“…the committee finds it plausible that the Northern Hemisphere was warmer during the last few decades of the 20th century than during any comparable period over the preceding millennium.[emphasis added]” Plausible? That’s not a very strong word. In IPCC-probability terms it must rank well below ‘likely’ (66-90% probable) and I guess even below ‘medium likelihood’ (33-66% probable). Hardly a ringing endorsement – which I think is a shame, because as the posting says, the basic conclusion of unprecedented global warming during the millennium is supported by a whole raft of other studies. Again, my feeling is that there’s a lot more politics here than science.
[Response:According to the statements in the press conference, they chose 'plausible' becuase they didn't want to quantify likelihood a la IPCC, but I would read it as equivalent to 'likely', which is of course what MBH said all along. - gavin]
So, if I read the press release accurately, they say that there was a significant cool period (LIA), and there is high confidence that recent temperatures are higher than that period. They also say there was a warmer period at approx 1000 AD, but uncertainties in the reconstructions make it unclear if that period was warmer than today or not.
The part which we have high confidence in appears to say little about todays climate in a long-term sense, but your comentary suggests that this is a significant finding – and dismisses the uncertainty about the difference between 1000 AD and 2000 AD temperatures.
Is not the latter the more significant data point? The press release does emphasise that further research on this datum seems valuable..
[Response: I don't think you read it correctly. The claim is that we know more about the situation over the last 400 years than for the previous period (which is obvious), but that only before 900 AD is the data basically useless for the NH mean. From the report and press conference, it is clear that they are saying that it is indeed likely that it is warmer now than 1000 years ago, but that is not as strong a statement as you can make for the last 400 years. Reducing the uncertainties further would of course be useful. Who implied that it wouldn't be? - gavin]
Comment by Sean Houlihane — 22 Jun 2006 @ 11:55 AM
“obtain additional, improved, and updated paleoclimate proxies of past climate that can aid in decreasing the existing uncertainties”
That’s an interesting one – ClimateAudit has been calling for “bring the proxies up to date” for some time. It’s nice to see that both CA and RC share some common ground!
I’d add to it that the sharing of data and methods would also be helpful. The NAS report does touch upon that issue somewhat, but not enough.
Re:#1 (gavin): “According to the statements in the press conference, they chose ‘plausible’ becuase they didn’t want to quantify likelihood a la IPCC, but I would read it as equivalent to ‘likely’, which is of course what MBH said all along.”
The sentences following the quote from #1 (NAS report page 4) suggest they weren’t equating the two:
The substantial uncertainties currently present in the quantitative assessment of large-scale surface temperature changes prior to about A.D. 1600 lower our confidence in this conclusion compared to the high level of confidence we placed in the Little Ice Age cooling and 20th century warming. Even less confidence can be placed in the original conclusions by Mann et al. (1999) that “the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millenium.”
So their use of “plausible” seems to contain a lot more doubt than the “likely” used in the MBH sense. But maybe it’s just all semantics.
[Response: It's unfortunate that the committee did it like this. IPCC authors have spent a lot of time moving towards more precise language when communicating the strength of the belief of expert judgments, and I'd been under the impression that the bulk of the community was following this trend. However, the reversion to poorly defined ambigious language in this report seems to belie that. However, in the case of the 'late 20th C warmer that any period over the millennium' claim, the panel specifically gave roughly 2:1 odds in favour of the statement being true in the press conference and that translates directly to the IPCC 'likely' designation. - gavin]
Comment by Michael Jankowski — 22 Jun 2006 @ 1:17 PM
I downloaded a free copy. So, it is ‘plausible’ that the MWP was not as warm as the current warm period. This is one of those reports with something for everyone – criticism of methods and data, plus a rather half-baked call for data release:
“Our view is that all research benefits from full and open access to published datasets and that a clear explanation of analytical methods is mandatory. Peers should have access to the information needed to reproduce published results, so that increased confidence in the outcome of the study can be generated inside and outside the scientific community. Other committees and organizations have produced an extensive body of literature on the importance of open access to scientific data and on the related guidelines for data archiving and data access (e.g., NRC 1995).”……
Obviously there was a higher confidence in the less contentious LIA, than the MWP, so I think the controversy over the MWP is set to continue, particularly as most of the criticisms of MBH were accepted by the panel. Overall I feel, the NAS panel failed to ‘grasp the nettle,’ but have moved the debate forward.
I’m just an ordinary non-scientist trying to sort all this stuff out. This site has been invaluable in helping me understand the science. I read the press release and then the conclusions section of the report. I found the form of the conclusions both confusing and disappointing. The report never explains what it means by “high level of confidence”, “less confident” or “plausible.” Listening to the press conference, I understand that the first term means something like 90-95% confidence, the second means 2:1 odds, and the third means “we can’t quantify it at all.” I dont’ pretend to understand all the technical details in the report, but is it too much for us lay folks to expect some degree of precision and clarity in the conclusions of a report of this type?
So why is there also global warming on Mars?
Why does this not address global overpopulation of say the billion plus Chinese, Indians, Muslims? At what population (human and animal) level does the earth need to be reduced to based on this study?
Why does this not address the global warming that has occurred since the last ice age, which I find ice ages more of a problem then global warming. There have been 60 glacial advances and retreats in the last 2 million years as noted in the link below. Why does this not address eccentricity of the earth’s orbit, the tilt of the earth’s axis, and the precession of the equinoxes? Or even plate tectonics, continental uplift, reduction of CO2, and changes in the earth’s orbit? All contributors to climate changes.
There is another MWP proxy – vineyards – The History of the Wine Trade in England by A L Simon, 1906:
“Towards the middle of the twelfth century, we are told by William of Malmesbury, vineyards were no longer confined to a few places, but extended over large tracts of country, producing a great quantity of excellent wine: “You may behold,” he observes, when describing the fertility of the vale at Gloucester, “the paths and public roads fenced with apple trees, which are not planted by the hand of man but grow spontaneously. …”
“This district, too, exhibits a greater number of vineyards than any other county in England, yielding abundant crops and of superior quality; nor are the wines made here by any means harsh or ungrateful to the palate, for, in point of sweetness, they may almost bear comparison with the growths of France.”
In the reign of Stephen, there is a mention, in 1140, of two vineyards at Mealdon, and, in the same year, the Sheriffs of Northamptonshire and Leicestershire were allowed, in their accounts,”for the livery of the King’s vine-dresser at Rockingham, and for necessaries for the vineyards.” There is also an Act of this monarch, which is undated, but which from internal evidence may be safely attributed to A.D. 1143, ordering that restoration should be made to Holy Trinity Priory, London, of its land in Smithfield, which Geoffrey, Earl of Essex, had seized and converted into a vineyard.
In the fourth year of the reign of Henry II, payments appear to have been made and charged to the Royal Exchequer for the keeper of the vineyard, who received on one occasion sixty shillings and tenpence, as well as for the expenses of the said royal vineyard. Later on, during the same reign, in 1159, 1162, 1165, 1168, 1174 and 1175, there are frequent mentions of the royal vineyards at Windsor, Purley, Stoke, Cistelet, and in Herefordshire and Huntingdonshire; in 1165, there is an entry of a vineyard at Tenham, the produce of which seems to have been devoted to the sick at the infirmary.
