Skeptical Science Comments

Comment on A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming

Chris

Polar jet stream, is maybe a bit confusing sicne the southern antarctic oscillation is also a polar jet stream?Polar air intrusion during the winter because of the higher jet stream amplitude. The UK will likely expereince much more pronounced floods, with Jet Stream blocking patterns, when the rain system just keeps sitting there.What about downward bursts/microburst? Greenland is according to Jennifer Francis a prime spot for blocking patterns to occur, see Sandy - caused 90 degree turn.Where exactly is the Jet Stream, if not with the Jetstreaks? Are these visible from the ground - do they come with clouds or is this different?In regards to tornadoes and Jet Stream:âAs with hurricanes, I think frequency needs to be separated from intensity.Climate change increases the available energy for tornadoes through a warmer and moister atmosphere. Wind shear decreases in the global mean, but this might be irrelevant locally when the jet stream dives southward like it did last weekend across the Plains.âI believe there is evidence that the strongest tornadoes are getting stronger. They are certainly getting longer and wider.â - James B. Elsner, an atmospheric scientist at Florida State University Humid air and the Jet Stream help to fuel more intense thunderstorms/tornadoes

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

s_gordon_b

I'm having a problem interpreting this study. The banner conclusion is that "among abstracts expressing a position on AGW, 97.1% endorsed the consensus position that humans are causing global warming." But in the Results section it states: "To simplify the analysis, ratings were consolidated into three groups: endorsements (including implicit and explicit; categories 1–3 in table 2)..." This is where I'm experiencing a disconnect. Categories 2 and 3 are too ambiguous - as defined in table 2 - to equate to the consensus that humans are not only a cause of industrial era global warming but the dominant cause since the middle of the last century (at least). Am I not reading that right? And if so, shouldn't only those abstracts that take an unambiguous stand on the consensus of dominant human causation be counted and the others excluded in the same way that abstracts that take no stand at all were excluded?

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

scaddenp

I think this confounds physical and statistical modelling but I will look at the paper. The success of more recent techniques (like F&R) would strongly suggest that this paper is mistaken. The indices might be an imperfect measure of the large scale process, but they are good enough for predicting unforced variation in global temperature due to ENSO.

Comment on On the value of consensus in climate communication

DSL

I don't have much to say. Kahan's points are fair, but they're also academic. No actual model for communication is given, other than a link to a page that has, near the bottom, something useful--the ambivalent partisan approach or mode. Cook makes good points as well, but he's responding to a game being played behind the curtain, one that Kahan never really addresses. Indeed, that game should be fully recognized in any strategy for moving the public on this issue. The other players are trained in rhetoric and have absolutely nothing to lose. It's as if they play the game with a full deck and science is limited to no face cards (and aces count as 1).

Detailed, practical approaches need to be available to anyone who is willing to enter "the trenches." The "ambivalent partisan" mode is one I try to emulate, with a few additions. More powerful than ideology is the need to remain valuable, and that need is amplified when the discussion is public. No one wants to be dismissed out of hand--to be categorized, labeled, boxed, stamped as innocuous. I will only once in a blue moon use any sort of label, including "denier," when I speak with people in a general public forum on this issue. I ask questions, and not questions that have a rhetorical edge, but well-explained questions that invite the interlocutor to express a speculative opinion. No ivory tower. I try to give uncertainty when it exists. It's better to provide and discuss uncertainty than it is to leave it out. Tom Curtis is very good at that, and I think to the consternation of a few other SkS regulars. Also, as Kahan points out with the example of Hayhoe (though he gums it up with academic jargon), it's better to step into someone's else's castle and recognize it as a valid construct than it is to remain in your own castle and stand at the battlement throwing taunts and unexplained bits of heavy science. I've had good success with this general approach (a variety of private FB messages/emails thanking me not for explaining things but for doing it in a way that wasn't antagonistic. I often get the "I'll respond to you because you seem like a reasonable person." That's the response I aim for.).

Ultimately, the Cook study is only valuable to me as a conversation starter and a casual debunking of the "there is no consensus" myth. I think Kahan doesn't understand that there are a great many people who don't understand the greenhouse effect and who are susceptible to suggestions that AGW is something different than the greenhouse effect. That's really what the consensus is all about for me as I find myself discussing it in various places. People aren't sure what points of the theory the consensus is providing agreement on, and so they respond to it as they do to every other article talking about global warming. In other words, the consensus doesn't mean anything specific. It's like how the word "catastrophic" is used in professional "skeptic" circles--it means whatever you need it to mean at the moment.

A bit rambling. Sorry. I started out with my two cents and it turned into a pfennig, a pence, and half a yen (to revise it).

Comment on A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming

jmorpuss

Nice John

One thing I thought might add more understanding to your post would be to include some sort of acknowladgement and recognition for this natural interaction process. http://en.wikipedia.org/wiki/Electric_force I tried a site search but could not find any reference to Coulomb's Law so link is provided.

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

MS1

#46 scaddenp at 08:54 AM on 17 May, 2013

"MS1 "I think their paper failed " really?... If the ENSO index was substantially flawed or there was significant non-linearity, this isnt born out by the success of their prediction. If you believe that the prediction can be improved significantly by other indexes or method, then show us."

---------------------

Compo et al 2010 have addressed this issue.

http://www.esrl.noaa.gov/psd/people/gilbert.p.compo/CompoSardeshmukh2008b.pdf

"Because its [ENSO's] spectrum has a long low frequency tail, fluctuations in the timing, number and amplitude of individual El Nino and La Nina events, within, say, 50-yr intervals can give rise to substantial 50-yr trends..."

"...it also accountd for an appreciable fraction of the total warming trend..." (see figure 9b )

"...It [The Pacific decadal oscillation or the interdecadal Pacific oscillation] is strongly reminiscent of the low-frequency tail of ENSO and has, indeed been argued to be such in previous studies (e.g. Alexander et al 2002, Newman et al 2003, Schneider and Cornuelle 2005, Alexander et al 2008)..."

"...In this paper, we have argued that identifying and removing ENSO-related variations by performing regressions on any single ENSO index can be problematic. We stressed that ENSO is best viewed not as a number but as an evolving dynamical process for this purpose..."

Comment on Has the rate of surface warming changed? 16 years revisited

Dumb Scientist

Farmer Dave @24: Last year I noted that the deep ocean's heat capacity is much larger than the cryosphere's. So I think Kevin C was right to focus on the warming deep ocean purely on thermodynamic grounds.

I mentioned melting land and sea ice not because of their total effect on surface temperatures, but because those independent measurements also confirm that the climate is still gaining heat, even over the last 16 years. Here are relevant links and a short movie.

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

JasonB

barry,

Rather than going round and round in circles arguing over definitions, let's make this concrete:

Earlier you claimed that there is a difference in meaning between the wording in the graphic and the wording in Dana's example of a paper that would be classified as endorsing the consensus ("we are the cause" vs "we are causing").

I propose a test: Can you give any examples of abstracts that were rated as level 2 or level 3 that you feel do not endorse the statement in the graphic?

If your argument is correct, there should be papers that you feel do not support the claim and based on the number of them we can ascertain the impact that would have on the results.

Note that unless you're going to do an exhaustive search, you need to count how many papers you looked at as well as how many examples you found. This is so we can get a percentage that can be used to estimate the impact. You can also propose what you view as the "correct" classification for the examples you find.

Until then, this argument is merely academic.

Comment on Has the rate of surface warming changed? 16 years revisited

william

Being completely unscientific and speaking anthropogenically, Gaia is fighting back and keeping the temperature constant. A sort of light switch phenomenon. Look out when we have pushed the switch beyone Gaia's capacity to thermo-regulate. The next time we have an El Nino should be interesting. Sept 15, 2016 likewise.

Comment on Has the rate of surface warming changed? 16 years revisited

Farmer Dave

Dumb Scientist @2

I agree with your question about the impact of ice melting on reducing the rate of air temperature increases. I presume that earth energy balance models include the latent heat required to achieve all the ice melting we have seen over the last few years. Does anyone know of any estimates of the effect the melting has had on moderating changes in sensible temperature over, say, the last decade?

Comment on 2013 SkS News Bulletin #13: Alberta Tar Sands and Keystone XL Pipeline

william

You have to agree with the article on Canada. Even if the heads of their government officials are so far up where the sun doesn't shine that they can't recognize the disaster they are helping to cause, at least they could be accute business men. Why on earth would Canada send raw oil, only just separated from the sand, to the USA for them to make most of the profit. As the writer says, Canada is seeing precious little benefit from the exploitation of it's resource. They should be pipeing or trucking refined petrol, diesel and other products to the US. As far as her ecological record goes, look at how she has destroyed her east coast fisheries resources through glaringly faulty science and through bowing to the very short term interests of her fishing companies. They behave like grasshoppers rather than ants (aesop fables) and show zero intestinal fortitude. They went so far as to try to shift the blame onto the seals for the decline in their fisheries resources and actually subsidized seal hunters when the immages of the slaughter of baby seals trashed the fur market. If you want an account of the stupidity of successive Canadian governments, get Sea Of Slaughter by Farley Mowat.

Comment on It's satellite microwave transmissions

Rob Honeycutt

grindupBaker... I'm really unclear on what you're attempting to say.

Comment on A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming

Esop

Brilliant article. Very informative!

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

Dumb Scientist

Mod: please delete #99. Dunno why it came out empty...

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

Dumb Scientist

Just to be clear, my comment #96 didn't refer to Dikran's comment #95 above. I linked to Dikran's comment on another page which is much more interesting.

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

Dumb Scientist

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

KK Tung

In reply to post 95 by Dikran: I liked your work investigating the effect of the change in baseline offsetting on the apparent model uncertainty.

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

KK Tung

In reply post 95 by Dikran and post 96 by Dumb Scientist: I like the tone of our exchanges now. To understand the point I was trying to make, please first do not view my comments as saying there is anything wrong with the IPCC models. My comments concern the forced response vs internal variability. Since I do not know what the forced response is in the observation, I was using the model ensemble mean as a proxy for that. In fact this is an assumption that the model is perfect. Now we cannot do ensemble mean of the observation, because our climate is just one realization and we do not have the other ensemble members. So we cannot compare observation's forced response with the model's forced response. My statements were never intended to be a comparison of the two and see if the models are correctly simulating the real forced response. Subject to the caveat of my assumption of perfect models, my statement concerns the presence of internal variability. When the observation is below the model ensemble mean, I tentatively suggest that the explanation could be that there is an internal variability that is in a cool phase in the observation but is not (and should not be) in the model ensemble mean. The point I made previously was why we need it now during the hiatus period and not during the period of accelerated warming.

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

scaddenp

rhJames - firstly, a consensus does exist. Secondly, while a consensus is not proof of a theory, it is the only reasonable basis for public policy so it is important to know what it is.

