Playing Devil's advocate on climate

[Skyhunter]

Climate until recently is closely correlated with solar activity. No surprise since aside from orbital and volcanic forcings, it has been the strongest variable. That fact has no bearing on the radiative forcing of CO₂.

Also, the highest resolution of the proxies in the links you provided is 20 years, and generally 30 to 50 years. If the Sun is entering another Dalton or Maunder minimum then it is a good thing. It means we will have more time to stabilize atmospheric CO₂.

 

[Saul]

What sun spots?

The current minimum is the greatest minimum since about 1911, which globally was a very cool period unlike our current situation.

There is a reason why the planet has not cooled due to the increase GCR. GCR has increased 18%.

There is direct correlation of planetary temperature change with solar wind bursts (see the attached paper). The solar wind bursts remove the cloud forming ions that are created by galactic cosmic rays (GCR) by a process called electroscavenging. (The solar wind burst create a space charge differential in the ionosphere which creates a potential difference from the ionosphere and the surface of the earth.)

Although the sun is mostly spotless this year there has continued to be solar wind bursts produced which is masking the affects of the weak solar heliosphere. The heliosphere blocks GCR from striking the earth. The solar wind bursts are still occurring but are starting to weaken.

An observed change that accompanied the reducing of the solar wind bursts is a curious sudden weakening of the super El Nino. This winter should be anomalously cold.

http://wattsupwiththat.com/2009/09/...of-long-range-forecasters-and-climatologists/

http://www.agu.org/pubs/crossref/2009/2009JA014342.shtml

If the Sun is so quiet, why is the Earth ringing? A comparison of two solar minimum intervals.

Observations from the recent Whole Heliosphere Interval (WHI) solar minimum campaign are compared to last cycle's Whole Sun Month (WSM) to demonstrate that sunspot numbers, while providing a good measure of solar activity, do not provide sufficient information to gauge solar and heliospheric magnetic complexity and its effect at the Earth. The present solar minimum is exceptionally quiet, with sunspot numbers at their lowest in 75 years and solar wind magnetic field strength lower than ever observed. Despite, or perhaps because of, a global weakness in the heliospheric magnetic field, large near-equatorial coronal holes lingered even as the sunspots disappeared. Consequently, for the months surrounding the WHI campaign, strong, long, and recurring high-speed streams in the solar wind intercepted the Earth in contrast to the weaker and more sporadic streams that occurred around the time of last cycle's WSM campaign.

http://sait.oat.ts.astro.it/MSAIt760405/PDF/2005MmSAI..76..969G.pdf

Once again about global warming and solar activity K. Georgieva, C. Bianchi, and B. Kirov

We show that the index commonly used for quantifying long-term changes in solar activity, the sunspot number, accounts for only one part of solar activity and using this index leads to the underestimation of the role of solar activity in the global warming in the recent decades. A more suitable index is the geomagnetic activity which reflects all solar activity, and it is highly correlated to global temperature variations in the whole period for which we have data.

In Figure 6 the long-term variations in global temperature are compared to the long-term variations in geomagnetic activity as expressed by the ak-index (Nevanlinna and Kataja 2003). The correlation between the two quantities is 0.85 with p<0.01 for the whole period studied.It could therefore be concluded that both the decreasing correlation between sunspot number and geomagnetic activity, and the deviation of the global temperature long-term trend from solar activity as expressed by sunspot index are due to the increased number of high-speed streams of solar wind on the declining phase and in the minimum of sunspot cycle in the last decades

 

[vanesch]

Don't let's fall into the mistake of "journalistic balance", in which we simply presume all voices are equally worthwhile for study and serious consideration. Understanding all sides of an open question is good; but not all the questions or challenges being raised are actually open questions with two sides of comparable standing.

Well, we tend to try to establish indeed some kind of "journalistic balance", but to get it "biased" towards the scientifically sound, we are rather strict (much more so than anywhere else) on the "peer review of sources" side.

The reason for that is simple and down-to-earth: the staff at PF doesn't feel qualified enough to do so in an unanimous way. This is much less of a problem in most other forums of PF: we have quite some very knowledgeable people on board in physics, engineering, mathematics and so on. If something obviously wrong is posted there, there is very soon a consensus by "those who know" amongst staff and regular posters, and appropriate action is taken. If you know a field rather well, it is not too difficult to make the distinction between "an open question" and a "basic error".

But in Earth sciences we haven't such a set of staff members, especially for the topic of AGW. So we had a few options:
- leave the Earth sciences forum evolve by itself (but that's against the basic philosophy of PF)
- close it down
- impose the current policy which is a kind of "coward's moderation": discuss what you want, but have peer-reviewed sources.

This debate comes up regularly.

 

[sylas]

Well, we tend to try to establish indeed some kind of "journalistic balance", but to get it "biased" towards the scientifically sound, we are rather strict (much more so than anywhere else) on the "peer review of sources" side.

This is an excellent solution, and a perfectly good resolution of the problem. It still leaves the field wide open to all the genuinely open questions on climate.

The reason for that is simple and down-to-earth: the staff at PF doesn't feel qualified enough to do so in an unanimous way. This is much less of a problem in most other forums of PF: we have quite some very knowledgeable people on board in physics, engineering, mathematics and so on. If something obviously wrong is posted there, there is very soon a consensus by "those who know" amongst staff and regular posters, and appropriate action is taken. If you know a field rather well, it is not too difficult to make the distinction between "an open question" and a "basic error".

I've heard the problem mentioned already, of a lack of a staff member with a particular expertise in climate.

It seems to me that this shouldn't be that much of a problem... and that you've collectively hit upon an ideal solution.

As you say, the reason it would be nice to have an expert available is that they would be well placed to identify straight away what arguments are disconnected from scientifically sound engagements. But you might find that the application of such expertise in this way is more trouble than it is worth. It works okay with relativity and maths and engineering, because there isn't a huge popular support for the few cranks that we get. That's not the case with climate. I am quite sure you will find that even if you had a climate expert available, even the staff would be divided on whether they were "balanced".

(And it doesn't matter which side you think has most of the cranks. Whether you accept AGW, or reject it, or are on the fence; it is still not hard to see that there is a particular problem here with unscientific argument -- whether you think it is in the IPCC or in the ranks of their critics.)

I think it is much better to have a simple clear guideline, which is a natural extension of the overall physicsforums guidelines. It is expressed without any reference to the particular claims that may not be argued.

Even if you had an expert on staff, you are still best to enforce this rule in the Earth forum, simply because there is so much more material being passed around on the subject which is not scientifically sensible, and because there are such widely divergent views amongst people interested in the subject.

On being a mentor, and being a debator

Even if you had such an expert on staff, my own suggestion (for what it is worth) is that they would be better as a participant in the Earth forum than as a mentor. I've been a moderator in other forums (evcforms.com), and a general rule was that moderators don't moderate threads in which they are involved as participants. It runs into problems with conflict of interest. If an issue turns up in a thread where a moderator is participating, then a new staff member must be called into deal with it.

A moderator is not there to give the answers to questions, but to manage the way discussion is engaged. Having someone to give answers is great; but you don't need special moderator powers for that. The mentors here do often seem to have excellent knowledge in their own major fields of interest, and their input as experts is very welcome. But that input is distinct from acting as a moderator of the debate,

And by the way; I love the fact that you speak of "mentors" here rather than "moderators". It's a great way to look at this special role.

A mentor role in general does include giving guidance on substance, as well as conduct or rules of debate. Unfortunately, that is not going to work in a debate unless the mentor is recognized as an expert by participants; and that is going to be a particular problem in climate discussions.

Therefore you're going to have to give some enforced rulings to people who don't want them; and for that we are back to being a moderator and having a clear guideline that does not require special expertise to apply, and which someone can understand without having to accept your expertise.

But in Earth sciences we haven't such a set of staff members, especially for the topic of AGW. So we had a few options:
- leave the Earth sciences forum evolve by itself (but that's against the basic philosophy of PF)
- close it down
- impose the current policy which is a kind of "coward's moderation": discuss what you want, but have peer-reviewed sources.

