A Few Things Ill Considered: The Medieval Warm Period was just as warm as today

Thursday, February 23, 2006

The Medieval Warm Period was just as warm as today

(Part of the How to Talk to a Climate Sceptic guide)

This article has moved to ScienceBlogs

It has also been updated and this page is still here only to preserve the original comment thread. Please visit A Few Things Ill Considered there. You may also like to view Painting With Water, Coby Beck's original fine art photography.

Labels: Sceptic Guide

78 Comments:

At March 14, 2006 5:43 AM, Anonymous said…

Link to a review of ice core records which cover the medieval warm period

http://www.co2science.org/scripts/CO2ScienceB2C/Index.jsp
At March 14, 2006 5:48 AM, Anonymous said…

here's the right link

http://www.co2science.org/scripts/CO2ScienceB2C/articles/V6/N6/C1.jsp
At March 14, 2006 8:06 PM, coby said…

This study is specific to one region of the Antarctic and as such can not be taken as a global indicator.

It is interesting to note that the authors do claim a global occurence of the LIA and the MWP but the studies they cite as support are from 1965 and 1988. That is *really* out of date in climate science.

I see nothing in there compelling enough to reject NOAA's conclusions.
At March 20, 2006 6:24 AM, Anonymous said…

we cannot say anything useful about the middle ages temperature, because the crosscorrelation of the proxies is zero. (Wahl and Ammann, 2006)
At April 17, 2006 1:35 AM, Anonymous said…

Coby
But yhe MWP and LIA awere noticed in Europe and N America as well as in "one region of the Antarctic" I could argue that tree rings selected from just a few areas are used to deny what was accepted History.
At April 17, 2006 10:40 AM, coby said…

All I know is that all the latest studies are indicating that these were not as pronounced or as global as the current warming trend. I think we need a much more compelling reason than a socialist conspiracy to toss out a whole branch of science.
http://en.wikipedia.org/wiki/Image:2000_Year_Temperature_Comparison.png
At June 30, 2006 4:13 AM, Anonymous said…

Hi Coby

I know that one of the arguments about climates was that grapes for wine were grown in england, and people cite roman times. However an interesting snippet: you may well have heard of hadrian’s wall in the north of england. Well, there is a pre-wall fort near there called Vindolanda, and excavations have been continuing for years. The most spectacular find has been loads of wooden writing tablets where the actual writing has been preserved.

To cut a long story short, it seems the better off romans got their wine imported from gaul, and didn’t drink the local stuff. So wine might well have come from england in the period, but it wasn’t any good. So what does that say about the climate?

John Mann
At June 30, 2006 7:20 AM, coby said…

Hi John,

This is the problem with anecdotes like wine-growing. There are so many social and economic factors that are different, direct comparisons are misleading. I had already heard people mention that transport was not as global and cheap by far during Roman times so wine from England does not necessarily mean it was good wine! Your addition illustrates that nicely.
At November 06, 2006 4:28 PM, Anonymous said…

The standard error in these graph is quite large:

http://www.ncdc.noaa.gov/paleo/globalwarming/medieval.html

Since it is 2 standard deviations, about 5% of the readings will fall out of the yellow interval, so I guess about 25 years there will have similar temperature to 1998.
At November 06, 2006 6:49 PM, coby said…

Your hypothesis relies on there being no relationship between individual years. While there is an amount of random interannual variability, it is not remotely likely that a given year would just pop even half a degree above the temporally local average.

I am not the one to give you the correct odds on one particular period being higher than today, but I am sure it is low. No one has said it is impossible, btw.
At November 13, 2006 5:39 AM, Anonymous said…

So all of the records of a third growing period in Europe are false?

Seems that a lot of historical works, Guns Germs and Steel for instance, would beg to differ
At November 13, 2006 8:30 AM, coby said…

What do you mean by "third growing season"?

Regardless, don't confuse regional climate with global climate. Europe is Europe, all global reconstructions indicate that globally the climate was not warmer 1000 yrs ago. Do you know of one that does? And cries of "MBH was flawed!" do not mean we therefore know the MWP was warmer.
At November 15, 2006 10:14 PM, coby said…

Hi jo_bobtwc,

I'm just presenting the current scientific findings. There are no global temperature reconstructions that show the MWP to have been warmer. That's a simple statement of fact, not dogma. If new evidence comes to light, I will change my opinion as the facts dictate.

FWIW, even if the MWP had been globally as warm as tody this would not change much in the big picture.

In your investigation of "both sides" have you managed to read through the TAR report?
At November 16, 2006 12:44 PM, coby said…

I havn't read the TAR report...do you have a link?

It is in the side bar: Climate Change 2001: The Scientific Basis. It is long, but at least read the chapter summaries.

...but I did manage to read through the links that you posted and I don't think they make a very strong case to your statement that all reconstructions do not support the MWP.

What I say is that no global reconstructions show a pronounced and global MWP. This is very different from how you paraphrased me, and they way I am saying it was carefully constructed.

Also please note that my "simple statement of fact" is "There are no global temperature reconstructions that show the MWP to have been warmer." If it is wrong, please show me the study I am unaware of and I will correct my misimpression.

Additionaly, most of the data in support of MWP comes from ice cores in both Greenland and Antarctica.

I am not aware of Antarctic ice core data showing a MWP, do you have a reference?

When it all comes down to it, we are trying to interpret data with so many variables and potential confounding factors it is mind boggling. It is really a lot of guesswork and those who already believe stongly in AGW will more readily attribute data that sort of resembles the theory of global warming to the validity of that theory without seriously considering that there might be other equally or more viable explanations.

It is not guesswork, it is careful analysis, I agree it is complicated. Science did not start with this conclusion and then look for reasons to believe it, though individuals will take their own personal approaches. We are now at a point a long way down a slowly and carefully traveled road, everything anyone has thought of has in fact been seriously investigated, even to the point of seeing if the CO2 rising in the air is CO2 from fossil fuels (where else would our emissions go? but nothing has been assumed)
At November 16, 2006 11:15 PM, coby said…

That study was about sediment, not ice. One of your links is also about sediment not ice. I will try to answer your other comment tomorrow.
At November 17, 2006 5:40 AM, Anonymous said…

I have a report for you to read - however, I have noticed the weasel words you are using to ensure that you are correct "Regional Not Global". considerings that its difficult enough today to agree on a global mean temperature, your insistence on proving a global temperature difference for 1000 years ago would point you you never being wrong.

Have a look at this very interesting study of Glacier activity in the Swiss Alps. It breaks one of your self imposed rules in that it occurs in Europe. This means that you can claim that it was warmer in Europe, but it doesn't prove a MWP.

http://www.co2science.org/scripts/CO2ScienceB2C/articles/V9/N46/EDIT.jsp
At November 17, 2006 10:21 PM, coby said…

replying finally to jo_bobtwc's third latest comment:

Firts off you asked for references on antarctic ice cores showing a MWP. Here are a couple of abstracts though I am sure I have seen a graph on your site demonstrating this visually:

http://www.co2science.org/scripts/CO2ScienceB2C/articles/V9/N9/C2.jsp
http://www.ingentaconnect.com/content/ap/qr/2002/00000058/00000003/art02371
http://en.wikipedia.org/wiki/Medieval_Warm_Period

Thanks for the first, it fits the bill. The other is fine to add to the conversation but is not an ice core analysis. Interestingly, the first link shows a MWP 150 years after the NH warming. This fits with the only point I have been trying to make: there is no evidence to support the notion of a globally synchronized MWP that was warmer than today. It is also interesting to note the rather indirect method for deducing temperature that paper used. I have no trouble accepting that, but it sure seems that when the proxies don't say what the sceptics want they find all kinds of objections to "assumptions" and "processing" that goes into getting a temperature signal.

I won't spend the 57.64$ to read the other so cannot assess the maginitude or timing of the MWP warming shown in their sediment. I do note that they say there are many other comparable warmings and coolings perhaps implying that this region varied more than the global climate.

You said: "What I say is that no global reconstructions show a pronounced and global MWP. This is very different from how you paraphrased me, and they way I am saying it was carefully constructed."

That may be true that my paraphrase was not exactly how you planned it; if that offends you, then I appologize. However, I don't think that invalidates my point. Your point is that no model reconstruction shows a pronounced MWP. My point is that the modelers themselves admit that they don't have enough data to accurately model that time period so whether or not the models show a GWP trend is a mute point.

I'm not offended, I just want to set the record straight. I have been talking about proxy reconstructions and not modeling experiments, btw.
At November 18, 2006 6:43 PM, coby said…

I guess I'm not sure what the distinction is between the definitions of a model and a proxy reconstruction, it may be that I have been using the two (erroneously) interchangeably; would you mind clarifying that for me?

In its general useage, model would refer to a computer program that you feed data about the climate system, such as intensity of solar radiation, GHG levels, layout of land and ocean and it then outputs a representation of what the temperature and weather patterns would be. People do do model runs over the past, which involves using onther proxies to determine solar, ghg etc and then running the model over that time period to compare its output with what is known (or thought to be known) about actual past temperature.

A proxy reconstruction involves measuring some other property that is though to represent temperature, like thickness of tree rings, coral rings, pollen counts in sediment and then makin ga graph of temperature trends based on those measurements.

There is good stuff to be read about proxies here.

resembles the MWP, one would expect it to be warmer in the northern hemisphere and cooler in Antarctica. As it so happens, this is also the oberved state of things.

I don't know if I'd agree with that, that arctic region has warmed several degrees, while that antarctic has really changed very little. The latest data suggests a slight warming.

Here are some links to the sea-saw pages for those who haven't seen them (thanks Coby for digging them up)

I'm getting alot of credit these days, but I have to remind everyone that H.E.Taylor is the one to thank for all of those links in the GW news posts! But I'm glad people find interesting material in them.
At December 08, 2006 1:12 PM, Anonymous said…

I am not a climateoligist. I have, however, read everything I could get my hands on about the MWP and the LIA.I have drawn some conclusions which are tantamount to serious deception charges toward those who pooh-pooh, or outright dismiss, the MWP.

