This is course not totally true. The level of temperatures in the Medieval Warm Period (WMP) could be helpful to estimate how robust the Greenland Ice sheet really is, one of the main uncertainties for the projections of sea-level rise for the next centuries. Or to be assured that certain ecosystems, can or cannot, tolerate temperatures warmer than the ones we are experiencing today. However, for these purposes the MWP is not that critical, as possible it was not the warmest period in the Holocene. Most reconstructions and model results indicate that the Midholocene Optimum was warmer than the MWP, and even more so at high latitudes in summer in the Northern Hemisphere. This is not surprising since the orbital configuration of the Earth was also different. But to help us understand the functioning of the Earth's climate and global scales, including the thorny issue of the climate sensitivity, the MWP is not really relevant and even less so to constrain the skill of climate models. To illustrate my point, let us have a look at the following picture displaying the Northern hemisphere mean annual temperature in climate simulation over the past millennium until the end of this century.
The details of the temperature evolution is of course dependent on many factors that are burdened with high uncertainty, and I am not claiming that this temperature evolution represents the truth. For instance, the future scenario of greenhouse trace gas concentrations is of course not known to be realistic. Or the past variations of solar and volcanic activity are still debated. So the temperature level in the MWP could be, say a few tenths of a degree warmer or cooler than in this simulation. But in view of this picture, it is clear that this details are not really very important for the MWP. First, we see that the projected temperature increase much higher than any possible reconstruction of the MWP may indicate. Te question of whether the MPW was warmer or cooler than today is not relevant to tell whether or not the model future projections are wrong. The level of uncertainty in the climate reconstructions for the MPW is too large to discriminate between bad models or good models: all would probably reproduce temperature levels around the 20th century mean, the same as all reconstructions.
The message here is that if one wants to prove model projections wrong, one has to … ehem prove model projections wrong and not prove that the MWP was warmer than present temperatures. The MWP may be interesting stuff for the blogosphere, but does not say much in either direction about the skill of climate models or about the theory of anthropogenic greenhouse effect.
If one is willing to prove models wrong, it is much more reasonable to focus in the climate periods that are as dissimilar as possible to today's climate and there compare models and reconstructions. Within the Holocene, this period is quite probably the Little Ice Age., when on top of that the proxy data sets are much richer and even long instrumental series may be available. In this period is when the signal-to-noise ration, i..e the amplitude of climate change relative to the uncertainties in reconstructions and modelling should be larger. The possible climate feedbacks and their spatial fingerprints would be also stronger and perhaps detectable in the proxy records. This does not mean that the task of comparing reconstructing with model simulations is easy for the LIA. The uncertainties in the external forcing - volcanoes, solar irradiance, land use.. are not that small. I do not know if the variations of solar irradiance, for instance, really oscillate with a 80 year period, but it seems that our estimation of this amplitude do oscillate with a 5-year period. Starting with the first estimations by Lean et al (1995) of a change of about 0.25% between present and the peak of the Little Ice Age, towards the much smaller changes presented more recently by Krivova et al (around 0.15%) , and ending with even more recent numbers that I have got to know from private communications, in which we would get back again to the Lean et al values, it seems that these estimations display some type of periodic boundary conditions.
Nevertheless, a climate period as recent as the LIA with a flurry of information available should help us et lead to ascertain some of the robust predictions that may not be that dependent on the exact amplitude of the changes in the external forcing. They are not even predictions that are very much depend on a particular climate model. For instance, climate models predict, on large scales, an increase of precipitation in areas that are humid now and a decrease of precipitation in areas that are presently dry. This prediction is mostly based on relatively simple reasoning involving the fact that specific humidity near the surface should increase or decrease with global temperature following the Clausius–Clapeyron equation, whereas global precipitation would change at a slower pace (Held and Soden, 2006). At first sight, there is no reason why this should not be valid for colder periods as well. Thus we would have a clear target to test climate models and reconstructions regarding the global hydrological cycle: mean high-latitude precipitation in the LIA should be lower than present, subtropical precipitation should be higher than present.
Posts
51 comments:
"The message here is that if one wants to prove model projections wrong, one has to … ehem prove model projections wrong and not prove that the MWP was warmer than present temperatures."
No one need prove climate models wrong. Climate models bear the burden of being verified and validated. A burden yet to be met.
Hello,
During the little ice age the alpine glaciers were bigger than at any other period of the holocene.
What we might learn from the MWP is what would be the natural state of the climate. What would todays climate look like if men didn't exist? Judith Curry speaks about "the relative importance of the multi-decadal modes of natural internal variability".
In fact we don't really know very much about this natural variability. We are told about forcings but not about natural variability. Observations over the next decades will tell us more, and climate models will be tuned the same way weather forecast models are tuned today imho.
Everything in todays models depends on the climate sensitivity of the greenhouse gases.
Everything in natural climate forcing depends on "natural internal variability" of the climate.
Everything we observe today will be part of tomorrows climate models.
These are the most important questions for a skeptic lay man. Is the climate sensitivity of GHG'sreally that high? Is the global warming that we experience today really man made? What would it look like without mankind?
Everything we see today is a very theoratical climate forecast. The model predictions prove the models hability to predict the future. Todays real time climate observations would rather contradict the high climate sensitivity of the models.
In the beginning the influence of the GHG's on the climate should be less important, and it should become more and more important as time goes on. What we observe today is just the opposite.
This is what makes me doubt more than anything else.
Best regards
Yeph
Climate models have generally not predicted anything of consequence since they began making predictions. The streets of New York City are not awash in sea water (Dr Hansen), the arctic ice cap did not disappear (many), the Amazon rain forest has not turned into savanna nor have the Himalayan glaciers shrunk (IPCC).
As was pointed out above, the burden of proof is on those who want to shut down the entire coal/oil/gas powered electrical, transportation, and power industries in favor of windmills and solar panels and alcohol.
