Shindell, Methane, and Uncertainty

The IPCC Summary for Policy Makers states quite baldly on page 4 that the Level Of Scientific Understanding (LOSU) of the effects of aerosols, and changes in surface albedo from land use, is “medium-low.”
The report does not claim “high” LOSU for any Radiative Forcing Components except “Long-lived greenhouse gases” (includes methane and CO2).
Assuming their estimations of the level of scientific understand are correct, then how in the heck do you get so certain about a combined level of anthropogenic forcings, when many of the forcings are not well understood scientifically?
This does not compute. In essense they are saying, “We are uncertain about the level of the forcings caused by various major factors. But we are certain about the combined effects.”
Lunacy.

Economists have a well-known free market bias, so in the economist community, you would expect the authors with the strongest opinions on climate legislation–and hence those who published most frequently on it–to be those opposed to it. Remember, the study participants were publishing in economics journals, not climate journals, so if the peer review process produces any bias (assuming economics journals go through peer review), the bias would be against climate legislation, not for it.
Also, it’s worth repeating that the original post here makes no logical sense. Within the uncertainty ranges of the climate sensitivities presented, the warming from methane would still be massive. Just because studies disagree on the magnitude of warming does not mean the correct value is zero. Really basic stuff.

Uncertainties the way the IPCC treats them are not scientifically calculated.
I keep giving this reference to AR4 chapter 8 , the physics case:
More complex metrics have also been developed
based on multiple observables in present day climate, and have
been shown to have the potential to narrow the uncertainty in
climate sensitivity across a given model ensemble (Murphy et
al., 2004; Piani et al., 2005). The above studies show promise
that quantitative metrics for the likelihood of model projections
may be developed, but because the development of robust
metrics is still at an early stage, the model evaluations presented
in this chapter are based primarily on experience and physical
reasoning, as has been the norm in the past.
based primarily on experience and physical reasoning, as has been the norm in the past
They admit it out in the open as well as in the last sentence of the quote of above:
Note that a number of uncertainty ranges in the Working Group I TAR corresponded to 2-sigma (95%), often using expert judgement.
I suppose it justifies “the norm in the past”.
The spaghetti graphs are not error bars. They are according to the taste of the modeler clearly stated, so they cannot be sued . It is the small print.
How are true statistical error bars given for a model to data fit? They are given by creating a likelihood function with the independent variables of the model and then maximizing it by varying the parameters within their errors. The output is a chisquare per degree of freedom, which should be near 1 for a many variable problem, and the error bars on the output values sought ( example would be the mass and the widths of resonances).
What are the model runs? The modelers vary the parameters used to fit the temperature curve according to “their experience and physical reasoning” and make runs and give average values with their estimated by experience and physical reasoning feelings. Then a lot of such models are put on a graph, and voila a seemingly error band around the fitted temperature curve.
It means next to nothing.
WAG (21:01:05) :
Obviously you know nothing about statistics or economics. You can’t draw conclusions from comparing uncertainty ranges of different studies. In any case, pointing to a study that found a HIGHER sensitivity to methane than past studies, and claiming that the disagreement proves there is ZERO sensitivity to methane, is a logical fallacy.
I am sorry, but error bars are calculated just so that one can compare and make conclusions from different studies. That is the function of error bars and you are displaying your level of knowledge

I do like little dittys like that.
Short, sharp and to the point.
Kindest regards

Jeff Id (21:49:45), you ask:

Willis,
Is your previous work on a new sensitivity calculation being reviewed? An update would be appreciated if you find a chance.

If you mean my work on tropical tropospheric amplification, I am rewriting it for submission to a journal. It’s slow because I hate doing that, it always feels like I have to lobotomize myself to do it, but such is science.

“Well, the Shindell study first recalculated the values for the radiative forcing of a variety of greenhouse gases using the standard methods.”
Can anyone post a link to these methods please.
Since learning about Avogadro’s Law and number and moles etc. I can calculate the precise number of molecules of any “greenhouse” gas in a cubic meter of air at any temperature and density but I cannot find how to calculate the amount of longwave radiation absorbed, re-radiated or converted to heat by conduction. (the greenhouse effect)
I do this purely as a hobby for when anyone raises the subject of “global warming” or “climate change” I talk knowingly of numbers like 6.022 times 10 to the power of 23 and radiation bandwidths in microns and they tend to go a bit blank 🙂

You follow a preacher through the gates of heaven, and follow his children through the gates of hell. Everybody knows that the preachers’ kids are the worst of the bunch…

WAG (22:39:12), you are absolutely wrong when you say:

Bill Tuttle –
Ah, you’re on to something. You’re right, the author never *claimed* that the sensitivity to methane was zero–he *implied* it. He pointed out that there were two different estimates of the climate’s sensitivity to methane, and that therefore claims of certainty are “false” and “not valid,” and that “much is not understood” about climate. Of course, the uncertainty in the graph is whether things will be bad or really bad, not over whether methane affects the climate.

