Having only glanced over the Science Express study, I'm forced to ask a few questions. The first is, what was the baseline? I'm certainly open to the proposition that fire incidence and intensity have increased since 1970, and that CO2 related climate change could be a contributing factor to some of that fire behavior, but shouldn't we really be comparing those findings with a more historically relevant baseline, say pre-colonial? Maybe the increase is cyclical in some forests (high alpine forests in the West tend to burn in 150 to 300 year intervals) and management related in others.

Also, given the wide array of forest types throughout the country (Oregon alone has at least 12), perhaps the findings should be indexed by forest type instead of national origin.

And if climate change has indeed contributed to these changes, shouldn't we be asking ourselves, in addition to trying to rein in CO2 releases and other climate change drivers, what are the best policies to maintain and increase resiliency in the nation's forests?

As Jeff, I'm hopeful that Oregonians and indeed all Americans will see the folly in continuing our present course of atmospheric negligence. But studies like this one, like all good science, raises at least as many questions as it answers.

S

The Report:The authors found a jump of four times the average number of wildfires beginning in the mid-1980s compared with the 1970s and early 1980s JK: The current warming cycle started around 1850 (end of the little ice age) - if warming is the cause, why did it take 100 years to become apparent?

For background see: http://www.nap.edu/catalog/11676.html the recently released climate change report that found that the little ice age most probably DID exist (sorry Al Gore) and that we are the warmest since then. (So what!)

Page 111 (sheet 126) has the “OVERALL FINDINGS AND CONCLUSIONS” section where you can find that we know little about climate more than 1100 years ago. And that there was probably a medieval warming period and evidence is mixed as to whether we are warmer than that time. (Sorry agin Al)

They also said that “Even less confidence can be placed in the original conclusions by Mann et al. (1999) that “the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium”” (page 21 (sheet36)) Sorry again Al baby.

Oh, did I mention that the report is from the National Academy of Sciences, a very highly respected group of scientists, not groveling politicians or money grubbing international environmental corporations?

Thanks JK

Stryker:

You've got it all wrong: environmentalists PREFER to select a baseline that supports their thesis. That allows them to criticize the "flat-earthers" who challenge their findings, and then suggest THEY are the ones politicizing the baseline.

WE'RE SCIENTISTS, comes the angry defense, WE DON'T HAVE A POINT OF VIEW unless/until it is supported by the data. And the data is apolitical, right?

Wow, there certainly is some misinformation on this blog.

USE OF THE BASELINE: The study used the 1970 baseline for measuring fire incidence and severity. The effects on fire of the temperature increases are what is shown by this study. Independently(for instance the already cited NAS reort), the temperature record over longer periods can be provided - and over any time period it clearly shows that our current warming is significant and rapid. Just because a blogger takes a study's baseline out of the context in which it was used does NOT diminish the credibility of its argument - unless, of course, your last name is Inhoffe.

And as far as JK's tangled characterization of the National Academies of Sciences conclusions, citing ONE uncertainty in the data of the most studied (in terms of research dollars)question in the history of mankind does not reduce the clarity of the overall conclusions of the results of the science of global warming. Here is the conclusion of the NAS on what the science says (and I agree, the NAS is highly respected): "Despite remaining unanswered questions, the scientific understanding of climate change is now sufficiently clear to justify taking steps to reduce the amount of greenhouse gases in the atmosphere. .... Failure to implement significant reductions in net greenhouse gas emissions will make the job much harder in the future - both in terms of stabilizing their atmospheric abundances and in terms of experiencing more significant impacts." http://www.nap.edu/catalog/11676.html. Download free Brief, quote is on pg. 18.

I think the NAS is very clear on where the science stands. And their recommendations are remarkably direct for scientists.

OregonJ:

I agree the Earth is warming, at least since the end of the little ice age. That warming trend has become more pronounced in the last century.

But that leads me to more questions than conclusive answers.

1. Is human activity the primary driver of the warming?

2. Even if humankind did everything possible (elimination of CO2 emitting automobiles, elimination of coal fired electric plants, massive investments in nuclear and "sustainable" energy and manufacturing practices) would it make any substantive difference?

3. Is this warming trend simply the inevitable conclusion of the current inter-glacial which is merely accelerated by human activity? If so, will natural mechanisms force a correction, leading to the next ice age?