During the first year of the reign of King Richard, there are three mentions of vineyards, and others occur during the reigns of Henry III., at Lincoln, Bath and Hereford, of Edward II at York, and as late as that of Richard II., in 1385 and 1392, at Windsor II and Kennington. At the beginning of Edward I’s reign, in 1276, Cantilupe, Bishop of Hereford, either planted or renewed the vine-yard which his pupil and successor, Swinfield, had at Ledbury. In 1289, the Bishop made seven casks (dolia) of white wine and nearly one of verjuice at Ledbury. This wine was chiefly transferred to Bosbury, another estate of the Bishop, and it was mostly drunk during the ensuing summer.
Ledbury must have been particularly well suited for the culture of the grape vine, since as late as the end of the seventeenth century,” Ah! – the LIA was bad news for wine production in England, but it is booming again:
[Response: By that proxy it is clear that it is warmer now since there is more wine produced today than there was 1000 years ago. Still not very good to drink (though I hear there are a few exceptions). - gavin]
“Response: Absolutely certainty exists only in mathematics, not the real world. -gavin”
As an applied math major in my undergrad days, I am deeply offended! Plenty of math is “real world!” I think this response should have been censored and the responder warned! :)
I can say with “absolute certainty” that it’s warmer today where I live (90s) than it was back in December when I was getting snowed on.
Comment by Michael Jankowski — 22 Jun 2006 @ 4:39 PM
RE: #11 – I can say with certainty that after one of the crummiest Springs in recent memory where I’m at, the current outbreak of a dry, compressive interior SW US airmass is really nice. I can also say with certainty that the inevitable coastal stratus and seabreeze that always follow with a vengence will have me breaking out my sweater by some time next week. :)
Also, for what it’s worth, in this neck of the woods, 1998 was a record cold year, especially in the Fall – snowed down to sea level of the last day of Fall that year. For us, it was 2000 that was the hot one – an interior outbreak hit just right during high sun angle in late May and early June, and it hit 115 F at my place – I have no AC (as is true of 90% of the folks in my immediate locale). Not fun? …. for some actual fun via Google, looking up oddities such as Santa Anas, Sundowners and Diablos, and their ability to transform normally mild coastal areas into a weather pattern that is typically Iraqi, for a couple of days, can be quite interesting. Variation makes life interesting? Perhaps … so long as I can have a cold Margarita!
The Times has a story up about the report already.
While its not a bad piece overall, the part near the end where they cite since-discredited critiques of the original Mann et al. article is rather dissapointing, given that the only reported rebuttle is that the Mann et al. paper made numerous caveats regarding uncertainties.
Comment by Zeke Hausfather — 22 Jun 2006 @ 6:03 PM
I am having trouble reconciling two points of the report as summarized in an AP article (I am assuming they got the facts right.) Over the last 2000 years, give or take, the earth probably has experienced significant global temperature swings, both hotter and cooler, yet the levels of CO2 and methane have stayed fairly constant over the last 12,000 years, except for the most recent history. This alone would suggest that within the ranges over the last couple of thousand years CO2 and methane levels have had little impact on global temperature. What am I missing?
[Response: Here are a few things you are missing. First, it's simply not true that there are documented temperature swings in the past 10,000 years that are clearly comparable on the warm side to what has been seen in recent times. It is only for the past 1000 years that one can tentatively estimate hemispheric averages, and there it is increasingly clear that the recent warming is unusual. With regard to earlier times, the main problem is that it is currently not possible to reliably estimate global or hemispheric averages from the proxy data, so it is not possible to say if warming in the earlier Holocene were as widespread as the current warming. That goes especially for the "climatic optimum" in the early Holocene, which is almost certainly due to the Earth's orbital fluctuations --specifically the precessional cycle. There is some global mean signal from the precessional forcing, but theory says the warming should be mostly regional and seasonal -- proxy data is largely silent on how global the real warming was at the time. The second thing you are missing is that there are actually multiple causes of climate change, and the existence of other climate forcings does not in any way negate the importance of CO2. Other things that have varied during the Holocene include volcanic activity, solar activity, and the precessional cycle. Just because some of these things can also cause climate change doesn't mean that CO2 can't. If you can die of cancer, does that mean you can't die of a heart attack? The final thing you neglect is that currently we are only comparing the relatively modest warming so far with the warming of the past several thousand years. However, so far we haven't quite gotten to 400ppm CO2, but we'll eventually go to 700 or more without controls. We haven't even seen the full warming effects of that 400ppm yet, because it takes time for the ocean to warm up. So, the striking thing is that it has already gotten to the point that the recent warming stands out from the natural variability of the past thousand years or more , despite the fact that so far we've only experienced the barest beginnings of the warming. That's not just striking. It ought to be alarming. --raypierre]
In the interest of the public, is it possible for real climate and climate audit to run a parallel analysis of the NAS report. This may not resolve the debate but at least it will give us a more balanced approach than to go through the comments in each of the web sites.
I doubt if comparing the wine production in UK 1000 years ago and today would be a good proxy that the climate is warmer today. The volume of wine produced is a function of a large number of natural and human factors other than climate. One major factor is the preference to wine and acloholic beverages as well as the human population.
Re #14: What you are missing is correct logic. If one variable has remained constant (CO2 levels) while a second (temperature) has varied, you can’t learn anything about the sensitivity of the second to variations in the first…because the 1st hasn’t varied. It could be that temperature is exquisitely sensitive to CO2…In fact, it could even be that the very small changes in CO2 drove those supposed significant temperature swings. [However, in reality, your premises are questionable too. First, while there have been some swings in temperature, the evidence suggests that they have not been that strong. And, while CO2 has been fairly constant, it has not been completely so.]
Re #10: Maybe I am being ignorant here and someone with more knowledge of wines can clue me in but I have never understood how wine-growing in England is much of a proxy. We grow wine here in upstate New York and I can bet that at least our winter climate is considerably colder than it has ever been in England even during the LIA. I also imagine our growing season is shorter. (Or, is it the summer climate that matters more?)
[Response: I never much liked wine-growing as a proxy either; it's too confounded by extraneous factors. For example, changes in the demand for liturgical wine, owing to changing religious practices, can alter the profitability of growing local low-quality wine. --raypierre]
Jason, what you are missing is the difference between what is possible and what is probable. Prior to 400 years ago, large swings in temperature cannot be ruled out, because (to grossly simplify) the error bars are too big for the older reconstructions. This does not mean that large changes did occur during that time period. It just means that today’s body of knowledge is not sufficient to exclude large changes. Wheras for the last 400 years, we have enough data to say with some measure of confidence that variations were relatively minor.
Are grapes a proxy for growing season, winter minimum temperatures, or socioeconomic/religious/political factors? How does one deconvolve 17th century cooling from Cromwell’s puritanism?
The NAS panelists said that the principal component method was incorrectly used in that context. The climate before 1600 was almost entirely uncertain and even the level of confidence can’t be quantified. The MBH results were oversold by the community. The divergence problem exists and does not want to go away. The uncertainty and natural variations are larger than thought previously.
Are the NAS members wrong? Are all of them paid by ExxonMobil as I believe?
[Response: Read the report itself, not Lubos Motl's blog. Motl's take on the report has almost no resemblance to what is in it. What do you expect from somebody who describes himself as a "reactionary physicist"? Unfortunately, some un-necessarily ambiguous wording at the press conference makes it all too easy for people like Motl to misrepresent the contents. --raypierre]
We are getting off topic again. In mathematics you can prove something and be certain it is correct, subject of course to possible mistakes in the proof, in the sense that the conclusion follows logically from the assumptions. A model for this is Euclidean geometry, which is as true now as it was over 2000 years ago. But as a statement about the actual geomtry of the world, we know it is false. In science, you are more concerned with conforming to observation, and you may even in some cases accept arguments which don’t stand up to the requirements of mathematical rigor, as long as they make accurate predictions.. (You sometimes do that also in applied mathematics.) I believe that is the distinction that Gavin was trying to make. You can’t expect the kind of certainty you find in pure mathematics in any science, particularly a messy one like climatology where you have to bring together many different kinds of evidence. That doesn’t of course mean that anything goes. There are rather severe restrictions on what can pass as an acceptable argument. But it is not an axiomatic system.
