Arguments
Recent Comments
Prev 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 Next
Comments 45201 to 45250:
-
rockytom at 04:21 AM on 24 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
John, another fantastic article with the best graphics I've seen integrated with the text. I wish we (John Cook and I) had had the graphics when writing our textbook (Climate Change Science: A Modern Synthesis) as we certainly would have included at least some of them (with permissions, of course).
-
KK Tung at 04:09 AM on 24 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
In reply to post 106 by Dikran: The effect of offsetting on the perceived spread of models has been underdiscussed in literature. I agree with what you said about it here, and I would encourage you to develop it into a publishable paper. The procedure of offsetting with a baseline is needed for model projections because projection is different from a prediction. In a prediction of ,say weather for the next few days, today's measured weather is our baseline, and such a baseline is assimulated into the model. The model attempts to predict both the forced and unforced response. Due to chaos, models start to deviate after today, and after two weeks, the prediction becomes mostly useless. But it is useful for a week or so.
The IPCC projections of future climate change is different. The model is initiated in the preindustrial period, 1850-1870, runs about 150 years in the 20th century simulation (when what is to be simulated is known), and then runs forward under different scenarios of future emissions. There is no hope of doing a prediction of both the forced and unforced response over such a long period. Instead it is hoped that the forced response of the climate is simulated with the ensemble mean of the model runs. If, in the presentation of the results, all models are offset against their initial condition at 1850-1870. The intermodel spread is rather large, even during the period of 20th simulation, where the observed response is known before hand. This is caused by systematic errors in each model. This intermodel spread is reduced by offsetting each model's ensemble mean by its own climatology in a specified period, say 1980-1999, as used in Chapter 10 of AR4. It reduced the intermodel spread during the period of offset, and also for a decade or so after that. AR4 uses different offsetting period in different chapters, and there is no consensus on how to do it. You have found that a longer offsetting period makes the pre-2000 results less anomalous. On the other hand, for the purpose of evaluating projections to the future, perhaps it may be fairer to the models to offset it with the lates known data. That is, year 2000 for AR4 projection and year 2005 for the CMIP5 projection. We however do not know what the observed forced response is, but since AR4 models have simulated the observed 20th warming quite well with forced (ensemble mean) solutions, it may not be a bad idea to offset the model prediction at year 2000 for AR4 projection with the observation at year 2000, and then attribute the subsequent deviation of the model ensemble mean from the observation to the presence of internal variability. Have you tried it yet?
-
R. Gates at 03:34 AM on 24 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
Wow, fantastic post. Lot's a great information. One bit of information, perhaps advanced but very important for understanding a negative AO index at certain times of the winter and the havoc it can bring to lower latitudes. Sudden Stratospheric Warming events (SSW's) where air is descending over the pole form the upper stratosphere and even the mesosphere bring of course high pressure over the pole, warming, and often times a very negative AO index. These SSW events in essence "open the freezer door" on the Arctic and shunt this very cold air down to lower latitudes. The normal winter westerlies turn to easterlies as the Polar Vortex is often shattered, and you get real nasty weather at lower latitudes. Looking back historically, very negative AO events in the winter are highly correlated with these very disruptive SSW events.
But again, a great article!
-
nealjking at 03:00 AM on 24 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
s_gordon_b:
You wrote:
"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?"
From looking at the paper, what I find as the first statement of the consensus (in the abstract) is: “Among abstracts expressing a position on AGW, 97.1% endorsed the consensus position that humans are causing global warming.” So the definition of the consensus position is that “humans are causing global warming”. But how is this to be understood?
In my view, it has to be understood as "common speech": When the proverbial “man in the street” asks the question, “Are we (humans) causing global warming?”, he is NOT necessarily asking, “Is the degree of responsibility for global warming that is due to human activity greater than 50%?” or "Is human activity the dominant cause of global warming?" He is asking something much closer to, “Is human activity contributing to global warming big enough that we ought to be doing something different?” And I believe most scientists would agree with this understanding of the AGW issue: Not that the human contribution is necessarily greater than 50%, but rather that it is important enough that we should be seriously thinking hard about whether we want to change what we are doing, on a global scale.
My understanding of the Levels of Endorsement (LOEs) 2 & 3 is that they indicate agreement, explicit or implicit, with the spirit of the underlined statement above, which I regard as a filled-out "common speech" version of the statement in the abstract.
Therefore, I have no doubts about including LOEs 1 - 3 together as indicating support for the AGW consensus.