The greatest detractors appear to be those with a particular axe to grind, including NOAA, Al Gore, Junior, the Environmental groups, the News Media, and government-funded "study" groups. Each of the foregoing have something to gain by continuing the myth that the MWP did not exist. Each of them have subscribed to the "Hockey stick" temperature charts.

There is rather solid evidence from tree-ring studies, from ice-core studies, from evaluation of the decline and return of glaciers all over the world, the historical fact of cereal-grain farming in Estonia, the rise of Southern England viniculture during this period, the Hopi, Mayan and Aztec drought-driven cultural migrations, the dryness of the African sub-Sahara during this period, and the LIA famines in Estonia following the period.

It may be an inconvenient truth for the aforementioned groups, but they seem to have their collective head in the sand over this one. It would appear that honesty in climatelogical study is about as elusive in those circles and honesty in Politics is in Washington, D.C.!
At December 18, 2006 5:33 AM, Anonymous said…

Global Medieval Warm Period?

I saw the debate about sources of evidence for a global MWP. It took me about 10 minutes to find this one:

Evidence for a ‘Medieval Warm Period’ in a 1,100 year tree-ring reconstruction of past austral summer temperatures in New Zealand

http://www.agu.org/pubs/crossref/2002/2001GL014580.shtml

Notice that the data source is not Europe, that the journal is GEOPHYSICAL RESEARCH LETTERS, and two of the authors are/were at Lamont-Doherty.

The literature is there, but you have to look for it.
At December 18, 2006 5:57 AM, Anonymous said…

Hockey Stick and Proxy Variables

There are lots of data series that are correlated with climate, some series more closely related to rainfall and others more closely related to temperature.

Not all scientists agree how relevant the rainfall series is to the question of temperature variation.

To analyze so many variables, scientists have to reduce the data by extracting fundamental components. The "Hockey Stick" graph depends on the use of principal components analaysis (PCA).

One critique of the Hockey Stick graph was based on two claims: the PCA analysis was flawed by inclusion of data that has low correlation with temperature; the conclusions are overly sensitive to higher order components that are usually ignored when using PCA.

The critic claims that these issues were not adequately addressed when Nature published the corrected version of the "Hockey Stick" graph and remain to be resolved.
At December 18, 2006 12:25 PM, coby said…

Thanks for the reference (http://www.agu.org/pubs/crossref/2002/2001GL014580.shtml) Frederick. I hae no problem accepting it, but it is still not a global reconstruction. So while it is evidence supporting a global MWP it seems it is not enough.

Regarding the Hockey Stick, see my take here. The short version is this is a single 8 year old study and all the criticisms are highly contested, so let's just forget it and look at all the other reconstructions that support the same conclusion.
At January 26, 2007 4:18 AM, Anonymous said…

Eric the Red settled Greenland and grew grops in Greenland... try that today (its all permafrost today). just a regional warming-- right! the chinesse also have records of ships sailing in the artic (where its ice today).
At January 26, 2007 6:37 PM, coby said…

"The Greenlandic climate is Arctic, but owing to the country's large landmass there are huge variations with regard to both humidity and temperature. Climatologically, a distinction is made between a northern high-Arctic, middle low-Arctic and southern Sub-arctic zone.

The richest plant growth is found in the Sub-arctic belt, which includes only the very southernmost part of Greenland. Here, there are low-lying tracts of forest with birch scrub, while in the low-Arctic area one finds dense, tall willow scrub. In the high-Arctic area, there is only low-lying vegetation of arctic willow, in addition to many expanses of moorland, marsh and ponds."
http://www.greenland.com/Comprehensive_Guide/Basic_facts_about_Greenland.php
At February 01, 2007 1:57 PM, Anonymous said…

Objection:
It was just as warm in the Medieval Warm Period as today, in fact Greenland was green and they were growing grapes in England.

This one often comes with additional anecdotal evidence, but it is not often useful to get into those details, just refer to the wealth of proxy studies that refute this idea.

___________________________

Definitions of Anecdotal Evidence on the Web:

* Information passed along by word-of-mouth but not documented scientifically.
www.nechakowhitesturgeon.org/sturgeon/glossary/index.php

* Anecdotal evidence is unreliable evidence based on personal experience that has not been empirically tested, and which is often used in an argument as if it had been scientifically or statistically proven. The person using anecdotal evidence may or may not be aware of the fact that, by doing so, they are generalizing.
en.wikipedia.org/wiki/Anecdotal_evidence

____________________________

The Medieval Warm period is not anecdotal evidence, but empirical.

_______________________________

Definitions of Empirical Evidence on the Web:

* evidence based on direct experience or observation.
iws.ccccd.edu/tsmith/glossary.htm

* Evidence derived from direct observation and sense experience. Contrasts: Intuitive insight, metaphysical speculation, and pure logic.
academics.smcvt.edu/geography/posing.htm

* Empirical research is any activity that uses direct or indirect observation as its test of reality. If atheoretical, it is a form of inductive reasoning. It may also be conducted according to hypothetico-deductive procedures, such as those developed from the work of R. A. Fisher.
en.wikipedia.org/wiki/Empirical_evidence

______________________________

the UN's 2001 report DELETED the medieval warm period, and replaced it with white noise to create their hockey-stick graph.

Socialists are liars, do not trust them.
At February 01, 2007 2:20 PM, Anonymous said…

"Animal bones and other materials collected from archaeological sites reveal Icelandic Vikings had large farmsteads with dairy cattle (a source of meat), pigs, and sheep and goats (for wool, hair, milk, and meat.) Farmsteads also had ample pastures and fields of barley used for the making of beer and these farms were located near bird cliffs (providing meat, eggs, and eiderdown) and inshore fishing grounds. Fishing was primarily done with hand lines or from small boats that did not venture across the horizon (McGovern and Perdikaris, 2000.)"

http://www2.sunysuffolk.edu/mandias/lia/vikings_during_mwp.html

_____________________________

"There are 3 times of lies. Lies, damned lies, and statistics." Mark Twain.

Maybe he was refering to Democrats.
At February 01, 2007 3:00 PM, coby said…

Your quote is about Iceland. The MWP mythology is about Greenland. They are different islands.

Do you understand?
At February 01, 2007 5:30 PM, coby said…

BTW, Anonymous at 1:57 - thanks for the definition of empirical evidence. Now do you have some?
At February 04, 2007 10:24 PM, Anonymous said…

I would have to agree with jo_bobtwc when that individual said "leaning toward the side of the skeptic because their arguments seem to be based more on logic and facts than wishful thinking and biased hypothesis dependent upon priori convictions."
Trying to cover your ears and ignore the WMP is just plain silly. In just this thread you have had evidence from America, the North Atlantic, Northern and Southern Europe, the Antartic and New Zeleand illustrating how the period was warmer. Still, you dogmatically counter these and the wall of historical evidence indicating the WMP through stating "all global reconstructions indicate that globally the climate was not warmer 1000 years ago." This is like the "smoking is not statistically proven to cause cancer" argument. Make the burden of proof so impossible to illustrate, then claim scientific victory. The trouble is holding to such stances greatly undermines credibility.

Andrew
At February 05, 2007 2:03 PM, coby said…

hi Andrew,

You have that backwards, statistical evidence *does* indicate that smoking causes cancer. Backwards like the rest of your points...

If all global reconstructions indicate that globally the climate was not warmer 1000 years ago then logic and facts indicate that the MWP was not globally warmer than today. Regional indicators are just that, regional.

Thanks for the comment!
At February 09, 2007 8:10 AM, Kent said…

While admittedly off the track of the thread here, I must address what seems to be a hinderance to the very honest discussion here. Coby's mission statement, (prefacing "How to talk to a skeptic"), is to: "provide a layman's guide to defending against the assorted specious attacks that are out there, both by pointing out the basic logical fallacies they are based on and providing some appropriate reference material to avoid the typical "is too, is not" exchanges these things frequently devolve into. Nothing like a nice link to an authoritative resource to refute the factually incorrect pontifications. Nothing like a calmly presented and solidly logical rebuttal to put the scaliwags in their place!"

I've been reading the posts here for some time. While they are engaging and contain loads of great information and links, they are moderated in a way that inhibits free discussion. Controversial concepts (like the proposed MWP) are met with such vociferation that they do devolve a bit, don't they, into the kind of arguementitive (albiet scrupulously cited and linked arguementation) that Coby proports to avoid.

While Coby is "Fighting the good fight," there are many posters here admittedly on two sides of a number of these issues and simply trying to get their head around them. The moderation of discussion here, by Coby's admission, has an agenda, however. I guess this fact must be kept in mind.

I did not mean this to sound as scathing as it does. Coby should be congratulated also, as this forum is engaging and thorough.
At February 09, 2007 10:12 AM, coby said…

Hi Kent,

It is appropriate to keep in mind the purpose of this HowTo guide, and you are right that the MWP is a messier issue than most. Interesting and honest discussion is certainly possible about just what spatial and temporal extent it exhibited and how well synchronized it was around the globe. The simple points I try to make about it are that regional evidence by itself can not be used to support any claim of a pronounced and global MWP and that even if it had been a period of warming similar to today this does not in any way alter what we know about what is happening now or what we expect for the future.

As for moderation, I really do not delete anything unless it is abusive or vulgar. so any qualities of discussion you perceive in the threads are just my style of discourse, I certainly encourage others to join in and take it where they may. I don't know what meaning you really had in mind with "moderation". I admit my part of this article's discussion is not as well managed as I would have liked.

I hope that sincere people with honest questions do not feel berated or belittled.

Thanks for the comment and the feedback!
At February 16, 2007 1:39 PM, Anonymous said…

xI have some issues with your treatment of the climate history - as part of and independent of the climate debate.