This debate comes up regularly.

I think you've got this one nailed. The first solution is obviously wrong, and would make this forum no different to a thousand other venues. It is the second solution that is the one which is a coward's moderation.

The third is not cowardice at all. It is recognition not only of a lack of a particular expert, but of the problem that you will NEVER get anyone who is recognized as a legitimate expert by the people who want to discuss this topic. There's a huge need for improved understanding of the physical science behind climate disputes -- and again, this is a point that would be recognized by both sides, even if they might differ on who it is that needs to improve their understanding!

Cheers -- sylas

 

[D H]

Well, we tend to try to establish indeed some kind of "journalistic balance", but to get it "biased" towards the scientifically sound, we are rather strict (much more so than anywhere else) on the "peer review of sources" side.

This is an excellent solution, and a perfectly good resolution of the problem. It still leaves the field wide open to all the genuinely open questions on climate.

That would be an excellent solution if the science behind AGW was not suspect. It certainly looks suspect from the outside. More importantly, it looks suspect to some very well-qualified meteorologists and climatologists. Because PF does not have a supply of meteorologists and climatologists onboard, the PF solution is, as vanesch mentioned, a bit of a cowardly solution.

 

[sylas]

That would be an excellent solution if the science behind AGW was not suspect. It certainly looks suspect from the outside. More importantly, it looks suspect to some very well-qualified meteorologists and climatologists. Because PF does not have a supply of meteorologists and climatologists onboard, the PF solution is, as vanesch mentioned, a bit of a cowardly solution.

Bingo. As it happens, I disagree with you... but it doesn't matter.

The whole reason for this solution is that it doesn't matter if you think it is the science behind AGW that is suspect, or the science of the critics that is suspect. In either case, the case can be found in the scientific literature, and moderators don't have to rule on the basis of choosing sides.

There are also well qualified meterologists and climatologists who think the science behind AGW is just fine. Not settled in every respect of course! There are plenty of open questions.

This is precisely why having an expert won't work. Which expert would be acceptable? The experts you are thinking of, who consider science behind AGW to be suspect? Or the ones I am thinking of, who think AGW is a well supported scientific hypothesis, confirmed to good confidence by a large amount of perfectly good scientific research and still subject to open questions in the details?

As I said previously, you will never find an expert who is acceptable to all sides -- even all sides within the staff!

You've said the science behind AGW is suspect. All I am really saying is that almost everyone can agree that there's a lot of suspect science involved... even if we disagree as to which is the suspect science!

The proper thing to do is to allow the various arguments to be considered, on all sides, and on their own merits... as long as those sides are presented in the scientific literature. That strips out a lot of really bad argument, consistent with the general physicsforums guidelines, and allows us to look at the arguments that have at least passed through the first level of check for credible scholarship. We do NOT rule on the basis of "consensus", or by some method of evaluating the "expertise" of authors, or by deciding which side the argument is on and either binning it or lauding it on that basis.

We look at the actual evidence presented, case, by case, by case.

I don't expect this process to resolve all the differences, but it sure as heck will let you learn a lot, if you are serious about looking at the arguments on their own merits. I've benefited enormously in learning about all the background physics as I've been working on this. Not just arguments for or against AGW, but about the underlying physics that let's me start to follow the details of the arguments being presented. And I'm still learning on that.

I especially disagree with you that this is "cowardly".

There's nothing cowardly about it. What would be "courageous"? To open up physicsforums to all arguments of any kind? Of course not. That would be a complete cop out. To step in and rule that one side or the other is disallowed? That would be just as bad.

So what? How do you decide... and WHO decides? You need something that let's you and I work together on this; not a ruling that rejects the experts you are thinking of or rejects the experts I am thinking of.

Cheers -- sylas

 

[Galteeth]

"Physicsforums also deals with open questions. From the guidelines again:
There are many open questions in physics, and we welcome discussion on those subjects provided the discussion remains intellectually sound. It is against our Posting Guidelines to discuss, in most of the PF forums or in blogs, new or non-mainstream theories or ideas that have not been published in professional peer-reviewed journals or are not part of current professional mainstream scientific discussion.
In climate, there are many open questions, relating to sensitivity, cloud effects, paleoclimate, approximations in modeling, the carbon cycle, and on, and on. We aren't going to resolve them, but understanding the credible alternatives is well worthwhile.

There are also a lot of questions which are not actually intellectually sound open questions at all, but simply misunderstandings or even outright crackpottery. There's a lot that is said outside the professional mainstream which has been enthusiastically passed around in the public domain as being of equal standing to genuine science. In some respects, a lot of this public debate (not all of it!) bears a significant similarity to the whole "intelligent design" movement."


Yes! And it would be quite useful for a lay person to be able to distinguish between legitimate questions and crack-pottery. There is so much noise on this issue that's its hard to get to what's substantive. It is so frustrating when you have people convinced with no evidential basis that global warming is a hoax, then you have "scientists" who post things like "global warming is a 100% certainty" (this was a statement I saw posted on the NYT by a suppossed climatologist which made me raise my eyebrow).

A general overview of what is relatively certain, what's generally agreed upon, what's questionable, and what's controversial would be great. Perhaps I should start a new thread for this?

 

[Andre]

well as far as I'm concerned, there may be relative agreement about a BASIC climate sensitivity of about one degree celsius / Kelvin warming for doubling CO2.

So if you want to increase that to IPCC main figures of something like 2-4 degrees per doubling, you need predominance of positive feedback factors. That is questionable to controversial, like it or not.

Two approaches for that. On one hand statistics, investigating actual dynamic random walk temperature variation to be non-persistent, which suggest dominance of negative feedback, (several publications http://www.aai.ee/~olavi/). On the other hand direct measurements as suggested http://www.leif.org/EOS/2009GL039628-pip.pdf.

 

[Skyhunter]

then you have "scientists" who post things like "global warming is a 100% certainty"

Global warming is a fact. The instrumental record proves it to the very limits of scientific certainty.

Why should a scientist lend credibility to the global warming is a hoax crowd by giving a confusing nuanced answer about open questions and probability distribution curves?

 

[sylas]

A general overview of what is relatively certain, what's generally agreed upon, what's questionable, and what's controversial would be great. Perhaps I should start a new thread for this?

Yes, I think you should; but your topic is going to be too general.

We have different ideas about what the problem really is.

What is "generally" agreed upon is not the same as "universally" agreed upon. For someone on the fence, who is confused, and who doesn't want to have to learn a whole pile of background physics, it is a perfectly sensible question to ask about the "consensus", in the sense of what is the view of the majority of scientists working on the subject. And by majority I mean almost overwhelming majority.

If you want to know a wider consensus going beyond the working scientists, then the consensus is weaker, and in the general public it is gone.

Terms like 100% certainty are not useful, and only rarely used by the working scientists. AGW is not a single proposition, but a whole body of propositions, some of which are more certain than others.

• That the planet is warming, significantly, on decadal scales, is a measurement about as certain as you can get. It's ongoing work to measure that more accurately, and also to find how the warming is distributed, and to separate the warming trend from stationary variations.
• That human factors have a major contribution is about as certain as you can get. But it is also certain that they are not the only factor, and there's a lot of ongoing work to identify and measure the various factors involved.
• In particular, that CO2 is rising rapidly and that this is by far mostly from human industrial emissions is a fact about as certain as you can get. That this necessarily has a significant impact on Earth's energy balance is basic physics, about as certain as you can get.
• A big open question is the one identified by Andre. What is the sensitivity of climate... how much does temperature change in response to energy balance forcing? The best we have is a range of possible values, which as Andre notes is about 2-4 degrees per doubling. It is more usually quoted as 2-4.5, or 1.5-4.5, which is the IPCC range in the 4th AR. That's not a 100% certainty range; more like a 90% certainty range. There continues to be work published from time to time which proposes smaller values, and that is legitimately part of the whole scientific project. If you just want the majority view, then 2-4.5 works. If you want to really get into the debate, then you'll have to look at other proposals also, on their own merits. But there are very few.