"Lets stick to the scientific evidence" _ well I wish deniers would but they instead prefer blog "science", cherry picking and misrepresentation. Cook13 is effectively a survey of the published scientific evidence.

Comment on It's satellite microwave transmissions

grindupBaker

Rob Honeycutt #26 This is true but I have a single-tasking mind and like to keep the waters clear by considering physical realities as the indifferent entities that they are as much as I can. If I can ever manage to grasp them, might move on to spiritual & socio-political. I've scaled mentally by 5,000,000 because I can picture the Earth sphere knocking a small hole in the ceiling with the electromagnetic shining in, 1/8" 90% air, 1/20" oceans, gently warming until they lap the ice away, burping disasters across the land, and so on. It's a human scale.

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

Dumb Scientist

Dikran Marsupial has performed an analysis which is relevant to this conversation.

Dr. Tung, if you'd like to comment on Dikran's method, we'd all appreciate your insight. Thanks.

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

Rob Honeycutt

I have to say, one of the most compelling aspects of Cook13 is that the resulting consensus figures for the SkS rated papers almost precisely match the consensus figures coming out of the scientists' self-ratings. (97.1% vs 97.2% respectively)

If there was ever a great example of self-skepticism, this was it. John Cook made sure that we tested our own biases here at SkS against the evaluation of the scientists themselves. And not just a few cherry picked scientists. We tested against a very large number of scientists.

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

Rob Honeycutt

rhjames said... "Let's stick to scientific evidence."

You seem to be operating under the erroneous assumption that Cook13 is a survey of scientists (a "show of hands"). It is not. It is a survey of the published research.

It's entirely likely that there is research within the survey that reflects different positions on papers coming from any one scientist. A researcher that has published a large body of research could potentially have papers that fall into each of the 7 endorsement categories. Certainly most of the researchers who have multiple papers in the study have them falling into at least two or more of the categories.

So, really, the opinions of the scientists themselves matter little. What matters is what their data show.

Comment on A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming

John Russell

If anyone wants to keep track of the jet stream position over the N Atlantic/UK on a daily basis, I've found this site to be very useful.

Damn good article, by the way. I'll be coming back. Thanks for the hard work, John M.

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

Composer99

rhjames:

Claims identical to yours have been examined before and rightly dismissed, for three reasons.

First, most orthodox or consensus positions before the scientific revolutions in various disciplines were not based on anything like as rigorous the methodologies used to generate consensus positions in the sciences today, and are an inappropriate point of comparison. Who cares whether or not there was a consensus about bloodletting in the past? The consensus about AGW is comparable to the consensus of other contemporary scientific topics: quantum mechanics, relativity, and the like. (*)

Second, the consensus of experts follows from the preponderance (or, if you will, the consensus) of the evidence, a point that has been raised on several occasions on this thread and any other occasion where the scientific consensus has been discussed.

Third, research shows that the public perception of the scientific consensus is an important component of public advocacy for action to reduce emissions and mitigate global warming. So it is in fact critical, if we want to avoid the worst consequences of rapid global warming, to spread the word about the consensus.

(*) In point of fact I have a hard time thinking of any case where a scientific consensus, in the modern sense, of over 90% of scientists has arisen that has actually been overturned, with the possible exception of what caused gastric ulcers. In past cases either the consensus was non-scientific, or there was no consensus position to speak of.

Comment on Has the rate of surface warming changed? 16 years revisited

Kevin C

It has been suggested that we leave the video up but add annotations to explain where the problems are. This would retain the educational content (and in practice probably enhance it, because learning often progresses through correcting wrong understanding).

But the big advantage is that everywhere the video has been embedded the annotations will now be visible.

However, John is pretty busy with at the moment, so it may take a week or two.

Comment on Has the rate of surface warming changed? 16 years revisited

Kevin C

Keith: I wouldn't include ocean heat uptake in a fitting calculation, but it's the sort of effect you might detect more clearly having removed the other terms. In otherwords, a change in trend.Troy is working on doing this without using fitting methods, which means you don't have to assume the warming signal and thus gives you a much better basis for detecting changes in the warming signal.

Comment on Has the rate of surface warming changed? 16 years revisited

Dumb Scientist

jdixon1980: The total energy content of the climate system needs to be stressed much in the media. I've been making this point since 2009, and many of my colleagues have made similar complaints. So I'm inclined to place the blame on the media rather than on scientists.

I proposed this analogy:

Imagine filling a measuring cup at a constant rate while the water sloshes around. Sometimes the water will pile up against the side of the cup that doesn’t have the measuring tick marks. As it piles up, the water level against the tick marks might go down even as the faucet pours water into the cup.

In this analogy, the water level in the cup is the Earth’s total energy and the constant water flow is the extra radiative power added by human emissions. The side of the cup with the tick marks is the Earth’s surface, where most of our temperature sensors are. The other side of the cup is the deep ocean, which we can’t measure as well as the surface.

Water sloshing towards the tickmarks is like a temporarily warm El Nino, while water sloshing away from the tickmarks is like a temporarily cool La Nina.

Humans add extra water to the cup, but it sloshes around the cup naturally.

Humans add extra energy to the Earth, but it sloshes around the Earth naturally.

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

John Hartz

@Barry #189:

You state: I'm discussing the academic merit of the Cook et al study.

What exactly do you mean when you use the phrase, "academic merit"?

Comment on Has the rate of surface warming changed? 16 years revisited

keithpickering

Is it really correct to include both ENSO and ocean heat uptake changes? Aren't these pretty close to measuring the same thing?

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years?

Dikran Marsupial

Dumb Scientists yes I agree, however we need to determine if the basic approach is mathematically sound before worrying too much about the details!

Comment on Has the rate of surface warming changed? 16 years revisited

sout

Jdixon1980, is this what you are looking for?

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

Dikran Marsupial

Prof. Tung I do not understand the point you are trying to make with this image.

Nobody should expect the observations to lie any closer to the ensemble mean than is indicated by the spread of the model runs (as I have stated before). Note that in 1998 the observations were closer to the (upper) boundary of the 95% than current observations are to the lower boundary. However the 1998 event was not evidence that the ensemble mean was not a good approximation of the forced response, so I see no reason to think that the current observation-ensemble mean difference is indication of a systematic issue, but is probably just internal variability. Of course we are also interested in the physics of internal variability.

The diagram I gave uses the model projections actually used in AR4 and uses the same baseline period that is used in making the projection. Do you agree that it shows that the observations are consistent with the model projection, yes or no? If "no" please explain what is defficient in the figure I presented here.

Note that the choice of baseline has a large effect on the apparent uncertainty of the observations and the models at the boundaries of the baseline period. I suspect this is the issue that James Annan mentions on the twitter thread. Compare the width of the model spread using the two different baseline periods

Note the observations are less close to the edge of the model spread if the longer baseline period is used, as the baselineing procedure minimises the differences between models in the baseline period. The longer the baseline period, the less this can over-fit the variability within the baseline period, so less of the model uncertainty is attenuated.

Comment on It's satellite microwave transmissions

Rob Honeycutt

grindupBaker... But it would be the change in the Earth's climate system that matters to us tiny beings living on the planet's surface.

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years?

Dumb Scientist

Thanks Dikran! I have to rush off to a talk, but I wanted to nitpick: our CO2 emissions are rising faster than exponentially. Anthropogenic forcings might be rising quadratically...

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

KK Tung

Still can't insert. But the figure can be found here.

https://twitter.com/ed_hawkins/status/299161479268139009

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

KK Tung

I am still having problem inserting figures. I was able to insert a pdf but not a powerpoint figure previously on this site, but no more. I also don't have a server where I can host. SkS need to fix this problem.

I managed to find one figure, the one by Ed Hawkins, on his own twitter site. MA Roger's comment on the person who sourced Hawkins' figure is irrelevant. I thought it better to use a direct source and bypass the second quesssing of the motives of the person who sourced it.

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

KK Tung

[image deleted]

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

Rob Honeycutt

Jason said, "Next we'll be arguing what the meaning of "is" is!"

Exactly. At this point Cook et al 2013 is part of the published research on this matter. If there are people like Lucia and others who wish to challenge the findings, they should do so by the way of publishing their own paper.

They are more than welcome to craft their own methodology to test the level of consensus on AGW. But, like with the hockey stick, I think the results they would get would go against the conclusions they want to see, and to get the conclusions they'd prefer would require contortions that would not pass peer review.

Comment on It's satellite microwave transmissions

grindupBaker

I only started looking at "Global Warmage" for science & math interest 3 months ago. I linked here from a 2013-05 post about revised AST processing. Oh boy. They have absolutely no concept whatsoever of the orders of magitude difference between the vast energy delivered non-stop to Earth by the sun & the trivial bits shoved around on Earth surface. Signs are that this inability to grasp simple quantity concepts is endemic among the public at large.

Comment on Has the rate of surface warming changed? 16 years revisited

jdixon1980

A helpful image could be somebody on an elevator going up while playing with a yo-yo - the height of the yo-yo goes up and down, and might be above or below the hand at any given time, but it's average height is increasing just as quickly as the average height of the hand.

Comment on Has the rate of surface warming changed? 16 years revisited

jdixon1980

DS @2: "As you say, the total energy content of the climate is a more direct measure of global warming."

One thing that bothers me about the way the warming trend is presented to the public in the MSM is that whatever is happening with surface temperatures is always the focus of the headline and the focus first several paragraphs, if not the entire article. If there is any mention of total climate energy content, it is usually buried in a later paragraph and not represented in a prominent figure, such that I would venture to guess that most casual media consumers skim over it, if they even get that far in the article before moving on to something more scintillating. A perfect example is the recent Economist article on climate sensitivity (http://www.economist.com/news/science-and-technology/21574461-climate-may-be-heating-up-less-response-greenhouse-gas-emissions), which, when it finally addresses ocean heat content about midway through the article, focuses on the top 700 m with an accompanying graph showing a flattening (but still positive) temperature trend, and only mentions the Balmaseda et al. study of trends in the total ocean temperature profile as an afterthought.

Do you think that climatologists need to do a better job of conveying the greater long term significance of total climate energy content (as opposed to surface temp fluctuations) to the MSM, so that the MSM might focus more on the significance of total climate energy?

Would it help to use more or better analogies of ocean heat content to something intuitive and mechanical, like Verner Suomi's famous "great and ponderous flywheel," but maybe not so lofty? What about the ocean heat content as a "hand" and surface temperatures as a "yo-yo," which can go up and down but is always tethered to and pulled back towards the hand?

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

JasonB

barry,

I'm making no claim as to what the consensus statement is meant to be.

You said "there is no doubt that the consensus is that human activity is causing at least some global warming". Cook et al's results are far stronger than that, as I already explained.