They grow wine in England today. Whoop-de-doo. After 1000 years of breeding, including cold-hardy varieties, and 1000 years of developing cold-climate growing techniques (e.g., sheltering like Washington did with his vegetable garden) and in a much wealthier and more liquid society where there is credit and in which starting a vineyard doesn't mean investing your family's fortune or tying up land desperately needed for food crops - which you wouldn't do unless you were darn sure the climate would tolerate a vineyard - and with a wine consumption market several orders of magnitude greater than the market in 1100 AD, as well as much better abiliy to ship to that market, the British wine exporting industry is finally larger than it was in 1100. And????

We grow vine grapes in Nashoba Valley, too, where it's 10 degrees F today. Just not the kind of grapes they grow in the South of France and Italy. Which is what they did in England in 1100.

The question remains - how?

The "so-called MWP may have been a regional phenomenon but not a global phenomenon...." is pretty transparent too. Does 'global' mean something other than the sum of all of the regions? So-called "anecdotal" evidence isn't exactly limited to the North Atlantic - tree lines were 300 feet higher in the Sierra Nevadas - do they share a climate with Greenland? With Germany, where fig and olive trees grew? There's only one part of the world - a small area in the Pacific - that was cool during the MWP, and supposedly it's cool there now as well.

"The predictions were spot-on" - many weren't - they keep changing the predictions for the Northeast US, curiously in line with whatever's happening at the time -and the ones that were correct are in line with what happened last time.

The Southwest is in essence experiencing a drought that will if the warming continues get worse and perhaps resemble the drought it experienced in the MWP.

The temperatures kept climbing beyond the first 90 or so years, as predicted but also similar to the MWP.

I might have a theory as to why the Yankees win the AL East each year, but just because my prediction that they'll win at least 90 games this year comes true doesn't mean my theory as to why they win is correct....

What about the contemporaneous observations - they didn't just grow grapes, they wrote "we can grow grapes now because it's warmer." Were they part of the VRWC, 1000 years ahead of their time? Shipping routes changed dramatically in the 1200s because the North Sea was full of drift ice - - which could come from only one source, arctic icecaps breaking off. The Pope wrote that he would no longer send missionaries to the Greenland settlement for precisely this reason - or maybe Karl Rove and James Inhofe went back in time and forged this? Oh wait, the Pope was a religious leader, so maybe he WAS part of the VRWC.

I can't get past "our proxy model differs from the physical evidence therefore we go with the proxy model" without any serious attempt to explain how the various events that have been attributed to a warm climate - and many of which were at the time attributed to a warm climate - in fact occurred if not for a warm climate.

If someone found Alexander's remains and ran some tests on them and based on the results argued that Alexander never in fact made it to India, would anyone accept this without his explaining how then did all those people at Massaga die? Isn't that usually required - when you contend that X, which has been universally accepted as having happened since it happened 1000 years ago, didn't in fact happen, don't you have to at least suggest how all the things that have been attributed to X in fact happened if not for X?

Unless it's changed to "they didn't actually grow grapes in England 1000 years ago" which I hope isn't next!

Even if it WERE just the North Atlantic - which it isn't - in the 1990s when glacial retreat in the North Atlantic was the only proof of global warming, we were told that the North Atlantic was the canary in the coalmine, the indicator of what was going on on a global scale - - was that NOT the case 1000 years ago? You can't farm those areas with a John Deere tractor now - the Vikings did it with simple hand tools. Their diet was 80/20 land/sea and in the 1300s switched over to 20/80 land/sea. HOW?

The Alps could be ice free by 2100 - but they've BEEN ice free before, and tree lines were much higher than today during the periods when they were much higher in the Sierra Nevadas than today. They were ice free during the Holocene Maximum, which somehow you folks have decided went away at night....

The MWP doesn't DISPROVE AGW but it means you can't just infer AGW from GW and it's thus a key part of the AGW debate, otherwise why would anyone try to rewrite it?

The only actual tangible evidence of AGW seems to be the inability to prove it's something else (my life would have been much easier were that to have been the standard when I was prosecuting - Judge, I can't prove a case against anyone else, so we should convict this guy!), and the fact that for the last 10-15 years the upper stratosphere has been cooling - which to the extent it indicates that we're largely responsible for the last 10-15 years also indicates that we're not likely responsible for anything before the last 10-15 years - i.e., about 3/4 of the 1.1-1.2 degrees F warming in total.

The MWP also indicates that the world isn't coming to an end with another century like the last one. There's more coastal development now, I'll give you that, but malaria and locusts in Europe? And what's with the sea level predictions - I've literally seen 20MM to 40 CM. 40CM??? Wha?

No matter what you folks come up with in the next 3-5 years, there's going to be some piece that isn't proven - on which we'll have to take your word for it.

And it's your burden of proof - Inhofe, right or wrong, isn't trying to limit my commute or make it and my electric bill cost more - you are - this is supposed to be a free society, so the burden really rests on you. People can't be expected to prove that otherwise free activity DOESN'T cause some alleged harm every time someone alleges harm (although Monsanto does this all the time it seems).

So credibility is important. Not relative to Inhofe but on its own.

Re-writing the MWP without explaining how the events that undisputably occurred and have since they occurred been attributed to warmer climes actually happened doesn't build credibility.

If you're going to say Alexander didn't make it to India you have to explain how someone else killed all those people at Massaga - or at least suggest possible alternative explanations. When I was prosecuting, not only couldn't I rest on "I can't prove it isn't someone else" but if a similar crime had occurred nearby or earlier and we knew that the defendant hadn't committed that crime, I had some explaining to do.

No amount of calibrating and re-calibrating the model or explaining the model does this. Plugging more data from other sources - even if the results agreed with what you have so far, which when other people like Cook run proxy studies somehow doesn't seem to happen - doesn't do this.

You don't have to prove that it was something else but some supportable theory as to how the events happened if not for a warmer climate, or how it could have been warmer in a number of parts of the world that don't share the same weather pattern, but sufficiently cooler in other places that the average wasn't warm.

There seems to be a gradual backtracking on the MWP and LIA from some circles within the AGW crowd - my guess is that if and when they decide that the recently-cooling stratosphere counts as physical proof of AGW, which I think they will if in another 10-15 years the stratosphere is still cooling and the troposphere warms another 0.2 or 0.3 degrees (and maybe they'll be right), it'll revert back to the 1995 IPCC report's version: "the MWP and LIA happened just like the history books say but this time it's man-made and thus we can't expect it to end, like the MWP did."

And if that's how it works out, fine - my issues are (1) I think the burden of proof ought to be on the side demanding restrictions of otherwise free activity, especially productive activity, rather than "we" should "err on the side of caution" (if you dropped the standard to that level for everyone seeking to limit some activity there wouldn't be much left that anyone could do); and (2) independent of the significance to the AGW debate, re-writing the climate history to eliminate or downplay the MWP to convince people to accept a political agenda, even if the agenda turns out to be right for other reasons, is just too Orwellian for me. It sounds too much like that guy who re-wrote the history of the old west to support the notion that the so-called "gun culture" is an invention of 1950s Spaghetti Western movies. WHATEVER the underlying debate is about, you can't say "new evidence indicates that X, which has been accepted as having happened for 1000 years, didn't actually happen" without explaining all the old evidence that was the reason people have assumed X for 1000 years.

Not only don't you do this, you suggest that nobody thought the Middle Ages were warm until 1965!
At February 16, 2007 2:03 PM, Anonymous said…

And in not so many words, I no longer believe a single word a Socialist says.

Even when they say, "I am not a Socialist, I am a Republican," I do not believe it.
At February 16, 2007 2:41 PM, Anonymous said…

Another item is the increase in CO2 concentration since 1800 - this is almost always referred to as a "30% increase" when that's relative to the immediately prior CO2 level. You don't hear "1/11,000th of the atmosphere," which wouldn't have the same effect. Sometimes you hear 90 ppm and sometimes they explain that ppm means parts per million but the portion of the audience likely to panic is not the same portion that is likely to take a step back and do the math.

Now, 1/11,000th could be material but then just SAY 1/11,000th and explain this.

It sounds a LOT like a numbers game played with "cancer clusters" in the 1970s - the "frequency of X type of cancer" was "50% higher than average" within some range of a nuclear power plant - - - - except they never told you that that meant 6 out of 500,000 people instead of 4, and that the standard deviation was 3....

And wasn't that the Union of Concerned Scientists doing that?

And the fact that the CO2 level is higher than it's been for 650,000 years - that, if you accept the MWP, Roman warming and Holocene Maximum as being warmer, as warm and warmer, respectively, than today, means something other than CO2 is a bigger driver of climate on a multi-century scale. Is THAT why we "must get rid of the MWP?"

Again, the MWP doesn't mean it's NOT us this time - it just means you can't ASSUME it's us simply because it's warmer.

Look, remember acid rain in the 1980s? Remember that National Geographic article that spelled it all out? They PROVED that. They showed the clouds before they got to the Midwest - mostly water. Then they showed the chemicals in the smoke coming from the smokestacks. Then they showed that the smoke reached the clouds. Then they showed that the clouds after passing over the factories had compounds that were acidic and that were formed when water met with the chemicals in the smoke. Then they found these same compounds in the rain and the lakes in New England.

THAT's what I'd like to see on global warming before we start tripling my electric bill and doubling the cost of my commute. And the IPCC report doesn't do that. Not close.

I think that (a) in a free society where the burden of proof ought to be on the side that wants to limit otherwise free activity, and (b) given the spotty track record of the environmental / anti-business movement so far (it seems that for every acid rain there's a Monsanto butterfly or a Teflon bird or a Patagonian sheep), the government shouldn't impose the kind of drastic limits that meeting Kyoto in a growing society would require until you have a proven, tangible case laid out like they had with acid rain.

You might have that someday.

You don't now.

That doesn't mean huddling up and deciding to declare victory like the IPCC just did.