That's a brief road map of some of the questions associated with AGW, as I see it. The two biggest open questions are the magnitudes of other forcings and sensitivity to forcings.

Other forcings include in particular cloud and aerosol effects -- and identifying causes for them as well. There are significant anthropogenic factors in these other forcings as well, and most of these are much harder to sort out than CO₂, which is comparatively straightforward by comparison.

The sensitivity of climate is being better constrained as time goes by, but there is still a substantial range of likely values, and a handful of published arguments for radically different values.

The guidelines at physicsforums do not limit us to the majority or consensus view. We are free to consider any work published in the peer reviewed literature. That includes a very wide range of perspectives; and being able to examine those on their own merits is great. This thread speaks of playing "devil's advocate". That means actually knowing and understanding the arguments you don't agree with yourself; both for those who tend to accept the reality of strong anthropogenic effects on climate, and those who are skeptical of strong human effects.

Some of these arguments are very technical. Quite apart from anything else, getting to follow them is going to involve learning more about the background physics, and that's what PF is about.

Cheers -- sylas

postscript.

On the other hand direct measurements as suggested http://www.leif.org/EOS/2009GL039628-pip.pdf.

There's no such thing as a direct measurement of sensitivity; and the paper you cite makes this clear as well. This is one of the legitimate handful of low estimates. It uses ERBE data. There's a fair bit of work been done with the ERBE data and sensitivity, and if you want majority views, then most of the ERBE based estimates are significantly higher than Andre's citation. To actually follow the details of how the estimates are made, either the low estimates in the paper by Linden and Choi, or the more conventional estimates from ERBE made by Wang, or Gregory and Foster, and others, you have to actually pull apart the details on their own merits. Just declaring one paper to solve the whole thing, or be a "direct" measurement, is foolish.

 

[Xnn]

Within climate science, nothing is 100% certain. However, with respect to CO2 influence on the climate, the following can be said:

Equilibrium climate sensitivity is likely to be in the range of 2C to 4.5C with a most likely value of about 3C, based upon multiple observational and modelling constraints. It is very unlikely to be less than 1.5C.

page 88: http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-ts.pdf

Notice:
Likely = 66% probability
Very Unlikely < 10% probability

In other words, it is more than very likely (>>90% probability) that climate sensitivity is > 1C, while the most likely value is about 3C.

So, while some may wish to argue that climate sensitivity is less than 1C, the odds are greatly against them being correct. However, to suggest that climate sensitivity may be less than 2C while an extreme statement is not out of the realm of possibility since the chance of it being correct is about 33%.

Probably the best thing to say is that there is a small, but not negligible, probability that climate sensitivity is less than 1C.

 

[vanesch]

Yes! And it would be quite useful for a lay person to be able to distinguish between legitimate questions and crack-pottery. There is so much noise on this issue that's its hard to get to what's substantive. It is so frustrating when you have people convinced with no evidential basis that global warming is a hoax, then you have "scientists" who post things like "global warming is a 100% certainty" (this was a statement I saw posted on the NYT by a suppossed climatologist which made me raise my eyebrow).

You've got it. That's what makes this forum so hard to moderate. It is what I personally (I'm not talking on behalf of PF here) disliked most in some IPCC discourse and publications at a certain point: a certain lack of the typical self-criticism one usually finds in well-established science. When a supposed scientific discourse starts to sound like a commercial, or the program of a political party, I'm a bit lost.

BUT, but, how to express some reserves towards that, without opening the flood gates of crackpottery and low-level denial of basic established scientific fact ? That's the hard problem to solve here. And, as sylas pointed out, how can you solve it when certain experts have publicly shown not to show some "scientific self-criticism" ? Even a genuine renowed climate scientist wouldn't be recognized as an "objective expert" by "the other camp".

 

[vanesch]

Notice:
Likely = 66% probability
Very Unlikely < 10% probability

In other words, it is more than very likely (>>90% probability) that climate sensitivity is > 1C, while the most likely value is about 3C.

I really wonder how one gets to these "probability" numbers. I know that they are Bayesian estimators, but as we know, Bayesian estimators need a priori probabilities of our "belief", and only work under the hypothesis that our error probability model is assumed correct.

This looks to me like trying to say that "Newtonian mechanics has 95% chance to be correct", no ?

 

[sylas]

I really wonder how one gets to these "probability" numbers. I know that they are Bayesian estimators, but as we know, Bayesian estimators need a priori probabilities of our "belief", and only work under the hypothesis that our error probability model is assumed correct.

This looks to me like trying to say that "Newtonian mechanics has 95% chance to be correct", no ?

That is an excellent question. Such "probabilities" or "likelihoods" are inevitably subjective. Technically, they are obtained using a Bayesian analysis with assumed prior distributions, as you say... and it is the choice of prior distributions where you can't avoid being subjective.

There is a thread about this very point I started just recently. See [thread=334005]A low likelihood for high climate sensitivity[/thread]. This is about a new paper just out by Annan and Hargreaves, who argue that it is reasonable to reject with high confidence the likelihood of sensitivity values above 4.5; higher confidence than suggested in the 4th AR. The whole basis for the paper is not any new data; but a more "reasonable" choice of priors in the analysis.

Annan and Hargreaves do not propose any new "objective" likelihood measure, but face up to the inevitable subjective aspects of quantified likelihood estimates for a certain unknown real world number.

We've mentioned the range 1.5-4.5 which is widely used, on the basis of the IPCC 4th AR. This is obtained using a "uniform" prior, in which unreasonably high sensitivities are given the same prior expectation as any others, in a certain range (0 to 10, for example). A uniform prior is sometimes taken as a way of avoiding results that incorporate information other than the data being applied; Annan and Hargreaves argue that this is dubious. From their abstract:

In this paper, we investigate some of the assumptions underlying these estimates. We show that the popular choice of a uniform prior has unacceptable properties and cannot be reasonably considered to generate meaningful and usable results. When instead reasonable assumptions are made, much greater confidence in a moderate value for S is easily justified, with an upper 95% probability limit for S easily shown to lie close to 4^oC, and certainly well below 6^oC.[/color]​

It seems to me that this is a well grounded criticism, and that exceptionally high sensitivities are less likely than you would think from the 4th assessment report.

Note that the choice of priors has more effect on the upper bound than the lower bound; this is a consequence of the "long tail" of sensitivities, explained in the thread.

Felicitations -- sylas

 

[vanesch]

That is an excellent question. Such "probabilities" or "likelihoods" are inevitably subjective. Technically, they are obtained using a Bayesian analysis with assumed prior distributions, as you say... and it is the choice of prior distributions where you can't avoid being subjective.

This is one of the criticisms I naively have, but apparently it can be dealt with.

However, there's a second, more fundamental criticism, and that is the assumed inherent correcctness of the error probability model.

Imagine I have an unknown system of which I have to make a prediction of response for a given input signal. Now, we can take our system as a black box, a grey box, or a white box, which means that for the black box, we only take former input-output relationships and try to fit a "general-purpose" behavioural black box model on it (for instance, a dynamical neural network), or for the white box, we can study the physics of what's in the box, and write down the supposed dynamics of the model, with or without free parameters, or we can be somewhat in between (grey box) where some physical modeling is done, and where some behavioural modeling is done based upon experimental data.

Now, in order to do any Bayesian estimation, I do not only need a correct model of my system, I also need a correct probability estimation of the errors on my model. If I have a biased model, and/or erroneous error estimations of this model, my Bayesian estimator will be totally off, concerning its probability distribution. Its expectation value might be still more or less right, but its probability distribution will be totally off.

In fact, it is much more difficult to have a correct probability distribution for a Bayesian estimator than to have a more or less good estimator expectation value.

This is why I always expressed my reserves towards these probabilities.
Now, maybe this is due to my naivety, but I've been working in system identification, and usually people are much more prudent when they do such things, than what I've seen from the IPCC.