I don't know how many times I can keep saying this; the original authors were asked whether their papers endorsed AGW. The results are being reported as the percentage of papers that endorse AGW. There is no discrepancy. What the general public wants to know is "is human activity causing global warming?". That's exactly the statement that the authors of 97.2% of the papers that expressed an opinion on the matter said their paper endorsed. QED.

Comment on Has the rate of surface warming changed? 16 years revisited

sout

Kevin, I particularly like your animation of the possibly different effects of the volcanoes. I expect that each large-ish volcano can have different effects on climate to some extent, depending on what part of the world it erupts in, time of year etc. So that looking at other eruptions won't necessarily give an answer to what happened in any other case.

Comment on Has the rate of surface warming changed? 16 years revisited

sout

@JohnRussell I wouldn't worry too much about what Bob Tisdale says. He's a one-trick pony just going on about ENSO jumping up and down and leaping and cavorting with 'natural' but completely unexplained magical warming (by Bob himself, that is). I've noticed many of the WUWT faithful don't put much credence on him these days. He's missed the main point that Kevin is making altogether in his haste to push his ENSO barrow.

I don't have a view one way or another on the video. I found it useful myself but didn't take it to be the last word on the subject (nothing ever is). Still, I'm happy to wait to see what new science comes out over coming months. Or for Bob T's El Nino - maybe next year? I wouldn't be surprised if it's a doozy when it comes.

I have to say articles like this are refreshing. It forces one to think about things more and realise that there is a lot to consider when it comes to what climate change will bring - and when.

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years?

Dikran Marsupial

I thought I would have a go at testing Prof. Tungs method via a simple thought experiment, where we can have ground truth. I've used MATLAB, so I'll add code snippets and diagrams as I go. I should however point out that it is possible that I have misunderstood the method, in which case hopefully setting things out very explicitly will help Prof. Tung to identify where i have gone wrong.

Lets assume that that anthropogenic emissions have been rising quadraticaly

anthro = 0.00002*(T + T.^2);

where T is time and goes from 1 to 150 years in the diagrams shown below. Rather than model ENSO, volcanic activity and solar forcing separately, for convenience, we can lump them all together as a single term "natural", and we will make it sinusoidal to keep things simple.

natural = 0.1*sin(2*pi*T/150);

For the sake of this thought experiment, I shall assume that AMO actually has no effect at all on global mean surface temperatures, so the observations are an equal combination of anthro and natural and some additive Gaussian noise

observations = anthro + natural + 0.1*randn(size(T));

Now lets assume that AMO is actually a consequence of anthropogenic and natural forcings/variability, so it is correllated with the observations, but only because the observations and AMO have shared causes.

AMO = 0.4*anthro + 0.6*natural;

Now this presents a stren test for Prof. Tung's method, but if his method is sound, it ought to still be able to deduce the correct anthropogenic forcing even in this case. If we plot everything, we get this:

Note I have set up my thought experiment, so the observations are vaguely similar to the actual observations.

The next step is to linearly detrend AMO, which can be easily achieved via linear regression:

X = [ones(size(T)), T];

beta = (X'*X)\X'*AMO;

AMOd = AMO - beta(2)*T;

Plotting the detrended AMO gives this:

Now linear detrending obviously does not remove the all of the effects of anthro from AMO as anthro is quadratic. Also if natural has a linear trend over the period considered, then that also will have an effect on the detrending.

We can now perform the regression analysis, where the means have been subtracted from the explanatory variables so that any offset in the observations are explained by the bias term, rather than using the explanatory variables.

X = [ones(size(T)) anthro-mean(anthro) natural-mean(natural) AMOd-mean(AMOd)];

beta = (X'*X)\X'*observations;

We can look at the values of beta that we have extracted, and we find

beta = [0.1577; 0.6382; 0.1927; 1.1731]

Note that the regression model is using AMO to explain more of the variation in the observation than it uses anthro or natural, even though the observations are in no way causally dependent on AMO! The true set of regression parameters are:

beta = [0.1577; 1.0000; 1.0000;0.0000]

We know that by construction. This is a good illustration of why using regression methods for attribution is tricky. In this case, the problem is co-linearity. AMOd is correlated well with the observations, in face more so than anthro or natural are individually, and regression is a correlation based method.

We ccan then find the output of our regression model

model = X*beta;

and plot it, giving

So we can see that the regression model (blue) "explains" the observations (green) almost as well as the true model does.

The last step is to find the deduced anthropogenic forcing. My interpretation of Prof. Tungs explanation given in the post above is that we first find the residuals

residual = observations - model;

compute their least-squares trend

X = [ones(size(T)), T];
BETA = (X'*X)\X'*residual;

and adding the trend in the residuals to the deduced anthro

infanthro = beta(2)*anthro + BETA(2)*T;

but if you do that, you get

where you can see that the deduced anthro is much less than the true anthro, which suggests that Prof. Tungs method is not reliable.

UPDATE: If we exactly deduct the anthropogenic influence on the AMO using

AMOd = AMO - 0.4*anthro;

then we get more or less the correct answer:

which suggests that the way in which the anthropogenic influence on the AMO is accounted for is very important, and linear detrending is unsatisfactory unless the anthropogenic forcing actually is linear.

I have also noticed that in both cases, the trend of the residuals is to all intents and purposes zero, so adding the trend of the residuals to a*anthro(t) as Prof. Tung suggests has only a negligible effect on the outcome.

Now I should stress, there are at least two possible explanations, either (a) Prof. Tung's method isn't reliable or (b) I have not propely understood or implemented Prof. Tungs method for my thought experiment. I try to be a self-skeptical sort of person, so I am assuming (b) is more likely. Hopefully Prof. Tung can point out the problem, providing MATLAB (or other) code for the thought experiment would be a really good way of getting his idea accross efficiently.

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

barry

Jason,

I'm making no claim as to what the consensus statement is meant to be.

barry, the authors were asked to state whether or not their papers endorsed the proposition that human activity is causing global warming.

I agree. But if Authors rating at 2 and 3 (which comprise a huge bulk of the endorsement ratings) take that to mean anything between, say, 'some' influence and >50%, and Cook et al take it to mean >50%, then the rating criterion is different and this may signficantly affect the comparitive results.

Would I be correct in assuming you would say that options 2 and 3 rate the human influence on global warming as dominant (b)?

I'm hoping to garner clear responses to see if there are different interpretations by commenters here. Tom Curtis began as an author on Cook et al, but declined participation after a while. Judging by comments he has made at Lucia's he is saying that ratings 2 and 3 refer to >50% influence. Eg,

Lucia, excluding papers dealing with impacts and mitigation, 92.9% of papers surveyed (and that indicate a position in the abstract) implicitly or explicitly affirm that >50% of recent warming is due to anthropogenic causes.

http://rankexploits.com/musings/2013/on-the-consensus/#comment-113388

You write;

If they felt that their paper either implied or stated that human activity was a contributing factor but not the primary cause then they could have categorised their paper as level 5, 6, or 7, depending on how it was presented. (Remember, level 5 includes any proposition that something other than humans was the main cause, and level 7 includes any quantification less than 50%.)

Apart from 1 and 7, none of the ratings are quantified. The descriptors are "endorses" and "minimises" AGW. These are qualitative statements, and that was how I read them. That is also how Zeke Hausfather read them.

Categories 2 and 3 as well as 5 and 6 do not make any explicit assertion of attribution percent (e.g. they don’t assert < 50 percent, they simply don't provide enough information to imply a percent).

http://rankexploits.com/musings/2013/on-the-consensus/#comment-113263

That 2, 3, 5 and 6 relate to >/< 50% human contribution may be inferred in context, but other inference is also possible.

My point is, if reasonable people disagree on the ratings criterion (and the 2 I've cited are 'friendlies', there is yet more disagreement between other parties), then original Authors may have had different interpretations, and this may well undermine the comparitive results that are a strong corroborative feature of the paper. The similarity of results could be a fluke.

The only way to test that, that I can think of, is by asking the original Authors who rated their own papers what they assumed the criterion was for 2 and 3 (and 5 and 6).

If the point of the paper is to demonstrate there is a consensus that more GHGs in the atmosphere should cause some warming, then that is not as impactful as endorsing the IPCC statement. It's a much lower bar with a much smaller target audience. None of the contrarian climate scientsts dispute that, and neither do most prominent skeptics (including Anthony Watts, for example) and most of their followers.

The basic message is fine - and the effort has been successful on that regard. I'm discussing the academic merit of the Cook et al study.

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

barry - "And yet, KR, the ridiculous interpretation is how many reasonable people have taken 2 and 3."

Reasonable people? Perhaps... But many of the people raising this issue (this obfuscation, in my point of view) are not climate scientists, and are not as aware of the IPCC reports. Or at all fond of of the IPCC and its conclusions, for that matter (cf motivated reasoning).

"Can you explain why abstracts saying "human greenhouse gas emissions are causing global warming" means that they are, perforce, positing >50% human influence?"

As I pointed out above, because the category titles are part of the description as well, and because, quite frankly, anyone familiar with the science knows that AGW means human caused global warming:

Definitions of each level of endorsement of AGW.
Explicit endorsement with quantification
Explicit endorsement without quantification
Implicit endorsement

Comment on Has the rate of surface warming changed? 16 years revisited

Yvan Dutil

The key issue here as many of the linear decomposition is the potential hiden cross-talk between factor. Solar signal as at least some linear component in. Depending of the model, volcanic too. The same situation apply to any long period oscillation fitting used by skeptics.

Without physics statistical analysis are pretty limited tools.

Comment on Monckton Myth #11: Carbon Pricing Costs vs. Benefits

MikeArney3@aol.com

I guess this has been out there a while, but I think the sentence in the 3rd paragraph, "Here Monckton is implicitly assuming that the cost of preventing consequences will be less than or equal to the cost of adapting to consequences," should say, "greater than or equal". And I'd also take out the "implicitly", since he's pretty explicit about this (and very wrong, of course).

Thanks for all the great work you do on this site. I am very grateful for it.

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

rhjames

Can we please stop talking about consensus. Science isn't about a show of hands. There used to be consensus that "bleeding" a patient solved most medical problems. So called consensus has proven to be wrong too many times in the past. Let's stick to scientific evidence.

Comment on Has the rate of surface warming changed? 16 years revisited

John Russell

Pathetic. Bob Tisdale makes a meal out of SkS withdrawing the video and the reasons behind it. Does he not realise that a constant incremental adjustment to the consensus position is good science and how our knowledge actually advances? I guess not. A head-in-the-sand, entrenched denial of human-caused warming is much more comfortable.