None of the alternative energy sources are remotely close to viability for any meaningful purpose, and the harm to billons of people from the insane demands of the CAGW crowd would be immediate and deadly. How can any rational human support this nonsense?
You seem very confused about the skeptic position here:
"whether the MWP was warmer or cooler than today is not relevant to tell whether or not the model future projections are wrong. "
This whole post seems to be based on a straw man argument.
Skeptics do not use the MWP to argue that climate models are wrong.
The point of the MWP is that it shows (A) that significant climate fluctuations have occurred in the relatively recent past, due to poorly understand natural fluctuations.
(B) that there is nothing unusual or unnatural about the current level of global temperature, or the rate of change of temperature.
The picture you show in this post is junk, but the reasons why it is junk have nothing to do with the MWP.
charles
Charles/24.
Two things: first, there is not ea general sceptics position (see Maris' survey), but many. Thus, stop this practice of declaring your own view as general.
Second - your claim that the figure would be "junk" is not acceptable - first the wording and second the failure to argue why the figure would be not of relevance.
Next time your submission is deleted, when it is limited to claimsmaking and unwanted language.
Thanks @Eduardo for that post. The MWP obsession is rather fruitless, since it really proves nothing at all about the CO2 forcing.
@Stan 1: Aren't theories usually falsified or valid until falsified? So usually you take the model and say "it's wrong because a) b) c) and my own model that cares about a) b) c) gets better results" ?
I don't know how much backtesting is done with climate models, but as long as the uncertainty is sufficiently high, there are probably enough models being labeled "valid" although their results aren't exactly overwhelming.
@Charles 4: The point about the "sceptic" MWP-position is that it is an illogical argument, because it basically states that similar effects always have to have the same causes.
"Temperature changed before, now temperature changes again, ergo it's not our fault."
That is like saying that hitting your thumb with a hammer won't hurt, because when you were a child you touched the stove and that hurt. So whenever the hand hurts, it must be due to touching a stove.
(apart from that you really should be better brought up than insulting a respected scientists on his own virtual front lawn)
Sorry, this post looks like a classic case of circular reasoning to me. Here's hoping you return quickly to your role of Honest Broker, which you usually do so admirably.
@7
in which sense circular? could you elaborate a bit further?
The MWP makes sense from a skeptic's standpoint regardless of whether it can be used to falsify models or not. There are two reasons for this: First, it is compatible with the idea that the internal variability (the "random walks", independent of external forcings) of climate is much larger than what is usually acknowledged by mainstream climate science. But second, and this may be more important: The main lesson from studying the relation of the climate of the last 2000 years to the history and development of man, is that a warm climate (the roman warm period, the MWP and the current warm period) is better than a cold climate (the dark ages and the LIA), and that claims that AGW is already claiming thousands of lives are not well-founded. In fact, if man had found some alternative cheap energy source 120 years ago and stopped all use of fossil fuels back then, AND the current temperatures had been 1 degree lower, one might argue that the climate would have been significantly worse.
Espen, perhaps a small history lesson is useful. Rather than me giving it to you, and thus potentially introducing personal values, you may want to look up what periods(!) the Dark Ages refers to, why it is generally referred to as the Dark Ages, and when the Renaissance started. You might find some inconveníent truths there in terms of timing.
I'm not sure I completely understand your point. If your premise is that "the MWP is not really relevant to the thorny issue of understanding climate sensitivity... and even less so to constrain the skill of climate models", you could not be more wrong.
The ultimate acid test for any model (of anything) is to compare it with reality. Good models correlate well with the past and accurately predict the future. The model simulation shown in Figure 1 does neither. It does however, illustrate why skeptics have little faith in climate models. Like your chosen example, they fail the simple acid test.
Over 1,900 peer reviewed papers present consistent, reproducible data showing the MWP was a robust, worldwide phenomenon:
http://www.co2science.org/data/timemap/mwpmap.html
No climate model to date accurately reproduces the MWP, and therefore, none of them can be trusted. Models that fail to correlate with known scientific data must be either reworked or discarded as they cannot possibly be correct.
Only 'Real Climatologists' are distracted by MWP climate porn: http://ecotretas.blogspot.com/2010/10/climategate-secret-meeting_22.html
The rest of the scientific community relies on the
voluminous database of established, peer reviewed scientific literature.
Louis,
'No climate model to date accurately reproduces the MWP, and therefore, none of them can be trusted.'
This requires some clarification. The IPCC models have not been used for such long simulations of the past centuries: only simulations with two models, among 22 IPCC models, have been published so far. The assertion that no climate model can reproduce the MWP is thus not very meaningful, although it is repeated once and again. Also the simulation I posted here does show a MWP with temperatures roughly equal to the 20th century mean. Whether these temperatures are above or below the 20th century mean, however, is not a big deal: since the solar irradiance at that time is not very well know, I can produce a MWP relatively easy by just increasing the solar forcing accordingly. This would not tell me much about the skill of the model itself.
I am however happy to be informed that there are so many papers that show the existence of the MWP- presumably based on proxies. Just a few weeks ago the blogosphere was celebrating the McShane and Wyner paper that purportedly demonstrated that proxy records do not contain information about past climates
Let's get the facts straight here. 1. Alarmists declared that the earth was warming in a way that was unprecedented. 2. Skeptics replied that this claim was false -- temperatures were warmer as recently as the MWP. 3. Alarmists decided that it was vital to get rid of the MWP. 4. The hockey stick was created for the purpose of eliminating the MWP.
So the focus on the MWP seems to be less about the models and more about the alarmist claim of unprecedented warming. It was the alarmists who put the focus on the MWP with their warming claim. And it was alarmists who obsessed about getting rid of it. And it was alarmists who turned the absurd hockey stick into an international icon by making it the most famous science story of our generation.
