I would not worry too much about methane.

 

[pattylou]

Am I missing something? Isn’t chemistry about changing compounds. If methane is changed chemically, it’s not methane anymore. isn’t it?

You got it! But the report is indicating that some of the chemistry (changing methane to non-methane) is creating trophospheric ozone. This is why the report recommends measuring methane emissions, not methane in the atmosphere.

This is a very misleading statement and it’s not true. CO2 is more than triple as strong as CH4 as greenhouse gas. But the logarithmic relation makes the first few ppbv and ppmv the most effective. If the CO2 was in the same very low concentrations as methane then the effect would have been about triple.

You lost me. Can you restate that? Methane is frequently cited as 25 times as potent as CO2. Are you saying that the mass comes into play? Or that the reactivity does?

I am given to understand that a molecule of methane in the atmosphere traps 20 - 25 as much heat as a molecule of CO2. I am also given to understand that methane does not remain in the atmosphere for long.

Thanks for any clarification you can give.

Since the decay time of CH4 in the atmosphere is about 12 years, I would not worry too much about methane.

Did you mean CO2? Or, is 12 years considered short? Is "decay time" the same as "half life?

Thanks Andre.

 

[CobblyWorlds]

The 12 year atmospheric residence time for CH4 is the mean time a molecule spends in the atmosphere. For water it's about 10 days, for CO2 it's of the order of a century.

I generally agree with Andre, that (I'd qualify by saying "at present") it's not as great a factor as CO2. Which given the increase in fossil fuel use by nations such as India and China is a far greater additive factor to radiative balance.

Garlic Bread also points out the amount of natural addition. However with issues such as the melting of permafrost, this ostensibly 'natural' addition, which is however driven by anthropogenic warming, could become far more significant later in the 21st century.

I agree it's a factor to watch, but nowhere near as serious as CO2. Although I'm prepared to be proven wrong on this.

As to the ModTran3 model I've not had the chance to check this out, so can't comment on the context of the figures it produces.

 

[CobblyWorlds]

Oh and PS, Andre thanks for the Modtran3 link, could be quite a useful tool.

 

[Andre]

Can you restate that? Methane is frequently cited as 25 times as potent as CO2.

Okay Let's play with http://geosci.uchicago.edu/~archer/cgimodels/radiation.html a bit more. The model calculates the absorbtion of reradiated energy and gives as output the radiated energy to space after the greenhouse absorbtion part. The temp gadget appears not to be working yet.

In my previous example I showed that 1 ppm of CO2 absorbs over 3 times as much radiation as 1 ppm CH4, falsifying the statement:

Molecule for molecule, Methane is 20 times more potent than carbon dioxide as a greenhouse gas,

But the relationship is approximately logaritmical, so you cannot compare a 1 ppm change on 375 ppm CO2 against 1 ppm change against 1,7 ppm CH4.

Now, I ran http://geosci.uchicago.edu/~archer/cgimodels/radiation.html with the default parameters (scroll down and hit "submit the calculation") and we see an output of "I out, W / m2 = 227.87".

Now, if we double the CO2 (750 ppm) the reradiated energy reduces to 225.546 W/m2. Not a lot really, because of the saturation effect that can be seen clearly in the graph in the model. The big CO2 chunk only grows minimally at the edges.

Now, put CO2 back (375ppm) and poke a double CH4 value (3.4 ppm). This gives an output of 227.367 W/m2, only 0.5 less than the original value. Note that we have to increase the CH4 to 19ppm, 11 times the current value to obtain the same effect as doubling CO2.

CH4 is oxidized in the atmosphere like this http://www.atmosp.physics.utoronto.ca/MOPITT/mdd_93/m93-b.htm
however their life time estimate is only 7 years. I hear 12 years more frequently.

 

[CobblyWorlds]

Andre,

Having checked out an article here http://www.nasa.gov/centers/goddard/news/topstory/2005/methane.html. Notwithstanding their problems with 'Challenger' I find it hard to see how NASA, not to mention many other sources, could be wrong with statements such as "Molecule for molecule, Methane is 20 times more potent than carbon dioxide as a greenhouse gas" (from the above article).