I implied nothing of the sort at all. I did not say it, I did not hint at it, I did not whisper it.
My focus, as I clearly stated, is on the false claims of certainty by the IPCC. They said that they were 99% sure that the methane forcing was between 0.4 and 0.6. The recent study has shown that their claims of accuracy were totally unfounded. I bring this up as an example of the false certainty that the IPCC claims for its results.
Despite your attempt to torture my words into another meaning, my statements were very clear. I did not say that this meant warming would be less bad or more bad. In fact, the authors of the study say (as they always do) that this will make little difference in the estimates of future warming. This is because (quite coincidentally I’m sure) their estimate of total forcing is not far from the IPCC estimate. The Shindell paper says:

We calculated
both the “abundance-based” RF owing to the net
atmospheric composition response by species
when all emissions are changed simultaneously
and the “emissions-based” forcing attributable to
the responses of all species to emissions of a single
pollutant (Fig. 1). The sum of the forcings that take
place via response of a particular species in the
emissions-based analysis (each represented by a
different color in Fig. 1) is approximately equal to
the forcing due to that species in the abundance-based
analysis. Likewise, the sums of all emissions-based
and all abundance-based forcings are similar.

This “coincidental” result, however, arises directly from the nature of the models used to do their calculations. Kiehl has shown that because of the way the climate models are tuned to match the historical temperature record, there is a close relationship between total forcing and climate sensitivity. As one goes up, the other goes down.
In the Shindell case, they have run a model “in reverse” to calculate the forcings. But the nature of the models guarantees that they will end up with a total forcing which is similar to the IPCC forcings. When the models are run “forwards” to calculate temperatures, the IPCC forcings yield a given temperature pattern. So when they are run “in reverse” to calculate forcings, a given temperature pattern will of necessity give similar total forcings.
However, this is meaningless to me. This is because I do not think that the change in the calculated methane forcings makes any difference at all, for the reasons that I explain in detail in my Thunderstorm Thermostat Hypothesis paper (q.v.). So your accusation, that I am trying to minimize the threat, is nonsense. I don’t think there is a threat from methane, but my reasons have nothing to do with the subject under discussion.
In short, your ideas about what I am saying are very far from what I said. I have no axe to grind regarding whether methane forcing is larger, smaller, or zero. Please read what I said. You are more than welcome to comment on what I have written … but your comments about what you imagine I was trying to imply are very wide of the mark.

WAG (22:39:12)
Congratulations, you’ve just had your first lesson in denial 101: how to imply something without saying anything.
Nup. I had my first lesson in Denial 101 about forty years back, when Lib journos insisted the NLF had won the Tet Offensive…

Willis Eschenbach (23:45:14) :
Thank you for taking the time to respond. I had assumed my own incompetence in failing to find the information.
So if warmists bug me I will ask “Please explain the exact mechanism that defines the radiative forcing of CO2 on the planets surface in watts per square meter?”
I always assumed that information would be easily available in the science literature.

I am more and more convinced, that the theory of “radiative forcing” is just hypothetical construction for explaining present temperature, which is caused by mere existence of bulk atmosphere. “Radiative forcing” on Mars is similar than here (no water vapor, but 15x more CO2 there) , and there is no difference between Martian blackbody and actual temperature. Hpowever, Mars has puny 600 Pa atmospheric pressure (95% CO2) compared to 100000 Pa on Earth surface.
I am curious what to do, if methane is the main villain now.
Fart.

WAG (22:39:12) :
Bill Tuttle –
Ah, you’re on to something. You’re right, the author never *claimed* that the sensitivity to methane was zero–he *implied* it. He pointed out that there were two different estimates of the climate’s sensitivity to methane, and that therefore claims of certainty are “false” and “not valid,” and that “much is not understood” about climate.

I think I see your problem: You can’t speak English. Another example is the article you refer us to on your blog:

it’s not just scientists who unanimously buy the climate consensus: 84% of economists also agree

Hint: 84% is not unanimous. And above, saying that claims of a particular degree of certainty of any given value of X are false is not even remotely related to claiming that X is zero. No connection. No implication. No nothing. They are as unrelated as the concepts of 84% and unanimity.

Re CO2=AGW, and measuring ‘radiative forcing’
I wonder if anyone has done the experiment using a real greenhouse?
AFAIK, commercial growers artificially increase the level of CO2 in their huge greenhouses because it boosts growth. Does it also decrease their heating bills?

