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Tom Curtis at 08:37 AM on 21 May 2015Why the 97 per cent consensus on climate change still gets challenged
Concerned @25, I have now recalculated the values discussed in my preceding post using the papers rather than author values. The results are:
X= Multiplier Value End% Unc%
Neutral 0.50% 3.82 96.90% 0.29%
All 0.33% 7.17 96.62% 0.58%
Adj 193.77% 13.90 96.20% 1.00%In each case, in calcuting the endorsement percentages, I rounded the value of X up. As you can see, even the most generous projection still makes little difference, only reducing the endorsement percentage by 1%. So, while Cook et al (2013) would have been improved had authors been given the option of an "uncertain" rating, it would have made no difference to the headline results.
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Leto at 08:03 AM on 21 May 2015Why the 97 per cent consensus on climate change still gets challenged
CBDunkerson,
My ealier post was about the fairness of your analogy, and explicitly did not go into the percentages of the consensus paper, which I will also not touch on this occasion.
Concerned raises two issues:
1) Relative to a debated scientific point, papers could potentially be divided into four categories: yes, no, undecided and irrelevant (Y, N, U, I). Concerned suggests that the headline percentage of consensus is best captured by Y/(Y+N+U), where U refers to papers that have actually attempted to consider the question, not merely mentioned a search term. This appears reasonable. He explicitly rejects I from the equation.
2) He wonders if this affects the cited 97% consensus.
My comments relate to the first issue. While it may be that Concerned has made mistakes in attributing papers to the categories Y, N, U and I, and that his percentages include papers from the I category, it is not fair to accuse him of misunderstanding the issue so badly that he needs to be told that the consensus ratio should not include I in the denominator. Your analogies suggested he was unaware of this, and in that sense were unfair and distracting. -
Tom Curtis at 07:53 AM on 21 May 2015Why the 97 per cent consensus on climate change still gets challenged
Concerned @25
(Correction: I have just noted that I used the numbers of respondents rather than the number of papers in calculating the values below. I don't have time now, so will recalculate later if you have not already done so before hand.)
A subsidiary survey found that among abstracts rated as neutral on AGW (category 4), only 0.5% expressed the position "... that human's role on recent global warming is uncertain/undefined" (category 4b). On the simplest assumption, therefore, only 0.5% of the 759 category 4 papers from the author self ratings would similarly fall into an "uncertain category" had one existed, so X would be 2, yielding a 96.26% endorsement rate rahter than the 96.38% actually obtaind for the paper.
Arguably that is too simplistic a way to project the results of the subsidiary survey onto the author ratings. Presumably the reduced percentage of category 4 ratings in the author ratings would have come from truly neutral (category 4a) papers rather than from those with a discernable opinion in the abstract (category 4b). That being the case, we should project the percentage of category 4b papers as a percentage of all papers. Doing so lifts the value for X to 3.99.
Arguably the category 4b papers would also have expanded in relative number in the same way as the affirming and rejecting papers did. On that basis, we should multiply our projected X by the ratio of papers taking a positon in the author rating divided by the ratio of papers taking a position in the abstract ratings, ie, by 1.96 yielding a value for X of 7.8 which we can round to 8.
Using this value for X, the endorsement percentage for author ratings drops to 95.4% with an projected uncertain (category 4b) rate of 1.02%.
So, even with this most generous estimate of X from the only available data, the endorsement rate scarcely falls. Specifically, it does not drop outside the uncertainty interval of the original estimate. And it does not drop to values which would support any contesting of the idea that there is a scientific consensus on AGW.
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MA Rodger at 05:58 AM on 21 May 2015Why the 97 per cent consensus on climate change still gets challenged
Concerned @25.
You are incorrect to suggest that the self-assessment is assessing the opinion of the authors. The survey is asking for a self-assessment of their work, not the authors personal opinion of AGW.
Also the suggestion that a histogram would be a more appropriate presentation of the results - I find this unconvincing. The reason a paper is rated, say,1 - Explicit endorsement with quantification rather than 2 - Explicit endorsement without quantification is more to do with the type of analysis being employed rather than the finding of that analysis. There is in all this the truth that there are very few pieces of research 1991-2011 attempting to prove what all climatologists know to be true. A tiny handful of researchers continue the struggle to undo this truth but without result. These denialist climatologists may say this is 'without result so far' or 'without an accepted result so far' but I have not seen a thing in a decade to suggest the truth is in any way in doubt.
Your histogram can be gleened from the uploaded self-assessment data I linked to @21 (although the total is six short):-
1 - 242
2 - 557
3 - 539
4 - 759
5 - 25
6 - 5
7 - 9 -
Concerned at 04:30 AM on 21 May 2015Why the 97 per cent consensus on climate change still gets challenged
CBDunkerson @24,
Your first analogy about boys is not correct, as Leto said. Of course boys would be the denominator, as that is how the question was posed.
What I was driving at is that the data should be presented as a histogram of those who have considered the question and have an opinion on the cause of global warming. If some value the X out of the 35.5 % who adddressed and considered the issue were undecided on the cause, those X people have an opinion on the cause. Then the histogram would have three values, yes AGW = 1342/(1342+39+X), undecided = X/(1342+39+X), and no AGW = 39/(1342+39+X).
My basic question is, what is the value of X? You are assuming that all 35.5% are irrelevant, so X is 0. The words used to describe the 35.5% were "no position". That is not the same as "irrelevant". Some of those "no position" people could have considered the cause and be undecided.