4. Perhaps global climate change will lead (inevitably) to an earth capable of sustaining a much smaller global population. If so, shouldn't our emphasis be on population control strategies (or coping mechanisms, like hydroponic farming), rather than simply trying (like Sisyphus) to push the rock up the hill. If it's too late to reverse global warming, then our economic resources and brainpower should be focussed on dealing with the aftermath.

5. Is there any benefit in making half the world a "greener" place? If we do everything in our power, but the Middle East and China continue to depend on fossil fuels, aren't we simply transferring the point of CO2 origin?

Here are some answers for A.S.

1. The scientific consensus (IPCC) is that it is anthropogenic. http://www.ipcc.ch/present/graphics/2001syr/large/06.01.jpg

2. Yes, a very substantive difference - policy choices are estimated to cause the difference in temp increase, just until 2100, of 3.6 degrees F vs 8.1 degrees F. And that 4.5 deg. difference(maybe another 20 feet or so of sea level increase)only sets the stage for the rates of increase your descendents will deal with in the 22nd century. http://www.ipcc.ch/present/graphics/2001syr/large/05.24.jpg

3. NOT ONE peer-reviewed scientific papers predicts a sudden atmospheric cooling to counteract anthropogenic global warming.

4. I have no comment on the desirability of mass reductions in human populations - but the assertion that it is 'too late'to reverse GW does not get at what is the critical policy question: should we pursue public policies that will reduce GHG emissions so that the scale of human-induced global warming is mitigated

5. Leadership, especially in technology, will come from the rich, developed economies - we have already seen it in the dramatic reductions(magnitudes of 10x, 100x....)in the price of wind power and photovoltaics, etc..and the energy efficiency technologies(green bldgs etc). Now we need to get our policies right on spreading the use of these tools through the economy, and also get to expediting the deployment of the new technologies such as coal with CO2 sequestration, etc. The tools exist for us to take the slower temp. increase path, and the Chinas of the world, etc need to get this low carbon stuff into their economy as soon as possible - but the developed countries need to be the first movers (and Europe and Japan are coming along better than us ; policy choices matter, and thats why the US and Australia are falling the farthest behind.

oregonj: Wow, there certainly is some misinformation on this blog. JK: Including your posting that I am now responding to!

oregonj: And as far as JK's tangled characterization of the National Academies of Sciences conclusions, citing ONE uncertainty in the data of the most studied (in terms of research dollars)question in the history of mankind does not reduce the clarity of the overall conclusions of the results of the science of global warming. JK: I think you completely missed the point of the most recent report: It shredded the very foundations of current climate studies. The most compelling indication of serious warming is the famous “hockey stick” chart of Mann et.al. It DOES NOT show a medieval warm period or little ice age. By affirming that these two climate events DID INDEED EXIST, the credibility of that chart is shredded. (Along with it the alarmist babbling of Gore et al.) Also shredded is the credibility of the methods used by Mann et.al., which are widely used in much of the whole field.

Reread the single MOST CERTAIN conclusion (From Page 111, sheet 126): “ high level of confidence that global mean surface temperature was higher during the last few decades of the 20th century than during any comparable period during the preceding four centuries. “

Now apply their other HIGHLY CERTAIN conclusion: “The existence and extent of a Little Ice Age from roughly 1500 to 1850 is supported by a wide variety of evidence”

There is only one way to read this: WE ARE WARMING UP AFTER THE LITTLE ICE AGE. (So what!)

Now consider this: “Very little confidence can be assigned to statements concerning the hemispheric mean or global mean surface temperature prior to about A.D. 900"

And don’t forget ( page 21 sheet36): Even less confidence can be placed in the original conclusions by Mann et al. (1999) that “the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium...”

If we can’t look back further than 1100 years, we know almost nothing on a geological scale, which is what climate changes are. For instance some data shows that it was warmer in the time of Christ than now - but we don’t know. Some data shows that the temperature raises BEFORE CO2 increases, but we really don’t know.

oregonj: Here is the conclusion of the NAS on what the science says (and I agree, the NAS is highly respected): . . . http://www.nap.edu/catalog/11676.html. Download free Brief, quote is on pg. 18. JK: That report appears to have been created BEFORE the more recent report which shredded the foundations of your cited report. Why don’t you study the “OVERALL FINDINGS AND CONCLUSIONS” of the real report “Surface Temperature Reconstructions for the Last 2,000 Years” It is free at http://www.nap.edu/catalog/11676.html