Willis Eschenbach (23:45:14):
“None of these radiative forcing numbers can be calculated directly.
You have to use a climate model to calculate them. f course, since we
don’t understand the climate, to me it is somewhat circular to build a
model of a climate system we don’t understand and then use the model
to try to understand the climate system we don’t understand…”
etc. etc.
Willis, thanks for this. It’s a great relief. Now, finally, I understand why I don’t understand “climate science.” The climate model business reminds me of the Marxist claim that they have penetrated the secrets of the laws of history (i.e. “the historical science is settled”) and can therefore – what?
Tell the rest of us what to do, of course, and use force whenever we dare to object!

WAG the Liberal Southern Baptist appears to be of the Holy Roller” ilk of the Warmist religion. He has seen the “Consensus”,and it is Good, Praise be to Gore.
We here are all unwashed sinners and he is here to “save” us.
Please, do teach us, O Knowledgeable One!

supercritical (04:11:01) :
“Re CO2=AGW, and measuring ‘radiative forcing’
I wonder if anyone has done the experiment using a real greenhouse?
AFAIK, commercial growers artificially increase the level of CO2 in their huge greenhouses because it boosts growth. Does it also decrease their heating bills?”
Not sure what you ask would prove too much about climate even if a saving in heating were made. The whole point of a greenhouse is it is an enclosed environment. The atmosphere, however is unbounded and won’t respond in the same way to extra CO2.

************************
WAG (21:26:32) :
Also, it’s worth repeating that the original post here makes no logical sense. Within the uncertainty ranges of the climate sensitivities presented, the warming from methane would still be massive. Just because studies disagree on the magnitude of warming does not mean the correct value is zero. Really basic stuff.
****************************
WAG – It is just these kinds of overreaching conclusions and statements that are causing warmists to lose credibility. The guy didn’t say the effect was zero – you did. But he did adequately illustrate that the uncertainty is not being correctly quantified, which was his point. You warmists just pull stuff out of the thin atmosphere.

*****************
WAG (06:29:33) :
When we talk about climate science, we’re ultimately trying to decide what we should DO: pass legislation or do more of the same.
***************
WAG – You hit the nail on the head there. Doing something in this case carries a huge cost. It has already cost the country 150 new coal plant, an aluminum plant, and that is just a small part of the cost already. New climate-change based legislation will cost much more than that. The science has to be dead certain that we will have catastrophic warming before we take any action. We have lots better things to do with the money that is lost to climate-change initiatives like solar and wind and all the other stuff that goes with it. And we need the energy to run our economy and ensure our safety. The science MUST be certain!!

Since the greenhouse carbon dioxide generators I have read about burn either a bit of propane or natural gas to obtain the added carbon dioxide, I am quite certain that this burning increases the temperature within the greenhouse. Carbon dioxide concentrations rose, as did the temperature inside the greenhouse, so the correlation between the increased concentration of carbon dioxide gas and the temperature increase is quite clear.

In Italy my brother runs a 1.6 Rover on Methane, if he fills the tank with gasoline he pays €68.00 and get about 550km if he fills with Methane he pays €10.00 and gets about the same, like millions of Italians he is a devout Methane man ( his city of 7,000 people has 2 methane distributors )

WAG,
Paraphrasing your first ( rather tasteless) sentence, you obviously don’t know anything about grammar. Assuming that 73% is equivalent to unanimity is not a grammatical mistake, it’s a semantic one.
I have a metaphor as puerile as yours; when mechanic #1 says my car will go another 100,000 miles and mechanic #2 says it will go another 100 miles, they’re basically saying the same thing.

Tenuc (05:41:41) :
The point is, does anyone really know the actual effect of increasing CO2 in the atmosphere?
I would be really surprised if this hasn’t already been done, but I propose a simple experiment using a commercial greenhouse. The temperature should rise with added C02. It would be nice to know the shape of that function, wouldn’t it?
Then, a further experiment could be run to include a shallow pond, and to increase the humidity by sprays to simulate rain, to tell us whether Henry’s law actually works or not, as well as giving some idea of the real airborne lifetime of added CO2 molecules.
Then we could look at other stuff such as methane, decreasing O2, and other related conjectures.
And I take your point about scaling, but we CAN say that the measured experimental effects would be a lot less in the Real World … maybe even vanishingly small/negligible!
So I suggest that this kind of experiment would be relatively cheap to do, and very quick. It could be funded directly via small donations from skeptics, and would be just the thing for the MSM and the Blogosphere to follow in real-time.
The hell with computer modelling! Let’s do some proper experiments we can all see!

UNCERTAINTY

WAG above espouses a frequently-seen point of view about uncertainty:

The implication of this post is clear: uncertainty means we should do nothing.