It doesn't mean consensus - that's a lot of people agreeing on a prime suspect, not proof that he's guilty, and most of the people agreeing on it have accused the same suspect of countless other things, with maybe a 50 accuracy rate.

It doesn't mean predicting that it will warm another 0.2 degrees in the next 15 years and then if it warms between 0.17 and 0.23 saying "the models prove it" - they just prove that it kept happening, not what caused it, and it would seem in line with prior warming periods, denial of which doesn't accomplish anything either.

The cooling stratosphere - another 10 years of that, in line with the warming, that would get you there - I'd think more highly of "yes there was an MWP and an LIA and yes it's supposed to be warming right now but here, the stratosphere cooling shows that we're adding to it and THAT'S why we need to act, whereas if we were heading into a cool period like we were in the 1300s maybe this would actually be a good thing" - - - now THAT makes more intuitive sense. Even before we get a long-term trend in the stratosphere THAT would make me more likely to give you some of the benefit of the doubt. Rewriting history - that makes me less likely.

But I still can't go based on stratospheric cooling in the last 10-15 years alone - to me that says that some of the warming in the last 10-15 years is us and that some isn't and all of the warming before the mid-1990s isn't.

I know, at some point there's a tipping point but look what you're asking - you're asking to empower a bunch of people who have wanted to limit these same activities for a half dozen reasons over the last 40 years (some of them even argued the opposite reason). You compare the "global warming deniers" to the cigarette industry denying that tobacco caused cancer, but it's not the same people. Conversely, skeptics point out environmental urban legends like the Monsanto butterflies and the Teflon birds (sure harmful chemicals are released when a Teflon-coated pan is heated - over 600 degrees F, just like any other pan would release harmful chemicals if heated that much) - and those ARE some of the same groups that presently push the AGW theory.

Pat Robertson says my soul will burn in eternity if I don't adopt his limits on my activity. That's a lot worse than a six inch sea level rise by the time my children's children graduate from college. We can't change the standard of proof based on the severity of the harm alleged.

And can the moonbats stop bringing up Venus? The severest alarmists say the earth will look like Venus. Venus is 10-12 times hotter than earth and has about 100,000 times our atmospheric CO2 concentration. Even before you consider it's half the distance from the sun and turns more slowly, the math just doesn't support a case for man-made CO2 having an effect. Maybe it does - but the Venus argument doesn't support it.

You must understand - I WAS a Lefty. I went for the class warfare thing - until I read actual BLS data and discovered that for the most part the comparisons were between people in their 20s and 30s starting out and people in their 40s and 50s at the height of their careers being misrepresented as comparisons among permanent groups of people.
I went gung ho for the "corporations are evil big greedy polluters" thing but the more I read up on it the more I came across examples where things were grossly exaggerated or just turned out to be urban legends, where the EPA concluded it just wasn't so, like the Monsanto butterflies.

Intellectual integrity is a really big deal for me - it's not the end pushing the means here, but the other way around. It's not that I work for an oil company (I don't) and thus am looking for reasons to find flaws in your analysis. It's the revision of history and the way some of the arguments are worded ("warmest year on record" when the record is 150 years old and we know we're coming out of the LIA, "30% increase in CO2" above) that make me more inclined to doubt your ultimate conclusion.

If you said "yes it's a tiny increase in CO2 relative to the atmosphere but that can still be a big deal" and "yes the MWP happened and was probably warmer than now at least in many parts of the world, this time it's partly us and the fact that we're ALSO expected to have natural warming means the COMBINED effect is something to worry about," THEN I'd be a LOT more inclined to buy in.
At February 20, 2007 3:12 AM, Anonymous said…

The medieval warm period wasn't "As Warm" as it is today, it was warmer.
At February 23, 2007 9:45 AM, Steve__M said…

Regarding co2science. When they claim the science supports them it is worth double checking. In their MWP info, the first evidence I looked at was:

http://www.co2science.org/scripts/CO2ScienceB2C/data/mwp/studies/l2_sajama.jsp

(as I understand it O18 enrichment in the ice core relates to temperature)

So I found the paper, online at:

http://www-bprc.mps.ohio-state.edu/Icecore/Abstracts/Thompsonetal-climatic-change-2003.pdf

It turns out that the graph they showed is one of 6 graphs (each one from a different glacier - 3 in Tibet, 3 in the Andes).The guys who wrote the paper combined all the figures and the results are quite different, and closely match Mann's hockey-stick. The authors actually say:

"The ice core results support meteorological evidence of a significant 20th century warming."
At February 23, 2007 10:54 AM, coby said…

Thanks, Steve__M,

That is precisely my experience with them whenever I have decided to verify something they have claimed.
At February 26, 2007 8:21 AM, Steve__M said…

Frederic quoted the following paper:

Evidence for a "Medieval Warm Period" in a 1,100 year tree-ring reconstruction of past austral summer temperatures in New Zealand

http://www.agu.org/pubs/crossref/2002/2001GL014580.shtml

If you look at it in detail, it actually says that it was very cold in New Zealand when the Vikings were starting to colonise Greenland which is a good argument against a global MWP.

I downloaded the full version of the paper. A quote from the paper is:

"Similar to the Northern Hemisphere, this Southern Hemisphere expression of the MWP is not homogeneous in time. Rather, it is composed of two periods of generally above-average warmth, A.D. 1137-1177 and 1210-1260, that are punctuated by years of below-average temperatures and a middle period that is near average. Overall, this translates to a MWP that was probably 0.3-0.5 C warmer than the overall 20th century average at Hokitika and, for the A.D. 1210-1260 period, comparable to the warming that has occurred since 1950."

But they don't seem to talk about another warming period at about 1500.

They also note:

"Of equal interest in the reconstruction is the sharp and sustained cold period in the A.D. 993-1091 interval. This cold event is easily the most extreme to have occurred over the past 1,100 years. Interestingly, Gellataly et al. [1988] reported evidence for a significant glacier advance in the Mount Cook area around the period 1100-950 BP."

The graph shows this period to be about 1C colder than average, and is probably the most noticable feature on the graph. Now this cold period pretty much coincides with the period when the Vikings were in Greenland.

In the conclusion they say:

"The identification of a MWP sensu lato in New Zealand adds an important new datum to the debate concerning its large-scale occurrence and supports Broecker's [2001] argument that it was indeed global."

I couldn't see how they came to this conclusion given that the MWP is supposed to be from 900-1300, but they'd found both very cold periods and warm periods within this time. Then I looked up the meaning of "sensu lato" which is Latin for "in the broadest sense". It seems to me that they've highlighted two warm areas within the MWP time frame, and ignored another warm period outside of it, merely to make their paper sound more exciting than it is.
At March 02, 2007 8:15 PM, Anonymous said…

Coby,

I just Googled this MWP/Hockey Stick graph issue (hadn't heard of it, actually), because a friend (right-wing Republican) brought it up, to discredit the global warming scenario.

I've previously read in the Jan 07 report from the Union of Concerned Scientists how ExxonMobil had been exposed as a major funder of several sham pseudo-science think tanks out to mislead the public about global warming. Here's the report: http://www.ucsusa.org/assets/documents/global_warming/exxon_report.pdf

I've scrolled through much of this blog, with anonymous' ramblings and links to co2science.org's articles...you should note: that group is one of the sham ExxonMobil mouthpieces, run by a Sherwood B. Idso (who also received major $$ from ExxonMobil for 2 other such groups).

I'd almost put my $ on the notion that one of these sham think-tankers was your "anonymous", hence the repeated attempts to discredit this blog's data.

Thanks for your own postings on the topic.

-Matthew
At March 02, 2007 11:19 PM, coby said…

Hi Matthew,

Thanks for your coment. I agree with your take on CO2 Science.

If you are new to the Hockey Stick stuff be sure to check this article:
http://illconsidered.blogspot.com/2006/03/hockey-stick-is-broken.html
At March 07, 2007 9:34 AM, Anonymous said…

Global warming is a scam, you people are pathetic.
At March 27, 2007 2:35 AM, Anonymous said…

To whichever 'Anonymous' claimed that global warming deniers appear to follow the facts more, just take an honest look at this thread here. We've heard 'all socialists (by which no doubt anyone who believes in global warming is referred to) are liars', 'moonbat', and been called 'pathetic'. So what was that you were saying?

I can understand that part of it may come from being a small minority faction in a heated debate. But if anyone out there's not willing to give out passes, there's no question as to which side it is. In global warming debates, UN/socialist conspiracies (improbable) are charged before oil industry shilling (probable, the existence of which is not disputed by either side), though strangely not here. (Does 'Socialists lie' come close enough?)

Global warming deniers' credibility will always be hampered by this perception of personal vendetta - even more so than the occasional backdoor bribery of some of their more promiment members. For the same reason you don't find creationist scientists who weren't Christians first, you don't find global warming deniers who don't harbour strong antipathy toward environmentalism in general and environmentalists specifically. Logically, the only conclusion is that the antipathy informs their position, which greatly harms their image. I'm not so patronizing as to expect any of them to take my advice, but I do believe this needed to be pointed out.

Furthermore, I wonder why it is that right-wingers always need to bring up the "I used to be a Lefty" line out, with the expectation to part seas with this proclamation even if true. Now that you mention it, there are right wing beliefs I used to entertain, even if I never could call myself an actual conservative. Take libertarianism. Had its charms for a leftist of the anarchist persuasion, until I learned that the movement has a whole had an extremely naive, cloistered view of capitalism and economics, particularly as it relates to the history of such policies in the global south. There's a few more I could list, as well as a bunch of beliefs that more or less stayed the same, but why bother? I don't expect any prefixing addendum to lend any more credibility to my argument than is inherent in it, and neither should anyone.

As a final note in this opening sidebar, that is an awfully simplistic interpretation of inequality, Anon. How does take into account, for instance, temporal and international differences in inequality? Or the decrease in movement among the income aggregates? Obviously, people can't be aging slower now. Even Botox can't work miracles.