Of course, there is a totally subjective way in which these numbers DO make sense: you can take them as "this is what we think, *to our best knowledge*. In other words, if I *had to bet my money* on the sensitivity, I would use this Bayesian probability distribution because it is "the best I can do with what I know".

But estimating "the probability that such event will happen to be 10% to the best of my knowledge", and claiming that the probability of that event IS 10%, is different. The first statement is: "ok, this is what I know, but I can be wrong". The second is "what's true".

 

[sylas]

But estimating "the probability that such event will happen to be 10% to the best of my knowledge", and claiming that the probability of that event IS 10%, is different. The first statement is: "ok, this is what I know, but I can be wrong". The second is "what's true".

These are not probabilities, but indications of confidence. The report is not saying that there is a known probability of an event. It is quantifying their level of confidence in a proposition.

In other words, the IPCC report, as I read it, more than any other scientific report I have ever seen, attempts to be careful about saying "this is what we think", with explicit acknowledgment of limited confidence. That's just my impression.

It doesn't matter all that much. I tend to use the IPCC assessment report as a secondary reference anyway. I nearly always go back to the primary literature to get at the details. The IPCC report is useful to summarize the state of play from many diverse working scientists; but it's not gospel. It's a useful resource. For reference, then, if anyone would like to check against the report itself:

• The Physical Science Basis is the section of the fourth IPCC assessment report that is relevant to physicsforums and the underlying science of climate. It is the report of "working group 1". From the link, you can download the whole report (996 pages) as separate chapters; also the http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-ts.pdf and other materials.

In such a large report, it has been important to have a high level of consistency in how the report expresses its limited confidence in different propositions. A set of guidelines has been worked out for use throughout the report for expressing the level of confidence. These are described in box TS.1 (Technical summary, page 22-23), with additional pointers to other parts of the report that go into details of error and uncertainty handling.

In particular, the estimates of sensitivity are given on page 66 of the technical summary; with a brief overview on page 88 (quoted above by Xnn) and with more detail in the main report. See especially box 10.2, on page 798 (chapter 10). I quote here the tail end of that box:

Since the TAR, the levels of scientific understanding and confidence in quantitative estimates of equilibrium climate sensitivity have increased substantially. Basing our assessment on a combination of several independent lines of evidence, as summarised in Box 10.2 Figures 1 and 2, including observed climate change and the strength of known feedbacks simulated in GCMs, we conclude that the global mean equilibrium warming for doubling CO2, or ‘equilibrium climate sensitivity’, is likely to lie in the range 2°C to 4.5°C, with a most likely value of about 3°C. Equilibrium climate sensitivity is very likely larger than 1.5°C.

For fundamental physical reasons as well as data limitations, values substantially higher than 4.5°C still cannot be excluded, but agreement with observations and proxy data is generally worse for those high values than for values in the 2°C to 4.5°C range.[/color]​

You could hardly be more thorough in avoiding a claim of "what's true"! They are explicit on the foundations of the estimate, and about the limits of their confidence. The values given of 2 to 4.5 are not probabilities of an event, but an indication of how confident they are about this range. The level here is "likely". For the "very likely" range, they give a lower bound only, of 1.5. The omission of an upper bound is deliberate, and reflects how hard it is to give a strong upper bound, given the nature of sensitivity and the "long tail".

In brief, they don't know the sensitivity. No-one does. The best they can do, as an assessment of the current state of knowledge, is that is it "very likely" more than 1.5, and "likely" to be in the range 2 to 4.5. You should read those as indications of how confident they are; not that this is a probability for an event.

In fact, the major criticism of the IPCC report, in this instance, is that it is too cautious in drawing conclusions. The paper by Annan and Hargreaves that I discussed is suggesting explicitly that the IPCC report could reasonably put an upper bound of 4.5, or even lower, in the "very likely" confidence level. It looks to me that they make a good case for this.

It doesn't bother me at all that people have different reactions to the IPCC assessment. One possible approach for moderating consistent with the guidelines would be to let the assessment be a guide to the range of views that are "mainstream", and rule out any argument that goes outside those bounds. I don't think that would be a good idea; but if you ever did decide to delimit boundaries for "mainstream" this would be your best option. But I think you have a much better approach already in place; which allows us to consider any view, from any individual, as long as they have taken that first step of getting it published in the peer reviewed literature.

So I don't mind at all that people differ in their reaction to the report. That's neither here nor there, and shouldn't be used to limit what propositions may be considered in the forum.

My own main interest is to help people understand better the physics of climate, and to learn more about it myself. It seems to me that a lot of debate on climate is based on visceral reactions rather than real physical comprehension of the various concepts.

Cheers -- sylas

---

PS. On reflection... I suggest that there is a problem in some quarters about how the IPCC report is used -- or indeed any scientific paper. Some people seem to treat the IPCC report as gospel, and that's dreadful. Same goes for treating any scientific paper as a final definition of what is known. Presenting a single paper as a final proof or disproof of a tricky scientific question is a misunderstanding of the nature of science. I don't personally think this is a fault of the IPCC report itself; which is more than usually careful about explicit recognition of limited confidence. It is rather a failure of understanding of a few people supposedly defending the report.

You may be able to identify in retrospect a major paper that has solved some problem; but that is generally something that is properly recognized some time after the publication, as other working scientists test and review its results. This is also why I would be against using the IPCC report as a limitation to define the mainstream for the purposes of moderation.

 

[Xnn]

Consider the 3C/CO2 doubling most likely value.

CO2 levels are going up about 0.5% per year.
That works out to 0.015C/year of warming.

Now; look at the amount of observed global warming over the last 30 years.

It's about 0.016C/year.

In other words, observations are tending to support the most likely value.

 

[Xnn]

Concerning criticism of the the IPCC; has anybody noticed that peppered throughout their report are the identification of areas that have a low level of understanding?

Ice Sheet dynamics come to mind. A fair number of people are concerned about just how fast they may melt, but the IPCC hasn't made a definiative statement regarding them and for good reason.

 

[sylas]

Consider the 3C/CO2 doubling most likely value.

CO2 levels are going up about 0.5% per year.
That works out to 0.015C/year of warming.

Now; look at the amount of observed global warming over the last 30 years.

It's about 0.016C/year.

In other words, observations are tending to support the most likely value.

That's technically incorrect on many levels.

First, the doubling value of 3 C/2xCO2 is an equilibrium response; not the transient response.

There's a lot more changing than just CO₂. Taken in isolation, CO₂ is the largest forcing, but there are a number of other forcings, both positive and negative, and they make a difference.

An increase of 0.5% per year is log₂(1.005) of a doubling, and this is 0.0072. At 3 degrees per doubling you would have 3*0.0072 = 0.021 C/year.

As it turns out, observations are consistent with the estimates of sensitivity, but the argument is a bit different. It is not sufficient to give a strong constraint on the sensitivity estimate. If you look at the section of the technical summary you quoted previously, the next paragraph deals with "transient response" as opposed to "equilibrium sensitivity". Chapter 10 deals with the difference between these concepts in more detail. Here's the extract (page 88, technical summary)

The transient climate response is better constrained than the equilibrium climate sensitivity. It is very likely larger than 1°C and very unlikely greater than 3°C. {10.5}[/color]​

With a transient response 2°C per doubling, and with an increase of 0.5% per year CO₂, and in the absence of all other forcings, you should expect a temperature increase trend of about 2*log₂(1.005) = 0.0144 C/year. Of course, there are other forcings as well; but all told this is why transient response is better constrained. The available data for the immediate present allows you to constrain it, where equilibrium response requires an additional level of indirection to get from observations to a number.

Also relevant is a recent thread with a discussion of the cummulative carbon emissions response (CCR), which tends to reflect transient climate response rather than equilibrium climate response. There were two recent papers on this, which are discussed in [post=2343088]msg #83[/post] and following of thread "Estimating the impact of CO2 on global mean temperature".

Cheers -- sylas

 

[Xnn]

Thanks sylas;

So, doing this in natural logs, the calculation is 0.016/0.0072 = 2.2 C/CO2 doubling; using the last 30 years of global observational data if other forcings are ignored.