To say that skeptics are obsessed with the MWP seems to me to be a rather bizarre interpretation of the facts.
Eduardo
You highlight a valid and important weakness of paleo-temperature proxies. McShane and Wyner’s discovery that “highly autocorrelated noise predicts paleo-termeratures better than proxies” should be a wake-up call to many researchers, especially climatologists. However, in the case of the MWP, we don’t have to rely completely on proxies. A plethora of historical data confirms its existence in Europe (paleo-timberlines in the Alps, Viking ruins in Greenland, pollen evidence showing wheat production at nearly latitude 70N, grape production in Scotland, etc.), and, as I pointed out, a large number of studies of “proxies” at least confirm its worldwide extent, (although they don’t give us reliable paleo-temperatures).
Our next goal should be to understand the natural factors and the forcings that produced the MWP, as they have HUGE implications for climate modeling. And the fact that IPCC models can produce a MWP just by increasing the solar forcing only makes me more skeptical of them, for as you point out: “This would not tell me much about the skill of the model itself.”
It is interesting to note that a conference on the MWP was recently held in Portugal and attended by the world’s most preeminent climatologists: http://mwplisbon2010.fc.ul.pt/. Unfortunately, some came ‘not to understand the MWP, but to bury it’: Malcom Hughes’ (of MBH98) abstract states that “The trajectories of these two concepts (“Medieval Warm Period” and “Medieval Climate Anomaly “) will be traced. A case will be made for the abandonment of both of them, on the grounds that they are inappropriate, uninformative, and that they very probably divert attention from more revealing ways of thinking about the Earth’s climate over the past two millennia.” http://mwplisbon2010.fc.ul.pt/pdf/Abstracts.pdf (page 7)
Louis,
I have noticed you are rather fond of conspiracy theories (did you already apologise to Mark Serreze for suggesting he cooks the books?). The "secret" meeting you referred to was SO secret that it was announced well in advance, and various aspects of the discussion there were published (how else did you get Hughes' abstract, eh?). with such a conspirational mindset, it is extremely likely you completely misinterpret Hughes' position.
Moreover, all those people that are so infatuated with co2science's list of papers with a MWP are kindly asked to overlay the various graphs, add the recent temperature record also (many stop well before 1950, or even 1900), and then come back with the analysis. Perhaps then you can also understand Hughes' comment about the MWP and MCA: it simply is not synchronous in time, but papers DO refer to periods of warmer temperatures anywhere between ca. 800 and 1400 CE as the MWP or MCA. Thus, warm period from 800-1000 in region A => MWP! Warm period from 1200-1400 in region B => MWP! The uncritical 'skeptic' translates that as "region A => MWP! Region B => MWP! See, global MWP!"
I am however happy to be informed that there are so many papers that show the existence of the MWP- presumably based on proxies.
When you are pointed to a valuable scientific resource, you would do well to investigate it instead of dismissing it based on incorrect presumption. There are very many kinds of evidence that do not give an estimate of temperature a thousand years ago, but nevertheless can be interpreted as evidence that temperatures were or were not as warm as today. (An example would be melting glaciers which recently revealed human artifacts buried since medieval times; but please do not waste time rebutting this particular example, it is only one of many hundreds that are conveniently archived for your consideration.)
It is no inconsistency to believe that temperature proxies are inadequate to reconstruct a global average temperature history on decade-to-century time scales that constrains temperatures a thousand years ago, and at the same time to judge that the weight of all the available scientific evidence is in favor of those temperatures having been as warm as recent ones.
Edurado said @ 12
Just a few weeks ago the blogosphere was celebrating the McShane and Wyner paper that purportedly demonstrated that proxy records do not contain information about past climates
Wouldn't it be more accurate to say that the " data from Mann et al. (2008) " (page 6-7 of McShage and Wyner paper) "purportedly demonstrated that proxy records do not contain more information about past climates?"
klee12
sciencedude: if it was all so simple why is there no single paper who has done the analysis with all that available data?
I know why, and hence I repeat my earlier challenge:
"all those people that are so infatuated with co2science's list of papers with a MWP are kindly asked to overlay the various graphs, add the recent temperature record also (many proxy records stop well before 1950, or even 1900), and then come back with the analysis."
Marco:
It's not simple. But you also need to actually look at the content of the papers. For many there are no temperature numbers, that is, nothing to graph. The conclusion of a given paper may be "it was warmer at location X a thousand years ago than at present" or "it was not so warm then as now."
I think your challenge could be reformulated into something very interesting, that is, a statistical analysis of categorical data with estimate of uncertainty (or perhaps some other flavor of statistical analysis). It would be a very substantial (and probably valuable) undertaking.
Until such time as a person with requisite expertise in statistical analysis of categorical data undertakes such a project, I think one can form a valid opinion by actually spending some time reading the papers, and looking at the fairly simple meta-analysis at co2science. If you want to convince me that their conclusion is wrong, you will have to show me that you know the data as well as they do. What you have shown so far is that you think all the research reported there has "graphs" that can be overlaid. Come back when you learn some more.
You got me. Although I never said the MWP conference was a secret, my conspiratorial mindset makes me distrustful of it. Here’s why: Michael Mann’s (purloined) e-mail to Phil Jones, Raymond Bradley, Jonathan Overpeck, Tom Wigley, Tom Crowley, Keith Briffa, Kevin Trenberth, and Michael Oppenheimer, states (paraphrased for clarity):
“Phil (Jones) and I submitted a paper using about a dozen NH (Northern Hemisphere) records (tree ring proxies) available nearly 2K back--I think trying to adopt a timeframe of 2K, rather than 1K, addresses a good point that (Over)Peck made, that it would be nice to try to "contain" the putative "MWP"…” http://www.eastangliaemails.com/emails.php?eid=319&filename=1054736277.txt
In light of the e-mail, it’s valid to ask: Did Mann and Jones write this paper (or others) with the intent to try to “contain” the putative MWP?