The problem here is the use of language. "no position" is ambiguous. I am asking how many of those "no position" people, X, have considered the question, perhaps very carefully, and are undecided. That value X affects the histogram.
If there were 7 categories of opinion, then the results should be shown as a 7-column histogram, not yes or no.
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CBDunkerson at 03:10 AM on 21 May 2015Why the 97 per cent consensus on climate change still gets challenged
Leto, your statement that "Papers that do not consider the question at all are not at issue here" is simply incorrect. That is precisely the issue.
The 35.5% figure Concerned cited actually came from the self-rating portion of the study. In that phase, abstracts for a total of 2142 papers were rated by their authors. Of those, 1342 (62.7%) endorsed the consensus, 39 (1.8%) rejected the consensus, and 761 (35.5%) did not address the issue.
1342 / (1342 + 39) = 97% consensus
Why not factor in the 761 abstracts, or some unspecified fraction of them, as 'undecideds'? Because this wasn't looking at opinions, but rather content... what the text of the abstract actually said. Either that text addressed the issue, or it did not... and for 35.5% of the papers their authors said that the issue wasn't covered.
In short, 'the fact that another 761 papers were on other topics is irrelevant'.
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Art Vandelay at 02:19 AM on 21 May 2015Breathing contributes to CO2 buildup
By def, Biomass (animal and plant) is considered to be the total mass within the carbon cycle at any given time so you can't change 'total' biomass, only its composition.
But again, the confusion here is due to my misunderstanding the original proposition - which specifically does not refer to human population growth perse.
Also, my proposition that population growth increases atmospheric CO2 assumes that it results in increased 'total respiration' and that is not necessarily the case - because human population growth is likely to be at the expense of other species.
Nonetheless, it would be interesting to know exactly what effect the rise of human population to 7 billion has had on the carbon cycle.
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KR at 01:14 AM on 21 May 2015Breathing contributes to CO2 buildup
Carbon in biomass is also "in circulation", which is the primary point I think you're overlooking. And CO2 in respiration comes from food consumption, with food still being part of the carbon cycle: carbon input = carbon output for any organism over both short terms and its entire lifecycle.
Side note: if total incorporated biomass has been raised by population growth (which requires an assumption that plant biomass isn't displaced) that sequestration of carbon in organisms can only decrease atmospheric CO2.
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Art Vandelay at 01:03 AM on 21 May 2015Breathing contributes to CO2 buildup
"changing the speed of carbon cycling between plant and animal, but not adding or subtracting from the sum carbon in circulation"
See Tom's diagram. The land based inputs are respiration and fire, so the 'sum carbon in circulation' (as you put it) is always equal to the 'respiration and fire' that's fed into the system.
However, that aside, I can see why we're in disagreement and it's because we're presenting two different arguments.
Your proposition (argument) that human breathing (respiration) does not increase C circulation in the cycle refers to a static population, whereas I'm proposing that human population growth increases the input 'C' into cirulation in the system and therefore increases atmospheric CO2.
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KR at 23:51 PM on 20 May 2015Breathing contributes to CO2 buildup
Note that CO2 in respiration and in carbon in plant and animal biomass is still in the biological carbon cycle. Increased respiration and CO2 output requires balancing increased food consumption and carbon input into the breathing organisms - changing the speed of carbon cycling between plant and animal, but not adding or subtracting from the sum carbon in circulation.
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Art Vandelay at 22:56 PM on 20 May 2015Breathing contributes to CO2 buildup
44@KR
"Atmospheric concentrations can only have net changes over the long term if more carbon enters or leaves the biological carbon cycle"
Yes, I agree, so it follows that baseline atmospheric CO2 will increase if either respiration increases or if photosynthesis decreases.
See Tom's attached IPCC flux diagram above which shows the exchange of CO2 in and out of the atmosphere. It shows that total respiration has increased since pre-industrial times - which is interesting.
"Breathing does not, and can not, influence long term atmospheric CO2 concentrations. It's a complete red herring in the discussion of climate change."
Well I do agree that it's a "red herring" in the dicussion of climate change because animal respiration is dwarfed by the burning of fossil fuels but I don't agree that human and other animal respiration cannot alter atmospheric concentations, and as Tom's diagram shows, respiration and fire are the only natural land based inputs into the cycle.
My argument isn't that animal respiration is in any way significant as a driver of global climate, but that doesn't mean that via modulation that it cannot or does not alter CO2 in the atmosphere over a given time scale.
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Leto at 22:39 PM on 20 May 2015Why the 97 per cent consensus on climate change still gets challenged
CBDunkerson @22,
I don't believe your analogy is at all fair to Concerned's question. I have agreed with you when you have made similar statements in the past, but those statements were made in response to a different question.
Putting aside the details of the 97% consensus paper (I am not sufficently familiar with the details), it is true that the relevant denominator to consider, when calculating a consensus, is the number of papers considering a position, including those that eventually adopt a conclusion of "undecided" after such consideration - not the number of papers adopting a position. Papers that do not consider the question at all are not at issue here, which is why your gravity analogy is unfair. If there were a large number of undecided papers (I believe there were not), that would indeed affect the validity of the consensus.