We are witnessing a turning point in climate science. Hopefully this is the beginning of the end of the warming panic and the start of more reasoned study. Maybe the alarmists will go back to trying to panic us about the coming ice age! (See: http://www.saveportland.com/Climate/index.html)

Thanks JK

oregonj: Here are some answers for A.S. JK: Most of the work of the IPCC has been cast in doubt by the “Surface Temperature Reconstructions for the Last 2,000 Years” The IPCC’s last report relied heavily on the now discredited “hockey stick” chart.

oregonj: 2. Yes, a very substantive difference - policy choices are estimated to cause the difference in temp increase, just until 2100, of 3.6 degrees F vs 8.1 degrees F. And that 4.5 deg. difference(maybe another 20 feet or so of sea level increase)only sets the stage for the rates of increase your descendents will deal with in the 22nd century. http://www.ipcc.ch/present/graphics/2001syr/large/05.24.jpg JK: This is the famous “Hockey stick” chart that was TOTALLY DISCREDITED by the more recent “Surface Temperature Reconstructions for the Last 2,000 Years” as I explained in my previous posing.

oregonj: 3. NOT ONE peer-reviewed scientific papers predicts a sudden atmospheric cooling to counteract anthropogenic global warming. JK: I keep hearing this provable lie. Please cite a credible source.

oregonj: ... should we pursue public policies that will reduce GHG emissions so that the scale of human-induced global warming is mitigated JK: Not until we know what the heck we are doing. And we don’t at the present time. See the above mentioned report.

Thanks JK

Sorry JK, you are the one who has missed the point (intentionally I think) of the NAS report.

From the NAS report - "The basic conclusion of Mann et. al. (1998, 1999)was that the late 20th century warmth in the Northern Hemisphere was unprecedented during the last 1000 years. This conclusion has subsequently been supported by an array of evidence that includes both additional large-scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators, such as melting on icecaps and the retreat of glaciers around the world, which in many cases appear to be unprecedented during at least the last 2000 years."

For those readers of this blog who are not already aware of it, the blog RealClimate is an excellent source of the scientific facts surrounding climate change.

I think JK also missed the part of the report (pg 23) that says: "It should also be noted that the scientific consensus regarding human-induced global warming would not be altered if, for example, the global mean surface temprerature 1000 years ago was found to be as warm as it is today.

I am also on the edge of my chair waiting for that peer-reviewed article that describes how sudden climate cooling is going to counteract human-induced global warming.

Patrick Kennedy: Sorry JK, you are the one who has missed the point (intentionally I think) of the NAS report. JK: Why are you accusing me of bad faith?

Patrick Kennedy: From the NAS report - "The basic conclusion of Mann et. al. (1998, 1999)was that the late 20th century warmth in the Northern Hemisphere was unprecedented during the last 1000 years. This conclusion has subsequently been supported by an array of evidence that includes both additional large-scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators, such as melting on icecaps and the retreat of glaciers around the world, which in many cases appear to be unprecedented during at least the last 2000 years." JK: First that is a different claim than the one I pointed out. Second, please reconcile your quote with the quote I used in my previous post from the same report (I’ll include the whole paragraph this time here from page 21,sheet36,11676.pdf , bold added ):

“Based on the analyses presented in the original papers by Mann et al. and this newer supporting evidence, the committee finds it plausible that the Northern Hemisphere was warmer during the last few decades of the 20th century than during any comparable period over the preceding millennium. The substantial uncertainties currently present in the quantitative assessment of large-scale surface temperature changes prior to about A.D. 1600 lower our confidence in this conclusion compared to the high level of confidence we place in the Little Ice Age cooling and 20th century warming. Even less confidence can be placed in the original conclusions by Mann et al. (1999) that “the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium” because the uncertainties inherent in temperature reconstructions for individual years and decades are larger than those for longer time periods, and because not all of the available proxies record temperature information on such short timescales.”

JK: Note that they only found it plausible and mention “substantial uncertainties”. This is hardly a ringing endorsement of Mann. I think that they are just avoiding calling the claim what it is: unsupported by enough facts to buy into. You will also note that they go on to say that they have even less confidence in Mann’s claim that “the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium” right after they re-affirm the “Little Ice Age”, a feature missing from the”hockey stick“ chart made famous by the IPCC and referred to in an above post. This ONE item alone destroys the credibility of the “hockey stick”. The endorsement of the mediaeval warming period further erodes Mann et al.