Not sure if how significant other forcings are.

 

[sylas]

Not sure if how significant other forcings are.

Neither is anyone else; there are significant uncertainties in other forcings. CO₂ is the simplest forcing to evaluate and is known to quite high accuracy. Other forcings are known, but with larger bounds of accuracy. The bounds are sufficient to conclude with strong confidence that greenhouse effects are the largest forcing, and that CO₂ is the largest contributor to that. But the lack of certainty in other forcings still means a large spread of uncertainty about total forcing.

I've given a widely repeated diagram in [post=2215403]msg #66[/post] of thread "Estimating the impact of CO2 on global mean temperature", outlining estimates and uncertainties for forcings. It can be found also as figure 2.20, on page 203 (chapter 2) of the http://www.ipcc.ch/ipccreports/ar4-wg1.htm" . The estimates are quantified, with 90% confidence bounds, in table 2.12, page 204.

Felicitations -- sylas

PS. As an added wrinkle... a forcing is a change from one time to another. The table I've shown is giving the forcings from 1750 to the present. But if you want to look at the last 30 years, then the picture changes again, generally making the greenhouse effects and CO₂ in particular even more significant for the immediate rate of change. The immediate rate of change also is affected by changes in heat uptake in the ocean, which will impact rates of change in much the same way as a forcing.

 

[Saul]

The other explanation for the 20th century warming is a decrease in planetary clouds rather than AWG, in particular CO2.

The observations do not show a steady increase in the base line planetary temperature about which planetary temperature oscillates. Planetary temperature has in fact cooled slightly post 1998.

http://www.woodfortrees.org/plot/hadcrut3vgl/from:1980/to:2009.8/normalise


http://wattsupwiththat.com/2009/09/04/uah-global-temperature-down-in-august-181%C2%B0c-sh-sees-biggest-drop-of-0-4%C2%B0c/

As I noted further up in the this thread planetary temperature in the 20th century has strongly correlated with geomagnetic field change measured by the parameter Ak that is in turn modulated by solar wind bursts. The solar wind burst remove cloud forming ions by a process called electroscavenging. The sudden warming events in planetary temperature records and the longer term warming and cooling trends correlate with Ak.


http://www.atmos-chem-phys.org/5/1721/2005/acp-5-1721-2005.html

Analysis of the decrease in the tropical mean outgoing shortwave radiation at the top of atmosphere for the period 1984–2000

All cloud types show a linearly decreasing trend over the study period, with the low-level clouds having the largest trend, equal to −3.9±0.3% in absolute values or −9.9±0.8% per decade in relative terms. Of course, there are still some uncertainties, since the changes in low-level clouds derived from the ISCCP-D2 data, are not necessarily consistent with changes derived from the second Stratospheric Aerosols and Gas Experiment (SAGE II, Wang et al., 2002) and synoptic observations (Norris, 1999). Nevertheless, note that SAGE II tropical clouds refer to uppermost opaque clouds (with vertical optical depth greater than 0.025 at 1.02μm), while the aforementioned synoptic cloud observations are taken over oceans only. The midlevel clouds decreased by 1.4±0.2% in absolute values or by 6.6±0.8% per decade in relative terms, while the high-level ones also decreased by 1.2±0.4% or 3±0.9% per decade in relative terms, i.e. less than low and middle clouds. Thus, the VIS/IR mean tropical (30_ S–30_ N) low-level clouds are found to have undergone the greatest decrease during the period 1984–2000, in agreement with the findings of Chen et al. (2002) and Lin et al. (2004).

http://news.yahoo.com/s/mcclatchy/20090819/sc_mcclatchy/3295216

WASHINGTON — Has Earth's fever broken?
Official government measurements show that the world's temperature has cooled a bit since reaching its most recent peak in 1998.

"It's entirely possible to have a period as long as a decade or two of cooling superimposed on the long-term warming trend," said David Easterling , chief of scientific services at NOAA's National Climatic Data Center in Asheville, N.C.

So far this year, the high has been 0.42 degrees Celsius (0.76 degrees Fahrenheit), above the 20-year average, clearly cooler than before.

 

[vanesch]

As I noted further up in the this thread planetary temperature in the 20th century has strongly correlated with geomagnetic field change measured by the parameter Ak that is in turn modulated by solar wind bursts. The solar wind burst remove cloud forming ions by a process called electroscavenging. The sudden warming events in planetary temperature records and the longer term warming and cooling trends correlate with Ak.

The problem is that the planetary temperature in the 20th century also correlates with the logarithm of the average number of transistors on an Intel processor chip...

 

[Saul]

The problem is that the planetary temperature in the 20th century also correlates with the logarithm of the average number of transistors on an Intel processor chip...

Do you have a paper to show the correlation?

Please explain the cooling post 1998.

I provided papers that shows the correlation, papers that provide a cause to explain the observations, and papers to explain the mechanism.

What is your point? Or problem?

 

[Saul]

Galteeth's comment was:

This is a fascinating forum, and these climate discussions are very interesting and educational. I couldn't help but notice however that it seems posters tend to line up along sides on the issue of AGW (or perhaps the degree to which they are skeptical of the consensus). I think it would be interesting to see people play devil's advocate and argue for the other position, or rather acknowledge data that does not support their view (on both sides).

There are most definitely basic observations that do not support the AWG hypothesis. There have been a series of papers that have been written concerning the discrepancy between prediction and observations.

The science is interesting. A pointless sarcastic monologue is not.

Because there currently appears to be a deep solar magnetic cycle minimum, there should be observational evidence and papers to clarify the problem situation. We can have some fun reading and discussing those papers and discussing the observational evidence.

The competing scientific explanation for the 20th century warming is solar modulation of planetary cloud cover. As noted in the past cosmogenic isotopes changes correlate with abrupt planetary temperature change. There is smoking gun evidence at each of the cyclic abrupt climate change events.

 

[vanesch]

What is your point? Or problem?

The point is that finding a correlation doesn't indicate a causal relationship, and even if so, it doesn't even indicate which way. Now, there can (I didn't check) be a correlation with solar activity, why not. The mechanism you mention can be active.

However, you are not going to convince me that the mechanism of cloud formation through solar activity is simpler physics, which is less prone to modelling errors, and to which there are less complex feedback factors working, than the heat transport problem of an atmosphere containing some gases that interact with IR radiation, which is based upon rather elementary thermodynamics, and of which several basic aspects are easily checked and known for tens of years (like the lapse rate, or the black body properties of gases).

In other words, the warming of the last century can be for sure find its origins in many elements, but the CO2 is definitely a part in it, and it is probably the easiest part to calculate, because at least the forcing due to it is easy to estimate.

The point is that even if you had a straight-forward model that no-body can doubt because based upon very elementary physics for your solar activity stuff that gives you the expected change in cloud cover as function of the solar activity, calculated from first principles only, and not using any climate data, still you would be faced with exactly the same problem as the one with CO2: the climate sensitivity. Even if you had the perfect model that gives you without an ounce of doubt, from first principles, the cloud cover as a function of solar activity, the only thing you would be able to get from that, is a forcing (so many watts per square meter). The question of how temperature is dependent on that is exactly the same as for the CO2 forcing: the sensitivity.

Now, at least the forcing is easy to calculate with CO2, because for that there DOES exist a simple and straightforward physics model based upon first principles.

So it might very well be that your mechanism ALSO exists, and is ALSO a significant drive - I don't know. But to say that it is a *more straightforward* explanation than CO2 seems to me to push things, no ?

 

[Skyhunter]

Do you have a paper to show the correlation?

Please explain the cooling post 1998.

I provided papers that shows the correlation, papers that provide a cause to explain the observations, and papers to explain the mechanism.

What is your point? Or problem?

Denier blogs are not scientific papers. Therefore you have failed to meet the standards of this forum.

There is no cooling trend since 1998. 1998 was an anomalous year, influenced by a very strong el nino event. The long term trend did plateau slightly, but has remained positive.