-
barry1487 at 02:39 AM on 24 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
John Hartz,
What exactly do you mean when you use the phrase, "academic merit"?
Quality of scholarship..
-
Dumb Scientist at 02:33 AM on 24 May 2013Has the rate of surface warming changed? 16 years revisited
jdixon @27: Sure, just return it when you're done so I can use it again. ;)
-
John Mason at 02:04 AM on 24 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
Eric - interesting question. I'll have a read of those papers and get back to you in a few days. However one point I would make is that because the Tropopause is such a strong temperature inversion, convective heat transfer between the troposphere and stratosphere is effectively blocked. I would therefore suggest the troposphere plays the main role.
-
jdixon1980 at 01:46 AM on 24 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
Wow that's a lot of info without having to buy a meteorology textbook - will have to look this one over a few times to absorb it.
-
Eric (skeptic) at 01:15 AM on 24 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
Good article. My main question is about how this explanation fits with prior explanations of changes in AO. For example: <A HREF="ftp://psrd.hawaii.edu/engels/Stanley/Textbook_update/Science_297/Moritz-02.pdf">ftp://psrd.hawaii.edu/engels/Stanley/Textbook_update/Science_297/Moritz-02.pdf</A> The explanation in this 2002 paper seems to be that GHG cooling of the lower stratosphere leads to an increased vertical gradient and a stronger polar jet. The explanation above seems to focus on the decreased horizontal temperature gradient causing a weaker jet. Is one gradient more important than the other? My opinion is that the 1950-present chart above appears to be mostly natural variation.
A question specific to Sandy is that the left turn came not just from blocking but from Sandy phasing with a strong short wave riding on the deeply diving longwave jet. I'm not sure why there would be any natural or GHG-induced trend in the strength of the short waves because their strength seems to depend on local temperature contrasts that greatly exceed any of the trends in wide scale temperature contrasts from GHG or natural cycles.
Finally, Andrew Freedman has a good perspective on climate change and tornadoes <A HREF="http://www.climatecentral.org/news/making-sense-of-the-moore-tornado-in-a-climate-context-16021">http://www.climatecentral.org/news/making-sense-of-the-moore-tornado-in-a-climate-context-16021</A> with a focus on strong tornadoes only.
-
jyyh at 01:03 AM on 24 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
Thanks for this informative post. I find it's a bit sad case that scientific articles like this one get pretty quickly buried in other kinds of articles on politics, opinions and rebuttals of denialist bullshit. After reading this, I remembered there was a good article on SkS about Sudden Stratospheric Warmings breaking the polar jet stream just recently... after some 10 minute searching I wasn't sure of it anymore. Eventually I found it. It's here :-D : http://neven1.typepad.com/blog/2013/04/sudden-stratospheric-warmings-causes-effects.html
I might some day (or week or two) go through the entire archives of climatology blogosphere to seek these kinds of articles I've found clear and approachable to my level students of climate, but as of yet this hasn't happened. I'll note here if I get to it. Thanks again.
-
jdixon1980 at 00:31 AM on 24 May 2013Has the rate of surface warming changed? 16 years revisited
DS @21 I like the water sloshing analogy better than the "flywheel" or the yo-yo because of the built-in illustration of measurement at a single location - I assume you don't mind if I borrow it?
-
Rob Honeycutt at 00:27 AM on 24 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
s_gordon_g... Instead of trying to over interpret the exact wording, take a step backward and look at big picture.
~97% of the research supports AGW.
~3% of the research rejects AGW.
The way you're approaching it, you're completely missing the forest for the trees. This is a common "skeptic" tactic when faced with data they don't like.
-
John Mason at 23:04 PM on 23 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
Chris, I'll split up your many questions and attempt to answer them in bold type:
Polar jet stream, is maybe a bit confusing sicne the southern antarctic oscillation is also a polar jet stream?
Yes, there is also a southern polar jet, but this post is specifically with regard to the Northern Hemisphere.
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.
This can be the case but more typically from a blocked pattern in summer - when it's warmer then the air can contain more moisture. Winter blocks tend to produce pronounced cold spells.
What about downward bursts/microburst?
These are features associated with high-precipitation thunderstorms and so occur in highly unstable atmospheric environments - an approaching upper trough with its attendant PVA will encourage mass ascent of air, but downbursts are storm-scale features.
Greenland is according to Jennifer Francis a prime spot for blocking patterns to occur, see Sandy - caused 90 degree turn.