So, we have two seemingly contradictory statements. I think that they are just avoiding rubbing salt in the wounds after ripping the foundation out from under the “hockey stick”: They put the sanitized version where the press will see it and be satisfied, then put the meat where the scientists will see it and learn from it. We should start seeing a whole new rationality in the science community as a result. This may even open the flood gates to a real criticism of the whole science fiction of climate change. Remember, it was just a few decades ago that some of these same people were in a thither about the coming ice age. One of them even talks about lying to the press to generate panic (Schnider in Discover, Oct 89, pg47)

RealClimate is run by Mann et al the creator of the “hockey stick” chart. The person who exposed some of Mann’s problems runs ClimateAudit.org. Take a look at that side too.

Thanks JK

oregonj: I think JK also missed the part of the report (pg 23) that says: "It should also be noted that the scientific consensus regarding human-induced global warming would not be altered if, for example, the global mean surface temprerature 1000 years ago was found to be as warm as it is today. JK: Many of the articles that go into that “scientific consensus” likely rely on the same flawed methods and data as used by the now discredited “hockey stick”. You have to give this time to play out.

oregonj: I am also on the edge of my chair waiting for that peer-reviewed article that describes how sudden climate cooling is going to counteract human-induced global warming. JK: See Science, 10 December 1976; Vol 194, Number 4270: Article titled: “Variations in the Earth’s Orbit: Pacemaker of the Ice Ages”: “6) It is concluded that changes in the Earth’s orbital geometry are the fundamental cause of the succession of ice ages” “7) A model of future climate based on the observed orbital-climate relationships, but ignoring anthropogenetic effects, predicts that the long term trend over the next few thousand years is towards extensive Northern Hemisphere glaciation.”

Admittedly a bit old and not exactly what you asked for, but close, and it must be the word of GOD as it is peer reviewed as you asked. (Would you believe everything you read in a peer reviewed journal of astrology?)

For a number of article from New York times, Wash Post, U.S News, Science digest etc., some of which are probably based on peer reviewed articles, see: http://www.saveportland.com/Climate/index.html

Thanks JK

To readers of this blog who are not familiar with climate change science, the origin of the term "hockey stick" is defined as follows (from the blog realclimate) - "The term "Hockey Stick" was coined by the former head of NOAA’s Geophysical Fluid Dynamics Laboratory, Jerry Mahlman, to describe the pattern common to numerous proxy and model-based estimates of Northern Hemisphere mean temperature changes over the past millennium. This pattern includes a long-term cooling trend from the so-called "Medieval Warm Period" (broadly speaking, the 10th-mid 14th centuries) through the "Little Ice Age" (broadly speaking, the mid 15th-19th centuries), followed by a rapid warming during the 20th century that culminates in anomalous late 20th century warmth (Figure 1). Numerous myths regarding the "hockey stick" can be found on various non-peer reviewed websites and other non-scientific venues."

Note: a proxy is a time series of a thing that can be related to temperature. Examples are tree ring widths or the advance or decline of glaciers.

Some conservative blogs, institutes and media work overtime to try to convince people that the overwhelming scientific agreement that global warming is caused by human acitivities and that it is a serious danger is incorrect. They have pretty much lost the battle because the facts just aren't on their side. Only a few holdouts continue to claim global warming is "science fiction."

The real challenges are not trying to convince the few remaining skeptics that they are wrong but in coming to grips with the solutions necessary to prevent dangerous global climate change. There are no silver bullets and the solutions will touch everyones lives.

PK, I agree that the "real challenges are not trying to convince the few remaining skeptics..". Not only is it a diversion, but Gelbspan has documented that 'diversion' from taking action is the exact intent of those interests (the 2 largest funders are ExxonMobil and the Western Fuels Assn. ) who are funding most of the climate skeptic 'science'.

That brings us finally back to Jeff's original posting about the increased fire risk - this I hope is a consequence of GW that finally gets Sen Smith to move on this issue.