Comment on A Detailed Look at Renewable Baseload Energy

JvD

The fact that SkS *is* ignoring the cost question is clearly evidenced by the comments in this thread. It has taken a lot of discussion even to establish the fact that a WWS-only scenario is extremely difficult / extremely expensive. All this discussion would have been unnecessary if SkS would simply come out clearly and say: "WWS as a solution to climate change is extremely difficult/ extremely expensive." But SkS does not do this. On the contrary, according to SkS, a WWS-only scenario is called 'plausible'! In another article, SkS even goes so far as to seek to 'debunk the myth' that WWS cannot provide baseload!

So sure, you can look at snippets of SkS articles and tease-out citations and lines that in a round-about-way suggest that costs are 'not ignored', but surely you must agree that the basic conclusion of SkS is that WWS is or will be competitive with coal sooner rather than later. Which is a conclusion that flies utterly in the face of all major scientific institutions, which conclude that is will be extremely difficult / extremely costly.

If necessary, read back through the comments in this thread. Surely, you can see that most commenters are or have been under the impression (from reading SkS articles) that renewables can provide baseload with little or no problem and therefore that nuclear power is unnecessary or 'too expensive'. This is an absurd position to take, do you not agree?

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

MA Rodger

Here is the Ed Hawkins graphic as sourced by the Daily Rail's David Rose (who is not the sort of person any self-respecting climatologists should associate with).

The AR4 projections are presented in fig 10.26 but also in fig SPM5 shown here. The shaded areas are 1sd. If you zoom really close in with your rulers (as I did), you will find the 2000 temperature sits at 0.241ºC with the 2012 central projection at 0.457ºC (1 sd +/- 0.18ºC) This would thus require a temperature drop (of 0.08ºC) below the 2000 level for the 2012 observed temperature to be below the AR4 model projection 95% range.

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

JasonB

I've been playing with the search tool to tabulate the results; I managed to collect results for 11,942 papers using a space as the search term; that's two fewer than Cook et al. Curiously, I ended up with exactly one extra paper in levels 1-3, two fewer in level 4, and one missing in levels 5-7. Could have been a typo when I was entering the numbers into the spreadsheet, although I just double-checked level 4 and got exacly the same result.

Anyway, of interest to this discussion is the breakdown between papers that quantify the human contribution to global warming as >= 50% and papers that quantify the human contribution to global warming as < 50% (i.e. levels 1 and 7), since there is no interpretation required for those. The former represent 88% of all papers that quantify the human contribution to global warming (64 of 73). A small difference to the overall percentage, but the level of endorsement still overwhelming, and due to the relatively small sample size, a small difference is to be expected. (I would also not be surprised if papers purporting to refute the consensus would do so with quantification, so this group is perhaps more likely to include a higher percentage of contrarian papers.)

For the papers that make explicit statements about causation without quantification, those that explicitly state humans are causing global warming represent 98.4% of the total (923 of 938).

For the papers that imply the impact humans are having, those that imply humans are causing global warming represent 98.2% (2910 of 2963).

My figure for the overall endorsement percentage is 98.06%. Not sure why the paper gives a lower figure.

In any case, no matter how the results are spun, or words are interpreted, it is pretty clear that the literature falls heavily on one side. I think anybody who seriously wants to challenge the results really needs to show papers that were mis-categorised; all the abstracts are available together with the category that was applied, so nothing is hidden, and if someone wants to apply their own "interpretation" to the rating system they have the means to do so.

Perhaps, to make the problem more tractable, they could start by checking for papers that they know disagree with the consensus and make sure those show up in the right place.

Comment on A Detailed Look at Renewable Baseload Energy

JvD

"In Part II of the study, J&D examine the variability of WWS energy, and the costs of their proposal. J&D project that when accounting for the costs associated with air pollution and climate change, all the WWS technologies they consider will be cheaper than conventional energy sources (including coal) by 2020 or 2030, and in fact onshore wind is already cheaper."

This is coded language which is actually saying that renewables will remain far more expensive than coal. There are many variables here: the price of coal in 2020 and 2030, and the cost of air pullution and climate change in 2020 and 2030. The authors assume great costs for these elements, which is how they arrive at the conclusion that WWS will be 'cheaper'. The elephant in the room is whether coal will really be more expensive in 10 or 20 years time, and more importantly: whether the external cost of climate change and air pollution will ever be internalised (requiring new international lawmaking).

In a way, J&D are saying: "if we get a global tax on carbon and air pollution, then WWS will be cheaper than coal".

But what if we never get such a global agreement? That is my point. 30 decades of complete failure on establiishing global climate and air pollution regulations could very well be followed by another 30 years of failure. Why should we take that risk? Why not use an energy source that is cheaper and more abundant and far cleaner than fossil fuels? That is the question SkS needs to answer. But rather than doing that, SkS is suggesting that replacement of fossils with WWS is 'plausible'. The message to the reader is: "Don't worry. WWS will (through international agreements on putting a price on air pollution and cliamte change) be competitive with fossils in time to stop climate change and air pollution (so we don't need nuclear power)".

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

JasonB

Next we'll be arguing what the meaning of "is" is!

barry, the authors were asked to state whether or not their papers endorsed the proposition that human activity is causing global warming. If they felt that their paper either implied or stated that human activity was a contributing factor but not the primary cause then they could have categorised their paper as level 5, 6, or 7, depending on how it was presented. (Remember, level 5 includes any proposition that something other than humans was the main cause, and level 7 includes any quantification less than 50%.)

I said that the statement Cook et al were testing was very strong, so let's look at what you claim the "consensus" is: "that human activity is causing at least some global warming". Papers classified by Cook et al as levels 1-3 would obviously also agree with your claim. But so would papers classified by Cook et al as level 5, some of the papers classified by Cook et al as level 6, and any of the papers classified by Cook et al as level 7 that had a percentage greater than 0.

In other words, the only papers that Cook et al counted as rejecting their proposition that you would also claim reject your rendition of the consensus are those in level 6 that explicitly reject that humans are causing global warming and those in level 7 that state humans are causing 0% or less of global warming.

Clearly, Cook et al's statement is a lot stronger than yours, as it filters out many possible papers that you would consider endorsing your consensus. I would guess that very close to 100% of the papers would pass your test.

Finally, to point out that the authors of the original papers, when asked if their papers endorsed the claim that human activity is causing global warming, resulted in the same percentage of endorsement as Cook et al did by examing the abstracts alone, is not "post-hoc reasoning", it's evidence that the same criteria were applied, because it would be absolutely staggering for both groups to have arrived at the same percentage by coincidence, especially when the original authors added a large number of extra papers to the mix that Cook et al were forced to assess as "neutral" based on the abstracts alone.

It also means that the abstract examination process provided an unbiased estimate of what the full paper would actually say.

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

barry

If Zeke was here, I think he'd say c) and/or d).

What do others think?

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

barry

To clarify, c) - significant influence - was what I took to be the criterion for rating options 2 and 3 when I participated in the public survey.

But another person might have rated those with a lower (d) or higher (a,b) bar.

Lack of clear definitions is a problem for the paper as I've argued upthread.

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

barry

Jason, I'll point out again that the match could still be a coincidence if the Authors interpretation of the ratings system for their papers, was different than Cook et al for the abstracts to those papers. Post hoc reasoning is not acceptable.

You ask,

...the graphic makes the statement that "97% of climate papers stating a position on human-caused global warming agree global warming is happening and [A] we are the cause".
How can you argue that a paper that says exactly the same thing — that [B] human greenhouse gas emissions are causing global warming — should not be categorised as endorsing that position?

[A] implies human influence as the dominant - in fact the ONLY cause.

[B] can be taken to mean that anthro influence is a contributing factor, but not necessarily dominant

They are different.

Whatever interpretation is taken, there is no doubt that the consensus is that human activity is causing at least some global warming.

If the consensus statement being tested by 1, 2 and 3 (and the rest) is meant to be whether human contribution is >50%, then I think the results are flawed, as this proposition is not explicit enough in the consensus statement emailed to Authros, and the rating system. It is also confusing in the paper, but I now strongly believe that this was indeed, the intention of Cook et al. (Why are they not commenting here?)

Perhaps participants here could select which of these statements is most accurate.

"97% of climate papers stating a position on human-caused global warming agree that human influence on global warming over the last 50 years is...

a) >50%

b) dominant

c) significant

d) a contributing factor

I think either of those are valid for rating options 2 and 3, depending on how the email is interpreted.

My own take doing the (public) survey was c).

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

JasonB

barry,

Can you explain why abstracts saying "human greenhouse gas emissions are causing global warming" means that they are, perforce, positing >50% human influence? The quote I've just given is from Dana, one of the authors of Cook et al, and that unquantified statement was suffcient for the abstract to be rated as endorsing.

Because the hypothetical abstract says that human greenhouse gas emissions are causing global warming? Just because the statement omits a number doesn't mean it isn't endorsing the proposition, which didn't include a number anyway.

As I've already pointed out, the graphic makes the statement that "97% of climate papers stating a position on human-caused global warming agree global warming is happening and we are the cause". How can you argue that a paper that says exactly the same thing — that human greenhouse gas emissions are causing global warming — should not be categorised as endorsing that position?

And again, I'll point out that the original authors, given the explicit request to state whether their paper endorses the proposition, rejects the proposition, or doesn't address it, gave the same percentage of endorsements and rejections as Cook's team did, even while finding that many papers that Cook's team relegated to "neutral" on reading the abstracts alone actually did make a statement when the whole paper was taking into account.

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

JasonB

barry,

Let's consider the original authors' ratings for the moment.

The authors were sent an email. That email quite clearly said, as you have already quoted yourself, "The second drop down indicates the level of endorsement for the proposition that human activity (i.e., anthropogenic greenhouse gases) is causing global warming (e.g. the increase in temperature)." They are not being asked to quantify the human contribution, nor state their certainty of the human contribution, but merely to say whether their paper endorses that proposition, rejects that proposition, or doesn't address or mention the issue of what's causing global warming. The very next statement says "we are not asking about your personal opinion but whether each specific paper endorses or rejects (whether explicitly or implicitly) that humans cause global warming". Then the seven "levels" are stated, and, sure enough, the only difference between 1, 2, and 3 is the manner in which that endorsement is manifested in the paper (i.e. implicitly or explicitly, and if explicit, with or without quantification), and the only difference between 5, 6, and 7 is the manner in which that rejection is manifested in the paper, in exactly the same way as the endorsement case.

Note, for example, that a paper classified as "level 1" could easily be less "alarmist" than a paper classified as "level 2" or "level 3". A level 1 paper is likely to be an attribution study whereas a "level 3" could be an impacts study and, as such, could well be far more alarming.

As I mentioned in an earlier comment, someone else at Lucia's managed to confuse the levels with a measure of climate sensitivity, which is nonsense. There is only one proposition being put, and that is whether humans are causing global warming or not.