 

[Saul]

The point is that finding a correlation doesn't indicate a causal relationship, and even if so, it doesn't even indicate which way. Now, there can (I didn't check) be a correlation with solar activity, why not. The mechanism you mention can be active.

However, you are not going to convince me that the mechanism of cloud formation through solar activity is simpler physics, which is less prone to modelling errors, and to which there are less complex feedback factors working, than the heat transport problem of an atmosphere containing some gases that interact with IR radiation, which is based upon rather elementary thermodynamics, and of which several basic aspects are easily checked and known for tens of years (like the lapse rate, or the black body properties of gases).

In other words, the warming of the last century can be for sure find its origins in many elements, but the CO2 is definitely a part in it, and it is probably the easiest part to calculate, because at least the forcing due to it is easy to estimate.

The point is that even if you had a straight-forward model that no-body can doubt because based upon very elementary physics for your solar activity stuff that gives you the expected change in cloud cover as function of the solar activity, calculated from first principles only, and not using any climate data, still you would be faced with exactly the same problem as the one with CO2: the climate sensitivity. Even if you had the perfect model that gives you without an ounce of doubt, from first principles, the cloud cover as a function of solar activity, the only thing you would be able to get from that, is a forcing (so many watts per square meter). The question of how temperature is dependent on that is exactly the same as for the CO2 forcing: the sensitivity.

Now, at least the forcing is easy to calculate with CO2, because for that there DOES exist a simple and straightforward physics model based upon first principles.

So it might very well be that your mechanism ALSO exists, and is ALSO a significant drive - I don't know. But to say that it is a *more straightforward* explanation than CO2 seems to me to push things, no ?

vanesch,

I am not trying to convince you of anything. I am trying explain these observations.

Those advocating the AWG position (AWG caused 90% of the 20th century warming. Deny the cooling occurred or attribute cooling to satellite problems.) in this forum have not acknowledge the most basic fact which is that the 20th planetary temperature changes did not correlate with the CO2 changes. Changes in planetary cloud cover do correlate with the 20th century temperature rise.

A scientific mind ask why, is interesting in a scientific explanation. You and the other AWG supports in the forum do not acknowledge that there is a problem situation. Something that requires explanation.

The point is you write in capital letters. I do not understand the emotion. Science is science. The truth is the truth. What will happen will happen.

The are multiple observations (for example the current cooling trend and the increase in sea ice in the arctic and antarctic) and papers that do not support the AWG hypothesis.

http://www.woodfortrees.org/plot/hadcrut3vgl/from:1980/to:2009.8/normalise

http://wattsupwiththat.com/2009/09/04/uah-global-temperature-down-in-august-181%C2%B0c-sh-sees-biggest-drop-of-0-4%C2%B0c/



http://www.atmos-chem-phys.org/5/1721/2005/acp-5-1721-2005.html


Analysis of the decrease in the tropical mean outgoing shortwave radiation at the top of atmosphere for the period 1984–2000

All cloud types show a linearly decreasing trend over the study period, with the low-level clouds having the largest trend, equal to −3.9±0.3% in absolute values or −9.9±0.8% per decade in relative terms. Of course, there are still some uncertainties, since the changes in low-level clouds derived from the ISCCP-D2 data, are not necessarily consistent with changes derived from the second Stratospheric Aerosols and Gas Experiment (SAGE II, Wang et al., 2002) and synoptic observations (Norris, 1999). Nevertheless, note that SAGE II tropical clouds refer to uppermost opaque clouds (with vertical optical depth greater than 0.025 at 1.02μm), while the aforementioned synoptic cloud observations are taken over oceans only. The midlevel clouds decreased by 1.4±0.2% in absolute values or by 6.6±0.8% per decade in relative terms, while the high-level ones also decreased by 1.2±0.4% or 3±0.9% per decade in relative terms, i.e. less than low and middle clouds. Thus, the VIS/IR mean tropical (30_ S–30_ N) low-level clouds are found to have undergone the greatest decrease during the period 1984–2000, in agreement with the findings of Chen et al. (2002) and Lin et al. (2004).

 

[Saul]

Denier blogs are not scientific papers. Therefore you have failed to meet the standards of this forum.

There is no cooling trend since 1998. 1998 was an anomalous year, influenced by a very strong el nino event. The long term trend did plateau slightly, but has remained positive.

Skyhunter,
Science is the discussion of observations. Planetary temperature is dropping. Antarctic and Arctic Sea ice is increasing.

Name calling "denier blogs" is a sign that you are not interesting in the problem situation from a scientific standpoint. Why the emotion? The observations do not support the AWG hypothesis.

http://news.yahoo.com/s/mcclatchy/20090819/sc_mcclatchy/3295216

http://www.woodfortrees.org/plot/hadcrut3vgl/from:1980/to:2009.8/normalise

WASHINGTON — Has Earth's fever broken?
Official government measurements show that the world's temperature has cooled a bit since reaching its most recent peak in 1998.

 

[vanesch]

Those advocating the AWG position (AWG caused 90% of the 20th century warming. Deny the cooling occurred or attribute cooling to satellite problems.)

This is not what I would call the defining position of AGW. AGW means, at least, that's how I understand it, that human emissions of greenhouse gasses are significant enough to cause an observable extra warming on top of all the other forcings that there might be, in the coming centuries. Then the scientific debate goes about how much exactly.

And then the non-scientific AGW debate goes about what this is going to do to humanity and the biosphere, and whether that is a bad thing in the first place, and if so, what, if anything, we should/can do about it.

 

[Saul]

This is not what I would call the defining position of AGW. AGW means, at least, that's how I understand it, that human emissions of greenhouse gasses are significant enough to cause an observable extra warming on top of all the other forcings that there might be, in the coming centuries. Then the scientific debate goes about how much exactly.

And then the non-scientific AGW debate goes about what this is going to do to humanity and the biosphere, and whether that is a bad thing in the first place, and if so, what, if anything, we should/can do about it.

The AWG position is that a doubling of from 280 ppm to 560 ppm will cause the planet to warm 3C to 5C.

The AWG position is not that an increase in CO2 from 280 ppm to 560 ppm will cause 0.75C increase in planetary temperature.

The scientific formula for CO2 forcing is logarithmic. The current increase (from 280 ppm to 380 ppm) will if the formula matches reality result in an increase in forcing of around 2.7 w/m^2 of the total calculated 3.7 w/m^2 that the formula predicts will result from a doubling from 280 ppm to 560 ppm.

Rather than discuss the recent planetary cooling, it is denied. There cannot be a long term cooling trend if there was an increase in forcing that never goes away of 2.7 w/m^2.

That is the problem situation from the AWG position. The CO2 must warm the planet every day if the mechanism exists as hypothesized.

What it appears based on the shape of planetary temperature change, is CO2 saturates or at least partially saturates from a perspective of the mechanism. The why and what will happen next due to the abrupt solar magnetic cycle change, is an interesting question.

The key question is the magnitude of up coming planetary temperature change.

 

[Skyhunter]

Skyhunter,
Science is the discussion of observations. Planetary temperature is dropping. Antarctic and Arctic Sea ice is increasing.

Name calling "denier blogs" is a sign that you are not interesting in the problem situation from a scientific standpoint. Why the emotion? The observations do not support the AWG hypothesis.

http://news.yahoo.com/s/mcclatchy/20090819/sc_mcclatchy/3295216

http://www.woodfortrees.org/plot/hadcrut3vgl/from:1980/to:2009.8/normalise

Denier blogs or fellowship for scientific truth, it doesn't matter what you call them. They are not credible sources and therefore against forum rules.

 

[Saul]

Denier blogs or fellowship for scientific truth, it doesn't matter what you call them. They are not credible sources and therefore against forum rules.

Skyhunter what is your point or problem? You appear not to want to discuss the science and instead try to stop anyone else from discussing the science, the problem situation.