So I suspect a problem with either your reasoning or the programme you link to. In the case of the programme, it'd be interesting to see it's code. But it seems likely it's a far more simple model than using a GCM to examine the same variation of parameters, I don't imagine it would account for issues such as cloud and convection.

However I'm just to busy to attend to this issue right now. However I think that, as you seem to agree, it's reasonable to view CH4 as a far lesser issue than CO2 at present(due to the current atmos concentrations and likely future trend in fossil fuel use).

I'll see if I can get the time to look at this over the weekend, but the way I'm going sometime next year looks more likely. ;)

 

[Andre]

No the statement is part of a slippery slope of a slight exagaration and older models. If the figures get less attractive there is a reluctance to update them.

There is nobody doubting modtran3. Global warmers use it. It's world famous. There is nothing wrong with the physics behind it.

So what happens when you increase the CO2 with one ppm to 376? The basic reradiation 227,87 w/m2 decreases with 0.032 W/m2, whilst increasing CH4 with one 1 ppm to 2,7 ppm, gives a decrease of 0.314 W/m2. So the most dramatic statement, that you could make accurately, is:

With the current concentrations, CH4 is tenfold more potent than CO2 with equal increases in concentrations

 

[CobblyWorlds]

Hi Andre,

I'm quite prepared to believe it is one of those oft repeated 'rumours' whose origins are lost/not updated with time (like the 'water is 98% of the greenhouse effect' one), but I like to check things out for myself. That said I'm happy to accept your reasoning as I can't see an immediate problem. But it may be a while before I come back on it. Just another issue to be attended to. Work eating sleeping etc all gets in the way.

 

[pattylou]

,,,but nowhere near as serious as CO2. Although I'm prepared to be proven wrong on this.

I think that is generally agreed upon. The article indicates simply that methane emissions may be twice as important (as a contributor to warming) than previously thought.

I don't know the various arguments on this, but it appears naively to me that the old estimate was around 15% (of warming was attributable to methane) and that the new estimate puts it closer to 30% (of warming is attributable to methane emissions, as opposed to methane in the atmosphere, as some of the methane is converted before becoming mixed in the atmosphere.)

At 30%, it seems to be something to take more notice of.

 

[pattylou]

Yeah. Pre-industrial baseline was 848 ppb. Natural additions have been 577 and man-made just 320.

That's at odds with this report from 2002, which indicates the reverse:

http://www.sciencedaily.com/releases/2002/10/021010065923.htm

But this is a minor point.

 

[CobblyWorlds]

Hi Patty,

I've not really looked into it. In terms of satisfying myself that the observed global temp increase was due to CO2, CH4 was not a point I investigated. I'll have to check all of these figures at some point. PS the Guy on the BBC board was wrong. The NASA GISS shows a clear warming trend in the US area as stated, its all here; http://data.giss.nasa.gov/gistemp/graphs/
"GISS Graph Annual Mean Temperature Change in the United States"

 

[pattylou]

That has been my argument in the past. The most recent thing I had looked at indicated that US warming was less than global warming. Look at this figure:

Which is from this article (from the goddard institute.):

http://www.giss.nasa.gov/research/briefs/hansen_07/


...and I have emailed the author with a few questions, I hope he has time to answer them.


So I am happy to agree that the US is warming, but not as much as other parts of the world. THe point is irrelevant, as we agree, because local effects are expected, due to ... local effects!

Would you *disagree* that the US may have enjoyed less warming than most of the rest of the planet as a result of the NAO? As I see it, my present position is consistent with your own, but perhaps you understand there to have been a larger scale effect in the US than I do.

 

[Andre]

Another reason why the US may not have warmed is that worldwide most rural weather stations closed in the 1980-1990 timeframe, wereas the USA maintained just about all of them.

 

[Bystander]

The 12 year atmospheric residence time for CH4 is the mean time a molecule spends in the atmosphere. For water it's about 10 days, for CO2 it's of the order of a century.
(snip)

Got a source for "century?"

How people can get water and methane residence times correctly and botch CO₂ every time is a mystery; !.5x10¹⁵ kg divided by the annual terrestrial biological production of starch and cellulose will get you within a factor of two or three; relative productivity of the marine environment (half as much, equal to, or twice as much as terrestrial) is still being argued.