I have just begun to take a look at the scientific debate on global warming. I am no climatologist but rather an individual with a doctorate in chemistry. What I find interesting is the focus by everyone on the term “warming” and all this effort at looking at historical temperatures. The relevant parameter to me is the amount of heat our global system has at any point in time. If you add heat to an ice cube, the temperature of the ice cube does not change. The heat is used to melt the ice and during this process of melting the temperature stays constant. This temperature is called the melting point or freezing point of the substance – in this case water. Once the ice has melted, the temperature of the water will rise depending on the amount of heat entering the system, the heat capacity of water, etc. So, if the earth retains more heat because of rising greenhouse gases, water temperatures may not rise signifcantly because the heat is used in melting ice. If all the ice melts, water temperatures will rise in accordance with the amoount of heat being absorbed and stored by the system (oceans, land, and air). From what I have seen, we have lost a fair amount of glacial and perhaps polar ice over the last thirty years or so. This means more to me than a debatable one degree rise in average ocean temperature over the last one hundred years. If the ice goes, temperature rise will be self evident. Perhaps some of the scientific committees should add a few physical chemists to their panel discussions.
“The National Academy scientists concluded that the Mann-Bradley-Hughes research from the late 1990s was “likely” to be true, said John “Mike” Wallace, an atmospheric sciences professor at the University of Washington and a panel member. The conclusions from the ’90s research “are very close to being right” and are supported by even more recent data, Wallace said.” http://www.newsone.ca/hinesbergjournal/stories/index.php?action=fullnews&id=197149
No more funding, no more research needed. Just ask Wallace since he’s the one knowing right from wrong.
[Response: Mike Wallace is one of the clearest thinkers in the field, a National Academy member and author of dozens of highly influential papers. Respect for his point of view (though not mandatory) is highly recommended. He does not make such pronouncements lightly. -gavin]
Comment by Wolfgang Flamme — 23 Jun 2006 @ 2:56 AM
Please don’t take my ‘vineyard proxy’ post too seriously, it was meant to be light-hearted, but it does indicate that Ledbury was particularly kind to the grape vine from the 13th century onwards until the end of the 17th century, which would coincide with the ‘maunder minimum.’ The current UK warm period peaked in 1997 (Armagh Observatory), and 1999 (Hadley CET)in our two long temperature series. I don’t see 2006 beating those annual average temperatures, but we’ll have to wait and see what happens in future years. Breaking the 11C barrier for an annual average would certainly be instrumentally unprecedented in the UK.
The UK now has some 400 vinyards but as you can appreciate the best ones lie in the deep south of the UK and have indeed WON awards especially in the sparkling wine categories. I have visited many of them and indeed the growing season appears to be around 1 month longer than it was in the year 1900. Indeed so popular has English Fizz become that the californians and the French Champagne makers are looking at buying land in the south of the UK in order to grow grapes and makes good fizz/bubbly.
Anyway onto the subject at hand. Fred Pearce in his book “the Last generation” devotes a chapter to this hockey stick proxy subject and states that the proxy data used has been suject to reanalysis and has been declared to be sufficiently (statisticlly) accurate that I thought that the subject has been laid to rest.
Indeed Realclimate has also made comment on this subject in relation to the climate skeptics and have also stated that independent reanalysis of the statistical data shows it to be accurate and correct within normal error thresholds.
Indeed the book even quotes Gavin at one point so I guess you guys at real climate know Fred Pearce?
I just ran across a paper from 1991 which seems to make a devastatingly impressive case that Solar activity has caused recent global warming. Amazingly, it’s not by Soon and Baliunas. Can anyone take a look at this and tell me where the mistakes, if any, lie? I assume this has since been discredited but I don’t know the details.
[Response: Devastating? Try made up. The figure only looks so good because the smoothing they use changes as you go along. With 15 years more data and uniform data treatment the correlation disappears. I would judge this the best example of researchers fooling themselves into finding what they wanted to find before they started. Read Damon and Laut (2004) for the details (and other examples). - gavin]
Perhaps a physical chemist just beginning to study the subject should do some more research before giving advice. A good place to start would be the IPCC reports, but much has happened since the last report. There are variety of factors which lead to delays in warming, one of which is the one he points to, and those who do research in the area, including, the Real Climate scientists are well aware of them.
You have a reasonable point here and it is not one nobody else has thought of. There is however good reason to focus on surface temperature and that is the simple fact that the surface is where we all live. It is also where the vast majorty of the biosphere exists if we extend it into the the upper ocean. You could also fundamentally alter the system simply by redistrubuting the heat, no net change required. So a total heat content metric is a good one, but I would argue that the change in surface temperature is more appropriate for policy discussion and impact assessments.
[Response: Indeed it's a reasonable point, and indeed it's already incorporated into calculations of climate change, though not necessarily into public communication about the results. The energy needed to melt ice, whether sea ice or land ice, is part of the thermal inertia of the system that slows the approach to equilibrium. The major term in the thermal inertia is the time required to warm the deeper ocean. So, properly speaking, the effect of added greenhouse gases shows up partly as warming and partly as melting, and that warming shows up partly as surface warming and partly as deep ocean warming -- until the system reaches equilibrium. With regard to the suggestion in the original post, the basic calculations on the physics of planetary climate have rested on energy balance ever since Fourier's 1827 paper. --raypierre]
The fact is that exchange rate of heat are more a limitation at this scale than at your drinking glass scale : so your interresting naive analysis of why temperature don’t increase so much is maybe not very relevant because of that.
However, so far we haven’t quite gotten to 400ppm CO2, but we’ll eventually go to 700 or more without controls. We haven’t even seen the full warming effects of that 400ppm yet, because it takes time for the ocean to warm up. So, the striking thing is that it has already gotten to the point that the recent warming stands out from the natural variability of the past thousand years or more, despite the fact that so far we’ve only experienced the barest beginnings of the warming. That’s not just striking. It ought to be alarming.
It is not only alarming, it is outright terrifying. And that, along with the self-reinforcing feedbacks that the “barest beginnings of the warming” are already apparently triggering — increased heat absorption by ice-free arctic oceans, release of carbon and methane from warming soils, etc. — is what makes me skeptical of the view expressed by Al Gore and others that we still have some ten years in which to prevent irreversible, catastrophic, runaway warming, and not only “climate change” but a global ecological collapse. I find it hard to see how we have not already passed the point of no return.
I do not understand why it is not rational to question models and trends which are being used to predict unkown future conditions but it remains perfectly acceptable to dismiss past, 10,000 year B.P., proxy data which may conflict with present models.
I realize proxy data is limited at this time, particulary for the southern hemisphere, but the existing data should not be ignored just to make recent history models stand up. I welcome the day when sufficient data has been collected so a confident model can be created which, when fed data up to a past point, can accurately predict past temperatures.