Sorry to derail the discussion, but when my pet peeves are rankled, I got to scratch back.

Your note on the burden of proof is well taken, Anon, but you must keep in mind the subjective nature of what constitutes 'proof', which you must know something of since you earlier accused Coby of setting an arbitrarily high standard of proof (for a global MWP, to be specific). The scientists have spoken, most people have come on board, and the political wheels are starting to turn, though mainly only at the state level at this point. The 'acid rain moment' has already come and passed in the eyes of other thoughtful citizens, and so in a way the burden of proof has already been met. It's still understandable to ask to be convinced, personally, but don't try and conflate it with the broad political sense. It's transparent.

In a logical sense, positive claims must meet the burden of proof, that is true. But in a society, something of a burden of proof also lies with anyone breaking an obvious consensus with a positive (as in non-normative, not non-negative) proposition.

As for whether the MWP is hotter or cooler than the present day, I guess we can only look past each other on this, Anon. These are the kind of data and charts I'm familiar with:

http://www.onlyblue.org/blog/wp-content/uploads/2006/08/2000_year_temperature_comparison.png

What I've seen clearly show that the present day is significantly warmer, but as Coby pointed out, this isn't even the point. Rather, it is the time frame and the synchronization of these events, which are both related to the RATE of increase of temperature that we're seeing.

Global warming deniers are drawing comparisons between the present day and the Middle Ages. Okay, so far, so good. What they are in fact doing, though, is parrying point by point a period that lasted over four hundred years with one that is less than four decades. As Steve generously showed, the record of those four hundred years is not uniform; one can only extrapolate an overall trend. The record today is far clearer pointing toward one direction.

I'll go more into the ins and outs tomorrow, but it's late and I've written enough already.
At April 18, 2007 4:18 PM, Anonymous said…

Hello I am a Canadian Geology student. Regarding Proxy Global climate reconstructions what is the verdict on the work done by Dr. Will Wei-Hock Soon (2003) showing that indeed the MWP was a global event.

I'll provide a link to a PDF I found.

http://www.marshall.org/pdf/materials/136.pdf

Sorry if this is a re post on something gone over earlier.
At April 19, 2007 12:09 AM, coby said…

Hi Easy,

As I glanced through that document I did not see anything new or intriguing enough to read its 32 pages. Hockey stick is broken, wine in England, etc, the usual arguments. Soon and Baliunas really have little credibility with me, I see no reason to give their writing any particular confidence, certainly no reason to accept their conclusions over those of NASA, NOAA, NAS or the IPCC.

If you have a more specific question I could try to provide a more specific answer.

Thanks for the visit.
At July 28, 2007 6:03 PM, Anonymous said…

Could someone explain to me what the point of such arguments as "it was warmer in such and such a period" are exactly? I don't understand in what way this refutes the current warming. Is it just that the are attempting to show that the climate ahs changed in the past by natural mechanisms and therefore any changes now are also just natural?

Maybe I'm missing something vital, but such arguments seem to be literally not even adressing the issue.
At July 29, 2007 11:18 AM, coby said…

I don't think you're missing anything, it is a misconception to believe if the MWP was warmer than today then GW is not real or not anthropogenic.
At October 03, 2007 10:12 PM, Anonymous said…

Hi Coby,

Thanks for providing this great resource. Lots of really useful information.

I'm a couple of months late to this discussion, but one reason for caring whether it was warmer during the MWP relates to tipping points: if it was really warmer then, and the world didn't go into a positive feedback loop, that's useful information to have.

Thanks again,
John
At December 04, 2007 2:15 PM, eskdi said…

Excellent comments coby.
I notice that jo_bobtwc uses some of his climate skeptic information from the website Co2 science-' The Center For The Study Of Carbon Dioxide And Global Change' which,according to Sourcewatch receives corporate funding,including from,er,ExxonMobil!
At December 09, 2007 2:58 PM, villandra said…

Problem with ice cores and similar data is it's theoretical reconstruction. We don't even know how much ice melted during the medieval warming period to be no longer there to exist as ice cores! Surely it did melt, since Greenland had actual green on it, and today Greenland does not have actual green on it.

Historical records are factual data, and theoretical reconstructions of whatever cannot supplant it. Never mind was was exaggerated about those reports about green in greenland, today, that is, today, not thirty years ago, Greenland is covered with ice with a little barren tundra near the shore. During the medieval warming period colonists went there, grew crops, adn grazed cattle and sheep. Greenland had more green than it does now.

I was brought to this site by the comment on grapes in England. Thanks for the comment, but I am specifically looking for HISTORICAL information on grapes in England, as well as for climactic data pertinent to growing grapes in England. Maybe some grapes have been grown in England right along for all I know, and the failure of industry in Britain has created every sort of back to the land and back to tradition and whatever movement in Britain.

Can anybody point me to such information? My e-mail address is tiggernut24@yahoo.com

Thanks!
At December 09, 2007 3:00 PM, Anonymous said…

oops. I meant thanks for the LINK on grape growing in England. Unfortunately the site doesn't seem to have any historical information opn grape growing in England, nor the climactic data taht would make the case that grape growing is as possible in England now as it was during the medieval warming period. If someone knows of this data, please point me to it.

I'm not unwilling ot think people are responsible for global warming, just need actual evidence that adds up.

That's evidence, people. I saw all the snide comments; the page is full of them.
At December 09, 2007 6:04 PM, Anonymous said…

Got some better data. See

http://www.ecn.ac.uk/iccuk//

and

http://www.climatehotmap.org/euroruss.html

Growing season in England has lengthened considerably. Now to compare it to the length of time it takes to grow grapes. I dunno if actual data exists on the length of the English growing season in the 11th and 12th centuries, or not.
At December 09, 2007 6:19 PM, Anonymous said…

Partial straight answers on English grape growing - http://www.ecn.ac.uk/iccuk//

Apparently, MOST English grape growers are urban escapists on their second career. And - tourists.

They grow mostly hardy German hybrids. Dunno if they existed in the 11th century...

Grape production did increase dramatically after 1989, but they no more have one reason for it than the other web site, which says the reasons for historical grape production in Britain are complex.

They discuss the impact of rain on quashing British grape growth in some detail. England still gets plenty of rain! Grapes need weather that is both warm, and sunny, like in Greece. Spring frosts also frequently squash the grape crop, and since 1960 or 1980 or something, most of the increase in the length of the English growing season has been because of warm weather coming earlier in the spring. So I dunno if in medieval times, England would quite be feeding wine to the French yet.
At December 09, 2007 6:47 PM, Anonymous said…

I was able to find at Google books, a partial copy of MK Hughes and HF Diaz's 1994 paper, Was there a medieval warm period, in Climatic Change, Col 26, 109-142, p 1994. This paper seems to be hard to find; it is not available in the Texshare database online. It has been republished in a book that sells for $199.

The partial copy presented reason to believe that the medieval warm period was not as small compared to the present warm period, as it was limited in geographic scope; it affected mostly northwestern Europe and the Alpine region, and the southwestern U.S. Worldwide it made little impact. So of course only a couple of small blips show up in the ice core data, duh!

That is possible, though hard to conceive. All the evidence may not be in. Air or ocean currents could have affected one or two regions, though for 500 years, and in the presence of a sunspot maximum? The Southwest was specifically affected by the Monsoon, which is a seasonal upper air current in and near the Pacific and not the Asian word for a major storm. There is clearly argument about it. I wonder if perhaps ice core shows little about it because that section of the ice melted during the medieval warm period, and does not exist.

This is the sort of data y'all need to present, instead of making snide comments, but maybe you lack the intellectual capacity to sort it through well enough to know what's a pertinent detail, or you're just plain too arrogant.
At December 21, 2007 3:28 AM, Anonymous said…

You establishment shill, don't think the ruling class will hesitate to stuff you in a death camp with the rest of us.
At February 22, 2008 2:58 PM, Anonymous said…

The NOAA site is basing its conclusions on Mann et al (1999), cf http://www.ncdc.noaa.gov/paleo/globalwarming/medieval.html

the famous "hockey stick graph". Unfortunately, this turned out to simply be based on faulty statistical techniques, and to be wrong.
The hockey stick graph, which was previously the principal argument for global warming, was unceremoniously dumped from the 4th Assessment Report, because it had been discredited. In fact, there now appears to be every reason to believe the medieval warm period was as warm or warmer as today,
see for example
http://www.ncasi.org/publications/Detail.aspx?id=3025
which says " The mean series shows the Medieval Warm Period (MWP) and Little Ice Age (LIA) quite clearly, with the MWP being approximately 0.3°C warmer than 20th century values at these eighteen sites."
At February 22, 2008 3:04 PM, Anonymous said…

Its also worth looking at http://www.sciencemag.org/cgi/content/full/316/5833/1844a/FIG1
an article from Science that shows a reconstruction of global temperatures going back 1200 years. Not only is the Medieval Warm Period clearly shown and comparable in warmth to the present, but a cursory glance at the curve (or the analysis in the paper) will indicate that the warming of the 20th century is not particularly surprising: the temperatuer graph basically looks like noise.
At February 22, 2008 3:53 PM, villandra said…

After I made my own comment, I researched it. Actually, during the medieval warming period, the northern Atlantic was a good deal warmer than it is today. This was caused by a local warming event, produced by changes in one air current over the Pacific Ocean. The air current also altered the climate in something like the American southwest and plains. It is possible that that one subtropical Pacific air current responds to changes in the sun's output.

I found a little bit of specific data on warming in Greenland at this moment. Despite softening of ice and so forth, bare land has hardly expanded, and the climate is warming so slowly that they just became able to successfully grow broccoli there a year ago. Broccoli is a cold weather plant that grows into December in upstate New York. It can grow with snow around it.