Of the 36 authors who presented papers at the Portugal MWP conference, at least one sixth (Mann, Jones, Bradley, Overpeck, Hughes, and Wahl) have either stated an interest in “containing” the putative MWP, and/or have published papers that have seemingly done just that. Additionally, bad scientific behavior by members of this group, (presented ad nauseam in the blogosphere) has created the perception that a small group of climate scientists (including several attendees of this conference) intentionally manipulated data to fit preconceived outcomes to support the hypothesis that CO2 emitted by humans is causing unprecedented, catastrophic global warming.
Given the above, my question to you is, if you’re not distrustful of this conference, “Why not?”
As for Mark Serreze of the NSIDC, I do owe him an apology. I never said he cooked data but I implied it, and that was undeserved. I have no evidence that he manipulated data to fit a preconceived outcome. My distrust of him is based on: 1) “guilt by association” with the researchers mentioned above, and 2) his belief in catastrophic anthropogenic global warming (CAGW), and 3) his “arctic death spiral” mantra that the arctic and/or the North Pole may be ice free by (2008, 2010, 2013, 2040, etc.). I believe this is an unwarranted (The sky is falling!) alarmist cry that will prove to be incorrect. Time will tell. I will again apologize for doubting him the day the arctic is ice free.
Last, your comment that the MWP may not be synchronous in time certainly warrants further research, especially in light of McShane and Wyner’s discovery about proxy data and paleo-temperatures. But regardless of whether the MWP was truly global, or an asynchronous warming period sweeping the planet over the course of six centuries, the implications for climate modeling are still huge: ‘What caused (whichever phenomenon occurred)?’, and ‘How do we incorporate the findings in climate models?’ Answering these questions will make climate models better. Viva la MWP! It illustrates just how “unsettled” climate science really is.
Marco:
Although I never said the MWP conference was a secret, I am distrustful. Here’s why: Michael Mann’s (purloined) e-mail to Phil Jones, Raymond Bradley, Jonathan Overpeck, Tom Wigley, Tom Crowley, Keith Briffa, Kevin Trenberth, and Michael Oppenheimer, states (paraphrased for clarity):
“Phil (Jones) and I submitted a paper using about a dozen NH (Northern Hemisphere) records (tree ring proxies) available nearly 2K back--I think trying to adopt a timeframe of 2K, rather than 1K, addresses a good point that (Over)Peck made, that it would be nice to try to "contain" the putative "MWP"…”
In light of the e-mail, it’s valid to ask: Did Mann and Jones write this paper (or others) with the intent to try to “contain” the putative MWP?
Of the 36 authors who presented papers at the Portugal MWP conference, at least one sixth (Mann, Jones, Bradley, Overpeck, Hughes, and Wahl) have either stated an interest in “containing” the putative MWP, and/or have published papers that have seemingly done just that. Additionally, bad scientific behavior by members of this group, (presented ad nauseam in the blogosphere) has created the perception that a small group of climate scientists (including several attendees of this conference) intentionally manipulated data to fit preconceived outcomes to support the hypothesis that CO2 emitted by humans is causing unprecedented, catastrophic global warming.
Given the above, my question to you is, if you’re not distrustful of this conference, “Why not?”
As for Mark Serreze of the NSIDC, I do owe him an apology. I implied he cooked data to fit a preconceived outcome, and that was undeserved. There’s no evidence that he manipulated data in any way. My distrust of him is based on: 1) “guilt by association” with researchers mentioned above, 2) his belief in catastrophic anthropogenic global warming (CAGW), and 3) his “arctic death spiral” mantra that the arctic and/or the North Pole may be ice free by (2008, 2010, 2013, 2040, etc.). I believe this is an unwarranted (The sky is falling!) alarmist cry that will prove to be incorrect. Time will tell.
Last, your comment that the MWP may not be synchronous in time warrants further research, especially in light of McShane and Wyner’s discovery about proxy data and paleo-temperatures. But regardless of whether the MWP was global, or an asynchronous warming period sweeping the planet over the course of six centuries, the implications for climate modeling are still huge: ‘What caused (whichever phenomenon occurred)?’, and ‘How do we incorporate the findings in climate models?’ Answering these questions will make climate models better.
Viva la MWP! It illustrates just how “unsettled” climate science really is.
Marco:
Although I never said the MWP conference was a secret, I am distrustful. Here’s why: Michael Mann’s (purloined) e-mail to Phil Jones, Raymond Bradley, Jonathan Overpeck, Tom Wigley, Tom Crowley, Keith Briffa, Kevin Trenberth, and Michael Oppenheimer, states (paraphrased for clarity):
“Phil (Jones) and I submitted a paper using about a dozen NH (Northern Hemisphere) records (tree ring proxies) available nearly 2K back--I think trying to adopt a timeframe of 2K, rather than 1K, addresses a good point that (Over)Peck made, that it would be nice to try to "contain" the putative "MWP"…”
In light of the e-mail, it’s valid to ask: Did Mann and Jones write this paper (or others) with the intent to try to “contain” the putative MWP?
Of the 36 authors who presented papers at the Portugal MWP conference, at least one sixth (Mann, Jones, Bradley, Overpeck, Hughes, and Wahl) have either stated an interest in “containing” the putative MWP, and/or have published papers that have seemingly done just that. Additionally, bad scientific behavior by members of this group, (presented ad nauseam in the blogosphere) has created the perception that a small group of climate scientists (including several attendees of this conference) intentionally manipulated data to fit preconceived outcomes to support the hypothesis that CO2 emitted by humans is causing unprecedented, catastrophic global warming.
Given the above, my question to you is, if you’re not distrustful of this conference, “Why not?”