[Response: What is being ignored? And what do you feel is inconsistent with the models? Simulations for mid-Holocene conditions driven mainly by orbital forcing do a good job of matching the obs. - gavin]
Your response supports my point. Certain simulations based on certain conditions match certain observations but a “golden rule” has not yet been created. The models “driven mainly by orbital forcing” are not the models currently being touted as future predictors of climate (in most cases solar influence is being ruled inconsequential for current conditions). So far, in order to match accepted historic and prehistoric observations something has to be ignored.
The stakes are high for supporting either side of the global warming issue. Regardless of the point you are arguing it is irresponsible to dismiss alternate views when there are still so many unknowns. Remember it was once “the scientific consensus” the sun orbited the earth, the world was flat, the sound barrier was unbreakable…
I agree with Williams response above – fund more research for creating more accurate models. Who knows, we may find we should be heading colder and the only thing maintaining temperature is Co2.
[Response: You have it completely wrong. The state-of-the-art models used for the 20th Century and future simulations are exactly the same ones that are being tested using paleo-climate conditions. Look up PMIP II for instance. At different times in the past different things were going on, and some are more important on some timescales than others. There is no 'golden rule'! Instead there is a complex system that can be pushed around by multiple different forces - including orbital variations, solar variability, the opening of ocean gateways, volcanoes and, yes, greenhouse gases. For the current situation: orbital forcing is very small and so doesn't play much of a role, solar variation is, as far as we can tell, a minor player, GHGs are a big factor, and so are aerosols, ozone, volcanoes, land use are all also minor but necessary. Why do you think things are being ignored? All of these things are tested to see if they are important, and the ones that are, are kept in. - gavin]
Paul Biggs need not apologize, Pfister’s record of monthly precipitation in Central Europe 1525-1979 does include information from diaries recording the time when grape vines blossemed and the grapes were ripe.
Your use of the absolute, completely, emphasizes my argument that no side should be closed and imflamatory. Ignore my use of term “golden rule” and acknowledge YES there is a mathematical equivalent for all the complex factors driving climate. An accurate model has just not yet been created. Your statement “All of these things are tested to see if they are important, and the ones that are, are kept in.” implies some things are left out. All influences, if found to be important at any time, have the potential to be important in the future. There are way to many unkown interactions in the complex system to leave out certain influences. It should be everyones goal to keep updating and improving models regardless of the findings. My concern is the tendancy of those with extreme support of current global warming understanding as an absolute to villanize others with legitimate questions – realizing there are those types on both sides but pro warming has the stage right now.
I agree there is currently work being done to make a more comprehensive model which address past and present conditions in order to accurately predict future changes but disagree there is a working model with published results clearly matching early and current observations. It is a frustrating data search when the vast majority of supporting information focuses on the last 1000 years and contrary information focuses on the paleo. I, like many others, am only asking for a link before jumping on the bandwagon of industrial reform. With proper support and open minded researchers (or at least the teaming of opposites) to tackle the endeavor this should not substantially delay any needed social change and could actually result in faster change if universally supported.
[Response: Oh, please.... If you would get off your high horse for a second and you would see that testing against paleo-data and putting in of new physics is what we actually do all the time (check out my own publication list for instance - you'll find solar and volcanic and mid-Holocene and LGM and PETM and Cretaceous...). - gavin]
An accurate model has just not yet been created. Your statement “All of these things are tested to see if they are important, and the ones that are, are kept in.” implies some things are left out. All influences, if found to be important at any time, have the potential to be important in the future.
If rational simplifications of mathematical models disturb you so, may I humbly suggest you never step foot upon a Boeing 787?
Thanks for the personal attack. Models are being tested, putting in and taking out of factors and many are good at matching certain timescales but nothing has been found to model accurately accross all timescales with known information. Yet many are taking data produced and circulating it as fact when even the persons generating the data referencing probabilities. All I’m asking is the same effort be put into research as is currently put into marketing certain findings and suggested responses.
Re #36 — there is the “Millenium Project” now that will have various modelling groups do the last millenium. Most groups do hindcasts over a period ranging from 50 to a few hundred years (i.e. covered by the “high probability MBH98 area” and HadCRU etc). For example my own project is currently doing a 1920-2000 hindcast and a 2000-2080 forecast in a large ensemble using the HadCM3 model, to quantify uncertainties in the model, try a large range of parameters etc. You really need to look at the actual literature & work done rather than jump to false conclusions.
Simplifications are fine if they return results that match observed occurences – and not just for certain conditions or timeframes. Boeing models work just as well at 500 feet as they do at 30,000 feet, over all temperature ranges and all forces – if they didn’t planes would fall out of the sky. Accurate models (even simplified) provide accurate results. All I ask is the same be applied for climate research. Thanks for the comparison.
All I ask is the same be applied for climate research.
And your posts make it clear you have no basis for assuming they don’t, given your lack of knowledge as to what’s being done. It appears that you’re one of those who assume the models aren’t accurate because you don’t like the implications of the results.
>…is what makes me skeptical of the view expressed by Al Gore and others that we still have some ten years in which to prevent irreversible, catastrophic, runaway warming, and not only “climate change” but a global ecological collapse. I find it hard to see how we have not already passed the point of no return.
32 is a very important point to reply to. So far when I encounter it I refer people to the following:
(3) Re: 40. Tom McKissic, why don’t you state what you know about how Newton’s theory of gravitation is applied to the solar system, so it can be illustrated how the scientific method is identical to this on the climate, with additional further complexities.
You will note that Hawking gives no reason for thinking this could happen. Global warming is bad – but not infinitely bad. When you start talking about stuff like “250 degrees centigrade and raining sulfuric acid” you need to explain; if simple assertion was enough, then Hawkng could go further and assert that global warming will
>Go Down Angel, Consume the flood
>Snuff out the sun, turn the moon the blood
>Go Down Angel shut the door
>Time has been, shan’t be no more
RE: #43, Gar, I am also skeptical of the view of Al Gore that we still have some ten years in which to prevent……
For one, I see measured global CO2 emissions increasing about a billion tons 2003 to 2005 — about 2 percent annual growth rate. Carry that out to 2015 and we see global CO2 emissions at 34.242 billion tons or a 25 percent increase from 2005 total.
In these ten years China and India will continue investing in conventional power generation equipment and vehicles. There is nothing else commercially available to steer the growth projection down….and to those quick to offer solar panels, wind turbines, hybrid vehicles as their alternative to the India-China markets, I say bring back the purchase orders and I’ll listen to your challenge of my pessimistic view.
Finally, the oceans, ice and biosphere already affected by the current 381 ppm MLO CO2 concentration increasing at 2.5 to 3 ppm/yr over the coming decade will have to accommodate between 25 and 30 ppm more CO2 in 2015. And, that (only the measure of fossil fuel consumption) is not accounting for the fact, as some predict, the Northern Passage may be ice free by 2015 and thus, further loss of Arctic ice albedo.
Yes, the public has to believe there is time to turn back the big energy knob before it takes us to a point of no return.
But, those who devote their training and expertise to understanding climate change have an obligation to also challenge policy makers and social scientists to consider it is time to consider what to do in the event of worst case (runaway climate change driven by positive feedback of CO2 and methane).
We, nations in the North and South, will need guidance to determine what will be needed to adapt to warmer, dryer climates and particularly those providing grain for the world. How about a serious discussion about lead times to develop modified crops capable of withstanding much harsher growing conditions in drought-stressed North America and the Ganges Delta.
What measures must we now begin to apply to adapt (and we will adapt, if only by cranking up our air conditioner) to short-term increasingly unpredictable weather patterns and long-term breakdown in civil structures? It may not be as stimulating as discussing use of tree-ring proxies but it is valid and essential nonetheless.