Patrick Kennedy: To readers of this blog who are not familiar with climate change science, the origin of the term "hockey stick" is defined as follows (from the blog realclimate) - "The term "Hockey Stick" was coined by the former head of NOAA’s Geophysical Fluid Dynamics Laboratory, Jerry Mahlman, to describe the pattern common to numerous proxy and model-based estimates of Northern Hemisphere mean temperature changes over the past millennium. This pattern includes a long-term cooling trend from the so-called "Medieval Warm Period" (broadly speaking, the 10th-mid 14th centuries) through the "Little Ice Age" (broadly speaking, the mid 15th-19th centuries), followed by a rapid warming during the 20th century that culminates in anomalous late 20th century warmth (Figure 1). Numerous myths regarding the "hockey stick" can be found on various non-peer reviewed websites and other non-scientific venues."

JK: The problem is that the widely distributed “hockey stick” chart DOES NOT SHOW THE Medieval Warm Period or “a Little Ice Age from roughly 1500 to 1850”. That is why the hockey stick chart is discredited. That chart is the foundation of the heightened concern about climate. Without that chart all you have is a normal warming coming out of the little ice age. Additionally the sharp rise at the end of the chart linked to, in a previous posting, ( http://www.ipcc.ch/present/graphics/2001syr/large/05.24.jpg) is a 100 year projection, not real data. It gives a false impression unless you actually read the labels-did you do that? I did.

Patrick Kennedy: Some conservative blogs, institutes and media work overtime to try to convince people that the overwhelming scientific agreement that global warming is caused by human acitivities and that it is a serious danger is incorrect. They have pretty much lost the battle because the facts just aren't on their side. Only a few holdouts continue to claim global warming is "science fiction." JK: Try this FACT from the peer reviewed report: “ Even less confidence can be placed in the original conclusions by Mann et al. (1999) that “the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium” because the uncertainties inherent in temperature reconstructions for individual years and decades are larger than those for longer time periods, and because not all of the available proxies record temperature information on such short timescales. (NAS report, 11676.pdf, page 21, sheet36, bold added)”

Patrick Kennedy: The real challenges are not trying to convince the few remaining skeptics that they are wrong.. JK: Actually the real problem is how to gather accurate evidence about past climate, so that we can judge where we really are. Please understand the ramifications of this quote: “Very little confidence can be assigned to statements concerning the hemispheric mean or global mean surface temperature prior to about A.D. 900 because of sparse data coverage and because the uncertainties associated with proxy data and the methods used to analyze and combine them are larger than during more recent time periods. (NAS report, 11676.pdf, sheet 127, bold added)”

That quote simply says that WE DON’T KNOW THE PAST. If we don’t know the past, we cannot judge where we are now. End of debate - you need to admit that we don’t know and avoid ruining the economy in the name of a false god.

That report effectively discredited the hockey stick chart, the claim of warmest decade in a millennium and the accuracy of past climate data. The global warming advocates are left with ONLY: we are warmer than the little ice age, almost for sure, and we might be warmer than the Medieval Warm Period. Oh, and man had something to do with the warming after the little ice age. This is hardly cause for the panic we see in some circles, or a call to radically alter our lifestyles.

All of my quotes are from the recently released National Academy of Sciences Report on global climate change (Report is free at: http://www.nap.edu/catalog/11676.html )

Thanks JK

At this point I have laid out, over several posts, why the NAS report reveals the shaky foundations of the global warming panic.

The report shows that there is warming since the little ice age, perhaps with man’s contribution, but nothing shows that we are out of the normal wide variations seen in the past, most of which is currently unknown (the climate further back than A.D.900 is not reliably known due to lack of data and accuracy uncertainties.)

In view of these facts, anyone continues to argue for radical climate action is simply arguing their religion. I do not argue religion, so this will end my postings in this thread unless something non-religious comes up.

Thanks JK

As a layman, I'm convinced that:

1. The earth is getting warmer.
2. The warming is caused, at least in part by human activity. After all, we inhale at 65 degrees and exhale at 98.6 degrees.
3. We know that there were epochs when the earth was much colder than it is now (the ice ages), and others when it was much warmer (when the dinosaurs roamed).

My question is, who knows what the temperature is supposed to be? Just because it was the average temperature a couple of generations or a couple of centuries ago, doesn't mean that is what Mother Earth has in mind.

I confess myself rather disappointed with the items that JK has posted in this thread. I had some exchanges with him about a month ago on a thread about the Gore movie. (I happen to be an Earth scientist although not a climate-science specialist. As I work for a public agency, I have to use a pseudonym so nobody tries to claim I am presenting an opinion on behalf of my agency.)