While it is true that uncertainty does not mean we should do nothing, it also does not mean that we should do something. If your doctor says “We’re not certain what’s wrong with you, so we’re going to perform open-heart surgery”, you would be justified in refusing.
Much of this confusion stems from a misunderstanding of the Precautionary Principle. This Principle is widely misinterpreted. A bit of caution about the Precautionary Principle is in order. It is not just a restatement of “better safe than sorry”, nor is it ordinary caution.
Let me start with an early and very clear statement of the “Precautionary Principle” (I’ll call it PP for short), which comes from the UN Rio Declaration on the Environment (1992). Here’s their original formulation:
“In order to protect the environment, the precautionary approach shall be widely applied by States according to their capability. Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.”
This is an excellent statement of the PP, as it distinguishes it from such things as wearing condoms, denying bank loans, approving the Kyoto Protocol, invading Afghanistan, or using seat belts.
The three key parts of the PP (emphasis mine) are:
1) A threat of serious or irreversible damage.
2) A lack of full scientific certainty (in other words, the existence of partial but not conclusive scientific evidence).
3) The availability of cost-effective measures.
Here are some examples of how these key parts of the PP work out in practice.
We have full scientific certainty that condoms and seat belts save lives. Thus, using them is not an example of the PP, it is simply acting reasonably on principles about which we are scientifically certain.
There are no scientific principles or evidence that we can apply to the question of invading Afghanistan, so we cannot apply the PP there either.
Bank loans are neither serious nor irreversible, nor is there partial scientific understanding of them, so they don’t qualify for the PP.
Finally, the Kyoto Protocol is so far from being cost-effective as to be laughable. The PP can be thought of as a kind of insurance policy. No one would pay $200,000 for an insurance policy if the payoff in case of an accident were only $20, yet this is the kind of ratio of cost to payoff that the Kyoto Protocol involves.
On the other side of the equation, a good example of when we might use the PP involves local extinction. We have fairly good scientific understanding that removing a top predator from a local ecosystem badly screws things up. Kill the mountain lions, and the deer go wild, then the plants are overgrazed, then the ground erodes, insect populations are unbalanced, and so on down the line.
Now, if we are looking at a novel ecosystem that has not been scientifically studied, we do not have full scientific certainty that removing the top predator will actually cause serious or irreversible damage to the ecosystem. However, if there is a cost-effective method to avoid removing the top predator, the PP says that we should do so. It fulfils the three requirements of the PP — there is a threat of serious damage, we have partial scientific certainty, and a cost-effective solution exists, so we should act.
Regarding the proposal that we pump CO2 into the ocean (or take any action regarding CO2), while there is at least a theoretical threat of serious or irreversible damage, there is no partial scientific certainty, nor are there any cost-effective solutions in hand, including pumping the oceans full of CO2. At the moment, therefore, no action regarding CO2 is justified by the Precautionary Principle.
So no, action on CO2 is not justified at this time. Instead, we should support what is called the “no-regrets” option.
This is to take actions that will be productive regardless of whether or not CO2 is the problem. What most people forget is that we have all of the threatened catastrophes which the models say will come from CO2 are with us today — droughts, and floods, and disease, and famine, and rising sea level and the seven Biblical plagues, we have all of them right now.
So the no-regrets option is to research and advance the knowledge and train people around the world in how to avoid the poverty and pain and suffering which comes from the vagaries of the climate today. That will pay huge dividends whether or not CO2 is the boogeyman. Doing that is the best way of preparing for an unknown tomorrow.
And that is what we should be advocating. The “no-regrets” policy is the only policy that makes sense in the face of the uncertainty that WAG correctly points out above, which is very real. We are not certain about climate science … but that doesn’t mean we should waste billions of dollars on any possible solution.

THE FALLACY OF THE “EXCLUDED MIDDLE”
This is a common mistake made by both sides in the debate. I’ll use WAG’s statement as an example, because it is to hand, but it is quite common from AGW opponents as well as AGW supporters:

When we talk about climate science, we’re ultimately trying to decide what we should DO: pass legislation or do more of the same.

The fallacy of the excluded middle is the assumption that we have listed all of the possible choices. In this case, they are listed as “pass legislation” or “do more of the same.”
In the real world, however, there are often a plethora of other options. In this case they might include
• put money into climate research to reduce the uncertainty.
• pursue a “no-regrets” path of actions that will have benefit whether or not CO2 is the secret global thermostat.
• put on a public education campaign to encourage the “three R’s” (reduce, re-use, recycle).
• fund research into alternate sources of energy.
and so on.
I find myself falling into this fallacy all too often, and to fight it I have my “rule of two”. This is that whenever I list only two outcomes (e.g. “Are my writing skills that bad, or are you just pretending you don’t understand”) I am wrong. In general there’s a host of options and explanations for any real-world situation, and I ignore them at my peril.