Comment by John L. McCormick — 24 Jun 2006 @ 5:09 PM
“A reading of today’s NY Times on the NAS climate report demonstrates clearly that Inhofe, Barton, and their familiars have decided to continue to focus on the Mann paper, as if nothing else has happened since. This is a political decision, not a scientific one.
The next and most interesting question would be how the NY Times reporters decided upon this emphasis. Is this from a press release from the contrarians? Will they please explain themselves?”
My reading of this piece is that they were explaining the background of the controversy over Mann et al, and the flap caused by Barton some months ago when he began to harass some government-employed climatologists.
It’s perfectly reasonable, in fact necessary, for the Times to report this background material. The NAS report was commissioned because of Barton’s committee’s actions. Commissioned by another committee whose Republican chair’s tired of Barton an Inhoue’s (is there any polite way of saying this?) lies.
“In these ten years China and India will continue investing in conventional power generation equipment and vehicles. There is nothing else commercially available to steer the growth projection down….and to those quick to offer solar panels, wind turbines, hybrid vehicles as their alternative to the India-China markets, I say bring back the purchase orders and I’ll listen to your challenge of my pessimistic view….”
Here’s a recent comment about China’s development.
Jun. 10, 2006 – Philadelphia Inquirer
China’s going solar
By Tim Johnson
Thriving firms that manufacture low-priced solar water heaters have helped build the world’s largest market for the rooftop devices.
Between 30 million and 40 million families have solar water heaters on their rooftops, allowing nearly 200 million people to enjoy hot showers and use warm water to wash clothes and dishes. Explosive growth is forecast for years to come, slightly slowing China’s surging appetite for conventional energy.
In Shandong province, which juts into the Yellow Sea, and in other rural areas of China, millions of rooftops hold the sloping panels of vacuum-tube heat collectors. The solar collectors cost from $160 to $750 for high-end models. In rural areas, the solar heaters are becoming standard appliances, like gas stoves. Those without them feel left behind.
The Chinese have embarked on a path using evacuated tube hot water collectors. These are very efficient, much more so than the flat plate collectors built in the 1970′s and 1980′s. As I recall, this idea was known back then, but it was thought to be too expensive to build. But, the Chinese are doing it. How long before Home Depot and Lowes, etc, are selling these? Or maybe your neighborhood Mal-Wart will jump on the band wagon too? We can only hope it’s not too late.
Re: 45. Now Gar you know darn well that 250 degrees centigrade and raining sulfuric acid may be “very” bad, or maybe “really really” bad, but there is just no way in hell that anything can be “infinitely” bad! That is a scientific impossibility! And you know darned well that sulfuric acid is in woefully short supply in U.S industry, and about half the U.S. Senate will probably get a piece of the action! So I’m not going to argue with you! And I’m definitely not going to argue with Stephen Hawking! Do I look like I want my ass handed to me? You go argue with Stephen Hawking!
Stephen McIntyre told BBC News that he felt the report had upheld “virtually all of our technical criticisms of MBH and did not reject or refute any direct points that we made.”
What did those technical criticisms amount to, in terms of altering the key findings of proxy reconstructions of past climate? Not much. The NAS commission backs the key findings of the original study. The report says it has very high confidence that the last few decades of the 20th Century were warmer than any comparable period in the last 400 years, and “plausibly” in the last 1,000 years. The “alarming” part of the hockey stick graph, the sharp upward spike in the late 20th century compared to the last 4 centuries, is vindicated with a high degree of certainty.
McIntyreâ��s technical criticisms of MBH 98 have provided cover for an avalanche of irresponsible attacks on the credibility of climate scientists themselves. Noisy complaints abound that the “hockey stick is broken”, MBH 98 is “rubbish”, the hockey stick is “religion, not science”, or “politics, not science”, a “scientific fraud”, or merely “alarmist scare tactics” by wild-eyed fanatics bent on extorting lucrative grant funding from government bureaucracies.
The idea is widespread that attacking the credibility of this graph undermines the scientific foundation of the AGW theory. This report repudiates, once again, this flawed reasoning. But in the minds of the public the hockey stick is about global warming, not arcane statistical technicalities. The scientific credibility of human caused global warming remains intact. The NAS report concludes that the hockey stick graph is credible, legitimate science, not a scientific fraud. That’s why this report is widely seen as a vindication of Mann’s work, and McIntyre’s criticisms are largely inconsequential.
CO 2 levels are higher than at any time in at least the last 650,000 years. The rate of increase is accelerating; 2005 saw one of the largest increases on record. China is building a new coal fired power plant every week.
Greenhouse gases warm the planet. Within the next 50 years, global temperatures are likely to be higher than at any time in the last 100,000 years. Unless of course, it’s all an artifact of the “urban heat island”: after all, we are just coming out of the “Little Ice Age”, the satellites show cooling, so the models can’t be trusted, and Mars is warming too, so it must be the sun.
Call me an alarmist, but I’m going to stick with the vast majority of actual scientists on this one.
RE: #48 Eric, I guess I set myself up by asking for China’s renewable energy equipment purchase orders. So, I ask if you or others can advance the discussion on China’s (and the US) reversal of its appetite for fossil fuels.
From British Petroleum’s 2005 energy statistics I see the following 2005 coal and electric generation data for China compared to US:
Coal (Million tons of oil equivalent)
US…….575.4……1.9% increase over 2004
China…1081.9…..10.9% increase over 2004
Electric generation (terrawatt-hours)
US……4239…….2.0% increase over 2004
China…2475……12.6% increase over 2004
China is reportedly building a new coal-fired electric generation station every week.
Private automobile ownership among newly employed Chinese shows every indication of continuing its fast pace.
According to the May 12 China Daily:
Total demand for new vehicles is forecast to climb by 12 percent to 5.6 million units this year, with sales of passenger cars rising 15 percent to 2.6 million units, it said.
I am more interested in the macro side of global energy demand because the new and existing fixed assets propping up the energy demand growth
are the sources of climate-forcing gases.
Without diminishing the importance of Chinese’ use of efficient roof top water heaters, I see no connection between that information and my opinion that adapting (NOT AT THE EXPENSE OF EVERY EFFORT TO MITIGATE CLIMATE-FORCING GASES) to what is about to hit us in the face is not a cop-out..it is a critical part of our discussion.
Comment by John L. McCormick — 25 Jun 2006 @ 11:00 AM
It would be pretty hard for heat and electrical generation in China NOT to become more efficienct, given the state of the art even ten years ago when I visited there.
“China is shifting the national energy policy by putting its first priority on energy conservation and improving the energy efficiency from its previous emphasis on energy exploitation.
The move will help the country control the emission of carbon dioxide to meet possible Kyoto Protocol obligations years ahead of schedule, experts said. ”
“…According to the government’s blueprint, the energy consumption for every 10,000 yuan (US$1,210) gross domestic product (GDP) is expected to drop by 16 per cent from 2.68 tons of coal equivalent in 2002 to 2.25 tons in 2010.
By 2020, the average consumption will further reduce to 1.54 tons of coal equivalent, 43 per cent lower the level in 2002.
By 2010, the energy consumption efficiency of major industrial products, such as steel, aluminum and electricity, is expected to reach the level of developed countries in the early 1990s. ”
“…After experiencing GDP growth of 204 per cent since 1990, Chinese carbon dioxide pollution increased by 44.5 per cent to 3.31 billion tons in 2002.”