The business about climate change and forest fires aside, JK claims that the Mann "hockey stick" has been discredited. (The "hockey stick" diagram shows changes in global temperature.) This claim will come as a shock to climate researchers--for example, the folks who maintain this website for a general audience. The exchange I had with JK a month ago dealt with just this "hockey stick" issue. He asked that I comment on a specific figure in a specific scientific journal article. I did so. JK had misunderstood the figure in question--one that seems to be at the crux of his statement about the validity or not of the "hockey stick". I would be happy to post again my final posting from the earlier thread (which got prematurely yanked from this website) if asked to do so by Monday evening (after which I leave for vacation).

By the way, the National Academy of Sciences report that is generating so much heat in this discussion thread is discussed here
here (realclimate.org again).

JK's statement that there are practically no data bearing on climate prior to AD900 is incorrect. People have been working assiduously for several decades to develop so-called climate proxies. The best known are ice cores from Greenland, Antarctica, and elsewhere (tropical glaciers from the high Andes, say), but there are a lot of other proxies. The nature of such proxies--what they are, how they are calibrated, and so on--is very nicely presented in:

Jones, P.D., and Mann, M.E., Climate Over Past Millennia, Reviews of Geophysics, vol. 42, RG2002, doi: 10.1029/2003RG000143, 2004

which is certainly available at the Portland State University library.

Well, enjoy what's bound to be a continuing lively thread, folks.

lin qiao

Posted by: lin qiao | Jul 10, 2006 5:37:38 PM

lin qiao By the way, the National Academy of Sciences report that is generating so much heat in this discussion thread is discussed here JK: Why not get it from the source: http://www.nap.edu/catalog/11676.html

lin qiao here (realclimate.org again). JK: ClimateAudit.org does a pretty good job of debunking realClimate, a web site established to defend the “hockey stick”.

lin qiao JK's statement that there are practically no data bearing on climate prior to AD900 is incorrect. JK: Here is the reality from From Page 111, sheet 126 of the report: ”Very little confidence can be assigned to statements concerning the hemispheric mean or global mean surface temperature prior to about A.D. 900 because of sparse data coverage and because the uncertainties associated with proxy data and the methods used to analyze and combine them are larger than during more recent time periods.”

Thanks JK

ClimateAudit.org is a website set up by one Steve McIntyre, a retired economic (i.e., mineral exploration) geologist. He is of course entitled to his own opinions. Readers can have a look at McIntyre's website, at realclimate.org, and at any number of other websites, and make their own judgments about whether anyone is debunking anyone else. A Google search on the keywords "steve mcintyre climate" returned 321,000 hits!! Kind of daunting.

Here are the summary conclusions of the National Academy report. JK correctly quoted a paragraph from that report, but out of context, unfortunately.

<hr/>

OVERALL FINDINGS AND CONCLUSIONS

Based on its deliberations and the materials presented in Chapters 1-11 and elsewhere, the committee draws the following overall conclusions regarding large-scale surface temperature reconstructions for the last 2,000 years:

• The instrumentally measured warming of about 0.6°C during the 20th century is also reflected in borehole temperature measurements, the retreat of glaciers, and other observational evidence, and can be simulated with climate models. • Large-scale surface temperature reconstructions yield a generally consistent picture of temperature trends during the preceding millennium, including relatively warm conditions centered around A.D. 1000 (identified by some as the “Medieval Warm Period”) and a relatively cold period (or “Little Ice Age”) centered around 1700. The existence and extent of a Little Ice Age from roughly 1500 to 1850 is supported by a wide variety of evidence including ice cores, tree rings, borehole temperatures, glacier length records, and historical documents. Evidence for regional warmth during medieval times can be found in a diverse but more limited set of records including ice cores, tree rings, marine sediments, and historical sources from Europe and Asia, but the exact timing and duration of warm periods may have varied from region to region, and the magnitude and geographic extent of the warmth are uncertain. • It can be said with a high level of confidence that global mean surface temperature was higher during the last few decades of the 20th century than during any comparable period during the preceding four centuries. This statement is justified by the consistency of the evidence from a wide variety of geographically diverse proxies. • Less confidence can be placed in large-scale surface temperature reconstructions for the period from A.D. 900 to 1600. Presently available proxy evidence indicates that temperatures at many, but not all, individual locations were higher during the past 25 years than during any period of comparable length since A.D. 900. The uncertainties associated with reconstructing hemispheric mean or global mean temperatures from these data increase substantially backward in time through this period and are not yet fully quantified. • Very little confidence can be assigned to statements concerning the hemispheric mean or global mean surface temperature prior to about A.D. 900 because of sparse data coverage and because the uncertainties associated with proxy data and the methods used to analyze and combine them are larger than during more recent time periods.