Marco (continued)
As for Mark Serreze of the NSIDC, I do owe him an apology. I implied he cooked data to fit a preconceived outcome, and that was undeserved. There’s no evidence that he manipulated data in any way. My distrust of him is based on: 1) “guilt by association” with researchers mentioned above, 2) his belief in catastrophic anthropogenic global warming (CAGW), and 3) his “arctic death spiral” mantra that the arctic and/or the North Pole may be ice free by (2008, 2010, 2013, 2040, etc.). I believe this is an unwarranted (The sky is falling!) alarmist cry that will prove to be incorrect. Time will tell.
Last, your comment that the MWP may not be synchronous in time warrants further research, especially in light of McShane and Wyner’s discovery about proxy data and paleo-temperatures. But regardless of whether the MWP was global, or an asynchronous warming period sweeping the planet over the course of six centuries, the implications for climate modeling are still huge: ‘What caused (whichever phenomenon occurred)?’, and ‘How do we incorporate the findings in climate models?’ Answering these questions will make climate models better.
Viva la MWP! It illustrates just how “unsettled” climate science really is.
Very good, Louis, "contain". Now read a dictionary to see what that word means. Your distrust of everything related to AGW makes you believe it means "remove it", while anyone objectively reading the word "contain" realises it has a meaning of "contain", i.e., "incorporate".
Claiming it means anything else is what constitutes bad scientific behavior and has created the perception that 'skeptics' are not skeptical, but rather deliberately dense because they don't like what the scientists are saying. There, my opinion and my answer to your question.
Regarding your comment about Mark Serreze: you may want to read the work of ANY arctic researcher, and you might then notice that the vast majority all say the same as Mark Serreze. But as you actually indicate, that will just mean you distrust them. You even already have added false claims attributed to Mark Serreze. His own estimates of a ice-free summer arctic are all around 2040 (although newer analysis with ice volume indicates it will likely be earlier).
Finally, you are aware of the criticism of McShane & Wyner's work? As Eduardo indicated, statisticians doing something they have no understanding of might have benefitted from involving actual paleoclimatologists. They would not have made the many, many, many mistakes and distortions of prior work if they had.
Stan 12-
"And it was alarmists who turned the absurd hockey stick into an international icon by making it the most famous science story of our generation."
Based on our climate change corpus I can tell you that the hockey stick does not figure prominently in the US or UK newspapers (even less so in Germany or France). There were less than 10 mentions on average per month in the Nexis archive for the UK and US. Peak attention was in mid-2006 with around 50 instances of the term "hockey stick" in the US and around 20 at the end of 2009 in the UK.
Maybe you are an (unwitting) example of self-exemplification of a skeptical position? The importance you attribute to the hockey stick does not have a correspondance in media reporting.
I try tu sum up what we have learned so far:
1) If the warming since 1970 is due to GHG's and their climate sensitivity is what we think that it is, the models are correct and we don't need to understand the MWP in any way.
2) If we would (still) like to find out wether the correlation "Warming - GHG's" is correct or not, the MWP may help us to understand what is going on today since 1970.
I can by no means accept, that natural climate cycles must not be understood. Everything we know about the future of our climate is based on the climate sensitivity of GHG's and climate models.
I understand that even in chaotic systems we can roughly tell what happens when GHG's increase if we know their climate sensitivity.
BUT, explaining the real climate change from 1900 to 2010 essentially with increasing GHG's is NOT a proof that we have understood the natural climate cycles. We have a very simple correlation and I can't accept that everybody who questions this simple correlation is a morone.
It might just as well be that climate sensitivity of GHG's is much lower than "we" think and that the warming since 1970 is part of a natural recovery from a very cold period, called the LIA.
Correlation prooves the climate sensitivity of GHG's and prooves the validity of the climate models. To question this sentence is "science", above all when the actual correlation of GHG's and climate is close to zero.
Maybe in 10 years we know more and doubters like me will be true believers.
Yeph
PS: I could explain this much better in German but I hope everybody understands what I try to say. ;-)
eduardo @8:
In broad outline, you assume that the model has skill at century time scales, and out to 2100. Specifics might follow if you explained a bit what the model is, and what caused the model to be high around 1100 and low at 1700? Was it all due to a presumed solar irradiance variation? Was internal variability on century time scales (physical and stochastic) negligible in the model? Perhaps you could give a pointer.
Louis,
if there is a certainty in climate science is that the meaning of the word 'contain' used by Mann in that email is 'to include'. I am so sure because this question was- and still is - discussed in almost all paleoclimate meetings and conferences: the need to extend the proxy records back in time to have the MWP in a broader perspective. This applies also to the few climate simulations existent. The earlier ones start in year 1000 whereas the later ones start in year 800 exactly for this reason.
You will probably not believe me, nevertheless it is true
@ 27
Sciencedue,
'In broad outline, you assume that the model has skill at century time scales, and out to 2100. '
No, I am not assuming this - please, read my weblog again. What I said is that the question of whether the MWP was warmer or cooler than today is not indicative of more or less model skill. As the external forcing is not so well known, I can produce a simulation with a warmer MWP if you wish, or a simulation with a colder MWP if you prefer. This is not related to the skill of the models, but to the uncertainty in the external forcing, and thus the discussion about cooler-warmer is futile until the external forcing is much better known.
'Was internal variability on century time scales (physical and stochastic) negligible in the model?'
I am not sure if I understand you here properly, perhaps you are using a terminology which I am not used to. Internal variability is all physical. There is not stochastic variability in the real wold, apart from quantum physics. The appearance of stochasticity in the real world stems only from the strong dependence on initial conditions. Perhaps you meant something else.