As someone who lives in hurricane prone South Florida and experienced massive power outages after Wilma, I was most struck by the gorgeous sunny weather that lasted for almost a week after the hurricane had passed. It ocurred to me that this was the week when power outages were most severe. No hot water, no electricity, no refigeration, and no gasoline because most gas stations didn’t have any working pumps. As I rode my bicycle past the downed trees and power lines I saw roof top after rooftop (most of them intact by the way) bathed in golden Florida sunshine and almost nobody was taking advantage of it. It bothers me to this day. Especially given that there seems to be a massive campaign under way to promote gasoline powered generators for emergency home use in this area. I won’t even get into problems such as potential carbon monoxide poisioning stemming from the improper use of such generators. Anyone who sat in long lines trying to get gasoline from the gas stations should wonder if that is such a good idea. Not to mention that there are already reports of home owners storing gasoline unsafely in their homes. Now wouldn’t it seem that South Florida among a few other states in similar circumstances might be the ideal candidates for some kind of emergency solar and wind powered survival kits. I think it should be possible for FEMA to promote something like that instead of gasoline powered generators. I did some research and with off the shelf components such as the equipment commonly availabe on your average sailboat or RV it should be feasible. Add to that a Solar evacuated tube hot water heater… I have relatives who own a small farm in Brazil and they use a few coils of black garden hose which works pretty well.
For a few hundred dollars retail it is possible to add a 12v DC refrigerator. I think it would sure beat trucking in 18 wheelers with ice and water that sit idling for days in parking lots without knowing where they are supposed to unload.
Is it just me or does anyone else see a potential for planting the seeds of change here? If anyone has the means to put these kits together I have a feeling there might be a market down here. Heck I’ll go door to door and sell them. Certainly Home Depot should carry them right next to the gasoline generators with the big red signs saying “Warning: Danger, improper operation of this device could cause serious injury or death to you and the global environment”. Sorry sometimes I get a little frustrated waitng around for things to start changing! I even have an acronym: H.A.E.S.S. Hurricane aftermath emergency survival system. BTW even if you don’t believe in global warming the consensus seems to be that we are in for a deacade or two of increased hurricane activity so there will still be a need…
Comment by Fernando Magyar — 25 Jun 2006 @ 1:59 PM
RE: #53, Eli, you are reading too much into a Dec., 2004, China Daily story. I will agree the Chinese gvernment realizes it has a masive energy challenge ahead and efficiency will be a priority in its planning.
However, China has virtually no domestic oil production and very limited economically recoverable reserves of petroleum. Thus, it is shopping around the world for supply while it is now capitalizing on coal liquefaction plants to provide domestic sources of oil. They are not building carbon sequestration into those facilities and we can be sure the continuing improvement in the Chinese lifestyle will cause greater pressure on the electric sector.
Efficiency improvements are vital to China’s future but it is working from a base of 1.35 billion real and potential energy consumers.
How, does the China of 2006 figure into your comment?
Comment by John L. McCormick — 25 Jun 2006 @ 3:26 PM
We’ve drifted way off topic, but here goes anyway.
RE: #52 – I agree that China is investing rapidly in coal for electric generation, which won’t be good as a result of the high CO2 emissions which will result. And yes, it appears that China is fast becoming another automobile nation, with freeways being built rapidly. Furthermore, there are reports that China’s air traffic is also increasing rapidly. Their oil imports are surging as a result. As you point out, they still have a way to go to catch up with our total electric production, which would still only give their 1,200 million people about 1/4 the kWh per person as we enjoy in the U.S. There is a small opportunity for them to do better, as they make the compact flourescent lights that use only 1/3 the kWh as incandescent bulbs. That with greater attention to overall efficiency and the use of more solar may reduce their impact for a while. The trends are all quite scary to my mind, as our government in the U.S. still appears to be unwilling to admit that there is much of a problem.
RE: #54 – Yes, there are lots of ways to prepare for an emergency. Campers have refrigerators that operate on propane, as well as electricity. Some can be powered 3 ways, with 12 volt as well as 120v. However, the typical RV refrigerator costs a bundle, perhaps $700. PV arrays aren’t cheap at about $4 per kW and one would also need storage, typically batteries. If the backup is to provide AC, then there’s the extra cost of an inverter. Generators are cheap, since they (hopefully) won’t be used very often. Most people could get by with 1000 watts, unless one wanted to heat water or pump a deep well. All one needs do is stockpile a 55 gallon drum of gasoline (or 2?). If one wants to go whole hog, a relatively large PV array can be installed and hooked to the AC grid, thus one actually gets a dollar return for having the backup system.
This is a link to the online version of the NAS report. This report is very easy to read, as it was written specifically to be understandable by laypeople. It is nearly 200 pages long, but much of the content consists of graphs and illustrations, plus a long bibliography, so that it is easy to read the entire report in a couple of hours.
Not to take too much more of time on this topic, I am aware of the costs involved in setting up a large grid tied PV system. I was thinking something much more modest we are talking emergency and very basic survival for a few days. Not luxury living in a five star hotel. Keep in mind that a few million users were completely without power for a few days after Wilma and they were literally in the dark for the duration. I came up with a minimal system for a cost of around $1700.00 dollars for off the shelf components including solar panels, a charge converter,an inverter to run a small ac TV, a couple deep cycle batteries a very small 16 quart portable 12v dc freezer/refigerator.
As for storing 55 gallon drums of gasoline, I think that our local fire marshalls have a tendency to frown on that practice within the confines of the city. Especially if large segments of the population were to suddenly adopt that practice all at once.
Comment by Fernando Magyar — 25 Jun 2006 @ 6:05 PM
Grid tied systems must shut down in power outages. The utilities understandably do not want their workers zapped when trying to repair outages.
For back-up power, I recommend a diesel generator and biodiesel. Biodiesel is not flamable and nontoxic; non-polluting when used as fuel and relatively green-house gas neutral.
Given that in a decade China had a 204 % increase in GDP with only a 45% increase in CO2 emissions, and a lot of possible future improvements in efficiency I would not be so pessimistic as John McCormick.
Another, important point, is that as the standard of living and energy efficiency increases in China, much of the Asian black cloud forcing will disappear which will couteract increases in CO2 generation.
[Response: Almost every thread seems to eventually drift into discussions of this sort, and I agree it's interesting. However, it's way, way off topic for this article. Please, let's find some other site for discussing issues like China's energy future, and get back to things related to the problem of estimating the climate of the past few millennia. --raypierre]
RE: #40 – I really must wonder the degree to which most “climate scientists” have been exposed to, or have taken the time to learn about, the sorts of finite element modeling systems commonly used in mechanical engineering, fluid dynamics, aeronautical engineering, hydraulics, thermal engineering and electrical engineering/electromagnetic engineering. I think many in this field, having developed their models in-house during the early days of supercomputers, may be sort of insular in their views regarding modeling and regarding just what is possible today. To be fair, I must give proper credit to the work that has been done to date. That said, a bit more openness to investigating new modeling techniques and tools, leveraging demonstrated effective applications used widely in industry, may allow some of the fundamental problems of developing effective GCMs to be solved.