Yes WRT Greenland, with stubborn high pressure over it and linking down to the Azores High being a good example of a blocked setup. The upper pattern played a part WRT Sandy's course, but I'm not sure of the exact figure without looking it up.
Where exactly is the Jet Stream, if not with the Jetstreaks?
See the diagrams up-post
Are these visible from the ground - do they come with clouds or is this different?
Cirrus can occur within jetstreaks and is obvious as it's moving rapidly. But in general no.
In regards to tornadoes and Jet Stream:“As 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.“I believe there is evidence that the strongest tornadoes are getting stronger. They are certainly getting longer and wider.” - James B. Elsner, an atmospheric scientist at Florida State University Humid air and the Jet Stream help to fuel more intense thunderstorms/tornadoes
Joe Romm has a post-Moore, OK, review of tornado climatology at Climate Progress:
-
Dikran Marsupial at 21:31 PM on 23 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years?
MA Rodger The degree to which Prof. Tung's method over- or under-estimates the true anthropogenic component depends on both the true "noise" (the variation not due to the factors explicitly included in the model - note this is not necessarily the same as the residuals from the regression) and on the nature of the non-anthropogenic factors. As linear and quadratic detrending are correllation based methods, they are highly susceptible to any correlation or anti-correlation between the anthropogenic and non-anthropogenic components of the AMO. Similarly any flaw in the detrending of the AMO that is correllated or anti-correlated with the noise in the observations may be exploited by the regression procedure.
Essentially Prof. Tung's regression approach appears only to be workable if we can eliminate the anthropogenic influence on AMO exactly without attenuating any of the non-anthropogenic component. We can't do this unless we already know what exactly the anthropogenic influence on AMO actually is. I don't think this is "chipping away"; if my analysis turns out to be correct (and I have no problem with being wrong - it is part of normal scientific procedure!) then the whole regression procedure is invalid and hence does not support the conclusion.
Even when valid, regression methods can only really show that something CAN BE explained by something else, not that something IS explained by something else. We really need physics to determine whether AMO actually does influence GMST. The work of Foster and Rahmstorf shows that we don't need AMO to explain the "hiatus" as it CAN BE explained using ENSO etc. Occam's razor suggests we shouldn't needlesly introduce new elements if an existing theory already explains the observations already; however that doesn't mean that AMO has no effect on GMST.
-
Dikran Marsupial at 21:04 PM on 23 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Prof Tung writes
"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."
Yes, I think that the majority of SkS readers would agree that the ensemble mean is probably the best method we currently have for estimating the forced response of the climate system and that any difference between the observations and the ensemble mean can be explained as being due to the unforced response due to sources of internal climate variability. This is of course, provided the difference is approximately within the spread of the ensemble (in reality this is probably an underestimate of the true uncertainty due to the small number of model runs and the limited number of models).
"The point I made previously was why we need it now during the hiatus period and not during the period of accelerated warming."
I do not agree with this statement. There are multiple sources of internal climate variability, which include for example ENSO and plausibly AMO. Most of the time these will be acting to warm or cool the climate essentially at random, and so most of the time might be expected to largely cancel out. This is why the ensemble mean, while being an estimate of only the forced response, is still a reasonable point estimate of the observed climate. However, sometimes multiple sources of internal variability may temporarily align in direction, causing the observed climate to stray away from average conditions. Under such circumstances one would expect the observations to stay reasonably close to the forced response most of the time, but for there to be occasional periods of little or no warming, or conversely more warming than expected.
Easterling and Wehner (2009) investigated this issue in some detail and found that
"...periods of no trend or even cooling of the globally averaged surface air temperature are found in the last 34 years of the observed record, and in climate model simulations of the 20th and 21st century forced with increasing greenhouse gases. We show that the climate over the 21st century can and likely will produce periods of a decade or two where the globally averaged surface air temperature shows no trend or even slight cooling in the presence of longer-term warming."
In other words, we should expect to see the occasional "hiatus" ocurr due to internal climate variability, the models predict that they will happen if you wait long enough, but being chaotic phenomena the models cannot predict when they will happen. As far as I can see, there is little evidence that the models need internal variability more in recent years than they did before.
It is also worth noting that the issue to do with baselines may look as if the observations were more central in the spread of the models during the baseline period as baselining removes any offset between timeseries exactly within the baseline period, but only approximately outside. Some of these offsets will be due to random rather than systematic differences, so the apparent uncertainty of the models in the baseline period will be lower than outside the baseline period. This effect will be smaller the longer the baseline period, as shown in my earlier post, but I suspect it does contribute to the observations looking less "anomalous" during the pre 2000 years than perhaps they should.