The internal variability - i.e. not driven by variations in the external forcings at centennial time scales in the annual global near-surface temperature is about 0.1 K (two standard deviations). Note that we cannot compare with observations, since the variability in the real world is a combination of forced and unforced variations, and since the external forcing and the climate sensitivity is not well known, and since we are uncertain about the total temperature variations in the past, we cannot really know if this number is realistic.
@ 26
Yelph,
I am starting to think that my text was very unclearly formulated, as some of you have misunderstood it.
In summary:
models have to be tested, but the MWP is the wrong test, as it does not discriminate between bad and good models until we have better knowledge about the external forcing.
Thus, the present discussion about the MWP is exciting but rather futile as far as models are concerned.
Marco:
We’re drifting off topic with Mark Serreze and the arctic, but I’ve made no false claims about him. Google Mark Serreze and Death Spiral. His “Death Spiral” quote appears regularly, accompanied by various predictions of when the arctic and/or North Pole will be ice free. He has also endorsed predictions of others:
2008: “Exclusive: Scientists warn that there may be no ice at North Pole this summer” http://www.independent.co.uk/environment/climate-change/exclusive-no-ice-at-the-north-pole-855406.html
2013: “Arctic summers ice-free 'by 2013'” http://news.bbc.co.uk/2/hi/7139797.stm Professor Wieslaw Maslowski predicts ice free arctic by 2013. In this article Mark Serreze says: “Wieslaw is a smart guy and it would not surprise me if his projections came out.”
2030: He continues (same article) discussing the possibility for an open Arctic ocean in summer months: "A few years ago, even I was thinking 2050, 2070, out beyond the year 2100, because that's what our models were telling us. But as we've seen, the models aren't fast enough right now; we are losing ice at a much more rapid rate. "My thinking on this is that 2030 is not an unreasonable date to be thinking of."
No one disputes arctic ice is declining. The question is why? Historical records show similar declines in the late 1800s / early 1900s, and in the 1930s / 1940s. Photographs taken during submarine voyages show the North Pole ice free in March of 1959 and May of 1987. If climatologists want to convince people that humans are causing “Death Spirals” and “Tipping Points”, they simply need to present solid scientific data (not models) that demonstrate human attribution.
As for the meaning of the word “contain”. Dictionary.com lists several definitions for “contain” including:
To keep under proper control; restrain: “He could not contain his amusement.”
To prevent the spread of: “to contain an epidemic.”
To prevent or limit the expansion, influence, success, or advance of a competitor, opposing force, natural phenomenon, etc.: “to contain the putative MWP”.
In Mann’s E-mail, note the context in which “contain” occurs with “putative” (meaning “alleged” or “suspect”). It is reasonable to interpret “try to ‘contain’ the ‘putative MWP” as “try to ‘limit the influence of’ the ‘alleged or suspect’ MWP. Again, I ask: Did Mann and Jones submit a paper that, by adopting a timeframe of 2K rather than 1K, presented and/or manipulated data to “limit the influence” of the “alleged or suspect” MWP?
Regarding statistics and paleoclimatology: You and Eduardo feel that “statisticians doing something they have no understanding of might have benefitted from involving actual paleoclimatologists". I completely agree, while pointing out that the reverse is equally true. If the authors of MBH 98, had consulted a professional statistician, there would be no “Hockey Stick” paleo-temperature reconstruction that can be reproduced by the staggering footsteps of a drunk.
Marco (continued)
As for the meaning of the word “contain”. Dictionary.com lists several definitions for “contain” including:
To keep under proper control; restrain: “He could not contain his amusement.”
To prevent the spread of: “to contain an epidemic.”
To prevent or limit the expansion, influence, success, or advance of a competitor, opposing force, natural phenomenon, etc.: “to contain the putative MWP”.
In Mann’s E-mail, note the context in which “contain” occurs with “putative” (meaning “alleged” or “suspect”). It is reasonable to interpret “try to ‘contain’ the ‘putative MWP” as “try to ‘limit the influence of’ the ‘alleged or suspect’ MWP. Again, I ask: Did Mann and Jones submit a paper that, by adopting a timeframe of 2K rather than 1K, presented and/or manipulated data to “limit the influence” of the “alleged or suspect” MWP?
Regarding statistics and paleoclimatology: You and Eduardo feel that “statisticians doing something they have no understanding of might have benefitted from involving actual paleoclimatologists". I completely agree, while pointing out that the reverse is equally true. If the authors of MBH 98, had consulted a professional statistician, there would be no “Hockey Stick” paleo-temperature reconstruction that can be reproduced by the staggering footsteps of a drunk.
Louis,
of course you can interpret the word 'contain' in many ways. But, honestly, reading the whole paragraph and being aware of the discussions in the climate conference, I have not doubt about its meaning:
'Phil and I have recently submitted a paper using about a dozen NH records that fit this category, and many of which are available nearly 2K back--I think that trying to adopt a timeframe of 2K, rather than the usual 1K, addresses a good earlier point that Peck made w/ regard to the memo, that it would be nice to try to "contain" the putative "MWP", even if we don't yet have a hemispheric mean reconstruction available that far back'
The paragraph is clearly about time frames and it is no secret that Mann didnt like the expression Medieval Warm Period. I think thats why he uses the qualifier 'putative'. This interpretation sounds to me at least as reasonable as yours
Louis, I think Eduardo addressed the MWP issue quite well already, so I won't get into that.
Mark Serreze indeed uses the word death spiral. He knows what is going on, his work is to analyse all data coming in about the arctic. Your claims are nothing more than that. There *is* historical data of the arctic, and none of it shows what you claim it shows. See e.g. here:
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seasonal.extent.1900-2007.jpg
I'm afraid the pictures on WUWT (I'm guessing that is where you get your claims about the submarines) don't prove anything. After all, the data analysis of NSIDC puts everything above 15% coverage of a certain area (25x25 km) as "100% covered" (hence the use of "extent", and not "area"). This leaves enormous holes. One would have hoped that after NCDC showing that the surface station pictures are not very good evidence, the Wattsians would have learned not to trust incidental information and pictures. No such luck, apparently...