 

[pattylou]

Another reason why the US may not have warmed is that worldwide most rural weather stations closed in the 1980-1990 timeframe, wereas the USA maintained just about all of them.

I don't believe that argumnent that the US has not warmed at all, holds up. In fact, I don't think there is any scientific dispute about this question. I believe any data that suggests that the US has not warmed, has been addressed, and the only question in my mind about this is whether the US has warmed less than other parts of the world.

question 1Can you give your source for stating that the US has not warmed? In my understanding, there has been overall warming, and climate disjunction (and other local anomalies) which may appear to balance out the*extent* of warming but also is completely supportive that climate is *changing* and species are threatened as a result.

question 2Shall I find a reference for you, illustrating earlier migrations/bloom times, which clearly show the biological "thermometers" of the country responding to a warmer (and warmer and warmer) environment?

I was under the impression that you agreed the climate is changing, and warming; I was under them impression that your argument is that the warming is natural. Can you clarify?

 

[Andre]

Can you give your source for stating that the US has not warmed?

Pattylou, that's what you did already: http://www.giss.nasa.gov/research/briefs/hansen_07/

How can the absence of clear climate change in the United States be reconciled with continued reports of record global temperature? Part of the "answer" is that U.S. climate has been following a different course than global climate, at least so far. Figure 1 compares the temperature history in the U.S. and the world for the past 120 years. The U.S. has warmed during the past century, but the warming hardly exceeds year-to-year variability

The last sentence is a bit misleading. The US has warmed mainly in the first quarter of the century, after that there is no distinct trend.

And check the figure: http://www.giss.nasa.gov/research/briefs/hansen_07/fig2x.gif
See that the West USA has warmed and the East has cooled. Nett effect cancel each other out approximately. Notice also that Greenland has not warmed. Yet there is a fuzz about the ice sheet dynamics.

There is no doubt that the general trend is warming currently. The big question is why the troposphere is not keeping pace with the surface warming despite all CW attempts to conceal that. A possible explanation is underestimation of urban heat island effect. That was embedded in the suggestion about the closure of rural weather stations worldwide except in the States. I'm sure we have tons more to discuss on this item.

Sure migration patterns change, species getting under pressure, other expand. But other than preserving the habitats physically, I cannot see anything else we can do about it.

 

[Andre]

Talking about

migrations/bloom times, which clearly show the biological "thermometers"

A complete different setting that puzzles science for centuries now:

http://www.yukonmuseums.ca/mammoth/abstrh-k.htm

... On the other hand, tundra-steppe insect assemblages include some species which are currently distributed much further south (e.g., in the steppe zone) and are either not known in northeastern Siberia at present at all (e.g., Stephanocleonus tricarinatus), or occur there in narrow refugia, isolated from their main southern range, thus demonstrating discontinuous relict distribution. The latter group is quite large, and includes several species of weevils (Stephanocleonus eruditus and others), ground beetles and leaf beetles of steppe origin, having their main present ranges in southern Siberia and Mongolia, and surviving in scattered refugia in Central Yakutiya and the Yana-Indigirka-Kolyma upstreams. Finally, the tundra-steppe assemblages include some extinct species (a few weevils, a leaf beetle, and a dung beetle). The recent discoveries of these extinct species provide additional evidence of the peculiar character of the tundra-steppe insect fauna...

Now would those insects much further south now also be a biological thermometer?

 

[pattylou]

Pattylou, that's what you did already: http://www.giss.nasa.gov/research/briefs/hansen_07/

Which is why it puzzled me that you mis-represented the auihor. The author of that paper claims the US is warming. The "does not exceed year-year variations" means that the error bars are high. You cannot say that the US has not warmed. All you can say - is what he said. The US is warming, and year to year variability is higher yet. The warming occurs at a slower rate than the rest of the planet. (He speculates this is due to the NAO, and that the NAO is entering a warming phase now. so the US may show even greater warming soon.)