If 1000 authors explicitly wrote about the possibility of an El Nino in 2015 and 97 of them said one was on the way, 3 said we were definitely not having an El Nino in 2015, and 900 said it was too early to call it, there would not be a 97% consensus we were having an El Nino in 2015. The fact that another million papers were on other topics would be irrelevant.
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CBDunkerson at 22:01 PM on 20 May 2015Why the 97 per cent consensus on climate change still gets challenged
Concerned, suppose you have a class of 20 students; 10 boys and 10 girls... and you want to calculate the percentage of the boys who are white. The Cook paper methodology would have you count the white boys (say there are 7) and divide by the number of boys total... to get 70%. Your proposed methodology would instead have us find that only 35% (7/20) of the boys are white, 15% of the boys are non-white, and 50% of the boys are not boys.
In short, you are asking why values not relevant to the calculation aren't included. That's a disturbing level of logical dissonance.
Note that by such 'logic' the consensus level is essentially reduced to a factor of the size of the pool of papers reviewed. To take the extreme; the percentage of all papers on every subject imaginable which state a position on any given single issue is going to be near 0%. So your methodology of 'include non-relevant data' would indicate that there is approximately 0% consensus on everything. For example, approximately 0% of all papers ever written clearly state that gravity exists. Ergo there is 0% consensus that gravity exists.
See 'where you went wrong'?
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MA Rodger at 21:14 PM on 20 May 2015Why the 97 per cent consensus on climate change still gets challenged
Tristan @20.
The size of the two different 'pots' are relevant but they do apply to different data.
Concerned @19.
The self-assessment asked authors to rate their entire paper rather than just the abstract so it was different things being assessed as well as the assessors being different. The self-assessment survey asked for ranged from 1 = Explicit endorsement with quantification through 4 = No Expressed Position to 7 = Explicit rejection with quantification. There was thus no means of differentiating between 'irrelevant' and 'undecided'.
The self-asessment results did a reasonable job of supporting the detailed findings of the Abstract assessment process, if anything strengthening the consensus finding. With the results so similar, it is likely relevant that the Abstract rating process only found a tiny proportion of 'undecided' Abstract, Tristran's "very few papers" (from Table 3 of Cook et al (2013) 0.3% of all abstracts were rated thus, ie "Uncertain on AGW"). It is thus likely that this tiny proportion would also have been found had the self-assessment allowed for such a catagorisation.
However an author approached over this self-assessment process may well consider that if their paper fell into this 'undecided' category and they themselves were not convinced by the evidence of AGW that it should be rated more as a mild rejection of AGW rather than entirely neutral. And likely visa versa. Were there such an effect, again it does not support the idea of a large volume of 'undecided' literature being missed by the survey.
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Tristan at 20:36 PM on 20 May 2015Why the 97 per cent consensus on climate change still gets challenged
If you change 'irrelevant' to 'unstated', that's exactly what the authors did.
There was an 'uncertain' pot as well as a 'no position' pot.
Very few papers were 'uncertain' -
Concerned at 18:46 PM on 20 May 2015Why the 97 per cent consensus on climate change still gets challenged
I endorse AGW, but I am confused about the calculation of 97%. The set of e-mail responses includes "no position on AGW (35.5%)". As I see it, there are two possible viewpoints among the 35.5% having "no position":
"irrelevant" — The cause of global warming is not part of the discussion.
"undecided" — The cause of global warming is considered, but the evidence does not support a yes or no vote for AGW.
As I see it, the "undecided" papers should be counted as opinions, but "irrelevant" papers should be omitted. If so, then there should be three fractions: yes, undecided, and no, which sum to 1. Then the yes votes would be less than 97%.
Kindly explain the logic and tell me where I am going wrong.
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Tristan at 14:30 PM on 20 May 2015Why the 97 per cent consensus on climate change still gets challenged
1) A clear acknowledgement that 'science is a process, not a body of knowledge' so that the consensus of scientists is irrelevant to science and should be ignored; and
Interesting. I just had this exact argument with Ms Nova. She refused to accept that Science was a noun as well as a verb (The noun was the original definition, even). -
Tom Curtis at 13:42 PM on 20 May 2015Why the 97 per cent consensus on climate change still gets challenged
mancan @18, what deniers seem to what is:
1) A clear acknowledgement that 'science is a process, not a body of knowledge' so that the consensus of scientists is irrelevant to science and should be ignored; and
2) A clear acknowledgement that only that which is 100% certain in science is an acceptable basis for policy.
Leaving aside that science is both a process and a body of knowledge, the second requirement above presuposes that science is a complete body of knowledge, ie, one that cannot require further expansion or correction. Their two desiderata, therefore, rely on contradictory and inaccurate conceptions of science.
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KR at 13:15 PM on 20 May 2015Why the 97 per cent consensus on climate change still gets challenged
PhilippeChantreau - "Do we really have to bother with this nonsense?"
While the Nth repetition of a denialist meme is rather tiresome to those who have been participating in forums such as SkS, I suspect that the occasional bit of nonsense is very instructive for undecided readers. Because they so clearly demonstrate the paucity of pseudo-skeptic positions.
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mancan18 at 12:58 PM on 20 May 2015Why the 97 per cent consensus on climate change still gets challenged
BBHY comment coveers the basics of the role that carbon dioxide plays in the argument.
Tom Curtis has dealt with the role of chaos theory in highlighting the differences between weather and climate.