The AWG position is that a doubling of CO2 from 280 ppm to 560 ppm will cause the planet to warm 3C to 5C. Based on the AWG formula the increase from 280 ppm to 380 ppm should have resulted in an increase in forcing of 2.7 w/m^2 of the total 3.7 w/m^2, 24 hours a day, seven days a week.

The AWG forcing mechanism cannot appear in January and then disappear in June.

There is no evidence in the planetary temperature changes of a steady increase in of 2.7 w/m^2.

The other explanation for the 20th century warming is a change in planetary clouds. The forcing mechanism that increases and decreases planetary clouds can change and hence can explain the observations.

http://www.atmos-chem-phys.org/5/172...1721-2005.html Analysis of the decrease in the tropical mean outgoing shortwave radiation at the top of atmosphere for the period 1984–2000

All cloud types show a linearly decreasing trend over the study period, with the low-level clouds having the largest trend, equal to −3.9±0.3% in absolute values or −9.9±0.8% per decade in relative terms. Of course, there are still some uncertainties, since the changes in low-level clouds derived from the ISCCP-D2 data, are not necessarily consistent with changes derived from the second Stratospheric Aerosols and Gas Experiment (SAGE II, Wang et al., 2002) and synoptic observations (Norris, 1999). Nevertheless, note that SAGE II tropical clouds refer to uppermost opaque clouds (with vertical optical depth greater than 0.025 at 1.02μm), while the aforementioned synoptic cloud observations are taken over oceans only. The midlevel clouds decreased by 1.4±0.2% in absolute values or by 6.6±0.8% per decade in relative terms, while the high-level ones also decreased by 1.2±0.4% or 3±0.9% per decade in relative terms, i.e. less than low and middle clouds. Thus, the VIS/IR mean tropical (30_ S–30_ N) low-level clouds are found to have undergone the greatest decrease during the period 1984–2000, in agreement with the findings of Chen et al. (2002) and Lin et al. (2004).

http://news.yahoo.com/s/mcclatchy/20...latchy/3295216

WASHINGTON — Has Earth's fever broken?
Official government measurements show that the world's temperature has cooled a bit since reaching its most recent peak in 1998.

"It's entirely possible to have a period as long as a decade or two of cooling superimposed on the long-term warming trend," said David Easterling , chief of scientific services at NOAA's National Climatic Data Center in Asheville, N.C.

So far this year, the high has been 0.42 degrees Celsius (0.76 degrees Fahrenheit), above the 20-year average, clearly cooler than before.

 

[Skyhunter]

The Earth is not cooling.

Short term trends are flat, not negative. As the current el nino event develops global temperatures are once again on the rise.

The CO2 must warm the planet every day if the mechanism exists as hypothesized.

This is a strawman argument.

There is nothing in the AGW theory that requires temperatures to rise everyday.

 

[Skyhunter]

Saul,

If you want to discuss science, then provide a scientific source.

We are not allowed to discuss psuedo-science on this forum.

 

[Saul]

The Earth is not cooling.

Short term trends are flat, not negative. As the current el nino event develops global temperatures are once again on the rise.

This is a strawman argument.

There is nothing in the AGW theory that requires temperatures to rise everyday.

Skyhunter,

The hypothesized 2.7 w/m^2 heating due to CO2 increasing from 280 ppm to 380 ppm does not go away. It is there 24 hours a day, seven days a week.

Fundamental science shows the CO2 greenhouse affect is logarithmic. Each additional CO2 molecule has less affect than the molecule that was added before. The majority of the climate forcing has already occurred based on the basic science.

Remember the AWG position is not only that additional CO2 will cause the planet to slightly warm (say 0.75C), but rather that the planet will warm 3C to 5C, due to a doubling of CO2 from 280 ppm to 560 ppm.

Significant planetary cooling this winter for example would be very difficult to explain if the AWG hypothesized mechanism is correct.

 

[Saul]

Saul,

If you want to discuss science, then provide a scientific source.

We are not allowed to discuss psuedo-science on this forum.

Skyhunter,
Your comment is irrational. Not logical. It does not match my comment. It makes sense if your objective is to try to stop me from commenting.

It has no connection with my comment scientifically. I am only interested in the science. I am not trying to change your personal point of view.

The other explanation for the 20th century warming is a change in planetary clouds. The forcing mechanism that increases and decreases planetary clouds can change and hence can explain the observations.

http://www.atmos-chem-phys.org/5/172...1721-2005.html

Analysis of the decrease in the tropical mean outgoing shortwave radiation at the top of atmosphere for the period 1984–2000

All cloud types show a linearly decreasing trend over the study period, with the low-level clouds having the largest trend, equal to −3.9±0.3% in absolute values or −9.9±0.8% per decade in relative terms. Of course, there are still some uncertainties, since the changes in low-level clouds derived from the ISCCP-D2 data, are not necessarily consistent with changes derived from the second Stratospheric Aerosols and Gas Experiment (SAGE II, Wang et al., 2002) and synoptic observations (Norris, 1999). Nevertheless, note that SAGE II tropical clouds refer to uppermost opaque clouds (with vertical optical depth greater than 0.025 at 1.02μm), while the aforementioned synoptic cloud observations are taken over oceans only. The midlevel clouds decreased by 1.4±0.2% in absolute values or by 6.6±0.8% per decade in relative terms, while the high-level ones also decreased by 1.2±0.4% or 3±0.9% per decade in relative terms, i.e. less than low and middle clouds. Thus, the VIS/IR mean tropical (30_ S–30_ N) low-level clouds are found to have undergone the greatest decrease during the period 1984–2000, in agreement with the findings of Chen et al. (2002) and Lin et al. (2004).

http://news.yahoo.com/s/mcclatchy/20...latchy/3295216

WASHINGTON — Has Earth's fever broken?
Official government measurements show that the world's temperature has cooled a bit since reaching its most recent peak in 1998.

"It's entirely possible to have a period as long as a decade or two of cooling superimposed on the long-term warming trend," said David Easterling , chief of scientific services at NOAA's National Climatic Data Center in Asheville, N.C.

So far this year, the high has been 0.42 degrees Celsius (0.76 degrees Fahrenheit), above the 20-year average

 

[Skyhunter]

Saul,

You said:

That is the problem situation from the AWG position. The CO2 must warm the planet every day if the mechanism exists as hypothesized.

and

The AWG forcing mechanism cannot appear in January and then disappear in June.

and

Significant planetary cooling this winter for example would be very difficult to explain if the AWG hypothesized mechanism is correct.

These are strawmen arguments, red herrings. The AGW forcing does not alter the fact that climate has other shorter and longer term oscillations that account for daily, seasonal, annual, decadal, and millennial climate or temperature changes.

 

[vanesch]

The AWG position is that a doubling of from 280 ppm to 560 ppm will cause the planet to warm 3C to 5C.

?

I think you are fighting a straw man.
First of all, even the IPCC is not giving these limits (and I have - as I said earlier - my own doubts on the rigor by which these are "hard limits" or rather "to the best of our knowledge today" kind of indications). As far as I remember, they give something like 1.5 - 4.5 C with a 90% confidence limit or something. If human CO2 exhaust would double the atmospheric content and would warm only 1.5 degrees, that would also be AGW. Even 0.5 degrees in my book would be AGW, although the guys from the IPCC consider that, given their current understanding, rather improbable. However, 0.01 degree wouldn't. Because that's not noticeable or measurable.

Second, warming with respect to what ? Warming with respect to what there would have been without CO2 exhaust. The base line doesn't need to be constant. So even a cooling can be under AGW influence, if it cools less than it would have cooled without CO2 exhaust. But that's not directly measureable.

The AWG position is not that an increase in CO2 from 280 ppm to 560 ppm will cause 0.75C increase in planetary temperature.

I would think that it is still AGW, although several people tend to think it will be stronger.

The scientific formula for CO2 forcing is logarithmic. The current increase (from 280 ppm to 380 ppm) will if the formula matches reality result in an increase in forcing of around 2.7 w/m^2 of the total calculated 3.7 w/m^2 that the formula predicts will result from a doubling from 280 ppm to 560 ppm.