Oliver – I admit, my initial remark was rather not tasteful. Willis has been respectful, and I should not have said it.
But there’s still an interesting debate here over uncertainty and how much certainty we need before taking an action. Jim writes that “doing something carries a huge cost,” and therefore “The science MUST be certain!!”
Barring the point that there’s no such thing as 100% certainty (any businessman will tell you that decisions must be made in uncertainty), I can turn this argument around and point out that the costs of climate legislation are also uncertain (and also rely on models). The Congressional Budget Office estimates that with cap-and-trade, US GDP will grow about 0.03%-0.09% per year more slowly. The National Association of Manufacturers’ worst-case estimate is 0.15% slower growth. And like past cost analyses of environmental regulations, neither of these models include the effects of technology – breakthroughs spurred by higher carbon prices that allow us to produce the same level of output with less energy (e.g. efficient manufacturing processes, cheaper solar panels, etc.). So models don’t agree on the exact costs of cap-and-trade, but they do agree that such costs will be relatively modest. And the dimensions of uncertainty – namely, how technology will respond to higher carbon prices – gives us reason to believe that the costs will be smaller than predicted. Why should we trust economic models and not climate models?
The costs of global warming are also uncertain. However, there’s much more variation in these estimates. They range from modest (e.g. money spent building sea walls) to catastrophic (permanent droughts). And the dimensions of uncertainty – namely, feedbacks – have generally pointed to greater-than-expected warming as more is learned (the original post refered to an estimate of greater-than-expected sensitivity to methane). If humans lack the foresight to predict how interventions in the market affect national wealth, why would anyone trust our ability to engineer the workings of Nature without unintended consequences?
The point is, while the costs of climate legislation fall within well-understood bounds (higher energy costs and short-term job losses), the costs of climate change range from modest to worse-than-expected to catastrophic to as-yet-unimagined. The economic crisis has taught us to ignore these long-tail probabilities at our own risk.
And I still haven’t seen a defense of the logic chain that I originally criticized:
“new study finds sensitivity to methane is higher than previously estimated –> scientists disagree over climate sensitivity –> the science is not settled –> we can’t be certain enough that we are causing climate change to justify action”
You don’t need to be certain it’s 25 or 30 degrees outside (F) to know you should put on a coat, and whether forcing due to methane is 0.5 or 1.0 W/m^2 does not reduce our certainty that adding more greenhouse gases will warm the planet.

Willis Eschenbach, very good article, and even better follow-ups (civility, uncertainty, excluded middle); all good things to keep in mind. The bit about the precautionary principle is a keeper.
Uncertainty, to me, is the greatest weakness of the alarmist view. When dealing with something as complex as the earth’s climate system, a model that’s only partly right is wrong, period. Yet the IPCC uses an “ensemble” of models–only one of which at most can be “right”–to predict (excuse me, “project”) the state of an intricate system decades into the future. And these projections are used to justify doing certain harm now to prevent uncertain damage at some constantly-receding time in the future. If that’s not a good definition of insanity…

WAG,
I appreciate the civil tone of your post, however I disagree with most of what you’ve said.
As regards the logic chain that you find flawed, I would make the point that the credibility of an advocate is germane to an assessment of the advice given. In this case, putatively, not only were scientists wrong about CH4 but they were, therefore wrong about CO2, unless they were wrong about the total forcings, instead.
The wider context of this dispute must be familiar to you; we don’t all agree on any aspect but, of course, the smaller the problem, the less urgent the remedy. I suspect there is absolutely no problem at all, but time will tell.
In the meantime, it isn’t certain that adding GHG’s will warm the Earth, it isn’t certain that a warmer Earth is a catastrophe, but, perversely, it’s not certain that expending enormous amounts of wealth and energy on a non-problem would be an economic disaster. Most of the global economy is concerned with the pursuit of luxury to some degree, since all we really need to perpetuate our species is enough to eat and a secure place to hang out. Economic activity happens because people don’t have what they want, not what they need. If they want a warm fuzzy sense of saving a planet from themselves and they’re prepared to pay good coin for it, then let them fill their boots. As long as it’s not too much of my coin.

Jörg Zimmermann (04:27:34), a further thought on the question.
If the initial estimate of the uncertainty of the forcing of methane and the other forcings had been correct, the uncertainty intervals would have overlapped after the “effects of secondary greenhouse gases are redistributed to the primary greenhouse gases “.
The fact that they were not overlapping shows that the uncertainty estimates were too narrow.
The uncertainty, of course, did not allow for our lack of understanding of the climate.
In addition, the uncertainty (both the old and the new) is obtained in a most curious way — from the variation in the results of different climate models.
However, this is not a measure of the uncertainty of our estimates of the underlying variable. It is merely a measure of the spread of the models, which may simply represent a commonality of shared incorrect assumptions …

I hate to even ask how many stations there are all over the globe that have the necessary equipment to measure the local radiative forcing W/m^2 contributed by each of the major GHGs. Something tells me that without proper mapping of the local values, it would not be possible to compute a (credible) mean global value.