I think it is very important to be highly skeptical of phenomenon that seem obvious from a visual inspection of the data. The human eye is very prone to seeing patterns in noise that don't actually mean anything. We should be reticent in claiming that there has been a real hiatus until there is statistically significant evidence for that assertion.
Incidentally, as Dumb Scientist points out, I have also made two posts in the previous thread addressing the issue of circularity, which seems to suggest that the regression method proposed does involve circularity. The posts are here and here. If you are a MATLAB user, I can send you the scrips used to perform the analysis.
-
MA Rodger at 20:39 PM on 23 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years?
Dikran Marsupial @57.
Assuming your method holds up, you have illustrated that by subtracting the AMO signal from global temperature to reveal the AGW, you can be also inadvertantly be subtracting a significant amount of AGW. Your "Question 2" @16 thus stands now with evidential support.
Commendable stuff but....
The question that would perhaps follow would concern whether the proportions shown within the example you present (ie that 33% of the AGW signal is lost by subtracting AMO in this manner) are sensitive or insensitive to the situation. Will it always be about 33% or will it sometimes be much more, or less.
And I am far more sceptical about T&Zh13., I feel this chipping away is not the best approach. Indeed I remain sceptical that there can be any significant contribution to the global temperature anomaly from AMO.
One point I would make runs as follows - If global temperature wobbles 0.3ºC peak-to-peak due to AMO (as T&Zh13 asserts) and if 67% of this is resulting naturally from AMO (ie if we factor in the suggested finding @57 = 0.2ºC) then how much energy will be required to wobble the global temperature that amount? With TRC=2ºC (this is one place where contrarians would find high Climate Sensitivity useful), the global wobble would require a forcing equatable to 10% of 2xCO2 or 0.37Wm^-2 or an energy flux of 6ZJ pa. If this energy flux originates solely in the N Atlantic (ie if it is a direct energy output of the AMO), it will incur significant losses as it spreads out around the world. If the AMO has some deliverable other than 'heating of the climate' then the T&Zh13 thesis has some explaining to do.I think I will go in search of my 6+ZJ pa. It is rather a large quantity to go unnoticed.
I suppose my feeling on all this is that the AMO is simply an ocean waggling like a continent and is driving zip. But such comment here is pure speculation. And I am prepared to admit as much.
-
Dikran Marsupial at 20:36 PM on 23 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
MA Rodger It seems to me that Prof. Tung has introduced the "hiatus" largely as a way of establishing the existence of internal variability, although I think the majority of SkS readers will already accept that without the need for it to be stated explicitly.
-
MA Rodger at 20:21 PM on 23 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
KK Tung @97.
The thesis we discuss (Tung & Zhou 2013) specifically addresses multidecadal episodes of warming and cooling. This "hiatus period" you now discuss has been evident within the temperature record for less than a decade. Given the present short duration of this "hiatus period," given the many other points presented within Tung & Zhou 2013, is it helpful to our discussion to introduce yet another topic into this discussion? Indeed, why is the "hiatus period" relevant?
So far the two posts on this thesis have encompassed (1a) The shape of the net anthorpogenic forcing profile. (1b) Sea ice as a driver of AMO, (2a) AMO in climate models. (2b) AMOC evidence. (2c) Pre-industrial AMO data. (2d) Remnant anthropogenic signal in AMO. (2e) Using AMO as a "forcing."
So far, most of these topics remain poorly addressed, if addressed at all. I would suggest adding a fresh item to this discussion (ie introducing the "hiatus period" ) which does not appear entirely relevant is the opposite of what we should be attempting. -
Dikran Marsupial at 19:45 PM on 23 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years?
As an update to my previous post on Prof Tung's method, I've now investigated quadratically detrending the AMO signal to remove the anthropogenic influence, using:
X = [ones(size(T)) T T.^2];
beta = (X'*X)\X'*AMO;
AMOd = AMO - X*beta;This doesn't work either, but this time it over-estimates the anthropogenic forcing, although the error is smaller than for the linear detrending.
The reason this doesn't work either is both subtle and interesting. Ideally the detrending would eliminate the quadratic anthropogenic component leaving only the sinisoidal natural component. However, the sinusoidal component has a linear trend, being positive in the first half of the time series and negative in the second. So when we quadratically detrend the raw AMO signal, we can erase both the anthropogenic component AND the linear component of the natural signal. However the linear component of the natural signal slopes downward and that of the anthropogenic signal upward, so this cancels out to a degree, and the resulting quadratically detrended AMO signal has an upward linear trend.