Climate is predictable. Tendencies in the weather that are central to all weather forecasting is also valid. It is based on weather records from each locality and comparing the situation of today with the average of all recorded situations at the same time in the past under the same conditions.
Choosing whether a climate scientist chosen at random will support or reject the consensus on climate change is also predictable. The results from the Consensus Project are fairly indicative. Such predictions are based on the probabilities that are involved in making the prediction or determining the outcome.
What deniers/obstructionists like TWFYSYWD seem to want is 100% certainty when in science there is none. That is why confidence intervals are used in making scientific assessments. There might be chaos in the phenomonen but that does not necessarily mean that it is entirely random or unpredictable. In a coin toss, the outcomes are entirely random and somewhat chaotic with H and T occuring around 50% of the time for each as more and more trials are conducted. However, that does not mean we will know exactly how many heads will come up, tails will come up, or whether the coin will come up on it's side, which is, although very remote, not entirely impossible. Coin on its side just doesn't occur with the same equally likely manner that the H/T outcomes do. There is no theoretical 100% certainty even with a coin toss.
Outcomes related to climate change, while perhaps being based on a somewhat chaotic phenomonen, will always be based on the tendencies determined by the underlying scientific principles of the phenomonen. So if you heat the planet by increasing the level of greenhouse gases, you will get more chaotic turbulence filtering through the weather systems which will ultimately impact on the climate. The idea that climate scientists can't precisely predict what is going to happen from their climate models is not a reason to negate the fundamentals of the argument. A statistical aggregation with related probabilities from all climate models is more likely to yield an accurate prediction and the IPCC does a faily good job of aggregating the research.
Personally, I prefer the paleoclimate data to indicate what is likely to happen. From what I understand, there is only a 4 degree or so global temperature difference between an ice age with all those huge continental wide ice sheets and an inter-glacial, with the polar regions we see today. I don't think returning the planet to the CO2 levels of the past when there no icecaps and it was up to 4-6 degrees warmer, by burning all known recoverable reserves of fossil fuels, is such a bright idea. As for those who think that climate change is all natural and it just magically changes, well I would suggest that you don't have any real scientific understanding of what "natural" actually means. Climate scientists, while not necessaly having a complete understanding, do have a pretty good understanding of what is happening and why. Based on the probabilites, I think the Earth has a problem that needs to be addressed.
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PhilippeChantreau at 11:49 AM on 20 May 2015Why the 97 per cent consensus on climate change still gets challenged
Do we really have to bother with this nonsense? I understand that mods give everyone the benefit of the doubt but, after a numberof years of this, I have learned to identify the signs showing that one has nothing of value to contribute.
TWFYSYWDI can't be bothered to go the right thread after several commenters indicate they have responded there, and are kind enough to include links. He/she uses one of the most basic tools of dishonest rethoric (quote out of context). And on top of it all coats his latest comment with snark when it is obvious he/she lacks the most basic understanding of the issue at hand.
It's not like any learning will happen here. No matter how the exchange proceeds, the individual will portray it elsewhere with the kind of faithfulness given to the IPCC quote. Can't we just dispense from the hassle?
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This Will Frighten You so You Will Delete It at 11:26 AM on 20 May 2015Why the 97 per cent consensus on climate change still gets challenged
Moderator - Thank you for your kind response and your helpful suggestions. But now I am utterly confused. Perhaps you can clear it right up.
I quoted directly from an official IPCC report which unambigously states that "In climate research ... we are dealing with a ... chaotic system..." I gave the source of this report so you and your readers may check for themselves:
http://www.ipcc.ch/ipccreports/tar/wg1/505.htm
You responded with an assertion for which you offered no supporting evidence, as far as I can detect. You wrote "climate, by definition, is not chaotic."
Now we must choose. Either we must believe the IPCC, or we must believe your contradictory unsupported assertion.
I don't wish to jump to the wrong conclusion. Please help me with this difficult choice.
Moderator Response:[PS] The points you made have been answered in the appropriate thread. See the pointers from posters above. As noted in comments policy, moderation complaints are always off topic. Please continue to discuss the main point but in the appropriate thread.
However, given your chosen pseudonym, I must say that if your intentions are simply snark and trolling rather than engaging with science then please find another forum for your entertainment.
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chriskoz at 11:12 AM on 20 May 2015Why the 97 per cent consensus on climate change still gets challenged
denisaf@11,
Your point narrows the issue unnecessarily. The man made increase of CO2 is the result of not only "the operation of technological systems using fossil fuels" but broader human activities such as:
- fossil fuels burning in a large sense, not only to operate technological systems, but e.g. burning coal/gas/petrol for heating,
- land use changes,
- cement production
One broad definition that encompasses all such activiteis is: permanently (on human timescale) and irresponsively changing composition of the atmosphere by adding to it carbon that belongs to other reservoirs.
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denisaf at 10:32 AM on 20 May 2015Why the 97 per cent consensus on climate change still gets challenged
Assessment of the hypothesis that rapid, irrversible climate change is under way would be more credible if the point was made that it is the operation of technological systems using fossil fuels that is producing the damaging greenhouse gas emissions. Saying climate change is man made does not help rational consideration of the evidence. People made unwise decisions but it was the operation of the systems that has caused the CO2 atmospheric concentration level to increase rapidly.