<hr/>

Again, as noted in my previous posting, there are indeed a plethora of paleoclimate proxy data prior to AD900. The context for the last paragraph in the blurb quoted above needs to be understood properly. The farther we go back in time, the sparser the paleoclimate record becomes. Far enough back, the data are so geographically sparse that indeed one can draw quantitative conclusions about some things but not other things. For example, the oxygen isotope record from a Greenland ice core might tell us quite nicely about temperature in the interior of Greenland X thousand years ago, but nothing specific about mean hemispheric temperature, for which we would need to have data from a lot of places.

Ice core records from Greenland and Antarctica go right back through the Eemian (the last interglacial period--that is, the one prior to the interglacial the world has been experiencing for the last roughly 10,000 years) and into ice that is more than 130,000 years ago. The depth distribution of oxygen isotopes in the ice cores tells us something about the temperature of the precipitation that fell at any given time.

The Jones and Mann Reviews of Geophysics article that I cited previously is a really nice overview of what exactly paleoclimate proxy data are.

There needs to be a branch of the environmental movement- call it teleoecology, maybe- that tries to figure out empirical ways to tell when a given trend is past the point of no return. Progressive social policy should have before/after versions. An inmodest proposal.

lin qiao: Here are the summary conclusions of the National Academy report. JK correctly quoted a paragraph from that report, but out of context, unfortunately. JK: I’ve inserted some comments in italics and bolded some of the original text that you posted to help your understanding of it. As to “out of context”, “Very little confidence” means just that, your qualifiers are not needed. See below.

lin qiao’s excerpt from the report OVERALL FINDINGS AND CONCLUSIONS

Based on its deliberations and the materials presented in Chapters 1-11 and elsewhere, the committee draws the following overall conclusions regarding large-scale surface temperature reconstructions for the last 2,000 years:

• The instrumentally measured warming of about 0.6̊C during the 20th century is also reflected in borehole temperature measurements, the retreat of glaciers, and other observational evidence, and can be simulated with climate models. • Large-scale surface temperature reconstructions yield a generally consistent picture of temperature trends during the preceding millennium, including relatively warm conditions centered around A.D. 1000 (identified by some as the “Medieval Warm Period”) and a relatively cold period (or “Little Ice Age”) centered around 1700. The existence and extent of a Little Ice Age from roughly 1500 to 1850 is supported by a wide variety of evidence including ice cores, tree rings, borehole temperatures, glacier length records, and historical documents. Evidence for regional warmth during medieval times can be found in a diverse but more limited set of records including ice cores, tree rings, marine sediments, and historical sources from Europe and Asia, but the exact timing and duration of warm periods may have varied from region to region, and the magnitude and geographic extent of the warmth are uncertain. This affirms the existence of the medieval warm period AND the little ice age. Since neither of these features show up on the “hockey stick” chart, this flaw casts serious doubt on the chart and the methods used to create it, as well as all other work using these methods.In plain English: the “Hockey Stick” Chart has been disproven. (Notice below that they compare current temperature to the medieval warm period, but on the “hockey stick” chart they are nowhere close in temperature-this difference alone should disprove the chart and its methods.) • It can be said with a high level of confidence that global mean surface temperature was higher during the last few decades of the 20th century than during any comparable period during the preceding four centuries. This statement is justified by the consistency of the evidence from a wide variety of geographically diverse proxies. Four centuries ago was 1600 A.D., right in the middle of the little ace age which ran from 1500 to 1850 per above. The committee basically said: we are warmer than the middle of the little ice age. Personably I’m glad! • Less confidence can be placed in large-scale surface temperature reconstructions for the period from A.D. 900 to 1600. Presently available proxy evidence indicates that temperatures at many, but not all, individual locations were higher during the past 25 years than during any period of comparable length since A.D. 900. The uncertainties associated with reconstructing hemispheric mean or global mean temperatures from these data increase substantially backward in time through this period and are not yet fully quantified. The use of the phrase“many but not all” hardly suggests the comprehensive knowledge that justifies a need for immediate action to stem global warming. It does, however, suggest that there might be something substantiateable here. • Very little confidence can be assigned to statements concerning the hemispheric mean or global mean surface temperature prior to about A.D. 900 because of sparse data coverage and because the uncertainties associated with proxy data and the methods used to analyze and combine them are larger than during more recent time periods. Very little confidence means just that (they merely go on to give the reason: we don’t yet know enough.)