Eduardo, perhaps it helps if you turn the sequence of sentences a bit around:
We do not know the magnitude and direction of the forcings during the MWP. Therefore, we cannot test whether models accurately describe the MWP, since they require those forcings as input values.
@Eduardo
I completely agree with you about the testing of models.
I just wanted to point out, that the cause of the warming of the last decades maybe the GHG's, but the simple correlation "GHG's -> Warming" is not a proof for this "theory" imho.
I also wanted to point out that the understanding of the natural climate cycles is important for our understanding of the climate and for the exact climate forecast.
Nonetheless a continious warming can be predicted without any complex models if the climate sensitivity of GHG's is what you think it is.
BUT this doesn't mean that this warming is a threat for humanity, biodiversity or whatever prophets tell us ... ;-)
Maybe I should explain this in German? I just want to explain exactly what "being skeptic" means for me. All that you write and explain is part of a scientific "consensus". Your scientific approach to this consensus is the best in my humble opinion.
What I write are my personal opinions and doubts. This differentiation is very important for me.
Best regards
Yeph
Marco, Marco, Marco...ye of little faith:
The USS Skate, photographed at the North Pole on St. Paddy's Day - March 17, 1959
http://en.wikipedia.org/wiki/USS_Skate_%28SSN-578%29
The 11th and 12th photos down show the USS Sea Devil, HMS Superb, and USS Billfish at the North Pole on May 18, 1987.
http://www.navsource.org/archives/08/08676.htm
Very nice these photos from submarines floating in open water right at the North Pole.
As far as I know (from colleagues of AWI) the North Pole itself has been several times ice-free. This in itself is nothing significant - there are all the time ice-free zones in the Artic sea ice cover - and cognant people found it amusing when the German BILD-Zeitung wrote (in the early 2000s or so) "Nordpol weg" (North Pole disapparead) (and Mojib Latif could not resist the temptation of commenting positively on this "story").
I guess the issue here is the overall coverage of Artic sea ice, and the reduction of this (spatially integrated) quantity is well documented by satellite images. If there is a interest, we could ask somebody from AWI for writing a short piece on this change. -- Hans
Hans, your comment:
"the North Pole itself has been several times ice-free. This in itself is nothing significant"
is absolutely correct. And no one disputes the recent decline in arctic sea ice coverage documented by satellite images. Alden Griffith has an excellent video on this subject at his website:
http://www.fool-me-once.com/2010/08/arctic-sea-ice-is-just-fine-rebounding.html.
However, my point to Marco (and everyone else) is that without solid scientific data (NOT models) that attributes the recent decline to something other than natural variation, no one should attach any more significance to the North Pole being ice free in 1956 or 1987 than in 2013, or 2040, or 2060. Current warming may well be due to the increase in anthropogenic CO2, but the North Pole surely experienced similar periods of warming and lack of ice during the Roman Warm Period and the MWP as well. That's why it is so important to understand the MWP and incorporate its causes into the climate models rather than to try and sweep it under the rug.
Louis,
the sea ice problem is a matter of Arctic sea ice distribution, whereas the North Pole is a specific location in the Artic. The variability is much larger at smaller locations, such as the vicinity of the North Pole, than in terms of the spatial average.
That we have reliable information about the change of sea ice extent during the MWP or Roman Times, is new to me.
In any case, this problem is just another "detection and attribution" issue, which we have discussed previously on this blog. The question is, as you Louis quite correctly point to , how large the level of "unforced" variability of change is. The question is not if we had similarly little sea ice, but if we had similar fast changes within very few decades.
I personally find the evidence provided by satellite coverage quite convincing; however, I can not with certainty disprove that we had never such changes in the past (i.e., that you are right), but I find such a hypothesis unplausible - in particular after we have a fully consistent "detection and attribution"-result for global mean air temperature (with a similar but weaker caveat).
-- Hans
Louis, yes, I am of little faith when I read your comments, and you managed to reduce it even further. You claimed "Historical records show similar declines in the late 1800s / early 1900s, and in the 1930s / 1940s." but provided no evidence. You then referred to photographs that showed an 'ice-free' North Pole, which in essence does not show anything other than that there were large gaps in the ice also earlier in history. But NOT that this was in any way similar to the current situation.
I'm also uncertain about your request to give you "solid scientific data (NOT models)". anything and everything we do is based on models. If you have multiple interacting factors, you will have to depend on a "model" that puts those factors together in an equation. for example, descriptions of the movement of the planets around the sun is based on a model. A model that fits the data. The same goes for GCMs. Of course, most GCMs are wrong about the arctic, but not in the direction some would think...
Marco,
I would agree with you. There are no solid data on sea ice coverage prior to the satelite age. There may be some proxies (I am not aware of any, but maybe ...).
But this lack of historical data does not solve our problem that we are facing a "detection and attribution" problem with an unertain estimate of past "unforced" variability. You can not prove that changes as presently have not happened before druing the Holocene. I do not believe that this was so, but I can not 100% exclude the possibility. So, if Louis prefers to believe otherwise, let him do it. But we should ask him to expect openly that his evidence is absent or at least subject to different interpretations.
When you use the term "model" you should be a bit careful, as this term goes with many different meaning. When our skeptical friends speak about models they usually refer to "climate models" of GCM type, i.e., maximum complexity models, which do not constitute knowledge but "only" an (engineering) experimental tool. What you referred to now was a conceptual model, meant to disentangle different drivers. (Peter Müller and I wrote a book on this issue - see Müller, P., and H. von Storch, 2004: Computer Modelling in Atmospheric and Oceanic Sciences - Building Knowledge. Springer Verlag Berlin - Heidelberg - New York, 304pp, ISN 1437-028X)
Marco,
I would agree with you. There are no solid data on sea ice coverage prior to the satelite age. There may be some proxies (I am not aware of any, but maybe ...).