I saw someone's comment about Romans and wine on this page. I learned a couple of things on this subject - one of which only the author of that message does not know. The Romans left Britain more than four to six hundred years before the medieval warming period began! Duh. That one is silly.

The wind in Britain story is a bit more complex than the TV program and book about the medieval warming period and hte little ice age give one to believe. During the medieval warming period, grapes were grown for wine at maybe 30 large, commercial scale abbeys in England. Grape production did not abruptly end after that time, and some wine has always been made in England, though I'm short on the details and it may not have been much nor high quality. At this time grapes are being grown for wine production in England once again. However, efforts to grow it commercially in large orchards are running into trouble, as many years the growing season isn't yet long enough. The greatest amount of both growth and success in grape growing is by urban retirees who have retired to little plots in the country and are growing grapes in their gardens. They do not face ruin during years when the crop is no good.
At February 22, 2008 4:00 PM, villandra said…

One other thing; I believe that commercial scale grape growing in England is running into two problems. One of them is unreliable length of the growing season; the English growing season has gotten significantly longer, and some years grape crops are successful adn other years not. I think that the other problem is not a high enough number or proportion (not sure which), of sunny days. Grapes need alot of sun. AGain, some years there is apparently enough sun, and some years not.

England has tried other ways to alter agriculture to respond to global warming. English livestock have always been fed oats because it grows in cool dank weather. The English government has been paying farmers subsidies to feed to a kind of corn intended to feed livestock, with mixed success. The corn doesn't always grow that well.
At February 22, 2008 4:09 PM, villandra said…

ACtually, I posted all my information with the sources, when I found it! Never thought I'd done that. Sorry for repeating.

However, I can comment on Eric's comments. I'm honestly a bit confused by his comments; nor sure he's saying the graphs show similar global warming to now, or little global warming at all - or both. No, Eric, don't answer that, because I'm not going to argue.

I have the graphs he's talking about, and Al Gore actually includes them. They are consistent with all of the reconstructed worldwide climactic data from that time, which is made from ice core data, tree ring data, and other natural phenomena that can be dated and show climactic variation.

All of the graphs actually show the medieval warming period as several minor blinks on the graph. Worldwide, and in the regions of the world where it is possible to collect data on the climate in medieval times, whatever was going on in the north Atlantic and Europe had little effect on the temperatures. Only in the mid-Pacific and the southwestern United States is it possible to pick up on changes logically consistent with the climate changes in the north Atlantic that in fact explain the climate changes in the north Atlantic.

So in other words, the medieval warming period has little relevance to current discussions about global warming. The medieval warming period was a local event, and hte temperature spike was much sharper.

I do still wonder why the greater level of melting of the Greenland glaciers, and other glaciers in the north Atlantic, didn't raise sea levels nine feet or whatever - or did it? Coastal areas of Europe have periodically fought the sea. It may not have struck people in Venice and Holland as strange.
At February 24, 2008 5:21 PM, Anonymous said…

CfA Press Release

Release No.: 03-10
For Release: March 31, 2003

20th Century Climate Not So Hot
Cambridge, MA - A review of more than 200 climate studies led by researchers at the Harvard-Smithsonian Center for Astrophysics has determined that the 20th century is neither the warmest century nor the century with the most extreme weather of the past 1000 years. The review also confirmed that the Medieval Warm Period of 800 to 1300 A.D. and the Little Ice Age of 1300 to 1900 A.D. were worldwide phenomena not limited to the European and North American continents. While 20th century temperatures are much higher than in the Little Ice Age period, many parts of the world show the medieval warmth to be greater than that of the 20th century.

Smithsonian astronomers Willie Soon and Sallie Baliunas, with co-authors Craig Idso and Sherwood Idso (Center for the Study of Carbon Dioxide and Global Change) and David Legates (Center for Climatic Research, University of Delaware), compiled and examined results from more than 240 research papers published by thousands of researchers over the past four decades. Their report, covering a multitude of geophysical and biological climate indicators, provides a detailed look at climate changes that occurred in different regions around the world over the last 1000 years.

"Many true research advances in reconstructing ancient climates have occurred over the past two decades," Soon says, "so we felt it was time to pull together a large sample of recent studies from the last 5-10 years and look for patterns of variability and change. In fact, clear patterns did emerge showing that regions worldwide experienced the highs of the Medieval Warm Period and lows of the Little Ice Age, and that 20th century temperatures are generally cooler than during the medieval warmth."

Soon and his colleagues concluded that the 20th century is neither the warmest century over the last 1000 years, nor is it the most extreme. Their findings about the pattern of historical climate variations will help make computer climate models simulate both natural and man-made changes more accurately, and lead to better climate forecasts especially on local and regional levels. This is especially true in simulations on timescales ranging from several decades to a century.

Historical Cold, Warm Periods Verified

Studying climate change is challenging for a number of reasons, not the least of which is the bewildering variety of climate indicators - all sensitive to different climatic variables, and each operating on slightly overlapping yet distinct scales of space and time. For example, tree ring studies can yield yearly records of temperature and precipitation trends, while glacier ice cores record those variables over longer time scales of several decades to a century.

Soon, Baliunas and colleagues analyzed numerous climate indicators including: borehole data; cultural data; glacier advances or retreats; geomorphology; isotopic analysis from lake sediments or ice cores, tree or peat celluloses (carbohydrates), corals, stalagmite or biological fossils; net ice accumulation rate, including dust or chemical counts; lake fossils and sediments; river sediments; melt layers in ice cores; phenological (recurring natural phenomena in relation to climate) and paleontological fossils; pollen; seafloor sediments; luminescent analysis; tree ring growth, including either ring width or maximum late-wood density; and shifting tree line positions plus tree stumps in lakes, marshes and streams.

"Like forensic detectives, we assembled these series of clues in order to answer a specific question about local and regional climate change: Is there evidence for notable climatic anomalies during particular time periods over the past 1000 years?" Soon says. "The cumulative evidence showed that such anomalies did exist."

The worldwide range of climate records confirmed two significant climate periods in the last thousand years, the Little Ice Age and the Medieval Warm Period. The climatic notion of a Little Ice Age interval from 1300 to1900 A.D. and a Medieval Warm Period from 800 to 1300 A.D. appears to be rather well-confirmed and wide-spread, despite some differences from one region to another as measured by other climatic variables like precipitation, drought cycles, or glacier advances and retreats.

"For a long time, researchers have possessed anecdotal evidence supporting the existence of these climate extremes," Baliunas says. "For example, the Vikings established colonies in Greenland at the beginning of the second millennium that died out several hundred years later when the climate turned colder. And in England, vineyards had flourished during the medieval warmth. Now, we have an accumulation of objective data to back up these cultural indicators."

The different indicators provided clear evidence for a warm period in the Middle Ages. Tree ring summer temperatures showed a warm interval from 950 A.D. to 1100 A.D. in the northern high latitude zones, which corresponds to the "Medieval Warm Period." Another database of tree growth from 14 different locations over 30-70 degrees north latitude showed a similar early warm period. Many parts of the world show the medieval warmth to be greater than that of the 20th century.

The study - funded by NASA, the Air Force Office of Scientific Research, the National Oceanic and Atmospheric Administration, and the American Petroleum Institute - will be published in the Energy and Environment journal. A shorter paper by Soon and Baliunas appeared in the January 31, 2003 issue of the Climate Research journal.

NOTE TO EDITORS: Photos of key climate indicators are available online at http://www.cfa.harvard.edu/press/archive/pr0310image.html

Headquartered in Cambridge, Massachusetts, the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists organized into six research divisions study the origin, evolution, and ultimate fate of the universe.

For more information, contact:

David Aguilar, Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
Phone: 617-495-7462 Fax: 617-495-7468
daguilar@cfa.harvard.edu

Christine Lafon
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
Phone: 617-495-7463, Fax: 617-495-7016
clafon@cfa.harvard.edu

I would think this should be here.
At March 05, 2008 7:01 AM, barry said…

This comment has been removed by the author.
At March 05, 2008 7:11 AM, barry said…

That 5 year old press release should not be here. The study it is based on (Soon and Baliunas) has been discredited by peer-review.

Willie Soon and Sallie Baliunas have been trying (unsuccessfully) to advance their theory that the sun is responsible for most climate change (check other threads on this website for the solar argument).

The skeptical point about the MWP (and Little Ice Age), is to try to demonstrate that climate sensitivity is greater than recommended by the mainstream climate science community. What this would mean is that large fluctuations in the current era may be attributed to natural variations. This does not break AGW theory, but it puts a dent in it.

However, the report done by Soon and Baliunas is terribly flawed. for example they have not correctly scaled figures from the various reports they looked at.

Here are a few posts from realclimate (RC) that look at generic problems and faults in various attempts to increase climate sensitivity values, beginning with a post on climate sensitivity itself:

http://www.realclimate.org/index.php/archives/2005/12/natural-variability-and-climate-sensitivity/

The RC post below deals specifically with Soon and Baliunas as part of a larger critique of the hockey stick 'controversy':

http://www.realclimate.org/index.php/archives/2004/12/myths-vs-fact-regarding-the-hockey-stick/

I'll cite the relevant bit:

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

MYTH #2: Regional proxy evidence of warm or anomalous (wet or dry) conditions in past centuries contradicts the conclusion that late 20th century hemispheric mean warmth is anomalous in a long-term (multi-century to millennial) context.

Such claims reflect a lack of awareness of the distinction between regional and large-scale climate change. Similar such claims were recently made in two articles by astronomer Willie Soon and co-authors (Soon and Baliunas, 2003; Soon et al, 2003). These claims were subsequently rebutted by a group of more than a dozen leading climate scientists in an article in the journal "Eos" of the American Geophysical Union (Mann et al, ‘Eos‘, 2003). The rebuttal raised, among other points, the following two key points:

[My addition - follow the links in this post]

"(1) In drawing conclusions regarding past regional temperature changes from proxy records, it is essential to assess proxy data for actual sensitivity to past temperature variability. In some cases (Soon and Baliunas, 2003, Soon et al, 2003) a global 'warm anomaly' has been defined for any period during which various regions appear to indicate climate anomalies that can be classified as being either 'warm', 'wet', or 'dry' relative to '20th century' conditions. Such a criterion could be used to define any period of climate as 'warm' or 'cold', and thus cannot meaningfully characterize past large-scale surface temperature changes.