Willis Eschenbach: I haven’t been through the other comments. Sorry if this is a duplicate comment or if it belongs on an earlier thread.
As I was reading your post, it occurred to me that Shindell et al were trying to rearrange greenhouse gas attribution in an attempt to explain the recent flattening of global temperatures and OHC. Since methane was relatively flat from 1998 to 2006…
http://www.esrl.noaa.gov/gmd/aggi/aggi_2009.fig2.png
…it appears they’re trying to make it the dominant greenhouse gas.

Bob Tisdale (14:03:12), good to hear from you. You say:

As I was reading your post, it occurred to me that Shindell et al were trying to rearrange greenhouse gas attribution in an attempt to explain the recent flattening of global temperatures and OHC. Since methane was relatively flat from 1998 to 2006…
http://www.esrl.noaa.gov/gmd/aggi/aggi_2009.fig2.png
…it appears they’re trying to make it the dominant greenhouse gas.

Having been accused of having nefarious motives quite often (including in this thread), I prefer to avoid speculation on the motives of the scientists involved. While what you say may be true, it also may be very untrue, and unfair to the scientists involved. I try to ascribe good motives to everyone unless there is strong evidence otherwise.

Does W/m^2 have any relation to atmospheric pressure? Would the value of a forcing fluctuate if atmospheric pressure changed?

carrot eater (14:26:32), you say:

Mr. Eschenbach,
I agree with the comments of Zimmerman that you are comparing apples to oranges. The values for “Abundance-based” and “emissions-based” are coming out of the same models; they are different from each other because they include different things: they are defined differently. The total RF from all forcings is about the same in the two cases; they are just distributed differently. In the “emissions-based” metric, methane gets credit for effects it has on atmospheric chemistry.

The issue is that the IPCC earnestly informed us that the effect of methane since 1750 was an instantaneous radiative forcing of 0.5 W/m2 ± 0.1 W/m2.
This means that if there were no methane increase since 1750, the most that it would change the forcing is 0.6 W/m2.
The current study, on the other hand, says that that if there were no methane increase, the least that it would change the forcing is 0.7 W/m2.
Clearly, both of those can’t be right …

Algebraic-Hypnotics 101 Primer
Academic statisticians “succeed” by hypnotizing their victims with volumes of algebraic abstraction. This concentrates power in their clan.
Practical consequences:
1) bad management,
2) bad policies,
3) etc., etc., etc. …
… i.e. intolerably costly for individuals, society, & civilization.
Clarification:
Data analysis (& *descriptive stats) is indispensable.
It is misapplied statistical *inference*, based on untenable abstract assumptions, that runs individuals, society, & civilization off-the-rails.
For those who lack the background to identify statistical inference:
Look for “error bars”, “confidence intervals”, “p-values”, “statistically significant”, & related “uncertainty” terms/measures.
No matter how well “mathematically defined” these things are, they are all based on abstract assumptions, which are not necessarily tenable in reality [for example in biological & climate systems].
Conclusions cannot be divorced from assumptions. Due diligence in assessing assumptions is not a part of the mainstream “p-value” “error bar” “confidence interval” culture that has gripped the scientific community as a major multi-decadal fashion.
Here’s an example of how it goes:
Say a medical expert & a stats expert are working together on a timeline…
Assessing abstract assumptions used in inference requires intimate subject-area knowledge. The statistician may not have this and so may decide to “go with it anyway and let the medical expert decide”.
Abstract-assumption assessment also requires intimate understanding of stats models. The medical expert may not have this and so may decide to “go with it anyway and let the statistician decide”.
And so we see a “hot potato” scenario …and keep in mind timelines, reputation, careers, grant money, etc., all of which have the potential to impact researchers families – plenty of motivation for 2 bright sparks to bluff a united front.
Anyone who thinks the solution is as simple as educating interdisciplinary hybrids is failing to appreciate how complex the realm of mathematics & statistics is. The solution is the careful application of common sense & appropriate qualifiers – along with sober, insightfully-penetrating [as opposed to malicious] audit by independent parties lacking conflict-of-interest.
We don’t all have multiple lifetimes to become cutting-edge experts in multiple fields, but that need not imply that our common sense should obediently & uncritically succumb to the wizardry of algebraic-hypnosis.

Willis: MASSIVE OVERSIGHT!!!! You have missed one key part of the IPCC chapter 2 in the Fourth Assessment Report: namely, pg. 205 Figure 2.21 and pg. 207 Table 2.13 both show the IPCC assessment of an “emission based value” as versus the 0.48 from the “abundance based value”. And the result showed in this figure and table in the IPCC 4th Assessment Report was…
0.856 W/m2!!!
That’s 0.57 for CH4 (some is destroyed by NOx which is why it is larger than 0.48), 0.2 for ozone, 0.07 for stratospheric H2O, and a dab for contribution to CO2 from fossil methane. No sulfate or nitrate interactions estimated, but well within the Shindell uncertainty range for the emission based value. Therefore, in order to make your above post accurate and honest, you need to correct the figure to include the IPCC estimate (or retract the post).
I’m also surprised that given the eagle-eyed scrutiny that posters on this board apply to any claim made by a “consensus” scientist, that not one has read the IPCC forcing chapter sufficiently carefully to notice that this number was in there in plain sight, in multiple places.