We defined the synthetic AMO signal as
AMO = 0.4*anthro + 0.6*natural;
so if we exactly remove the anthropogenic component, the correctly detrended AMO signal is just 0.6*natural (blue). However if we use simple quadratic detrending, we get the AMOd signal shown in red. The green line just shows the difference between the two.
The problem is now that the component shown in green is correllated with the anthropogenic component of the observations, so a quadratically detrended AMO still acts as a proxy or alias for BOTH the natural and anthropogenic components of the observations, which means that you can't use this method for attribution either.
The bottom line is that it seems that Prof. Tung's method only gives the correct answer if the anthropogenic component is exactly removed from the AMO signal before performing the regression. Adding the trend of the residuals does not solve this problem. Of course we can only exactly remove the anthropogenic component from AMO if we already know what it is, so using this method to estimate the anthropogenic component of the observations does require circular reasoning... provided I have not misunderstood the method, of course! -
johncl at 18:40 PM on 23 May 2013On the value of consensus in climate communication
I do believe the main problem for many now is not to accept that there is global warming happening, but that its caused by humans - as it implies that they are themselves guilty of it. Also, its very easy for people to put blame to others even if they believe humans are the cause of it. "Its the Chinese and all their coal plants!". So here in Norway there is constantly comments from people about e.g. electrical cars being bad because they are fueled by coal electricity - even though Norway has 99% of its electricity from hydro power. The general idea is that, if its not good for the general average over the whole globe, its not good for us as well. But this idea is rather silly in my opinion, and in most cases its rather impossible to change peoples view on this since its so securely rooted in the trandition of the fossil fuel car being the best choice. It doesnt help that Norway also gets its current wealth from oil as well.
The same odd argument is also used against building more windmills in Norway, because we already have enough hydro power. So its indeed like a snake biting its own tail, as many people seem to be unable to have more than one thought in their heads at one time. I do believe the more you are able to see things in a wider perspective your views will slowly creep towards more liberal viewpoints and are able to see the bad things about free market policies and the effect of e.g. globalism. Also there is general disconnect from nature in the way that we treat consumables as things that magically appears in the shelves. In general people need to be educated about the carbon footprint of anything we buy, almost to the point where every good has a carbon footprint estimate printed on its label. But with e.g. the clothes industry not even wanting to inform the public about which factories their goods are made in - its clear that the "truth" of globalism is one they would rather be kept secret since its generally bad publicity the moment another building collapses or is known for using child labour. So we need education of the masses that every choice we make in consumption is also a moral choice about the implication of globalism, its carbon footprint and human suffering that results from it.
I am very thankful that John Cook and SkeptialScience is keeping up with spreading the message and I was very happy to see the consensus research even presented in mainstream media here in Norway as well. The discussions in the comment fields were just littered with "AGW is BS" and all kind of denial ofc. But those comment fields are also a place were we should be active and promote real science information and preferably with links to sources, which is one the denialsphere often lacks as its generally based on feelings and not facts. Unfortunately when they do seek "facts" for themselves they very easily end up on WUWT and other denial sites because it seems they have been able to flood the search databases with classical spam link methods for getting high on the search results. Its easy to see this if you search for "global temperature" for images and see where those images lead to. So its indeed an information battle going on here to get real information. Good transparent research like this consensus project is definitely what we need more of.
To quote a song by Peter Gabriel: "Turn up the signal, wipe out the noise!".
-
Chris8616 at 18:27 PM on 23 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
A link between reduced Barents-Kara sea ice and cold winter extremes over northern continents
The recent overall Northern Hemisphere warming was accompanied by several severe northern continental winters, as for example, extremely cold winter 2005–2006 in Europe and northern Asia. Here we show that anomalous decrease of wintertime sea ice concentration in the Barents-Kara (B-K) seas could bring about extreme cold events like winter 2005–2006. Our simulations with the ECHAM5 general circulation model demonstrate that lower-troposphere heating over the B-K seas in the Eastern Arctic caused by the sea ice reduction may result in strong anticyclonic anomaly over the Polar Ocean and anomalous easterly advection over northern continents. This causes a continental-scale winter cooling reaching −1.5°C, with more than 3 times increased probability of cold winter extremes over large areas including Europe. Our results imply that several recent severe winters do not conflict the global warming picture but rather supplement it, being in qualitative agreement with the simulated large-scale atmospheric circulation realignment. Furthermore, our results suggest that high-latitude atmospheric circulation response to the B-K sea ice decrease is highly nonlinear and characterized by transition from anomalous cyclonic circulation to anticyclonic one and then back again to cyclonic type of circulation as the B-K sea ice concentration gradually reduces from 100% to ice free conditions. We present a conceptual model that may explain the nonlinear local atmospheric response in the B-K seas region by counter play between convection over the surface heat source and baroclinic effect due to modified temperature gradients in the vicinity of the heating area. Link to Source This study was submitted Nov. 2009.