[Response: Wonder no longer. First off, there have been a number of attempts to use finite element modelling in climate related problems - particularly in the ocean, but none have yet made it into the fully coupled models. It's worth stepping back and thinking about why that is. Finite element modelling is at its best in dealing with situations where you know a priori where the interesting small scale stuff is likely to happen so that you can concentrate your resolution and resources there. This works very well for aerofoil modelling (where you know where the wake is etc.), coastal ocean modelling (where you where the topogrpahy is) etc. It doesn't work well in situations where the small scale features are either ubiquitos or can appear anywhere. In those circumstances you are just as well off with a finite difference scheme on a regular grid and a uniform increase in resolution as resources allow. There is a substantial overhead in adopting a finite element grid over a finite difference scheme, so there has to be a big improvement in results for the same computational effort. In the atmosphere, you need resolution in the boundary layer, near the tropopause, in the tropics, in mid-latitudes, near mountains etc. This ends up requiring more resolution almost everywhere, and so it ends up being just as straightforward to stick with a finite difference model and having better resolution everywhere. It's more of close call for ocean models, but (as far as I'm aware) nobody has a functioning ocean model (including all the physics of mixing, isopycnal diffusion etc.) that is global in extent that could be coupled to an atmospheric model (though I am aware of efforts in that direction). However, the biggest problems with GCMs are not related to the grid or to advection, but to parameterisations of unresolved physics (clouds, moist convection, mixing etc.). Finite element modelling is completely irrelevant to that. - gavin]
Following up on Gavins’s response to Steve (#62):
Check http://www.nrlmry.navy.mil/PDE/2006/Program6.htm for a taste of the most recent developments in numerical methods for the fluid dynamics in atmospheric models (there is a bit on ocean models as well). By the way, most ice sheet models are finite element models.
Good discussion. RE: #62 – 63. The overhead challenge should be less of a factor, with increasingly inexpensive computing resources and supercomputer power in much more commerical, commodity servers. As for finite element vs finite difference, personally, I am not willing to abandon the former just yet. It would be particularly interesting to understand what the implications would be based on a finite element model geared toward picking up small scale turbulance and small scale thermal gradients. Maybe at some point, some sort of hybrid finite difference – finite element construct would be something to consider. Interesting link – the navy site.
Re # 64. Whatever numerical technique you use (finite difference, finite element, spectral elements) the grid will be too course to resolve the full range of turbulence scales. The smallest turbulence scales are of the order of a centimeter in the atmosphere. Even in the forseeable future it is impossible to resolve that. So the use of subgrid models for the turbulence in atmospheric (and also ocean) models is unavoidable, also when
finite elements are used. The question is just which method is the most accurate and efficient (a finer grid will of course increase the accuracy) and it not sure that finite elements are better in that respect.
Comment by Geert Brethouwer — 28 Jun 2006 @ 4:01 AM
Inhofe’s Senate Committee issed a statement yesterday in response to the AP report that climate scientists liked Gore’s movie. They cite the Academy of Sciences’ report as debunking the hockey stick!
“The AP also chose to ignore Gore’s reliance on the now-discredited “hockey stick” by Dr. Michael Mann, which claims that temperatures in the Northern Hemisphere remained relatively stable over 900 years, then spiked upward in the 20th century, and that the 1990′s were the warmest decade in at least 1000 years. Last week’s National Academy of Sciences report dispelled Mann’s often cited claims by reaffirming the existence of both the Medieval Warm Period and the Little Ice Age”
In the U.S. is there any law against the government releasing patentently false and/or misleading information ? Guess I am not surprised at this comming from Inhome’s comittee with the U.S. surpreme cout agreeing to hear the case related to the EPA and CO2 emissions.
Just back from a few weeks Ireland and a one-day course in Oxford (Unravelling Climate Change Models), I was not aware of the publication of the NAS report, until reading the discussions here and at the other side of the barricade…
I learned in Oxford with a simple climate model, that it is possible to change the different responses to forcings within large margins, where different sets have nearly the same (temperature) result for the 1900-2000 period (despite a truncation of the solar series). Like halving the sensitivity for 2xCO2 + halving the effect of aerosols + tripling the sensitivity for solar. The main difference was in the “projections”, where the expected warming was halved too, no matter what scenario was used.
Is this plausible? That largely depends of natural variability in the pre-industrial past. If there was a huge variability (as indicated by reconstructions of Esper, Moberg and Huang) then much of the last century warming is natural and the response to CO2 is at the low side. If there was little variance (as indicated by MBH98/99 and Crowley and Lowery,…), then the response to CO2 must be higher to cover the 1900-2000 period.
I hope that the millennium project really explores the full wide of the past variance and doesn’t restrict the responses by limits (like a minimum response to thropospheric aerosols). I just have read the report of the Cubasch e.a. (2006) simulations, which give more Moberg-like results, but I have the impression that they used a quite huge overall sensitivity…
Perhaps someone can answer three questions for me:
1) If I understand it properly, this report says that the variances in surface temperature measurements of the paleoclimate using proxies (e.g. ice cores) are too large to definitively compare those temperatures to today’s. Quote from the report: “Very little confidence can be assigned to statements concerning the hemispheric mean or global mean surface temperature prior to about A.D. 900 because of sparse data coverage and because the uncertainties associated with proxy data and the methods used to analyze and combine them are larger than during more recent time periods.”
Are the large variances in paleoclimate surface temperature measurements also present in measurements of CO2 concentrations using ice cores?
[Response: You need to distinguish our ability to calculate global or hemispheric means (which require enough data to average out the regional variations) from the quality if any one record going back into the past. Prior to 900AD the number of well dated high resolution series drop dramatically, and so that spatial averaging becomes much more problematic. This is a very different issue to the lower resolution but much longer data series like the Vostok ice core or the ocean sediment cores. While they do get less well resolved as you go back in time (due to compression effects etc.), they are useful for giving local climate information back much further (> 100,000 years). The greenhouse gas measurements are in some ways more useful because the gases are relatively well mixed in the atmosphere and so one point in the globe is enough to capture the main features over time. Indeed the match between the different ice cores for both CO2 and CH4 indicate that this is a good assumption. So in summary, the NAS conclusion is appropriate to mean temperatures, not to local records or the GHG history. -gavin]
2) In both the Vostok and the more recent EPICA ice core analyses, CO2 increase has been shown to lag temperature increase by several hundred years. The hypothesis seems to be that some other forcing starts the warming, and CO2 released by the warming continues it. So what stops the warming? If CO2 causes a temperature increase, and a temperature increase causes more CO2 (released from melting tundra, etc.), why does the warming slow and reverse?
[Response: The 'other forcing' is the effects of orbital variations which are a pace-maker for the glacial/inter-glacial cycles. CO2 responds to those changes, and in turn causes more changes but like many feedbacks the effect converges (and doesn't run away) because the strength of the feedback (the 'gain') is sufficiently small (though still positive). (I'll have a post explaining this a bit better up shortly...) - gavin]
3) Are the Vostok and EPICA data (estimates and variances) available somewhere for download?
1) Questions from a skeptical (but willing to learn) geologist. Are there any conclusive analogs from the geological record [Tertiary or Quaternary] where CO2 increases precede a significant warming event? Granted this would not exclude CO2 as a major climate forcer, but a good “real world” analog is always nice to strengthen any scientific argument.
It seems to me the models are forecasting a cause-effect relationship (CO2-initiated warming event) that appears not to have occured in nature for at least 65 my. That definately causes this contrarian to at least ponder the validity of the current equations and assumptions.