Oh. I see that both carrot eater and Zimmerman both beat me to the conceptual answer (eg, that Willis is comparing Shindell’s orange to IPCC’s apple), they just missed that IPCC kindly provided an orange as well so that in fact, we can do both apple to apple (abundance) and orange to orange (emission) comparisons.
This isn’t to say that the Shindell study has not advanced the science, which it has, adding new interactions and showing how they might change the calculations of forcing going forward into the future (the IPCC GWP estimate for methane uses very rough approximations for ozone effects). It also doesn’t say that the IPCC error bars were perfect – in general, my baseline assumption is that error bars should probably always be a bit larger than they are. Of course, that baseline means that things might always be worse just as easily as they could be better.
However, in any case, the thrust of this post, which is that the old IPCC result falls outside of the bounds of the new Shindell result, is clearly wrong, as carrot eater and Zimmerman both tried to argue.

Willis, let me try again.
“Clearly, both of those can’t be right …”
They are both right, or at least, they are consistent with each other. They are coming out of the same model. They are just different ways of describing the same physics.
The lower RF value for methane is calculated from the direct impact of ~1800 ppb of methane itself. Forcing due to stratospheric water and tropospheric ozone are calculated separately, and listed separately. You can see that in both the IPCC report and “Abundance-based” forcings in this paper.
However, increases in stratospheric water and low-level ozone are due, in part, to methane emissions. Methane reacts to form these compounds. So, the authors decided to group the radiative forcings in a different way, to emphasize which emissions lead to which forcings. Hence, methane gets not only its own direct contribution, but parts of the forcings due to stratospheric water and tropospheric ozone.
The two different RF figures are expressing very different things, and thus they are different from each other. They are different by definition. Methane’s direct impact is x, +/- some error. Methane’s total impact is y, +/- some error. x and y will be different things. There is no inconsistency here.

Marcus: many thanks for that; I totally forgot emissions-based figures are in the IPCC FAR. Yes, there’s a neat little table there on p207, showing the cross-interactions. In particular, the new paper adds interactions between sulphates and other species, beyond what was given at the time of IPCC FAR. But yes, this completes the loop. To really compare oranges to oranges, I’d remove the interactions considered in this paper but not the IPCC report.

Re: Decision making under uncertainty
There’s a number of different methods that have been developed in different places for trying to make ‘optimal’ decisions when faced with uncertainties of different types, but pretty much all of them require some form of objective or utility function. That is, what is the ultimate goal that we’re trying to achieve. This should be set long before any discussion/disagreements about how the world works, and basically involves all parties to lay they cards on the table. This is where I believe everything will break down as I suspect it would be virtually impossible to get any sort of consensus about what humanity’s long-term goals should be amongst 200-odd world governments (of course it would be much easier if we only had 1 😉 ). e.g., status quo in terms of standard of living, getting 90% of the earths population above some magical poverty line, maintain healthy and functioning ecosystems across most of the earths surface (possibly to the ultimate detriment of humanity)?
@ Paul Vaughan
I agree that misapplied statistical inference causes problems, but without some form of statistical inference how do you propose that scientific (not statistical) hypotheses of interest can objectively be compared? Where possible, assumptions should always be checked using the observed data so that you can have some faith that your reported conclusion are not too far off the mark. Unless you have a situation that is completely deterministic, with no potential for measurement uncertainty, I don’t know how you can compare hypothesis without some form of statistical procedure. Descriptive statistics can be useful of interesting, but have limited ability to advance hypothesis driven science.
As for your doctor and statistician example, yep, I’m sure that happens all the time and I’ve seen it happen, but that doesn’t mean people need to be an expert in both. It’s basically a communication problem. All fields have their own jargon which creates barriers. The parties need to either bring those barriers down themselves or find someone else to mediate (personally I’ve found beer to be very useful and breaking down such barriers, until I start babbling like a 6 month old). If people are too proud to admit they don’t understand something, then that’s an entirely different problem.
Sorry for the slightly tangential post.