(2) It is essential to distinguish (e.g. by compositing or otherwise assimilating different proxy information in a consistent manner—e.g., Jones et al., 1998; Mann et al., 1998, 1999; Briffa et al., 2001) between regional temperature changes and changes in global or hemispheric mean temperature. Specific periods of cold and warmth differ from region to region over the globe (see Jones and Mann, 2004), as changes in atmospheric circulation over time exhibit a wave-like character, ensuring that certain regions tend to warm (due, for example, to a southerly flow in the Northern Hemisphere winter mid-latitudes) when other regions cool (due to the corresponding northerly flow that must occur elsewhere). Truly representative estimates of global or hemispheric average temperature must therefore average temperature changes over a sufficiently large number of distinct regions to average out such offsetting regional changes. The specification of a warm period, therefore requires that warm anomalies in different regions should be truly synchronous and not merely required to occur within a very broad interval in time, such as AD 800-1300 (as in Soon et al, 2003; Soon and Baliunas, 2003)."

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

But it's better to click trough to the source material and read for oneself.

Other posts that touch on climate sensitivity and MWP - the 2nd post mention Soon and Baliunas again:

http://www.realclimate.org/index.php/archives/2004/12/temperaturevariations-in-past-centuries-and-the-so-called-hockey-stick/
http://www.realclimate.org/index.php/archives/2005/01/peer-review-a-necessary-but-not-sufficient-condition/
http://www.realclimate.org/index.php?p=7

Apologies for using a single site for source material, and one that raises the hackles of the skeptiverse. But, like wikipedia, this web site is a resource for links to more in-depth stuff (and they explain the issues in terms laypeople can understand, usually).

I hope this post has been useful.

barry.
At March 05, 2008 4:52 PM, villandra said…

I really can't follow the technicalities of the scaling and selection fo what to include in the model, but I very much doubt it's the sort of rocket science some are making out of it here. Usually people, even scientists, who are arguing with evidence of global warming are deliberately throwing smoke in our eyes.

As to the true relationship between teh medieval warming period and current global warming, there isn't one. The medieval warming period was strictly a local phenomemon caused by changes in one current. There, now I said it a third time. Or fourth.

Since clearly there was really a medieval warming period, and clearly it has no bearing on what is happening today, there is absolutely no reason to be quibbling about those charts.

Now, as to the completely irrelevant point about sensitivity of the climate, the climate is extremely sensitive, and dynamically unstable, and that is why it is very easy to upset. However, people who point out how sensitive the climate has historically proven to be, are usually arguing just the opposite; nature is in control and nothing can upset it.
At March 06, 2008 7:32 AM, barry said…

Hi villandra,

I really can't follow the technicalities of the scaling and selection for what to include in the model, but I very much doubt it's the sort of rocket science some are making out of it here.

If you can't understand it, how can you vouch that it is not difficult?

My above post was mainly in response to the post above that, which cited the Soon and Baliunas study of a great many other studies. Those other studies use different value scales in their figures. As an analogy, it's like trying to compare cubits to feet and meters, or, more to the point, Kelvin, Celsius and Fahrenheit, without properly adjusting the figures so that they all work off the one scale. this was one of the fatal errors in the S & B study. That's why I answered, in response to the last line of the post before mine, "it shouldn't be here" - the study is fatally flawed.

Usually people, even scientists, who are arguing with evidence of global warming are deliberately throwing smoke in our eyes.

I can agree with that. the best response to such misinformation and disinformation is to make one's own enquiries without relying on arguments from authority.

As to the true relationship between teh medieval warming period and current global warming, there isn't one. The medieval warming period was strictly a local phenomemon caused by changes in one current.

This is the best information to date, but there is still some uncertainty. The various temperature reconstructions don't agree exactly, even though they all suggest the MWP was cooler than the global climate of the last 30 years.

Just to be clear, I was not endorsing the skeptical view, I was trying to explain it as best I could. Let me drill down a bit more...

There are two main rebuttals to the issue of the medieval warm period. The first is more prevalent and less subtle than the second.

The first is based on the mainstream view that current global temps are unmatched for the last x thousand years. Critics attempt to demonstrate that the MWP was warmer than the current climate, so that they might say, "See, this assertion about current temps being the highest for 'x' thousand years is wrong. The clear implication is that climate mainstream science gets things wrong. It can't be trusted.

The second, more subtle, and to my mind more interesting rebuttal is predicated on climate sensitivity (how much climate changes). If it can be shown that the Earth has undergone equal or bigger climate change in the past (especially warming), then this suggests that natural variability could be the reason for the current warm period.

In effect, the skeptical view on this is, "what's so different about what's happening today"?

Regarding the MWP, even if the period was warmer, the time it took to achieve that warmth is still considerably longer than the rise in temps we've experienced recently. and CO2 levels haven't moved this far or this much for millions of years. In that regard, the current situation is a significant departure from what we can discern of past climate change.

But, that last paragraph is an answer to the general rebuttals. I really wanted to clarify my points and position in reply to your post. I'll try and restrain myself. :-)

Now, as to the completely irrelevant point about sensitivity of the climate, the climate is extremely sensitive, and dynamically unstable, and that is why it is very easy to upset. However, people who point out how sensitive the climate has historically proven to be, are usually arguing just the opposite; nature is in control and nothing can upset it.

I'm not sure I quite understand this paragraph, but I'll attempt an answer.

Climate sensitivity is a key factor in adducing climate change. I've listed a couple of reasons why above, but to reply on point, if it was discovered the the climate is more sensitive to changes in, say, solar variation, and that the global temperature fluctuated more widely than we have estimated, then that would make a serious dent in the case for AGW. Alternatively, if we have overestimated climate sensitivity, then we are potentially overestimating the effect that added CO2 would have to the global temperature. Assessing climate sensitivity (direct response and feedbacks) is fundamental to understanding how much the climate changes if certain constituents of it change.

To bring it back to topic (and repeating - apologies for lack of conciseness) if we discover that the climate is more sensitive to changes in its (non-greenhouse gas) constituents - that a small change in sunlight, for example, can have a big impact on global climate - then this means that we could be underestimating climate response to other factors, and consequently overemphasising the impact of increased GHGs. This is the subtler point raised by critics of the mainstream view when they attempt to show that the MWP was warmer than today. If the temperature was warmer then, when there was no human activity pumping CO2 into the atmosphere, that means that it is more likely that today's warming might be a consequence of natural forces, rather than industrial CO2 emissions.

Since clearly there was really a medieval warming period, and clearly it has no bearing on what is happening today, there is absolutely no reason to be quibbling about those charts.

Although I don't completely agree with the reasoning, I do agree with the conclusion. There was no industrial CO2 emissions then, but there is now. Whatever caused the MWP, it doesn't tell us what the effect of anthropogenic greenhouse gases is having now.

Regards,

barry.
At March 06, 2008 7:36 AM, barry said…

This comment has been removed by the author.
At March 06, 2008 7:41 AM, barry said…

This comment has been removed by the author.
At March 06, 2008 7:46 AM, barry said…

Here are a couple of web pages on climate sensitivity and why it is important:

href=http://www.realclimate.org/index.php/archives/2004/11/climate-sensitivity/
href=http://www.realclimate.org/index.php/archives/2005/07/climate-sensitivity-and-aerosol-forcings/

Here is a web page on the MWP from realclimate:

http://www.realclimate.org/index.php/archives/2004/1

(Coby, I've deleted some posts on various threads - edited them really. Pls consign the deleted ones to oblivion, if you will. I don't know the correct code for links on this blogsite - it's different than the code I use at the fora I visit and I keep messin' up. Is there a page where I can learn the difference for your cite, so I stop making a hash of thing?)
At March 07, 2008 4:55 PM, barry said…

I tried above to iterate the skeptical POV regarding climate sensitivity. An alternative reading, one that accepts the mainstream view of AGW under greenhouse gases, might result in the opposite conclusion. If climate sensitivity is greater than we think, then we could be in for more warming than projected.
At March 08, 2008 7:21 AM, villandra said…

Barry:

I'm trying to find who owns the blog, and who you are, and cannot do either.

You refer to editing posts and asking people to leave them edited - did you edit only our own post, or are you the blog owner?

Secondly, you've got me really confused. The blog was started by someone who thinks that things people are doing contribute to global warming. Who that was I cannot determine. You keep arguing with me, but I can't for the life of me figure out exactly what you are arguing with! It is possible to read your posts as arguing with every word I've said in order to reach the same conclusions. Are you the blog owner, or a "climate skeptic"?
At March 09, 2008 1:46 PM, coby said…

Hi villandra,

It's my blog, though I am not active here anymore since moving to scienceblogs.com/illconsidered

FWIW, I don't think barry is arguing with you, though I just look at the comments as they come in my email, not inline, rather he is addressing various points made above (?).

But he will probably come back and speak for himself! Thanks for your participation here, both of you. It is nice to have intelligent comments :)
At March 12, 2008 10:31 AM, barry said…

You refer to editing posts and asking people to leave them edited - did you edit only our own post, or are you the blog owner?

I'm just a contributor, not the owner or a moderator. I believe I can only delete, not edit my posts.