[Response: Well, the PETM (~55 Mya) is probably the most likely candidate for an 'clean' carbon driven climate response. But since most changes in climate are complicated by feedbacks, you need to be more sophisticated in your search for analogs. For instance, while acknolwedging that the glacial/interglacial cycles are paced by Milankovitch cycles, examining the record, it's clear that GHGs (CO2+CH4+N2O) were important feedbacks and contributors to the cooling (about half the LGM signal for instance). - gavin]
2) As a novice weather buff, I understand from ensemble weather forecasting that small changes in the initial state cause significant loss of skill at short forecast lead times. Even the ensemble mean loses all skill and approaches climatology after a relatively short lead time. How then do we have confidence of our skill to forecast a more complex climate system with many more loosely-contstrained variables, across mult-decadal periods? How do we know that largely unconstrained variables in the model such as potential variations in the THC, changes in the intensity of the hc, (ect. ect.) will not regionally counterbalance any averaged temperature change, and send certain climate zones (ie. North Atlantic, Europe) off in entirely different directions than now forecasted by the models? Are there really examples of a weak THC and very warm paleoclimates in the North Atlantic? If you could tackle a couple of these it would be appreciated.
[Response: The answer is (partly) contained in your question! The effects of the initial conditions die out after a while (a month of so for the atmosphere, longer though for coupled models) and the models converge to a statistically steady climatology. The projections into the multi-decadal future are based on the changes of that climatology - not the individual weather paths. When however it comes to big shifts in the ocean circulation, we are not as confident - partly because we don't have many good validation tests for those magnitudes of changes (but see here for some ideas) - and partly because of large range of responses in the models themselves (of course, the two issues are linked). We can test the sensitivity to the initial ocean state quite easily, and within any one model this seems to be small for our current conditions. But we can't easily test the dependency on parameterisation choices - except through these 'ensembles of opportunity' like the AR4 models - and they don't provide a statistically satisfying set. Hence the large amount of discussion on the topic and continued debate. - gavin]
Re 71.1) “It seems to me the models are forecasting a cause-effect relationship that appears not to have occured in nature…”
The superpositioning of Antarctic ice core data of temperature and CO2 concentration appear to show that they are in virtual lockstep, with sometimes one, sometimes the other apparently leading. That suggests to me a highly coupled dynamic system in which an external forcing that changes one parameter will trigger, through the coupling, same direction changes in the other. Much of the coupling is in the form of positive feedbacks that can substantially exacerbate the initial perturbation.
External forcing can be, for example, things like variations of solar radiance, orbital effects, or the addition of greenhouse gases to the atmosphere. To believe that the latter is not such a forcing requires suspension of the laws of physics. It is a little like adding a blanket to the bed, getting too warm in the night, then complaining in the morning that someone must have changed the thermostat setting.
This is the perspective of an engineer who has been concerned about AGW for almost thirty years. It is no doubt simplistic, but I trust the experts on this site to correct any conceptual errors.
Re: #72 “with sometimes one, sometimes the other apparently leading.”
Like you, I was previously under this assumption. I have never found any paleoclimate research that soundly backs this up however. In every study of paleoclimate (that I am aware of), where this relationship could be determined, temperature leads CO2 in every case. This seems to hold all the way back to at least the Eocene. (a proposed mechanism for the Paleocene event(biogenic methanogenesis) seems odd, but I will not dispute it here) That is a long time across numerous glacial-interglacial cycles!! It at least seems like an interesting pattern to me.
“To believe that the latter is not such a forcing requires suspension of the laws of physics.”
I only wish atmospheric physics was as easy to understand as your blanket analogy. If it had been, I might have been a meteorologist!!
Re: #74 Bryan, you do understand the physics about how CO2 traps infrared? Or is that something you are doubtful about?
Yes. So that we are all on the same playing field, Wien’s displacement law and the First Law of Thermodynamics are all on solid ground, although admittedly I don’t remember Wien’s constant off the top of my head (It’s been a few years since my last physics class).
The blanket analogy from Taylor however gives some insight into how many approach this complex climate problem. Its much like learning mathematics from a standard textbook. At the beginning of any unit, there is a fundamental principle, and a few very straight forward equations with only a few variables. (ie the blanket problem) At the end of the unit, there are usually a few more challenging problems that might include several variables. “Real” climate prediction is like trying to work all the challenging problems in the textbook simultaneously with an enormously long list of variables obtained from word problems that are printed backward, and coming up with the right answer. Not an easy problem, even if you have a brand new calculator with a fresh set of batteries!
Bryan, I am not suggesting that a detailed analysis of the problem is simple. However, it seems to me that at least the short-term (century or two) effect of adding massive amounts of CO2 to the atmosphere can only have one of three possible results: (1) the earth gets warmer, (2) the earth gets cooler, or (3) no effect at all. What physical process or processes could lead one to conclude that the answer is (2) or (3)? The models, which, while not perfect, are incredibly sophisticated and the best we have, point to (1). I am not trying to be overly clever here, I just do not understand the basis of your argument.
By the way, Jim Hansen used the blanket analogy long before I did.
Standard radiative physics based on a correct treatment of the top-of-atmosphere balance– physics going back at least to Arrhenius– yields a surface warming of about 1C in response to a doubling of CO2, when water vapor feedback is neglected (Real Climate, 2006).
We all agree that the physical equations suggest only a small warming due to the the insolating effect of doubling CO2 concentrations. Obviously other feeback mechanisms (water vapor) must come into play to get the type of AGW that is being hyped.
In thermodynamics, a minus sign on work is needed, because when work is done by the system, energy (heat) flows out of it. I just do not yet accept the notion that all the processess by which the dynamic ocean/atmosphere system recieves energy, performs work, then evacuates the energy to stay in balance, are well understood. For example, what is the exact interaction between the ocean conveyor and the climate? Since the THC must ultimately be fueled by solar IR, it would seem it must have an increased imput of energy to then perform more work (speed up) and in turn give off heat to the atmosphere, which is then evacuated out of the system though further work (atmoshpheric circulation). Does heat energy primarily flow from the ocean to the atmoshphere, or to some degree, the other way around? The model suggestions that the THC will slow down (and may eventually collapse) while much of the North Altlantic is warming drastically, seems to be in contrast to paleoclimate indicators that suggest the system does not work this way.
In a final thought, I like numerical modeling. I use them in my field of structural geology. It is a great tool to help the scientist understand the interaction of the physical processes involved, and quantify uncertainty. One must use a model with great caution however to make forecasts. It must show repeated skill to be used as a predictive tool. Even the most robust model with a good data set is subject to uncertainty. After all, it is a model and not reality. That will be my last blog for now on this website. I hope it gives the readers some insight into the nature of my skeptisism. I now have to go back to my real job of exploring for more greenhouse gas.
RE: #78 – I like your approach, very agnostic. I have increasingly come to realize that in order to understand what is happening with the climate, there needs to be a major bump up in the use of quantum physics. It’s almost as if we need to work in this broad range, from the macro level currently embodied in the GCMs as well as the quantum level drilling down a whole lot more into what is happening in terms of all the actual interactions between the actual EM / photonics and all the matter in question. Probably what has been missing in the main stream “climate science” thread or research has been the presence of some really good photonics spectra, cosmic radiation, thermo, atomic physics folks and others along these lines. Without having a more in depth understanding of the true, real world energetics that are in play from the macro down into the sub micro, we are all pounding sand.
Minimal role of cosmic radiation. Interesting I guess that the tempature of the earth’s surface must be more dependant on internal nuclear decay? Sorry I’m sure you meant to say changes in cosmic radiation. The problem is of cource that any measure of changes in cosmic radiation are not going to go back very far. What I find disturbing about these discussions is that there is very little discussion of what temperature curve the human element is plotted on to. There may be a lot of evidence of global warming but it is not very predictive of future conditions without some understanding of what the temperature conditions would be minus this or that factor.