Keywords:
Arctic sea ice;atmospheric circulation;nonlinear dynamics -
Chris8616 at 18:24 PM on 23 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
NAO
Timeseries of the winter (December to March average) of the Jones et al. NAO index, updated to the winter of 2011/12. Note the upward trend from the 1960s to the early 1990s, but also that the trend has not been sustained and has significant year-to-year variability superimposed on it. Note also that the winter 2009/10 had the most negative NAO index measured during the almost 190-year record.
Another pathway for temperature chaneg in the northern polar region is freshwater flux from increased thaw in the siberian region, which changed the Arctic curretn setup NASA video arctic ocean current Though freshwater can isolate sea ice
A new wind regime is another change in the nothern hemispheric aquatic environment, which is ratehr chaotic i guess. The new winds will cause coastel erosion and there seems to be an uptake in more intense storms in the arctic, which happen to break up sea ice chunks of the size 1300 km length (happened a few days ago and in Februar similar).
.
"As we lose all the summer ice, the response in the fall may plateau somewhat (although Arctic Amplification will continue via the other factors), but as ice in the other seasons declines, we should see the response become stronger all year long"
Maybe we get kind of permanent blocking pattern, without the ice.
-
Chris8616 at 17:53 PM on 23 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
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:“As 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.“I believe there is evidence that the strongest tornadoes are getting stronger. They are certainly getting longer and wider.” - James B. Elsner, an atmospheric scientist at Florida State University Humid air and the Jet Stream help to fuel more intense thunderstorms/tornadoes -
s_gordon_b at 15:04 PM on 23 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
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?
-
scaddenp at 13:51 PM on 23 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
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.
-
DSL at 13:48 PM on 23 May 2013On the value of consensus in climate communication
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).
-
jmorpuss at 11:40 AM on 23 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
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.
-
MS1 at 10:30 AM on 23 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
#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..."
-
Dumb Scientist at 10:26 AM on 23 May 2013Has the rate of surface warming changed? 16 years revisited
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.
-
JasonB at 09:50 AM on 23 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
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.
-
william5331 at 09:47 AM on 23 May 2013Has the rate of surface warming changed? 16 years revisited
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.
-
Farmer Dave at 09:32 AM on 23 May 2013Has the rate of surface warming changed? 16 years revisited
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?
-
william5331 at 09:26 AM on 23 May 20132013 SkS News Bulletin #13: Alberta Tar Sands and Keystone XL Pipeline
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.
-
Rob Honeycutt at 08:59 AM on 23 May 2013It's satellite microwave transmissions
grindupBaker... I'm really unclear on what you're attempting to say.
-
Esop at 08:57 AM on 23 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
Brilliant article. Very informative!
-
Dumb Scientist at 08:55 AM on 23 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Mod: please delete #99. Dunno why it came out empty...
-
Dumb Scientist at 08:54 AM on 23 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
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.
-
Dumb Scientist at 08:52 AM on 23 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
-
KK Tung at 08:33 AM on 23 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
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.
-
KK Tung at 08:24 AM on 23 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
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.
-
scaddenp at 07:52 AM on 23 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
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.
-
grindupBaker at 07:45 AM on 23 May 2013It's satellite microwave transmissions
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.
-
Dumb Scientist at 07:32 AM on 23 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
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.
-
Rob Honeycutt at 07:15 AM on 23 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
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.
-
Rob Honeycutt at 07:03 AM on 23 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
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.
-
John Russell at 07:00 AM on 23 May 2013A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming
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.
-
Composer99 at 06:41 AM on 23 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
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.
-
Kevin C at 05:51 AM on 23 May 2013Has the rate of surface warming changed? 16 years revisited
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.
-
Kevin C at 05:47 AM on 23 May 2013Has the rate of surface warming changed? 16 years revisited
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.
-
Dumb Scientist at 05:26 AM on 23 May 2013Has the rate of surface warming changed? 16 years revisited
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.
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.
Prev 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 Next