Note that it's really quite a strong statement as well. There's no wriggle room here. If someone wrote a paper that accepts that greenhouse gasses cause global warming, and that humans are responsible for GHG emissions, but that e.g. natural variability had a larger role to play in the warming to date than humanity, their paper would be classified as rejecting the proposition.

Now for Cook et al. In the introduction to the paper they clearly state that

We examined a large sample of the scientific literature on global CC, published over a 21 year period, in order to determine the level of scientific consensus that human activity is very likely causing most of the current GW (anthropogenic global warming, or AGW).

This is simply a restatement of the IPCC consensus statement, quoted by KR, and it doesn't matter if other restatements of it elsewhere in the paper are less precise because this is the proposition they are evaluating.

"Most" translates into "> 50%" when expressed numerically and answers your question:

It can be argued that 'primary cause' or 'dominant cause' of global warming could mean as little as 33%, if other contributing factors are each not greater than 33%. Is this what 2 and 3 refer to?

No. If a paper quantified the human contribution to global warming at 33% then regardless of other contributing factors it quite clearly would have been categorised as "level 7": "paper explicitly states that humans are causing less than half of global warming".

There is no room for interpretation here. Level 1's "Explicitly states that humans are the primary cause of recent global warming" has to be read in the context of Level 7's "Explicitly states that humans are causing less than half of global warming", which rules out any possibility other than ">= 50%" for Level 1.

Likewise, levels 2 and 3 are symmetric with levels 6 and 5, respectively.

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

barry

And yet, KR, the ridiculous interpretation is how many reasonable people have taken 2 and 3.

(the quote is linked a few posts upthread)

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

barry - In 2001 the IPCC consensus states that:

In the light of new evidence and taking into account the remaining uncertainties, most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations.

In 2007, the IPCC stated:

From new estimates of the combined anthropogenic forcing due to greenhouse gases, aerosols and land surface changes, it is extremely likely that human activities have exerted a substantial net warming influence on climate since 1750.

And also:

Greenhouse gas forcing has very likely caused most of the observed global warming over the last 50 years. Greenhouse gas forcing alone during the past half century would likely have resulted in greater than the observed warming if there had not been an offsetting cooling effect from aerosol and other forcings.
It is extremely unlikely (<5%) that the global pattern of warming during the past half century can be explained without external forcing, and very unlikely that it is due to known natural external causes alone. The warming occurred in both the ocean and the atmosphere and took place at a time when natural external forcing factors would likely have produced cooling.

Given that as the widely understood "consensus", I find claims of categories 2 and 3 not supporting a majority factor for human causes to be simply ridiculous.

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

barry

Jason, Dana said:

Our basis was the IPCC statement that humans have caused most global warming since the mid-20th century.

If that was the basis (and you, argue that ratings 5, 6 and 7 should be viewed as rejection of AGW at >50%, implying, in a symmetrical ratings scheme, that 1, 2 and 3 are endorsement at>50% (implied or explicit)), then I don't see much wriggle room.

Can you clearly state in a sentence, if you think ratings 2 and 3 refer to an endorsement at >50% level, or only that anthropogenic warming is signficant in a qualitative sense. Just something clear and simple.

It would be good to have clear statements from others. I'm pretty sure Tom Curits was arguing that 2 and 3 are >50% endorsements.

If you read the introduction to Cook et al, this is one statement of consensus:

We examined a large sample of the scientific literature on global CC, published over a 21 year period, in order to determine the level of scientific consensus that human activity is very likely causing most of the current GW (anthropogenic global warming, or AGW).

It is confusing in the paper, as other statements on what the consensus is are less exact, as in the abstract.

It is confusing in discussions about it because there is little agreement on what the ratings reflect. This disagreement does not fall on ideological lines (regulars at Lucia's are arguing about them, too).

The problem is that the definitions are unclear and open to misinterpretation. It doesn't matter that results are so similar if there is ambiguity in the methodology. Indeed, if Cook et al have a unified understanding that is different to interpretations made by original Authors, then that is a problem, weakening a number of key points in the study, namely to do with corroborating the impartiality/conservatism of Cook et al. The close matchup of results may be a result of these extraneous factors due to the ambiguity of definitions in the ratings schema.

It can be argued that 'primary cause' or 'dominant cause' of global warming could mean as little as 33%, if other contributing factors are each not greater than 33%. Is this what 2 and 3 refer to?

It's simply unclear. I'd like to know in simple terms how others view the ratings. When I took the survey, I only applied >50% to 1 and 7, and the rest were qualitative. If Cook et al rated all but option 4 as an endorsement/rejection at 50% human contribution, then they rated differently to me, and possibly to many of the responding Authors.

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

JasonB

barry,

I think you (and others I saw at the earlier link you posted) are getting hung up on the "> 50%" figure, when that is not the outcome of the survey, it was a tool for categorising a certain subset of papers.

The title of this post says:

Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

The first sentence is:

A new survey of over 12,000 peer-reviewed climate science papers by our citizen science team at Skeptical Science has found a 97% consensus among papers taking a position on the cause of global warming in the peer-reviewed literature that humans are responsible.

The graphic says:

97% of climate papers stating a position on human-caused global warming agree global warming is happening and we are the cause.

The email sent to authors asked them to state whether their paper endorsed the proposition:

that human activity is causing global warming

Every one of them is consistent. Not one of them mentions the >50% figure. Why? Because the point of the exercise is whether global warming is happening and we are the cause.

The only reason categories 1 and 7 exist is because some papers actually quantify the various causes, and so in papers that quantify the human contribution, the rule was > 50% counts as an "endorse" while < 50% counts as a "reject". That's all.

If the graphic said "97% of climate papers state that humans are responsible for > 50% of global warming" then you'd have a point, but it doesn't. As I said, the numbers 1..7 are not meant to be interpreted as a confidence levels, or degrees of agreement with the proposition, but merely to categorise the manner in which the agreement or rejection was expressed in the paper. The fact that the authors of 97.2% of the papers that stated a position claimed that their paper agreed with the proposition and the reviewers of the abstracts found that 97.1% of those that stated a position agreed with the proposition is very strong evidence to me that they used the same interpretation.

I don't agree that this should be seen merely as a matter of opinion or interpretation. The email is very clear. The paper is also very clear. The only thing I would change is the word "level" rather than "category" since that is apparently confusing some people.

Dana's comment is also saying the same thing.

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

barry

Jason,

we are agreed that different interpretations are possible. This is a weakness of the consensus statement sent in the email, and the ratings scheme. The only way I can think to test for differences is to email all the Authors who rated to clarify that they though was meant by options 2 and 3. A subset of respondants should give a clue.

Because if a good number of respondants interpreted as I, Zeke Hausfather and a number of other reasonable commenters did, then the bar for them was much lower than yours/Cook et al, and this would significantly weaken the results. For example, Cook et al's claim that their ratings were more conservative than the original Authors' would be undermined.

Consider Dana Nuticelli's comment at another blog on the Cook et al ratings as he sees it.

Note that if a paper said humans are causing less than 50% of global warming, or that another factor was causing more than 50% (or ‘most’, or some similar language), we put it in our rejections/minimization of the human influence category. Our basis was the IPCC statement that humans have caused most global warming since the mid-20th century. But if a paper simply said ‘human greenhouse gas emissions are causing global warming’, that went into the endorsement category as well. After all, there’s no reason for most climate research to say ‘humans are causing >50% of global warming’ (except attribution research), especially in the abstract.
If you just want to get into the quantifications, as Bart notes, nearly 90% agreed that humans are the main cause of global warming.

http://ourchangingclimate.wordpress.com/2013/05/17/consensus-behind-the-numbers/#comment-18747

Huh? If a paper (abstract) simply said anthro GHGs are causing global warming (with no quantification), that went into the endorsement category. It seems that the raters (or Dana at least) assumes that any paper that endorses the notion of GHGs causing global warming, perforce endorses a >50% human contribution.

Comment on Has the rate of surface warming changed? 16 years revisited

Dumb Scientist

Oops... "less uncertain" should be "less certain." Sorry.

Comment on Has the rate of surface warming changed? 16 years revisited

jmorpuss - I believe this topic was discussed ad nauseum (and dismissed due to actual evaluation of energy levels) in earlier, more appropriate threads.

Comment on Has the rate of surface warming changed? 16 years revisited

jmorpuss

Dumb Scientist OK then I'll retract the word large scale and replace it with what was stated large number, Just read it all and come back with something relavent to the paper. You may need a refressure cource in how electric and magnetic fields interact LINK " If the electron enters the field at an angle to the field direction the resulting path of the electron (or indeed any charged particle) will be helical as shown in figure 3. Such motion occurs above the poles of the earth where charges particles from the Sun spiral through the Earth's field to produce the aurorae. " Quote directly from Schoolphisics article. So all that is needed is a manetron, masser or laser to generate and beam electrons into a system and you will increase the magnetic part of the wave and its force.

Comment on Has the rate of surface warming changed? 16 years revisited

Dumb Scientist

jmorpuss: Large scale in terms of the global energy budget? I doubt it, and don't see any such claim in that paper.

Comment on Has the rate of surface warming changed? 16 years revisited

jmorpuss

Dumb Scientist @7

Do you think man contributed to the unsetled period from the 80's to 97 In the introduction to this accepted paper in 98 http://hal.archives-ouvertes.fr/docs/00/31/64/49/PDF/angeo-16-1212-1998.pdf states that the time period disgused coinsides with the same period were large scale weather modification was carried out. Don't you think these experiments would have corrupted the data from this period? This is only one experiment in that time period , does anyone have links to other experiments carried out in the time period being disgused.

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

Bert from Eltham

The best analogy I could think of to describe the current situation of the large gap between the publics' knowledge and published climate scientists is the knowledge gap between the passengers of a very large airliner and the flight crew.

Would you board an aircraft where the passengers have a vote on what control inputs should be used at all times. These votes would be open to the most shrill passengers that made the most noise without any knowledge or evidence. Even if the full instrument panel was displayed on all the screens in the passenger compartment the passengers do not even have the slightest idea of what they all mean. The self appointed 'knowledgeable' passengers who are not trained pilots are a cacophony of conflicting interpretations of how to fly the aircraft. They cannot even agree amongst themselves how their 'expert' opinions should be implemented.

This is the situation Space Ship Earth finds itself in.

The first aircraft to fly from England to Australia was a Vickers Vimy Bomber flown by Keith and Ross Smith in 1918. Their call sign was GEAOU. Both Keith and Ross (not related) jokingly said it stood for God 'elp all of us! Bert

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

Rob Honeycutt

Dr Tung... You first hit the "insert" tab above the comment text box. That where you find the little tree image for image insertions.

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

KK Tung

Post 88: My figure insertion did not work. I will try later. Any advice on how to do it?