Also, the same article states that

"The strongest warming has been in Alaska and northern Asia. "

This is *completely* consistent with a geographical explanation (the NAO buffering much of the contiguous 48 states) , and not consistent with the idea you propase, that the US maintained rural stations. Unless you argue that Alaska removed its rural stations as well.

A geographical explanation for the NAO providing a cooling buffer to the US, is consistent with the data, and illustrated here:

Sure migration patterns change, species getting under pressure, other expand. But other than preserving the habitats physically, I cannot see anything else we can do about it.

It's not a question of "species under pressure." The changes in ecology are consistent with warming. This is an independent measure of warming, independent of man-made devices. Again, would you like me to spend time finding you some references? It sounds as though you find the idea of entire biotic systems behaving differently, irrelevant to the question of warming. Surely that isn't the case?

(if this sounds adversarial, it isn't intended that way.)

 

[pattylou]

Talking about

A complete different setting that puzzles science for centuries now:

http://www.yukonmuseums.ca/mammoth/abstrh-k.htm



Now would those insects much further south now also be a biological thermometer?

That's an interesting contribution. I'll have a look at it. But we're off to the beach for the afternoon --- It's *hot* here.

My first thought is that the new patch of organisms are existing in a micro-environment (one that receives greater snowpack due to climate change, for example), or that they are genetically distinct from the organisms further north. But not having read the article yet, I don't know. THank you for the reference. I'll read it and let you know.

Would you like to see some as well?

 

[Andre]

It's *hot* here

The Netherlands is experiencing the start of the new ice age today: 60F

The author of that paper claims the US is warming. The "does not exceed year-year variations" means that the error bars are high.

This is semantics. Hansen provides a graph that clearly shows visually that the last century does not show a consistent warming trend that lasts longer than 30 years (climate being defined as the average weather of 30 years). There are periods of warming and periods of cooling. The last years shows warming but what does it signify?

I showed some biological pecularities of North Siberia at the end of the Pleistocene, since this is the weakest link in the paleao climate reconstruction of the Ice ages. Things simply don't add up at all so it's ignored. But the current global warming myth is based on that same paleao climate reconstruction, which the author of that American climate paper, Hansen, presented in a Congress hearing in 1988. This was the start of the hype.

 

[pattylou]

This is semantics. Hansen provides a graph that clearly shows visually that the last century does not show a consistent warming trend that lasts longer than 30 years (climate being defined as the average weather of 30 years). There are periods of warming and periods of cooling. The last years shows warming but what does it signify?

But in any case one must be careful to not skew what the author reports.

The author does not report 'no warming,' (That's your interpretation of the graph, and most climatologists disagree with it) and I am aware of *no* peer reviewed work that says the US has not warmed. The statements are carefully phrased for a reason - we must not misrepresent the science. It leads to confusion in discussion. Someone may come away from such a discussion believing that there is science that shows in a black-and-white way, that the US has not warmed, and that is not the case. In many many ways, warming has been demonstrated. In no way, has "no warming" been demonstrated.

According to *this* paper, the warming in the US is less than other regions of the world, including Alaska. This result is completely consistent with the idea that there are local phenomena that affect climate, such as the North Atlantic Oscillation, which would not extend to Alaska.

I don't know much about the Siberian record. I haven't had a chance yet to look at the report on weevils yet, either. We are heading to the beach again in a few hours.

 

[CobblyWorlds]

Hi Bystander,

About a century is the figure that is quoted all over the place. I'll try to find a source, but do you know different?

I do not follow you reasoning:

"!.5x1015 kg divided by the annual terrestrial biological production of starch and cellulose will get you within a factor of two or three; relative productivity of the marine environment (half as much, equal to, or twice as much as terrestrial) is still being argued."

 

[CobblyWorlds]

Hi again Andre,

“The big question is why the troposphere is not keeping pace with the surface warming despite all CW attempts to conceal that.”

With respect to the discrepancy between surface and tropo- I accept it.(were you referring to me?) I don’t know the reasons and from what I read neither do the climate science community.