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chriskoz at 10:04 AM on 20 May 2015Why the 97 per cent consensus on climate change still gets challenged
For some reason, Tom's response on the apropriate thread cannot be "upvoted". I'd like to stress the valueable, insightful details of Tom's comment, especially its last paragraph (about the meaning of TWFYSYWDI web name), so I've upvoted Tom's link above here.
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KR at 06:53 AM on 20 May 2015Climate is chaotic and cannot be predicted
"...a threshold keyed of long term averages rather than immediate weather states can also cross a threshold for hysteresis randomly"
Indeed. But that is true of any system with both hysteresis and noise, and is what I meant when talking about the probablistic blurring of hysteresis thresholds.
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KR at 06:49 AM on 20 May 2015Climate is chaotic and cannot be predicted
Technically speaking hysteresis doesn't induce the possibility of chaotic behavior - chaotic dynamics require sensitivity to starting conditions, which requires non-linearity. And even non-linear systems can be largely or wholly deterministic - for example many power amplifiers are non-linear yet deterministic over their entire operating ranges.
It's important to distinguish between hysteresis states and chaotic bifurcation attractors. Hysteresis states are separated by unmatched thresholds - the threshold from state A to state B is closer to B than the threshold from state B to state A. But bifurcated chaotic attractors (and the bifurcation itself breeding additional attractor regions) vary with the state of the system, and describe where a chaotic system may range while in that particular state. They are not the same thing at all.
Summary; hysteresis alone doesn't induce starting condition or state history dependent chaotic dynamics. But a non-linear system with hysteresis may in addition exhibit chaotic dynamics.
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Tom Curtis at 06:43 AM on 20 May 2015Climate is chaotic and cannot be predicted
KR @107, for the sake of discussion, assume that ENSO is in fact random. If that is the case, it is possible that we could experience a long period of more frequent La Nina (or El Nino) states purely by chance. Such an occurence would reduce the long term average of the GMST. It follows that a threshold keyed of long term averages rather than immediate weather states can also cross a threshold for hysteresis randomly. The difference is that the probability of crossing the threshold will be smaller when keyed of long term averages (and hence the return interval larger).
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Tom Curtis at 06:33 AM on 20 May 2015Climate is chaotic and cannot be predicted
KR @106, while I agree that hysteresis does not directly imply chaotic dynamics, hysteresis plus chaotic weather does open up that possibility. As a simple case, we could imagine a system where the equilibrium level of the climate for a given forcing lies close to but above a threshold point, such that annual short term variability (forced plus internal) can kick it below the threshold with a return period fo 1/1000; and such that after crossing the threshold the same forcing results in an equilibrium level just below the threshold to return to the prior state, with short term variability again having a similar return period to kick it just above the threshold. In such a system, with stable base forcing, the climate will kick between the two states at unpredictable intervals, but with a mean duration in each state of a thousand years. It would be chaotic.
In fact, some climate scientists at least believe the Earth is in a similar state (with larger perturbations required to cross the threshold and unequal return intervals), and that that accounts for the glacial/interglacial cycle. (Science of Doom had a recent series of blog posts expounding, and linking to relevant papers, for just such a view.)
Of more concern as it is more likely to impact us in the near future, a steady increase in forcing over time may cross unknown thresholds which may result in changes in climate unpredictable from the emperical data prior to the crossing of the threshold. As I understand it, is is a common view of climate scientists that such thresholds do exist, but that the level of the thresholds is essentially unknown for most cases. While not strictly chaotic, this does introduce a level of uncertainty in projections which is the fundamental point of denier arguments about the supposed chaotic nature of climate. Of course, if it is in fact the case, it is bad news rather than good news for it significantly increases the probability of large impacts from AGW.
Anyway, just to be clear about what I am claiming, hysteresis introduces the possibility of chaotic dynamics in climate. That in turn means it is not true "by definition" that climate is not chaotic. Further, there is evidence that hysteresis has introduced some level of chaotic dynamics to climate in the past, most notably with snow-ball earth episodes, and potentially other ice ages. Consequently it is possible but not know to be the case that chaotic dynamics could be introduced at some threshold passed by warming in the next century or two from AGW. Therefore, it is not true in all realized climate states that the climate is not chaotic. I am not, however, claiming that we will experience chaotic dynamics in climate under current conditions or over the next few centuries. I am inclined to think that we will not. We just cannot rule out the possibility.
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KR at 06:09 AM on 20 May 2015Climate is chaotic and cannot be predicted
Tom Curtis - Continuing: I suppose this comes down to the differences between immediate weather states (including aperiodic fluctuations such as ENSO) and long-term climate averages. If the averaging period of climate is long enough to encompass and average multiple chaotic weather variations then the bounds of variability are non-chaotic, no matter how non-linear. A boundary question of averages is very different from an initial state question of precise trajectories.
I suppose that D-O events and their uncertain timing may reflect some chaotic climate behavior, changing long term climate averages; but if they're truly cyclic phenomena they then aren't chaotic by definition.
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KR at 06:00 AM on 20 May 2015Climate is chaotic and cannot be predicted
Tom Curtis - Keep in mind that system hysteresis does not directly imply chaotic dynamics. Many physical systems show hysteresis that is quite predictable, with consistent thresholds, irrespective of previous state trajectory histories.
And while chaotic weather variations may kick global climate energy levels about a fairly small range, initiation of a transition is still based upon rather fixed if unknown thresholds. The chaotic weather simply adds a probablistic blur to those thresholds - long term average climate isn't going to show variegated wandering paths due to initial state dependence.