Also the statement was a little confusing. In the AR4 projection comparing with the observed temperature, the latter has gone out of the model 95% range of all the scenarios shown. In Ed Hawkins' figure showing CMIP5 model projections since 2005, the observation has gone out of 90% of the model range.

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

KK Tung

In reply to post 85 by Dikran: You asked for a figure. I hope my attempt at inserting a figure to a post here works this time: The first figure is from AR4, and the projection was made in 2000. The projection has gone out of the model 95% range of the scenarios shown. The grey band is supposed to be observational uncertainty. The second figure is from CMIP5 by Ed Hawkins. The projection was made in 2005. The more recent projection is almost getting out of the 90% range.

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

Dumb Scientist

If the true anthropogenic response is linear, but we used a nonlinear regressor that increases faster after 1950, then the residual will show a negative trend after 1950 when it is only supposed to contain noise. When the trend from the residual is added back the combined trend becomes linear. [KK Tung]

Again: I've repeatedly pointed out that the form of the anthropogenic regressor or adding the residual back is not the problem that concerns me. Again, you're implying that anthropogenic warming can only appear in your residual or anthropogenic terms, not your AMO term. I think it could go into your AMO term if anthropogenic warming is nonlinear. So do papers like Enfield and Cid-Serrano 2010, etc.

In order for our result of a steady anthropogenic warming to be self consistent with our choice of the AMO index...

... nothing has to be true. Your result is always consistent with your choice of AMO index because that choice made your result inevitable. Regressing against the linearly-detrended AMO, which is highly correlated with global surface temperatures, causes any non-linearity to be absorbed by the AMO(t) function. The fact that you get answers which are "very close" regardless of using linear or nonlinear anthropogenic indices to suggest that the regression is more sensitive to the highly correlated AMO(t) function.

But please continue.

... the net anthropogenic forcing needs to be approximately linear without the ups and down in your red-dashed curve. We claimed that that is not unreasonable given the uncertainty in the aerosol component.

You've previously claimed that aerosol time evolution is so uncertain that a linear total anthropogenic forcing lies within its error bars. MA Rodger already asked where that uncertainty bound can be found, and I second his request.

We are more certain that anthropogenic warming affects the secular trend, but much less certain that it affects the oscillatory part. We know the former because the N. Atlantic temperature trend is less than the global mean trend, and that can be explained by...

... the fact that the N. Atlantic is filled with water, which has a higher specific heat than the rock making up some of the globe and the fact that oceans can evaporate without limit to shed heat. The land making up some of the globe can (and is) doing that, but those pesky severe droughts limit evaporative cooling on land.

Your mechanism probably plays a role too, especially if the N. Atlantic is compared to other oceans.

The other competing theory is to attribute the oscillatory part to the variations of the AMOC. The mechanism involves the Arctic ice melt and SST feedback on the formation of deep water. This theory is self consistent. The model simulations were consistent with observation. It could also be shown wrong given further evidence, but none of your arguments do it.

I'm not disputing that the AMO exists, and AMOC variations seem like a plausible mechanism. I'm just disputing your curve-fitting claim that ~40% of the warming over the last 50 years can be attributed to a single mode of internal variability, when Isaac Held and Huber and Knutti 2012 used thermodynamics to conclude that all modes of internal variability couldn't be responsible for more than about 25% of the warming. Even if the 10% limit from Anderson et al. 2012 is somehow wrong... didn't you say Isaac Held is one of the most respected climate scientists? I agree.

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

Tom Dayton

I just attended a talk by James Hansen at NASA Ames Research Center. One of his main points right up front is that a big part of the problem is the large gap between climate scientists' knowledge and public perception of that knowledge.

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

KK Tung

In reply to post 78 by Dumb Scientist: You have so many questions in one comment and I have to wait until I have a block of time to answer them. Often one question is convoluted with another and my answers may run the danger of further confusing the readers. You also prefer black and white, yes or no answers. In climate sciences, much is unclear. Let me try the best I could to convey to you my thinking. Your questions involve two groups. One group concerns the linearity of net anthropogenic forcing, and the other group concerns the AMO index.

In part 1 of my post, I attempted to address the claim you raised in your original post that our use of linear regressor (as a placeholder only in the intermediate step) in our multiple linear regression to arrive at an anthropogenic response that is almost linear is circular. This was a technical question and the way I rebutted that claim was to show that our methodology does not depend on what we used for the anthropogenic regressor. We showed this by using a regressor that is not linear. In fact we showed a few such examples. We showed that our procedure is not sensitive to using linear or nonlinear regressors for anthropogenic forcing as long as we add back the residual to the regressed signal. If the true anthropogenic response is linear, but we used a nonlinear regressor that increases faster after 1950, then the residual will show a negative trend after 1950 when it is only supposed to contain noise. When the trend from the residual is added back the combined trend becomes linear. Of course we do not know that the true anthropogenic response is linear, but this example is used here just to illustrate the procedure. This is intended as a technical rebuttal to your claim that our result follows from our assumption of a linear regressor for anthropogenic forcing. This technical rebuttal does not really address what the real anthropogenic forcing is and did not address the choice of the AMO index, the latter does affect the regressed anthropogenic response, as you correctly pointed out. The AMO part was discussed in part 2 of my post.

So what is the shape in time of the net anthropogenic forcing? We know the radiative forcing from the greenhouse gases well (your blue line), but the net forcing has other components that subtract from the greenhouse gas part. They include tropospheric sulfate aerosols, which are highly uncertain. In order for our result of a steady anthropogenic warming to be self consistent with our choice of the AMO index, the net anthropogenic forcing needs to be approximately linear without the ups and down in your red-dashed curve. We claimed that that is not unreasonable given the uncertainty in the aerosol component. This is not an assumption but a proposal. No one knows what the net anthropogenic forcing is with certainty. Therefore there is no inconsistency at our current stage of understanding.

On the AMO index and answering your two questions: Of course anthropogenic forcing can affect the North Atlantic temperature and hence the AMO index, no matter how you define it. It can affect both the secular trend of the N. Atlantic mean temperature and the multidecadal oscillation on top of the secular trend. We are more certain that anthropogenic warming affects the secular trend, but much less certain that it affects the oscillatory part. We know the former because the N. Atlantic temperature trend is less than the global mean trend, and that can be explained by the AMOC (Atlantic Meridional Overturning Circulation) slowing down secularly by the basin-wide warming, with the warm and less saline water sinks less at the Atlantic Arctic. So the Atlantic secular trend has a part that is a direct basin-wide warming by anthropogenic heating and a part that is a result of a change in the AMOC brought about by the warming. The two oppose each other.

At this point one can construct two competing theories. One involves anthropogenic forcing being responsible for both the secular part and the oscillatory part of the N. Atlantic mean temperature. Since the greenhouse gas forcing increase is secular, it cannot be responsible for the oscillatory part of the Atlantic temperature variability. So it falls upon the uncertain tropospheric aerosol to do the job. One needs to come up with an argument on why the aerosol forcing should have such an oscillatory behavior, and builds a model to demonstrate that such variations are sufficient for producing the observed oscillatory response. This job was not attempted by CMIP3 models, but Booth et al (2012) has put forth their HadGEM-ES2 model that produces an oscillatory multidecadal variability. Although the model response in other ocean basins and in subsurface Atlantic are not too consistent with the available observation, I would not rule out this theory, a theory for a forced AMO-like behavior in observation.

The other competing theory is to attribute the oscillatory part to the variations of the AMOC. The mechanism involves the Arctic ice melt and SST feedback on the formation of deep water. This theory is self consistent. The model simulations were consistent with observation. It could also be shown wrong given further evidence, but none of your arguments do it.

Comment on Has the rate of surface warming changed? 16 years revisited

Dumb Scientist

First, the uncertainty added by the delayed effect would have to be larger than decreased uncertainty due to removing the more certain immediate effect.

To clarify, this would only be true for timespans that overlap with the immediate volcanic effect.

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

Dikran Marsupial

Prof. Tung wrote "The CMIP3 models, which do not need internal variability to explain the accelerated warming since 1980, have projections that overshoot the observation in the recent decades, beyond the 95% range."

Please could you provide some supporting evidence for this statement, as far as I am aware, the observations currently lie well within the 95% range of the CMIP3 models (click on the image to access the source).

Last year I downloaded the model runs and was able to reproduce this figure with acceptable accuracy, so I am confident that it is correct (except for the last year of the observations).

Comment on Has the rate of surface warming changed? 16 years revisited

Dumb Scientist

The volcanic signal however can vary a lot with the duration of the effect (depending of the timing of volcanoes with respect to your trend period). As a result, I suspect that applying the volcanic correction actually increases the uncertainty in the trend of the adjusted series, because of the uncertainty in the correction. This shows up in the huge difference in the adjusted trend between the 16 years and Hansen calculations. [Kevin C]

Sadly, I don't know much about this debate over the duration of volcanic aerosol effects. However, I was impressed by how well Pinatubo's aerosol effects were modelled (page 2), which ironically comes from Hansen et al. 2006.

Perhaps the volcanic effect could be viewed as the sum of an immediate effect (which seems to be more certain) and a delayed effect (which seems to be less uncertain). Kind of like how earthquakes have both co-seismic and post-seismic effects.

Your video removed the immediate volcanic effect, which probably reduces the uncertainties on the trend. The delayed effect might have been insufficiently removed, which means that some of the delayed effect joins all the other confounding factors that haven't been removed. That doesn't seem like a reason to withdraw the video.

Now, this is a particular problem for the video because the video made two very specific claims concerning uncertainty: Firstly that for the adjusted data the recent trend was not significantly different from the older trend, and secondly that the recent trend was highly significant (i.e. different from zero).

One thing I didn't like about the video was that you showed the trends with no uncertainties. It might be better to show them as in the SkS trend calculator. But that's just nitpicking on my part.

Regarding the first claim. I think it's important to stress, as I did in my first comment, that the recent trend isn't statistically significantly different from the older trend even when using the unadjusted data.

Even without taking the values of the trends into account, these claims are compromised. If the uncertainty in the adjusted trend is large, the first claim is rendered meaningless and the second claim false. That is the basis for withdrawing the video.

I doubt that the uncertainty of the adjusted trend is larger than that of the unadjusted trend. First, the uncertainty added by the delayed effect would have to be larger than decreased uncertainty due to removing the more certain immediate effect. I haven't done the calculation, but the graph on page 2 makes me suspect that's not true.

Second, that difference would have to be bigger than the decrease in uncertainty due to removing ENSO and solar variations.

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

MA Rodger

KK Tung @80.

I would suggest that the tiny up-tick at the end of the black trace (which is evidently HadCRUT3 annual data) makes this HadCRUT3 to at least 2005, not 2004.