JK: Now lets add one more quote (Again I bolded parts of the original and added comments in italic; from page from page 21, sheet36): Based on the analyses presented in the original papers by Mann et al. and this newer supporting evidence, the committee finds it plausible that the Northern Hemisphere was warmer during the last few decades of the 20th century than during any comparable period over the preceding millennium. Note the use of the word “plausible”. This is not a very high degree of confidence. The substantial uncertainties currently present in the quantitative assessment of large-scale surface temperature changes prior to about A.D. 1600 lower our confidence in this conclusion compared to the high level of confidence we place in the Little Ice Age cooling and 20th century warming. Even less confidence can be placed in the original conclusions by Mann et al. (1999) that “the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium” because the uncertainties inherent in temperature reconstructions for individual years and decades are larger than those for longer time periods, and because not all of the available proxies record temperature information on such short timescales. The committee has even less confidence in this claim than they had in something that was only plausible. In Plain English, this claim sucketh. Also keep in mind that his report is basically debunking the politically correct position and therefore needs to tread lightly.

JK: Over the years, the public has paid little attention to the climate debate, until the “hockey stick” chart and the claim that “the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium” The report basically destroys both of these claims. Scientists usually pick up on this stuff, reporters usually don’t. I expect to see future papers in the scientific journals substantially changed by the committee’s report. Eventually the press will come around and the warming panic will subside. Heck the climate might just resume a down cycle and then the alarmists will cry about the coming ice age as they did in the 1960's (gotta keep those research grants coming). See http://www.saveportland.com/Climate/index.html

lin qiao: .. The context for the last paragraph in the blurb quoted above needs to be understood properly... JK: It is pretty clear: “Very little confidence can be assigned to statements...” The rest is the why. Or am I misinterpretating “very little confidence”?

lin qiao: The Jones and Mann Reviews of Geophysics article that I cited previously is a really nice overview of what exactly paleoclimate proxy data are. JK: Can I presume this paper uses the same flawed methods as those that lead to the fatally flawed “hockey stick.” Or do I have to print out and read it?

Thanks JK

I am leaving in a few minutes for a week's vacation with family and this will be absolutely the last thing I have to add to this thread. I am changing my approach here from trying to made rational, conservative scientific commentary to something else: something about methodology.

Scientific research is about trying to understand how nature works. Part of this process is stating explicitly what data one has, how confident one is in the data, and what the errors are. Quantitatively. What we call "error bars" in the business, when we represent data on graphs. Error bars are commonly represented qualitatively in a textual manner by terms such as "high confidence", "moderate confidence", and so on. This is usage familiar to anyone who does scientific research for a living. Investigators claiming inerrancy do not get their papers published, because no peer reviewer or editor would accept such an absurd claim.

On the other hand, lawyerly cross-examination and debate-team tactics are not about trying to understand how nature works. They are, too often and sadly, about playing linguistic tricks and trying to trip people up, or what is known in the legal business as "impeaching the witness' credibility." The scientist's error bars are turned on their head and "spun" as meaning "these dingbats don't actually know this and are trying to pull a fast one."

I will leave it to readers to determine whether either of these characterizations meaningfully describes commentary in this thread.

Sorry, after sending that last item, I realized I should give a specific example of the cross-examination / debate-team approach.

I mentioned in an earlier posting a very nice review article about just what paleoclimate proxy data are, how they are calibrated, how they are applied, and so on. It's an article that I personally learned a lot from. Reviews articles like this one (in the journal Reviews of Geophysics) are invariably invited submissions (meaning the editors solicit them) and are the sort of thing that a grad-school adviser is likely to send a grad student off to consult, because they are a jumping off point for the pertinent technical literature.

JK's comment about this article is as follows:

"Can I presume this paper uses the same flawed methods as those that lead to the fatally flawed 'hockey stick.' Or do I have to print out and read it?"