Your Hansen link is interesting. As an aside, when you compare the graph quoted there to the GISS Graph Annual Mean Temperature Change in the United States.(Annual and five-year running mean surface air temperature in the contiguous 48 United States relative to the 1951-1980 mean.) Available here http://data.giss.nasa.gov/gistemp/graphs/Fig.D.pdf there seem to be a difference, in Hansen’s an upward trend from 1880 to 1920. Anyone know why?

I hate to tread on Hansen’s feet, after all I’m no expert. But: The graph is below the 1951 to 1980 mean until 1920, oscillating between 0 and -1 anomaly until it then rises to a peak in the 30s and descends to a minimum in the late 60s. From then on it goes upwards and recently indicates a downwards slope.

Carry out a simple visual integration on it. It becomes clear that when counting the area between the red trend line and the 0 anomaly centre line, the area is predominantly negative in the first part of the graph and becomes predominantly +ve (above the 0 anomaly line) in the second part. i.e there is a clear trend from below the 0 anomaly to above the 0 anomaly with time. This is a real long-term component, i.e. it is there, it could not continue indefinitely without exposing itself eventually. The question that this graph cannot answer is what the significance is, if any. Hansen is totally correct in pointing out that this does not agree with the global trends and that understanding this will be a key pre-requisite for improving modelling.

But as this is a regional indicator it cannot be used to question the global temperature which, on a global basis, by all measuring means, shows a clear upward trend across the data available for those measuring means.

 

[CobblyWorlds]

Correction "Hansen is totally correct in pointing out that this does not agree with the <degree of increase> shown in global trends... "

 

[pattylou]

As an aside, when you compare the graph quoted there to the GISS Graph Annual Mean Temperature Change in the United States.(Annual and five-year running mean surface air temperature in the contiguous 48 United States relative to the 1951-1980 mean.) Available here http://data.giss.nasa.gov/gistemp/graphs/Fig.D.pdf there seem to be a difference, in Hansen’s an upward trend from 1880 to 1920. Anyone know why?.

I flicked back and forth between the two graphs. They're awfully close, but not quite the same, aren't they? Ex: the 1889 point is off in the two graphs.

Can you provide an article that references your graph? They may be correcting for some factor that wasn't corrected for in the other link.

 

[Bystander]

Hi Bystander,

About a century is the figure that is quoted all over the place. I'll try to find a source, but do you know different?

I do not follow you reasoning:

"!.5x1015 kg divided by the annual terrestrial biological production of starch and cellulose will get you within a factor of two or three; relative productivity of the marine environment (half as much, equal to, or twice as much as terrestrial) is still being argued."

Residence time: for a "steady state" system, quantity in a reservoir divided by flux is residence time. Quantity? 1.5x10¹⁵ kg. Flux? Sum of ALL processes contributing to addition or removal of material to or from the reservoir: for CO₂ in the atmosphere, photosynthesis is the big removal mechanism. How much plant mass (dry) is produced in a year's time?

Your 100 year residence time implies a global productivity of 15 billion tons of vegetable matter a year, ton per terrestrial hectare per annum, pick your units. There are "estimates," we know what those are worth, that marine productivity is two to three times that of dry land, cutting the ton per hectare down to 1/3 or 1/4. When's the last time you raked leaves? Mowed lawns? Cut wheat? Baled hay? Ran cattle in N. Mex. or Wyo.? 1/3 to 1/4 ton per hectare per annum is very high for the Sahara, Antarctica, Kara Kum, Serengeti, but is NOT close to a reasonable figure for average global productivity.

 

[CobblyWorlds]

Thanks for that Bystander, I did have the figure wrong and from a textbook ("nd hand O.U. textbook) it's 3.6 years. Where the 100 years came from I do not know.

I get the basic derivation of the residence time, what I didn't get was how you'd go about estimating the flux. But even your rough calculations show how wrong the century was.

Notwithstanding my screw up the 3.6 years still dwarves the 11 days for water - which was my original point in stating it.

Thanks again.

 

[CobblyWorlds]

"Can you provide an article that references your graph? They may be correcting for some factor that wasn't corrected for in the other link."

Hi Patty,

As I post in my breaks (and at times when I shouldn't) at work I've not got the time to look into it(and I've not got the 'net at home). I don't consider the issue significant enough for the purposes of my argument to look into it at present. Sorry.