Comment on Has the rate of surface warming changed? 16 years revisited

Kevin C

Dumb Scientist: I think you've hit the nail on the head - reducing the uncertainty in the trend is the key part of Foster and Rahmstorf. But I disagree with your conclusion about the video. Here's why:

The Foster and Rahmstorf calculation reduces the trend uncertainty because it takes out a lot of the confounding factors which act as noise in the trend calculation. However, the uncertainty in the result does not arise from the deviations from linearity alone - it must also account for uncertainty in the adjustments which have been made. So if you are uncertain about the duration of the volcanic response, that needs to be figured into the adjusted trend. (Propogating the uncertainties is possible but not easy - I haven't done it.)

So how uncertain are the contributions? The ENSO term seems very robust - it's comes out much the same whatever calculation you do. So the ENSO-removed temperature series will indeed give trends with reduced uncertainties.

Solar is a bit less certain, but it's not very large.

The volcanic signal however can vary a lot with the duration of the effect (depending of the timing of volcanoes with respect to your trend period). As a result, I suspect that applying the volcanic correction actually increases the uncertainty in the trend of the adjusted series, because of the uncertainty in the correction.

This shows up in the huge difference in the adjusted trend between the 16 years and Hansen calculations.

Now, this is a particular problem for the video because the video made two very specific claims concerning uncertainty: Firstly that for the adjusted data the recent trend was not significantly different from the older trend, and secondly that the recent trend was highly significant (i.e. different from zero).

Even without taking the values of the trends into account, these claims are compromised. If the uncertainty in the adjusted trend is large, the first claim is rendered meaningless and the second claim false. That is the basis for withdrawing the video.

I'd really like to wait for new results on coverage and SST bias before redoing the video (it was a lot of work), but it's a shame to lose the educational material about contributions to the temperature trend.

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

Dr. Tung - "...I think I have answered your questions in part 2 of my post, in the last section"

I would strongly disagree; Bob Loblaws' points about the circularity in definition of temperature from temperature (or rather, the difficulty of distinguishing between components of the same measure) are unaddressed - forcings have not followed a linear trajectory over this century, hence a linear detrending of the AMO is guaranteed to leave external forcing in that definition. (Aerosol uncertainties, I will point out, do not linearize total forcings.)

Enfield and Cid-Serrano 2010, who you refer to as support for your methods (as I noted before), consider Trenberth and Shea 2006 correct about the failings of a linear detrending, and they instead use a quadratic detrending - a much closer fit to the upwards acceleration in total forcings over the last century. Ting et al 2009 using EOF analysis find that linear detrending is inappropriate for an AMO definition, and they "...argue that the globally averaged surface temperature appears to be a good proxy for the temporal march of externally forced variability and that most of the latter is globally synchronous, albeit nonuniform spatially".

I therefore cannot consider a linearly detrended AMO appropriate in a global warming attribution study - that is contradicted by a significant part of recent literature, as aliasing significant portions of the forced signal.

As a separate piece of evidence, the thermodynamic considerations pointed to by Anderson et al 2012 and by Issac Held (thank you for that interesting reference, Bob) argue that the 40% contribution to warming found with a linearly detrended AMO is inconsistent with observed ocean heat content by a factor of 2-4x. OHC is a constraint upon internal variability, and a 40% internal variability fails that constraint. I'm disappointed that you have not responded to that issue in any fashion.

---

It would be quite interesting to evaluate and compare the attribution percentages under other definitions of the AMO (detrended with global MST or a quadratic, for example) - and whether such estimates are consistent with external constraints such as OHC. But I believe there are significant issues with the attributions you have derived in the current work, issues coming from the AMO definition used - issues which require consideration.

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

Dikran Marsupial

Prof. Tung There is no statistically significant evidence for a change in the underlying rate of warming since 1998, so I think it is not scientifically correct to claim there has been a hiatus in global mean surface temperatures since then. The statistical power of the appropriate hypothesis test would be even lower for a trend starting in 2004. As OHC has continued to rise, it seems clear that the apparent hiatus is likely to be due to transport of heat between surface and deep oceans, and so it would be unwise to assume that the apparent hiatus means anything with regard to the forced response. However I think it would be better to discuss this sub-topic on the other thread that Dumb Scientist mentioned so as not to dilute the discussion of the paper.

In short, in order to claim there has been an actual hiatus in warming, rather than merely an artefact of the noise, that hypothesis should be subjected to a formal statistical hypothesis test. The eye is only too prone to seeing patterns in noise that don't actually exist, which is why as scientists we use statistics.

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

Bob Loblaw

Dr. Tung @80:

Your last section says "It is in the same spirit that the AMO index, which is a mean of the detrended North Atlantic temperature, is used to predict the global temperature change." [Emphasis added]

As Dumb Scientists has given a far more detailed discussion you may wish to respond to, I will temporarily step back again by saying that "in the same spirit" is not particularly convincing. You may have good intentions, and you may have some insight as to why you think that the AMO is good enough, but you haven't conveyed it here and it is a hugely important assumption.

On the other hand, Dumb Scientist is providing a much more convincing argument as to why your methodology causes problems.

Comment on Has the rate of surface warming changed? 16 years revisited

wingding

good question. Has the rate of surface warming changed?

There are many ways of looking at that question. Dumb Scientist above points out one method. Another, more inferior, method is to just compare how longterm trend has actually changed with more data. Using skepticalscience trend calculator and HadCRUT4:

The 1970-2000 trend is 0.169 +- 0.056C/decade

The 1970-present trend is 0.164 +- 0.031C/decade

There's no major change there then.

A better way of looking at it using GISTEMP is this animation from Tamino which shows there is no inconsistency with the prior rate of warming:

http://tamino.files.wordpress.com/2012/12/giss.gif

The important feature of all three of these methods is that they compare two periods. This cuts to the heart of the question "has warming stopped" or "has warming slowed down". To answer that you need to compare some statistic of a recent period with the same statistic of a prior one.

But in contrast the popular method, that pushed by fake skeptics, involves just analyzing a single period. Just sticking a trend line through a recent period (eg 1998-present) and declare it has no warming with no comparison to a prior period (or at least no mention of the confidence ranges).

Fake skeptics have been banging this drum so much that I am afraid even many scientists are being influenced into believing faulty conclusions repeated often based on incorrect methods for assessing warming trends.

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

KK Tung

In reply to post 77 by MA Roger: My typo. Not 17 years. Some said the hiatus is since 1998, but I don't want to count that because 1997/8 was a warm El Nino. I personally would say the broad leveling off of warming is since 2004/5. You cannot see the leveling off in Figure 9.5, which is up to 2004. The figure up to 2011 using HadCRUT4 is in our paper. 2012 is now available, and it is even lower.

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

KK Tung

In reply to post 75 by Bob Loblaw: I think I have answered your questions in part 2 of my post, in the last section.

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

Dumb Scientist

In my first post, I discussed the uncertainty regarding the net anthropogenic forcing due to anthropogenic aerosols, and why there is no obvious reason to expect the anthropogenic warming response to follow the rapidly increasing greenhouse gas concentration or heating, as DS seemed to suggest. [KK Tung]

I suggested that anthropogenic forcings were faster after 1950. In response, you discussed logarithms and aerosols that were already taken into account in the IPCC radiative forcings chart I originally linked:

Then you linked to that same forcings chart and linked to another:

The estimates you linked both show that anthropogenic forcings increased faster after 1950. So do the GISS and Potsdam estimates. Perhaps all these estimates are wrong, but you can't prove them wrong by assuming linearity for anthropogenic forcing.

We did not assume linearity for anthropogenic forcing. In the post we used a number of nonlinear anthropogenic indices. [KK Tung]

Again: You regressed global surface temperatures against the AMO in order to determine anthropogenic warming. Because the AMO is simply linearly detrended N. Atlantic SST, this procedure would only be correct if AGW is linear. Otherwise you'd be subtracting AGW signal, sweeping some AGW into a box you've labelled "natural" called the AMO.

Physical justification of AMO being mostly natural or anthropogenically forced needs to precede the choice of the index. This was what we did in our PNAS paper. [KK Tung]

I already addressed this point: Removing the AMO to determine anthropogenic warming would only be justified if detrending the AMO from 1856-2011 actually removed the trend due to anthropogenic warming.

There is a concern that the AMO index used in our multiple regression analysis is a temperature response rather than a forcing index. Ideally, all predictors in the analysis should be external forcings, but compromises are routinely made to account for internal variability. [KK Tung]

Predictors are compromised to the extent that warming the globe also changes those predictors. Not all such compromises are created equal.

The solar forcing index is the solar irradiance measured outside the terrestrial climate system, and so is a suitable predictor. Carbon dioxide forcing is external to the climate system as humans extract fossil fuel and burn it to release the carbon. Volcanic aerosols are released from deep inside the earth into the atmosphere. In the last two examples, the forcing should actually be internal to the terrestrial system, but is considered external to the atmosphere-ocean climate system in a compromise. [KK Tung]

These barely qualify as compromises. Global warming doesn't force humans to burn fossil fuels. Also, there's no published mechanism (that I know of) linking global warming to volcanic activity.

Further compromise is made in the ENSO "forcing". ENSO is an internal oscillation of the equatorial Pacific-atmosphere system, but is usually treated as a "forcing" to the global climate system in a compromise. [KK Tung]

This is more of a compromise, as I noted: "Even though global warming might indirectly affect ENSO, it's important to note that it hasn't yet: the ENSO index doesn't have a significant 50-year trend. This means it can be subtracted without ignoring AGW."

Because ENSO doesn't have a significant multidecadal trend, this ENSO compromise can't (and doesn't) ignore AGW over multidecadal (i.e. climate) timescales.

It is in principle better to use an index that is not temperature, and so the Southern Oscillation Index (SOI), which is the pressure difference between Tahiti and Darwin, is sometimes used as a predictor for the ENSO temperature response. [KK Tung]

I agree: it's better to use an index that isn't temperature.

However, strictly speaking, the SOI is not a predictor of ENSO, but a part of the coupled atmosphere-ocean response that is the ENSO phenomenon. In practice it does not matter much which ENSO index is used because their time series behave similarly. [KK Tung]

It wouldn't matter much even if you forgot to regress against ENSO altogether, because ENSO doesn't have a significant multidecadal trend. Regressing against ENSO primarily reduces the uncertainties on the recent multidecadal trend; it doesn't significantly change that trend.

It is in the same spirit that the AMO index, which is a mean of the detrended North Atlantic temperature, is used to predict the global temperature change. It is one step removed from the global mean temperature being analyzed. [KK Tung]

The AMO index is a seriously compromised predictor because warming the globe also warms the N. Atlantic, and anthropogenic forcing is faster after 1950. I've obviously failed to communicate this point, which is why I asked you two questions:

Question 1

Would regressing global surface temperatures against N. Atlantic SST without detrending the SST remove some anthropogenic warming from global surface temperatures?