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Tom Curtis at 04:36 AM on 20 May 2015Climate is chaotic and cannot be predicted
The moderator (RH) responded to TWFYSOWDI elsewhere by saying, in part
"First case in point, climate, by definition, is not chaotic."
That is not quite true, and certainly not true by definition, in that cases of hysteresis open up the possibility of chaotic responses in climate. Indeed, as hysteresis in climate typically involves a threshold effect, and as individual climate states are not predictable, in principle with some levels of forcing, the climate response must be chaotic in that the crossing of the threshold may only occur (with that level of forcing) with the occurence of a particularly improbable realizable state given that forcing. Of course, with a steadilly changing forcing, the threshold will be crossed at some time, though the actual timing of crossing the threshold may vary considerably given a forcing history.
Of course, deniers will not entertain this possibility. Any broaching of the possibility is dismissed as "alarmist" and "hysterical". Nor can they consistently allow for such possibilities in that for such responses to be chaotic, they must involve some combination of large climate sensitivity and/or significant lags in climate responses, both of which they deny (and both of which would be very bad news). So, it may be the case that future climate response to anthropogenic forcing is unpredictable - that we may suddenly transition to an entirely different base climate at an unknown threshold of warming. But that would be a far more alarming situation requiring a far more rapid mitigation response than that indicated by standard projections of future climate found in the IPCC.
Moderator Response:[RH] I'm thinking in terms of a very broad definition, as in, deserts don't become rainforests in the short term. Climate is weather averaged over 30 years or more. It can change but it isn't chaotic in the sense that you don't know what the weather is likely to be in coming years.
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Tom Curtis at 04:10 AM on 20 May 2015Why the 97 per cent consensus on climate change still gets challenged
Like KR (and MARodger), I have also responded to TWFYSYWDI on the appropriate thread.
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Tom Curtis at 04:05 AM on 20 May 2015Climate is chaotic and cannot be predicted
TWFYSOWDI elsewhere illustrates a desire to use one of the standard tools of pseudoscience, out of context quotation. Typically understanding the full context requires not just quoting the full paragraph from which the quote derives, but sufficient background information to understand what is meant by it. So in this case, TWFYSOWDI should have quoted the full paragraph, which reads:
"In sum, a strategy must recognise what is possible. In climate research and modelling, we should recognise that we are dealing with a coupled non-linear chaotic system, and therefore that the long-term prediction of future climate states is not possible. The most we can expect to achieve is the prediction of the probability distribution of the system's future possible states by the generation of ensembles of model solutions. This reduces climate change to the discernment of significant differences in the statistics of such ensembles. The generation of such model ensembles will require the dedication of greatly increased computer resources and the application of new methods of model diagnosis. Addressing adequately the statistical nature of climate is computationally intensive, but such statistical information is essential."
Had he done so, however, he would have undercut his message by showing that the authors of Chapter 14 of the IPCC TAR believed that there where some things that could be predicted about future climate, ie, the probability distribution (aka, the statistics) of future climate states. He would also have shown that the authors believed a particular strategy was needed to make such predictions of the statistics, a strategy they in fact followed.
However, full context requires understanding what the climate is, specifically:
"'Climate' refers to the average weather in terms of the mean and its variability over a certain time-span and a certain area. Classical climatology provides a classification and description of the various climate regimes found on Earth. Climate varies from place to place, depending on latitude, distance to the sea, vegetation, presence or absence of mountains or other geographical factors. Climate varies also in time; from season to season, year to year, decade to decade or on much longer time-scales, such as the Ice Ages. Statistically significant variations of the mean state of the climate or of its variability, typically persisting for decades or longer, are referred to as 'climate change'. The Glossary gives definitions of these important and central notions of 'climate variability' and 'climate change'."
So not only are the statistics of climate states in principle predictable, but climate itself is just the statistics of those states so while weather is not in principle predictable beyond a few days into the future, climate is. At least according to the IPCC TAR. Despite this, by unscrupulous (I would say dishonest) selectivity in quotation, TWFYSOWDI makes them appear to say the opposite.
Note to the moderator: Every now and then we get some insecure individual who is so lacking in confidence that their message can stand on it own that they feel they must give it a boost in their "nom de web". I find such attempts at persuasion outside of reason annoying. I particularly find them annoying when the consist of caclulated insults to their hosts. May I suggest that such names be banned from SkS.
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MA Rodger at 01:32 AM on 20 May 2015Climate is chaotic and cannot be predicted
KR @102,
Indeed, had This-Will-Frighten-You-So-You-Will-Delete-It read the remainder of the paragraph he quotes fron IPCC TAR 14.2.2.2 he would have learned that long-term averages and probability density functions are predictable, as the line following his quote reads "The most we can expect to achieve is the prediction of the probability distribution of the system's future possible states by the generation of ensembles of model solutions." And that is what is being delivered.
And what fun, his nom-de-web was chosen especially for us.
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Cooper13 at 01:21 AM on 20 May 2015My Research with Steve
These are the stories you don’t read about in scientific papers, which out of necessity detail the methodology as if the authors knew exactly where they were going and got there using the shortest possible path. Science doesn’t often work like that. Science is about messing around and exploring and getting a bit lost and eventually figuring it out and feeling like a superhero when you do. And then writing it up as if it was easy.