Yes. So ? There can be long delays before the final value is reached. These delays can be of the matter of decades or centuries.

Rather than discuss the recent planetary cooling, it is denied. There cannot be a long term cooling trend if there was an increase in forcing that never goes away of 2.7 w/m^2.

Of course there could be if there were other forcings that were negative and larger. If tomorrow the sun "goes out" then it will for sure cool. But according to AGW, it will cool slightly less (fast) than it would without CO2. That's still AGW.

The anti-AGW position is rather that human CO2 exhaust doesn't have the slightest noticeable influence on the climate system.

But the other error is to think that you can do statistics over a decade or so. You need of the order of a century to be able to see small trends like these because the average values are only that: averages. And the statistical spread around them is very big. They are the "high frequency" components that are not understood, that are chaotic,...

That is the problem situation from the AWG position. The CO2 must warm the planet every day if the mechanism exists as hypothesized.

No, of course not. There must only a trend on the scale of centuries or many decades. And even then, a trend with respect to an unknown "base line" which is what there would have been without human exhaust, but which we can of course not measure.

Of course, the stronger the trend, and the less the baseline is supposed to change, the sooner the data will show up evidence.

The absolute temperature variation BY ITSELF doesn't say anything about AGW by itself.

 

[Saul]

?

Vanesch & Skyhunter,

I think we have beaten this subject to death. Let's agree to disagree.

Let's summarize.

I have provided papers that show the 20th century planetary warming could be due to a reduction in planetary cloud cover. See above if anyone is interested.

There is currently an abrupt interruption of the solar magnetic cycle which has reduced the strength of the heliosphere and has caused GCR to increase by 18%. There has not been an increase in planetary clouds because there has been a three times increase in solar wind bursts during this current solar cycle minimum. I have provided papers to support these statements.

The solar wind bursts have started to abate.

Based on the planetary cloud mechanism, planetary cloud should now start to increase, due to a reduction in the solar wind bursts and due to the increased GCR.

So rather than argue whether the solar modulation of planetary cloud mechanism exists or does not exist, we can just watch planetary temperature and see if it does drop. I am interested because I do not understand the delays in the mechanisms and I am unsure of the magnitude of the change.

I will keep an eye out for any interesting planetary temperature observations. Have you been watching the current Arctic and Antarctic sea ice cover anomaly?

 

[Skyhunter]

I have provided papers that show the 20th century planetary warming could be due to a reduction in planetary cloud cover. See above if anyone is interested.

Your sources are not scientific, therefore may not be discussed here.

There is currently an abrupt interruption of the solar magnetic cycle which has reduced the strength of the heliosphere and has caused GCR to increase by 18%. There has not been an increase in planetary clouds because there has been a three times increase in solar wind bursts during this current solar cycle minimum. I have provided papers to support these statements.

I have been following the current solar minimum, solar winds have been relatively calm for the past year.

[edit] Although they have been much higher than during the cycle 23 minimum. [/edit]

Based on the planetary cloud mechanism, planetary cloud should now start to increase, due to a reduction in the solar wind bursts and due to the increased GCR.

Planetary cloud cover should have begun increasing 18 months ago according to the GCR hypothesis.

So rather than argue whether the solar modulation of planetary cloud mechanism exists or does not exist, we can just watch planetary temperature and see if it does drop. I am interested because I do not understand the delays in the mechanisms and I am unsure of the magnitude of the change.

I am uncertain that the mechanism even exists. And even if it does, since temperatures are still rising it has little effect on global temperatures.

I will keep an eye out for any interesting planetary temperature observations. Have you been watching the current Arctic and Antarctic sea ice cover anomaly?

I visit the NSIDC site 3-5 times a week.

 

[Saul]

Your sources are not scientific, therefore may not be discussed here. I visit the NSIDC site 3-5 times a week.

http://www.agu.org/pubs/crossref/2009/2009JA014342.shtml
Skyhunter,

You must have missed this paper. Let's agree to disagree about the prediction of what is about to happen. Let's wait until there is new planetary temperature data to discuss. I will keep an eye out for new papers.

This should be an interesting scientific period if I understand the mechanisms.


If the Sun is so quiet, why is the Earth ringing? A comparison of two solar minimum intervals

Observations from the recent Whole Heliosphere Interval (WHI) solar minimum campaign are compared to last cycle's Whole Sun Month (WSM) to demonstrate that sunspot numbers, while providing a good measure of solar activity, do not provide sufficient information to gauge solar and heliospheric magnetic complexity and its effect at the Earth.

The present solar minimum is exceptionally quiet, with sunspot numbers at their lowest in 75 years and solar wind magnetic field strength lower than ever observed. Despite, or perhaps because of, a global weakness in the heliospheric magnetic field, large near-equatorial coronal holes lingered even as the sunspots disappeared. Consequently, for the months surrounding the WHI campaign, strong, long, and recurring high-speed streams in the solar wind intercepted the Earth in contrast to the weaker and more sporadic streams that occurred around the time of last cycle's WSM campaign.

In response, geospace and upper atmospheric parameters continued to ring with the periodicities of the solar wind in a manner that was absent last cycle minimum, and the flux of relativistic electrons in the Earth's outer radiation belt was elevated to levels more than three times higher in WHI than in WSM. Such behavior could not have been predicted using sunspot numbers alone, indicating the importance of considering variation within and between solar minima in analyzing and predicting space weather responses at the Earth during solar quiet intervals, as well as in interpreting the Sun's past behavior as preserved in geological and historical records.

 

[Skyhunter]

You are speculating that

1. GCR drives cloud formation, as yet a still unproven hypothesis.
2. The solar wind modulates this as speculative process.

Since the global temperature trend is still positive, and we are entering a positive ENSO phase, then it is likely that global temperatures will continue to rise.

 

[Darryl]

My take on this is, it's not a valid scientific experiment, there is no control subject and it it was "an experiment" that should be allowed to run it's course then what happens if the global warming does swing out of control.

talking about control, I see this as a feedback control loop issue, if you have 'tuned' a feedback control loop you generally have 2 knobs, gain and damping.

Too little damping and the process will go out of control, it will not just swing to one extreme it will begin to oscilate until it hardlines on one extreme.

Too little damping or too much gain will achieve the same result.

To me, cutting down CO2 absorbing trees is reducing the "damping" parameter, and releasing fossilised CO2 in increasing the gain in the system.

It's not an experiment, we don't have anywhere els to go if we are wrong, So possibly erring on the side of causion might be wise.

"Lets wait and see" is not good enough.

 

[D H]

My take on this is, it's not a valid scientific experiment, there is no control subject and it it was "an experiment" that should be allowed to run it's course then what happens if the global warming does swing out of control.

What experiment are you talking about?

It appears you have a misperception of how the scientific method is employed in fields such as anthropology, astronomy/cosmology, and climatology/meteorology. We don't know how to build a time machine, and even if we did, going back in time and experimenting on Mitochondrial Eve would not be deemed as kosher. Anthropologists can only observe, and their observations are limited to ancient bones and shards of flint. Astronomers similarly cannot create in the lab galaxies that are billions of light years apart. They can observe them by telescope. Just because anthropologists and astronomers can't perform controlled experiments with all the trappings does not mean that anthropology and astronomy are not science.

The same goes for meteorology and climatology. Scientists can create scaled-down models of some phenomena, but scaling things down to lab size is always fraught with problems. (The scaling problem is why the aerodynamics industry likes to use full-scale wind tunnel as the ultimate test of what happens to a vehicle.) The best way to determine the weather and climate is to observe it. It is still science.

 

[Skyhunter]

This topic is interesting because there are competing scientific viewpoints in published papers and because there is currently an abrupt interruption to the solar magnetic cycle.

Saul,

I started a new thread.

https://www.physicsforums.com/showthread.php?t=346406

It is a new map of the heliosphere by the IBEX spacecraft . Since the heliosphere is a manifestation of the solar magnetic anomaly you might find the press conference interesting