Yes or no?

Question 2

Now suppose we regress global surface temperatures against N. Atlantic SST after linearly detrending the SST. In other words, we regress against the standard AMO index as Tung and Zhou 2013 did.

Just imagine that anthropogenic forcings increased faster after 1950. In that case, would regressing global surface temperatures against the AMO remove some anthropogenic warming from global surface temperatures after 1950?

Yes or no?

I'll start: my answers are yes and yes. In fact, I think answering yes to question 1 also implies a yes to question 2, but I'm willing to be educated.

Since you never answered these questions, I have to guess at your answers:

By "the upward trend of the AMO" I assume you are referring to the North Atlantic mean SST, because AMO is supposed to be detrended. I agree that anthropogenic forcing can force an upward trend in the N. Atlantic mean SST. In fact I am quite certain of it. [KK Tung]

Linearly detrended, which means that nonlinear anthropogenic forcing can force a recent upward trend in the AMO. Regardless, your certainty seems to imply that you'd answer "yes" to my question 1. That's fortunate, given that N. Atlantic SST are highly correlated with global surface temperatures:

You've repeatedly pointed out that you used a nonlinear anthropogenic index, and that the result is "very close" to the result using a linear index. Perhaps that's why you think that it's possible to answer yes to question 1 but no to question 2?

If so, I disagree. Because N. Atlantic SST and global surface temperatures are so highly correlated, I think bouke was right to point out that any other predictor will just be a distractor. I suspect that's why you get answers that are "very close" regardless of the assumed anthropogenic index. Unfortunately, I haven't found your code online, and don't have the time to independently reproduce your methodology.

There is a very nice blog by Isaac Held of Princeton, one of the most respected climate scientists, on the AMO debate here. [KK Tung]

I also respect Isaac Held, which is why I linked that post as well as this one:

"... While the specifics of the calculations of heat uptake over the past half century continue to be refined, the sign of the heat uptake, averaged over this period, seems secure - I am not aware of any published estimates that show the oceanic heat content decreasing, on average, over these 50 years. Accepting that the the sign of the heat uptake is positive, one could eliminate the possibility of [the fraction of the temperature change that is forced] < ~3/4 ..." [Isaac Held]

Note that Isaac Held's analysis is based on thermodynamics, not curve-fitting the AMO. As such, when he claims that the fraction of the temperature change over the last 50 years due to internal variability is less than ~25%, he's summing over all modes of internal variability, not just the AMO. As I've discussed, this is essentially the same conclusion reached by Huber and Knutti 2012.

As KR noted, Anderson et al. 2012 says that less than 10% of the warming over the last 50 years could be due to internal variability.

Your claim of ~40% is inconsistent with studies that base their claims on thermodynamics rather than curve-fitting.

You probably are aware of the discussions on the recent hiatus in warming for the past 17 years. [KK Tung]

I'm aware that there hasn't been a statistically significant change in the surface warming rate.

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

MA Rodger

@76 - "You probably are aware of the discussions on the recent hiatus in warming for the past 17 years."

I cannot say that I am.

"...the past 17 years" you say? Would that be 1996-2013? Where abouts on AR4 fig 9.5a is there such a "hiatus" evedent (bearing in mind that AR4 fig 9.5a shows "the observation ... (black curve)" to 2005 if not 2006)?

Comment on Has the rate of surface warming changed? 16 years revisited

Tom Dayton

I agree with Dumb Scientist, that there is no reason to withdraw the video. Don't let the perfect be the enemy of the good!

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

KK Tung

In reply to post 73 by Jason B and post 74 by Dikran: I accept your position. I understand that this is a necessary step for you before we can move forward. I was just becoming impatient because I was trying to make two simple points about Figure 9.5 in AR4, and then use the time available to go back to reply to some of the interesting (to me at least) comments that were posted here. I barely made the first point about that figure before being distracted.

The first point is, we can use the model ensemble mean as a proxy for the forced response in the observation. Since the observation contains both forced response and internal variability, comparing the ensemble mean from a model and the observation may tell us something about the presence of the internal variability. I saw the possibility of internal variability explaining about half of the observed early twentieth century warming. This is not a firm conclusion because afterall the models may contain systematic errors. If the models were perfect, this impression could be made into a firmer conclusion.

The second point concerns comparing Figure 9.5a with Figure 9.5b (the figure is shown in post 65 by JasonB), still assuming that the model ensemble mean serves as a proxy for the forced response in the observation. The interpretation is that in the second half of the twentieth century, CMIP3 models used by AR4 produced all the observed warming by anthropogenic forcing. Without anthropogenic forcing, Figure 9.5b shows that the all-model ensemble mean (the blue curve), has no warming or even negative warming. Figure 9.5a shows that with anthropogenic forcing, the all-model ensemble mean reproduces the observation very well (compare the blue red curve with the black curve). Since we all agreed earlier that the observation should contain internal variability as well as forced response, this is telling us that the AR4 models do not need internal variability to simulate the observation during the second half of the twentieth century.

You probably are aware of the discussions on the recent hiatus in warming for the past 17 years. A possible explanation is that that is caused by internal variability. The CMIP3 models, which do not need internal variability to explain the accelerated warming since 1980, have projections that overshoot the observation in the recent decades, beyond the 95% range. While we could still take the position that this is fine, because one can always add back internal variability when we need it to explain the difference, it becomes rather awkward to only insert an internal variability that cools for the past 17 years and not a warming internal variability during the period of accelerated warming. In any case, we do not have a coherent sense of the internal variability in the warm vs cool episodes in the observation.

Comment on Has the rate of surface warming changed? 16 years revisited

Dumb Scientist

A few months ago I calculated trends and uncertainties for the UAH data. The second page of that PDF has a black line for the trends of the UAH data up to 2012 for different starting years. The red lines are 95% confidence uncertainty bounds which account for autocorrelation with ARMA(1,1) noise. Notice that the larger uncertainty bounds of more recent trends overlap with the smaller uncertainty bounds of the longer trends. This means that there hasn't been a statistically significant change in the surface warming rate. Here's the R code if anyone's interested.

It's even easier to use the SkS trend calculator to confirm that there hasn't been a statistically significant change in the surface warming rate. Here's an example:

GISTEMP, 1990-2000: 0.201 ±0.322 °C/decade

GISTEMP, 2000-2010: 0.096 ±0.256 °C/decade

Note that the error bars overlap, showing that there hasn't been a statistically significant change in the surface warming rate. I've tried many datasets with many potential change points, and so far all their error bars overlap.

As you say, the total energy content of the climate is a more direct measure of global warming. It's also worth pointing out that global land ice and global sea ice continue to decline, absorbing heat without warming as they melt.

Troy's analysis is interesting; I'm still reading it. However, I don't think it's necessary to withdraw the video. In my view, Foster and Rahmstorf 2011 was merely trying to improve the signal-to-noise ratio of the surface temperature record by accounting for some extraneous influences. I even pointed out that other influences like multidecadal oscillations haven't been removed.

But that's not a fatal flaw, because it's impossible to remove all extraneous influences. Similarly, when a better estimate of the long-term effects of Pinatubo becomes available, that will build upon previous work rather than demolishing it.

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

Bob Loblaw

Dr. Tung.

OK. Let's follow up on my comment in #71, and apply it to your study. I am not an expert on AMO, but from what I have read here, I would state the following:

- temperature can be classified as an observation

- pressure can be classified as an observation

- I'd even be content classifying the pressure difference between two locations as an "observation" - e.g., Southern Oscillation Index based on Tahiti-Darwin - so when it comes to linking an oscillation (ENSO) to temperatures, SOI is a methodologically-independent observation and it is appropriate to use it to try to explain temperatures.

AMO, which from descriptions here and in the NOAA link is described as a detrended areal average of temperatures, is not an observation. It is an interpretation of a rather large number of observations, and it includes processing that removes part of the signal contained in the original observations (the detrending).

Once you start using that interpretation of the data as if it is an "observation", and then attempt to use your analysis to deternine the portion of the observed temperatures that is attributable to AGW, then you are at risk of making errors. The AMO, as an interpretation, has built-in assumptions. The detrending has changed the character of the information contained in the result (as compared to the original temperature observations). The averaging and detrending are based on a statistical model, and the remaining values (the AMO) represent the parts that the model doesn't remove or smooth.

Now, if your goal is to get people to accept your conclusions, then you are going to have to go back over the steps from observation, through interpretation, to your conclusions. You are going to have to provide an analysis that clearly demonstrates that the result you want us to believe is not affected by the assumptions (especially detrending) that are inherent in the application of processing/modeling to derive the AMO.

From what I have read here and elsewhere on the web, this is a serious methodological flaw, and you have not addessed the criticisms that have been made here. Please go back over Dumb Scientist's original post, and the comments to both it and your two posts, and address the issue of the detrending that is done in deriving the AMO.

This is not quibbling about definitions of words. The distinction between "observations" and "interpretations" is essential. You are attempting to explain temperatures using temperatures, which seems unsupportable - it involves a circularity that is hidden because you appear to be forgetting that AMO is not an observation.

Comment on Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

HJones

@ Kevin C 165,

Unless you know that the first 100 are representative of the 300, you can't make any comment on the 300. You can't assume anything. For all you know in your example is that right handed pirates hear better, so came forth with their reply before the left handed pirates did, or conversely, the left handed pirates hear better and come forward right away, and there is only three of them in total.

Comment on A Detailed Look at Renewable Baseload Energy

CBDunkerson

JvD, did you stop reading after the part of my message you quoted or did you just decide to repeat the same false claims anyway?

You do realize that no matter how many times you claim that this page (or my response) is misleading because it says renewables will be cost effective "in no short order" or that "money is no object" the actual page itself will always still say;

"However, detailed computer simulations, backed up by real-world experience with wind power, demonstrate that a transition to 100% energy production from renewable sources is possible within the next few decades."

and

"In Part II of the study, J&D examine the variability of WWS energy, and the costs of their proposal. J&D project that when accounting for the costs associated with air pollution and climate change, all the WWS technologies they consider will be cheaper than conventional energy sources (including coal) by 2020 or 2030, and in fact onshore wind is already cheaper."

Right? So no matter how many times you claim, "SkS ignores this [cost] question", it will never be true.

Comment on Has the rate of surface warming changed? 16 years revisited

miffedmax

No, no, no. This isn't how the game is played. If some of your evidence is incorrect, you don't withdraw it, you shout it louder.

(I am on a Heartland-friendly site, aren't I?)

Comment on The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.

Dikran Marsupial

Prof. Tung, I don't think we are wasting our time either. It is unfortunate that misunderstandings ocurr sometimes, but we wouldn't be so thorough in trying to get to the bottom of them if we didn't think understanding the science properly was important.