LOL - I think a LOT of scientists in just about any field of publication can relate to this!! Congrats on the first 'first author' article!
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dcpetterson at 00:25 AM on 20 May 2015Why the 97 per cent consensus on climate change still gets challenged
Part of denialism is based on the argument that if we don't know everything, it means we know nothing. I think ThisWillFrighten is making that same basic argument — if any part of the climate system (which includes daily weather) is chaotic, that means it all is, and models are useless.
This is also, I think, the basis for disputing the "consensus" argument. For example, if any questions can be raised about methodology, it means the study was imperfect, and therefore cannot be trusted (or "can be dismissed", which is the same thing).
Another example: Are you =certain= the "true number" for consensus isn't 96%? or 94%? or even 90%? If it isn't =precisely= 97%, that proves the study is flawed, and we shouldn't draw any conclusions from it.
This "reasoning" is insidious — even if all doubt could be removed that there is, in fact, a 97% consensus on this matter, that means 3% are unsure — if anyone is unconvinced, there must be legitimate question about the matter, and we shouldn't move forward.
I don't know how to combat this problem. It's funnny, because the same people who make these arguments are willing to, for instance, play poker, or bet on football games, or even cross the street when there could be cars around. The "if we don't know everything, we can't know anything" ploy is really a rationalization, not an argument that is sincerely held. It is an excuse for ignoring what is really a convincing reality.
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chrisd3 at 23:52 PM on 19 May 2015Why the 97 per cent consensus on climate change still gets challenged
@Frightened: You don't understand what that quote means. It means that we can't predict the exact state at any particular time. It doesn't mean that we can't project long-term averages or trends with reasonable confidence.
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KR at 23:47 PM on 19 May 2015Why the 97 per cent consensus on climate change still gets challenged
TWFYSYWDI - I've responded on the appropriate thread.
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KR at 23:46 PM on 19 May 2015Climate is chaotic and cannot be predicted
TWFYSYWDI - Weather is certainly chaotic, a non-linear phenomena strongly dependent on initial conditions and difficult to predict more than a week out. Climate, on the other hand, is a boundary condition problem where long term averages are driven by energy balance, and is not chaotic. Exact future weather can't be predicted. But those averages can.
Apples and oranges, as they say.
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KR at 23:41 PM on 19 May 2015Breathing contributes to CO2 buildup
Art Vandelay - In terms of the balance of biomass shifting from plants to humans with population growth, carbon has simply moved from one set of organisms to another - and not added to atmospheric concentrations. Again, breathing is carbon neutral, as what is exhaled simply cycles between food and CO2 and back again.
Atmospheric concentrations can only have net changes over the long term if more carbon enters or leaves the biological carbon cycle - from volcanic activity (no net long-term change), from weathering (slow drawdown, not relevant over century time-scales), fossil fuel burning (the relevant cause of change over the Industrial Age), etc. Breathing does not, and can not, influence long term atmospheric CO2 concentrations. It's a complete red herring in the discussion of climate change.
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This Will Frighten You so You Will Delete It at 23:35 PM on 19 May 2015Why the 97 per cent consensus on climate change still gets challenged
Scad, regarding your assertion that "climate...does not appear to be" chaotic, you are not in agreement with the scientific consensus. This is what the IPCC has written:
"In climate research and modelling, we should recognise that we are dealing with a coupled non-linear chaotic system, and therefore that the long-term prediction of future climate states is not possible."
http://www.ipcc.ch/ipccreports/tar/wg1/505.htm
Moderator Response:[RH] Welcome to Skeptical Science! There is an immense amount of reference material discussed here and it can be a bit difficult at first to find an answer to your questions. That's why we recommend that Newcomers, Start Here and then learn The Big Picture.
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Your previous post was delete for being baseless gish-gallop. If you're going to post here you're going to have to be able to support your positions, and when you can't, you'll need to have the capacity to concede the point.
First case in point, climate, by definition, is not chaotic. If you believe this to be an incorrect assertion you need to support that with research that shows otherwise. Merely repeating the assertion without support will lead to having your posts deleted.
(edit) Note that SkS has several articles on the issue of chaotic systems. Start here.
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jgnfld at 21:05 PM on 19 May 2015Why the 97 per cent consensus on climate change still gets challenged
It would be trivial to point out there is no overwhelming "evolution consensus" in the biological literature by counting up the number of published articles that explicitly endorse evolution in the text. Yet the argument is made that each climate paper must make an explicit claim or not be relevant to any consensus.
Odd reasoning.
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BBHY at 20:07 PM on 19 May 2015Why the 97 per cent consensus on climate change still gets challenged
Carbon Dioxide absorbs infrared heat energy. You can do 1000 experiments and get the same result 1000 times: that CO2 absorbs infrared heat energy.
I don't care if it's Freeman Dyson, Judith Currty, or just some guy in congrss or on TV, none of these people have come up with any way to refute this very basic fact.
Adding more CO2 to the atmosphere will cause the atmosphere to absorb more infrared heat energy. Adding sugar to water makes water sweeter. Adding black ink to white paint makes it darker. At the most fundamental level this is not so very difficult for people to understand.
It's far past time to stop with all this crazy denial of the basic, obvious physical reality.
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Art Vandelay at 16:22 PM on 19 May 2015Breathing contributes to CO2 buildup
@KR "Now, if a population increases, there is a corresponding sequestration of carbon in biomass - and in that fashion the 7 billion people on the Earth represent a carbon sink, not a carbon source. Breathing, however, is simply not a net cause of rising CO2."