“In particular, methane emissions have a larger impact than that used in current carbon-trading schemes or in the Kyoto Protocol.”
That statement isn’t talking about the historical forcing, but rather the future forcings and therefore GWPs. _Those_ are changed more significantly by the paper (as I said in my first post, the methane chemistry was only included in a very rough fashion in the IPCC GWP estimation of “25”)

Marcus (19:49:41), you say:

“In particular, methane emissions have a larger impact than that used in current carbon-trading schemes or in the Kyoto Protocol.”
That statement isn’t talking about the historical forcing, but rather the future forcings and therefore GWPs. _Those_ are changed more significantly by the paper (as I said in my first post, the methane chemistry was only included in a very rough fashion in the IPCC GWP estimation of “25″)

After rising for a number of years, the atmospheric methane emissions have levelled off during the last decade. Nobody knows why this has happened. Heck, nobody knows why they were rising prior to levelling off. Nobody knows which way they will go from here.
As a result, any honest scientist would have to say that we don’t have a clue what methane levels will be a century from now.
Yes, if we assume (as the IPCC and Shindell et. al do) that methane will start to rise again at some assumed value, it could make a difference. If their model is correct. And if methane levels rise. And if GHG forcing is the secret global thermostat.
Since we have absolutely no independent confirmation of the accuracy of the model, and no idea what future methane concentrations will be, and no data or observations saying that temperatures are ruled by GHGs, that’s a big stack of “ifs” to be calling science.
Thank you again, Magnus, for your contribution. Rather than merely state your ideas, you backed them up with clear citations to the literature. My hat is off to you.
w.

carrot eater (21:13:49) :

If you’re looking for significant change in the numbers, it’s probably in the updated GWP of methane. I’m too tired to chase down exactly how those have changed.
“Yes, if we assume (as the IPCC and Shindell et. al do) that methane will start to rise again at some assumed value,”
They do? The IPCC FAR report says, “The reasons for the decrease in the atmospheric CH4 growth rate and the implications for future changes in its atmospheric burden are not understood.” It goes on to give some discussion. Methane sources and sinks are not so well understood.

The IPCC gives forty different scenarios for the future changes in GHGs. Of these, 36 of them give an estimate of future methane emissions.
In each and every one of these 36 scenarios, methane is shown as increasing starting now. In some of them the emissions continue to rise through 2100, in some of them the rise peaks somewhere between 2040 and 2080.
But in all of them it is shown as rising. So yes, the IPCC does assume that methane will start to rise again, as I stated.
w.

“As a result, any honest scientist would have to say that we don’t have a clue what methane levels will be a century from now.
Yes, if we assume (as the IPCC and Shindell et. al do) that methane will start to rise again at some assumed value, it could make a difference. If their model is correct. And if methane levels rise. And if GHG forcing is the secret global thermostat.”
Shindell’s paper does not actually make any assumptions about the future path of methane growth. The way he calculates a GWP is to assume that we are at an equilibrium methane concentration, and then calculates the radiative forcing (not global temperature) perturbation resulting from emission of an additional ton of methane. This is also how the IPCC calculates GWPs. GWPs are the measure of radiative forcing of a substance relative to that of CO2. The key quote from the paper, as it relates to methane: “The 100-year GWP for methane is ~10% greater (~20 to 40%, including AIE) than earlier estimates (5)”.
I grant you that the IPCC scenarios almost entirely consist of rising methane concentrations. That is a separate discussion, and one that is likely to be revisited in AR5. I will note that the uncertainty there comes less from uncertainty about the chemistry and more from the uncertainty about trying to measure area sources of methane (rice paddies, swamps, etc.) and therefore get an accurate inventory of anthropogenic vs. natural emissions. I will also note that there has actually been a significant amount of methane emission reductions in the U.S., Europe, and Russia, through some combination of landfill capping, reduced gas infrastructure leakage, and better flaring of fugitive emissions. Therefore, to some extent the lower-than-expected methane growth may be, in part, a result of actual environmental policy. (to some extent it is understood natural variation – rainfall and wildfires and such interacting with methane sources, and to some extent it really is unexplained)

Willis, will you edit the original article to reflect the subsequent discussion? I sometimes refer back to older articles on WUWT, and I assume others do, too. It saves a lot of time if discussion-based corrections are folded back into the original story.

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Willis Eschenbach (20:17:18) :
After rising for a number of years, the atmospheric methane emissions have levelled off during the last decade. Nobody knows why this has happened. Heck, nobody knows why they were rising prior to levelling off. Nobody knows which way they will go from here.
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I remember from organic chemistry that UV light can break the C-H bond to form free radicals which are very reactive. Solar UV output has been going up. I wonder if that could account for the decrease in methane?
Solar UV
http://www.john-daly.com/hockey/solar.gif

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Jim (15:40:23) :
I remember from organic chemistry that UV light can break the C-H bond to form free radicals which are very reactive. Solar UV output has been going up. I wonder if that could account for the decrease in methane?
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Correction, I was remembering the UV initiated reaction between chlorine and methane. The UV breaks the chlorine into two free radicals which then react with methane.