Not arguing at all. Your expressed an alternative view to mine in the post before last and I was drawn to reply to that. If it seemed argumentative, then I put things poorly. I was bouncing happily off the opinions you gave.

barry.
At April 20, 2008 4:15 AM, Anonymous said…

Some way back one Anon posted: "Furthermore, I wonder why it is that right-wingers always need to bring up the "I used to be a Lefty" line "... Well, let me inform you. I'm one of them. Prior card carrying member of both Greenpeace and Sierra Club. Now I'm more "Libertarian who got tired of their myopic view of business and broken economics" and moved a bit more toward "Holding nose and standing left of Republicans a bit". Why bring it up? Because it says "Yes, I've been there, own the party books, sat on the protest lines, listened to the rants. Then I learned to think a bit more skeptically about all parties motivations and fact polishing." It says I'm not coming at this from a naive point of view either left or right wing. I learned and you can too.

Per the MWP, Holocene Opt. et al. They happened and are well attested. The nits being harvested are over exactly how hot and exactly how broad geographically. OK, keep harvesting. They raise an interesting point of "maybe GW is natural" AND "if we can't show MWP and HO data in any detail how can we make any statements about past climate with certitude?" Frankly, that we are still debating the degree and range of MWP and HO casts strong doubt on all the Hockey Stick Chicken Little folks and all the Don't Worry, Be Happy deniers. So until it gets sorted out I'm going to keep driving my car and heating my home. No, I'm not worried. We have a very long time to solve whatever it turns out needs to be solved. In the mean time I'm not following any lemming butts off any cliffs.

See "The Skeptical Environmentalist" by Lundborg (I think I spelled that right?). Not owned by Exxon. Also a "prior green" who did some fact checking. It ranges over a LOT of the green agenda, but does have a good chapter on GW. Don't bother with an Ad Hominem attack. The guy is a very legit Ph.D. at a European University (Copenhagen?). Statistician (I like statisticians, they know how to spot other folks math errors and lies really well...) and has done a great job of thinking straight. A minor gem from his work: Inside the computer models there is a "plug number" for degrees of warming per unit of time. The theoretical number is .8 while the observed value was .5 degrees. Since this is used in a compound growth formula, the actual number has a huge impact on the outcome. But it gets worse. The model makers used 1 degree. Why? To make things run faster and give more dramatic results.

Oh, and don't bother trying to ad hominem attack me either. I'm a semi-retired computer geek herder. (semi-retired means I made enough money that I don't have to work and that I'm not trying too hard to get a job, but feel like I ought to ;-) I report to no-one. All my attitudes and opinions are my own and not paid for by anyone (though the idea of getting paid for my ideas has a certain charm to it! ... ;-) I drive a biodiesel powered car (when I can get biodiesel, which is most of the time) and will be putting solar panels on the roof Real Soon Now. My agenda is simple: I like the results of the AGW Chicken Little crowd, and I hate their broken science and sloppy thinking processes. My only complaint is that they keep us using OPEC oil when we ought to be going to coal to liquids and telling OPEC to pound sand... but I'll take greener alternatives as an outcome if that's the only choice.

So what's the effect of that one plug number change in the models? Moves the potential "Aw Shit!" day from about 100 to 150 years in the future right up to in your face in your lifetime. Take it out, we got plenty of time. Basically, the computer model is based on a statistical lie. And this is the problem I see in much of the AGW crowd. A great faith in broken computer models, a willingness to bend the science to fit a political agenda, and a tendency to ad hominem attacks on the skeptics along with a huge tendency to Suck Their Own Exhaust (i.e. believe their own emissions endlessly recycled).

Oh, and a complete ignorance of just how much damage will be done by wasting resources tilting at GW windmills rather than using the money and energy to best advantage to cure diseases, drain mosquito swamps, feed people, et. al. GW, even AGW is NOT more important that curing malaria, advanced rice crops, water systems and CTL fuels for the next 50 years. Remember that the IPCC is a political body that edits scientists work... there are hundreds of billions to be made in carbon trading and manipulation schemes.

Another minor point? When the ex-Soviet Union collapsed, we lost about 1/3 of the worlds thermometers. Needless to say, a lot of them were in cold places like Siberia. This coincides with the most dramatic uptick in the "Global Average Temperature". While I agree with the guy who said that "The global average temperature is about as meaningful as the global average phone number"; even ignoring that, the loss of those thermometers damages all the temperature charts since. There is some kind of data massage done to try to adjust for it, but, well, we all know how reliable heavily massaged data is ... So if Las Vegas gets 5 degrees warmer, and Gorky gets 5 colder, nothing happened to the average, and just how to you take Gorky out next year? The very benchmark we use to discuss GW is fatally broken. In some ways more so than the MWP data. Thus the hockey stick breakage. Why graft broken thermometer data onto proxy data and get a broken hockey stick? Why not just use 100% proxy and avoid the problem? Maybe to make things more dramatic? I don't know. And if I don't know, I can't get on the bandwagon. Sorry. Try again.

And this pattern repeats. The more I dig into the AGW crowds data, the more I find what looks, smells, and sounds like a religious cult of true believers. Just trust us and drink our Koolaid ... see we have a web site with papers we've published reviewed by our friends. Even the insistence that scientific consensus somehow means something. If all it took was "consensus" to have truth we would all still believe that the earth was the center of the universe and that heavy things fall faster than light ones. BY DEFINITION science advances by breaking the consensus view. Einstein did it to Newton, for crying out loud. Get over it and stop with the consensus mantra.

Step up and say "We think we know some of this, but we need to work on it more and could have some bits wrong" and I'm with you. Tell me that "The science is all done and we have a consensus" and my Bull Shit O Meter goes off scale high. There is no consensus on MWP. Fine. The preponderance of evidence leans toward "It was very warm in most of the places I care about". I'm good with that. Similarly, I'm good with "We might be screwing things up with gigatons of CO2 but we have a few dozen years to work it out". Heck, I'd even back higher CAFE and carbon sequestration for enhanced oil recovery right now. I'd even love to see a plug in hybrid or pure electric car mandate. I'm not OK with "SHUT UP, SIT DOWN, and DO WHAT I SAY because I'M RIGHT!!! and it has to be done RIGHT NOW TO SAVE THE PLANET!!!" You lose me and I drive my 2 Ton car to the Diesel pump...

Bottom line? The Science isn't done and certainly isn't done cleanly. The venom, vitriol, hype and arrogance of the AGW crowd drives away folks who would be otherwise supporters of some action, even if tepid supporters. And the BS-O-Meter clanging doesn't help either. And oh, giving China and India a free pass on Kyoto was fatal. Just turned it into "move all heavy industry to Asia" time in the boardrooms of the west... And I'm certainly not interested in handing over control of the world economy to a group of unelected political hacks at a UN agency... Be logically consistent, dispassionate about data, and be honest about your failings and it will all work much better.
At April 23, 2008 11:47 AM, Anonymous said…

Step up and say "We think we know some of this, but we need to work on it more and could have some bits wrong" and I'm with you.

I read actual scientific studies, and this is pretty much what they all say. The folk at realclimate.org (a weblog run by real climate scientists) say it regularly. Some things are certain, some things highly likely, some things are little understood, and any decent scientist will tell you there is always a possibility that some completely unknown factor may yet be discovered.

It is erroneous to assume that because not everything is known or 'proved' it is impossible to formulate an useful understanding. No science theory is 100% accurate (or they wouldn't be caled 'theory', they'd be called 'law').

Thus we have a theory of evolution, of gravity, quantum field theory, big bang theory, relativity theory. None are laws ('proved' deterministically), and all have practical applications, but they are all provisional on better understanding. Same goes for climate theory. All are models of phenomena, imprecise, but variously useful.
At April 23, 2008 11:55 AM, Anonymous said…

Comments expressing certainty on this subject are more commonly found in the media and amongst the skeptical milieu.
At May 25, 2008 7:29 PM, Anonymous said…

Gentlemen,

This debate could go on and on forever since, depending on the data one sites,either position can be supported.
In the final analysis those who wish to impose anti-captialist regulations on a free market society will go for the "man made global warming" senario while the free market advocates will remain sceptical.
A word of warning. Before we rush headlong into governmentally imposed restrictions on such things as carbon emissions we need to consider the fact that there are eminent climatologists who have serious reservations about the concept of global warming pointing to the indesputable fact that the earth's temperature has varied widely over the millenia even in the pre-industrial ages.
We often hear the word "consensus"
used to describe the acceptance of the scientific community that global warming is a consequence of human activity, almost like a vote was taken and the GW side won.
Science isn't like an election but is the culmination of lots of hard work and scrupulous analysis.
I fear that this whole issue has become so highly politicized that rational debate is no longer possible.
So where do we go from here? Be careful, be very careful because the law of unintended consequences is one law thats not up for debate.
At June 03, 2008 10:02 PM, Anonymous said…

This debate could go on and on forever since, depending on the data one sites,either position can be supported.

'Either side'? I don't see it this issue as a stand off. Or rather, I'm aware of the foot soldiers but not interested in the skirmish. I reckon most people don't join forces but tend to want to make up their own mind. The socialist versus capitalist metanarrative is just silly.

There are multiple points of view. Politics oughtn't be confused for science.

In the final analysis those who wish to impose anti-captialist regulations on a free market society will go for the "man made global warming" senario while the free market advocates will remain sceptical.

Why pitch this as a battle between economic forces anyway? Why those ideologies and not any other?

We often hear the word "consensus" used to describe the acceptance of the scientific community that global warming is a consequence of human activity, almost like a vote was taken and the GW side won.

Again, you're confusing politics for science.

Science isn't like an election but is the culmination of lots of hard work and scrupulous analysis.

Yes, an ever-ongoing process.

I fear that this whole issue has become so highly politicized that rational debate is no longer possible.

I think I can debate this rationally. Do you think you can, too?

So where do we go from here? Be careful, be very careful because the law of unintended consequences is one law thats not up for debate.

I think climate scientists should be careful, meticulous, aware of shortcomings in their work, adjusting their findings in the light of better or additive knowledge, and publish their findings openly, allowing for intellectual property. Seems to me that this is pretty much what happens.
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A Few Things Ill Considered

Thursday, February 23, 2006

The Medieval Warm Period was just as warm as today

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