I agree with the latter - that a static human population cannot on its own cause CO2 to rise.
However, on the former point, 7 billion humans came into existence in a very short time frame in geo terms, and as we know, every carbon atom in every human is plant borne, which means that there must be less plants to sink the 'respired' CO2 with 7 billion people than there was before the 7 billion people existed. IOW, the carbon that was sequestered in plants is now sequestered in humans, and unlike plants human are combustion engines needing carbon and oxygen to produce energy and expelling CO2 as waste in the process.
Consider the position if only plants existed. Their growth would be ultimately limited by insufficient CO2 in the atmosphere from photosynthesis.
And now consider paradoxical the position if human population rises to the point where all vegetation is consumed as food.
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One Planet Only Forever at 14:31 PM on 19 May 2015Why the 97 per cent consensus on climate change still gets challenged
scaddenp,
Using the comments made on sites like WUWT as a basis for what is commonly believed is like looking at the insects near an outdoor light bulb at night to determine the ratio or relative proportions of different insects that are active at night in a region, or looking at the birds at a garbage dump to determine the ratio or relative proportions of birds in a region.
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scaddenp at 13:39 PM on 19 May 2015Why the 97 per cent consensus on climate change still gets challenged
A quick glance at commentators at say WUWT would contradict your first point. A UN/liberal plot to rule the world with falsified data when clearly climate is normal seems pretty common belief.
"for the same reason that a butterfly flapping its wings in China can have an influence on subsequent hurricane formation in the Atlantic."
Not remotely. Weather is chaotic but climate (weather averages over a 30 period) does not appear to be. Consider that you can get a wet cold day in summer but summer average temp is always going to be warmer than winter average temp because there is more irradiation of the surface during your hemispheric summer. Adding more non-condensing greenhouse gases to the atmosphere has same effect, but globally.
Plenty deny it. The point of consensus is that consensus may or may not be right, but it is the only rational guide to setting policy. The consensus is that we need to reduce emissions and it appears that majority are very unwilling to do so or hate proposal that would be effective in achieving that;
As to climate models not predicting slower warming, well what what part of "climate models have no skill at decadal level prediction" is hard to follow? You can for instance see more of this discussed here. However, if you want to discuss this further please do so on this topic. Take very careful note of the comments policy on this site, especially the on topic/appropriate thread.
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Tristan at 12:00 PM on 19 May 2015Climate sensitivity is low
Interesting, I would not have intuited that result at all!
bobl's difficulties in finding the sensisitivity to GHGs would be further compounded by the fact that you shouldn't be looking at the net antho effect anyway - as that ignores the negative anthro forcings.
It seems that you can't determine the ECS (or it's more relevant brother, TCR) from the recent temp record without first accepting the validity of quite a number of papers, something that bobl would never admit to doing in the first place. He's kinda stuck. -
Tom Curtis at 10:20 AM on 19 May 2015Climate sensitivity is low
Tristan @362, out of interest I just downloaded the forcing data from the IPCC AR5. From that I was able to determine the relative contributions of natural and anthropogenic components between certain dates and 2009 using five year running means:
1850 104.52%
1880 102.34%
1900 94.58%
1950 109.72%Note that the ratio of difference in forcing is not the same as contribution to difference in temperature. That is because there is some internal variability in temperature, because volcanic temperature responses are not commensurate with instaneous volcanic forcings due to thermal inertia, and because earlier forcings will have more fully worked through the system than will have later forcings. With these caveats, however, the relative contribution to change in forcing is a good first approximation to the relative contribution to change in temperature.
Allowing for the caveats, I believe the 1880 and 1900 figures significantly overstate the anthropogenic contribution. In particular, the anthropogenic contribution to change in forcing falls to 57% in 1885 and to 76% in 1904. Given the extent and intensity of volcanism that cause those falls, it would be foolish to assume a simple five year mean of the forcings captures the temperature impacts of that volcanism. Further, there is good reason to believe there was a significant contribution from internal variability to the temperature increase from 1910-1940 which will be diluted but also relevant to the temperature increase to 2010.
Of course, Bobl is not entitled to these caveats. In his calculation he ignores internal variablity (which of necessity cuts both ways), and by assuming TCR = ECS, he also ignores thermal inertia. Given that, it would be inconsistent of him to not use the relative contribution to forcing increase as the relative contribution to temperatue gain.
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Tom Curtis at 06:19 AM on 19 May 2015Breathing contributes to CO2 buildup
Phil @40, below is the most recent IPCC estimate of the various fluxes in the carbon cycle (with changes to the process since the preindustrial shown in red):
If you look closely you will see that "Gross photosynthesis" minus "Total respiration and fire" results in a positive flux of 2.6 +/-1.2 Petagrammes Carbon per year out of the atmosphere. That is an increase over the preindustrial value by more than the 90% uncertainty. Ergo it is simply false that "Of course land use change (specifically de-forestation) has been a significant carbon source, offsetting any increase in other forms of biomass." (As an aside, "respiration" in these terms includes natural decay.)
FYI, these values are known fairly well because they can track the decline in O2 in the atmosphere, which excedes the corresponding increase in CO2 from fossil sources, even after allowing for ocean uptake (CO2) and outgassing (O2).
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