But this lack of historical data does not solve our problem that we are facing a "detection and attribution" problem with an unertain estimate of past "unforced" variability. You can not prove that changes as presently have not happened before druing the Holocene. I do not believe that this was so, but I can not 100% exclude the possibility. So, if Louis prefers to believe otherwise, let him do it. But we should ask him to expect openly that his evidence is absent or at least subject to different interpretations.
When you use the term "model" you should be a bit careful, as this term goes with many different meaning. When our skeptical friends speak about models they usually refer to "climate models" of GCM type, i.e., maximum complexity models, which do not constitute knowledge but "only" an (engineering) experimental tool. What you referred to now was a conceptual model, meant to disentangle different drivers. (Peter Müller and I wrote a book on this issue - see Müller, P., and H. von Storch, 2004: Computer Modelling in Atmospheric and Oceanic Sciences - Building Knowledge. Springer Verlag Berlin - Heidelberg - New York, 304pp, ISN 1437-028X)
*hic!*
Well, there ARE actually proxy studies, cf. http://www.cgd.ucar.edu/oce/mholland/papers/Polyak_2010_historyofseaiceArctic.pdf
I'm not sure I follow you on the GCM versus solar system model. Planets orbiting the sun may be conceptual, but the calculations to determine the trajectory in space are not. We even have some who have argued the existence of another planet (#9, now that Pluto is only a planetoid) or even our sun having a 'dark' brother nearby based on the calculations of the various trajectories. Of course, that was mainly based on likely incorrect estimates of the mass of the outer planets...
Thanks, Marco. What do you think is the accuracy of the proxy data, and what would the time resolution be? Do the proxy-data discriminate between summer and winter coverage? Would they record short (decadal) intervals of summer ice-free conditions with which probability? - Hans
Hans, I'm afraid I will have to leave the answer to your questions open, and refer to the experts in the field. I could say what I *think*, but not having studied the issue in detail, I'd likely make too many mistakes.
All I can say is that the proxy record shows the same inverted hockeystick at the end as the last 30 years of the satellite record.
Same with me Marco. All what I wanted to say - usually these issues are really complex with many pitfalls. One other would be - is the coincidence of the "story" told by satellites and the proxies a matetr bof skill or is it because one has been trained on the other?
Maybe another readers comes forward, who knows more about this issue. - Hans
@Hans
"There are no solid data on sea ice coverage prior to the satelite age. There may be some proxies (I am not aware of any, but maybe ...)."
I think there some non-perfect proxies
http://www.scienceblogs.de/primaklima/2010/08/arktisches-meereis-eine-paleoperspektive-i.php
http://www.scienceblogs.de/primaklima/2010/08/arktisches-meereis-eine-paleoperspektive-ii.php
and at least one who is pretty good, called IP25.
Ordinarily, I am content to just read conversations between scientists but this time I'd like to have a say.
@eduardo #33
of course you can interpret the word 'contain' in many ways. But, honestly, reading the whole paragraph and being aware of the discussions in the climate conference, I have not doubt about its meaning:
You can interpret something in many ways when it is a work of art or literature. Precision must mean something for scientists. Curiously, if it were a law court that had to interpret the meaning of "contain" it would do precisely what Louis Hooffstetter did at comment #31; that is, by looking at the context and by consulting a dictionary. A judge would never dismiss the case by simply saying "the word can be interpreted in many ways". Why would a scientist do that?
Since context is so important why not look at the wider context. Here are two further examples that suggest certain climatologists wanted to suppress the WMP because it contradicted the intended narrative.
1- Presumably, the same [Over]Peck saying "we have to get rid of MWP".
http://azstarnet.com/news/science/environment/article_e5078cae-6655-5139-aa6c-3f7f33a670a8.html
and,
2- Briffa in a candid mode (since nobody will be reading their emails, eh!):
"I know there is pressure to present a nice tidy story as regards ‘apparent unprecedented warming in a thousand years or more in the proxy data’ but in reality the situation is not quite so simple. We don’t have a lot of proxies that come right up to date and those that do (at least a significant number of tree proxies ) some unexpected changes in response that do not match the recent warming. I do not think it wise that this issue be ignored in the chapter.
For the record, I do believe that the proxy data do show unusually warm conditions in recent decades. I am not sure that this unusual warming is so clear in the summer responsive data. I believe that the recent warmth was probably matched about 1000 years ago."
http://www.eastangliaemails.com/emails.php?eid=136
No, please, nobody has to be a climatologist regularly publishing in reputable peer reviewed journals to understand that much.
@sHx
Keith Briffa even points out in his e-mail:
"I do not believe that global
>mean annual temperatures have simply cooled progressively over thousands of
>years as Mike appears to and I contend that that there is strong evidence for major changes in climate over the Holocene (not Milankovich) that require explanation and that could represent part of the current or future background variability of our climate."
http://www.eastangliaemails.com/emails.php?eid=136&filename=938018124.txt
Would he ever have dared to write these reflections anonymously at "realclimate" or "Primaklima" he would have been censored, banned, dismantled, called a denier. ;-)
It might even be that dangerous skepticism like this is against the Geneva Convention? ;-)
Well, after all, that's climate science. Don't complain stupid!
Yeph
Would Keith Briffa have expressed his thoughts anonymously on the usual american and german alarmist climate blogs, he would have been dismantled, banned, called a denier.
K. BRIFFA: "For the record, I believe that the recent warmth was probably matched about 1000 years ago... and that there is strong evidence for major changes in climate over the Holocene that require explanation and that could represent part of the current or future background variability of our climate."
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