fire records go online medieval vs. modern warmth

The University of Arizona | 1

Spring 2004 Newsletter of the Laboratory of Tree-Ring Research

The VenerableBristlecone Pine

Fire Records Go Online

page 3

Medieval vs.ModernWarmth

page 4

The VenerableBristlecone Pine

page 6

2 | Laboratory of Tree-Ring Research

DIRECTOR’S NOTE

TREE-RING TIMES

VOLUME 4, ISSUE 1, SPRING 2004

The Laboratory of Tree-Ring Researchcontinues to benefit from the generosity offriends and donors. Here we thank thosewhose 2003 contributions to LTRR programsand scholarships were not reported in thesummer issue of the Tree-Ring Times.• Malcolm Weiner provided support for a

project to understand the connectionbetween “frost rings” in trees and volcanicexplosions.

• David R. Wilcox donated to the Agnese N.Haury Fellowship Fund that helps scholarsfrom overseas come to the LTRR for hands-on learning.

• Eileen Ferguson contributed to theBristlecone Pine Student Endowment,designated for students involved in researchon the bristlecone.

• The Eastern Sierra InterpretiveAssociation of Bishop, Californiamade a substantial gift to the BristleconePine Student Endowment. This check wasgratefully received by LTRR Director TomSwetnam at the 50th Anniversary celebrationof the discovery of the ancient bristleconepine near Bishop.

• Bruce and Ruth Balmat contributed togeneral lab programs.

• Alan Klier contributed a telescope.• An anonymous donor gave a generous

gift for continuation of the bristlecone pinefield and lab research led by ThomasHarlan.

The Tree-Ring Lab thanksall of these generous donors!

•

Recognition& Awards

LTRR Director: Thomas W. Swetnam, Ph.D.Editor: Melanie Lenart, Ph.D.

Production: Darla KenestonAHSC BiomedicalCommunications

© 2004 Arizona Board of Regentson behalf of the University of Arizona.All rights reserved.

The University of Arizona is anEEO/AA M/W/D/V Employer.

Just as some of our old walls are literally tumbling down (seephotos on page 7, and Steve Leavitt’s column) our new walls arefiguratively going up. On January 23, the Arizona Board of Regentsformally approved funding for planning the construction of thenew building – Environment and Natural Resources Building II –which will house the Laboratory of Tree-Ring Research, along withtwo other University of Arizona departments and a large contingent

of U.S. Geological Survey scientists.After 67 years of waiting for our new building,

this news is – to say the least – exciting!There are more approval steps ahead and

detailed design work to do, but the best estimateis that ground breaking will occur later this year,and we should move in by October 2006. Youwill no doubt be reading and seeing much moreabout this momentous development in thecoming two years within the pages of Tree-RingTimes.

During the course of the planning and building phase we willbe working hard to raise additional funds that may be used forelements of the building related to our needs and future use of thebuilding. We are extremely grateful to all who have given to ourbuilding fund, science and education programs. Your generosity ishelping us build new foundations and raise new walls!

For anyone who wishes to join in this endeavor, please see ourgift envelope at the center of this issue.

Best wishes,

COVER:Tree-ring researchers

core a larch tree in theQinling Mountains near

Foping, China. Thecollaborative project

between the Laboratoryof Tree-Ring Research

and China’s XianLaboratory of Loess

and QuaternaryGeology used ring

widths, wood density andisotopic analysis to

reconstruct theenvironment of these

mountains, a pandareserve. LTRR

professors Steve Leavittand Malcolm Hughes

headed the project.Photo by Steve Leavitt

LTRR professor Steve Leavitt is theincumbent editor of the journal Tree-RingResearch, and an elected member of theAmerican Quaternary Association (AMQUA)council. He represents paleoclimatology, thestudy of past climates, for the council.

LTRR Director and Professor TomSwetnam was appointed by Arizona GovernorJanet Napolitano to the Arizona ForestHealth Advisory Council. The Councilprovides advice to the Governor on scienceand policy matters pertaining to forest fires,forest health and management.

University of Arizona student DianaChandler, an LTRR volunteer, placed secondfor a poster and presentation in theAgriculture and Environmental division ofthe Student Showcase in November.

THOMAS W. SWETNAM


Making Fire HistoryPaleofire database puts fire-scar and charcoal data on-line• By Melanie Lenart

F or the first time in history, records ofprehistoric fires developed from treerings and lake-sediment cores are

freely available, even for those lackingconnections to fire historians. All it takes isan internet connection.

The International Multiproxy PaleofireDatabase (IMPD) made its debut earlier thisyear on the website operated by the NationalOceanic and Atmospheric Administration(NOAA). The “multiproxy” in the namecaptures the spirit of cooperation betweenthose who reconstruct proxy records of pastfire events from fire scars and other tree-ringevidence, and those who develop proxyrecords based on charcoal layers in thecores of lake sediments.

The paleofire database grew out ofinteractions during a weeklong workshop inTucson during the spring of 2002, when 65fire ecologists and climatologists gathered toconsider how to merge the results of thesetwo different ways of assessing pre-historicfire regimes. The workshop was co-organized by Laboratory of Tree-RingResearch Director Thomas Swetnam andCathy Whitlock, a University of OregonProfessor and leader in charcoal-based firehistory studies.

“I think the workshop really brought toeveryone’s attention how much data areavailable now,” Dr. Whitlock said. “We’rehoping the various labs will be willing andenthusiastic to contribute their data to thisinternational effort,” she added.

So far, 146 records based on tree ringsand 4 records based on lake sediments havebeen submitted, according to databaseorganizer Michael Hartman of NOAA.Hartman said he hopes to add another 25charcoal-based records soon, once he getspermission from the principal investigatorsinvolved.

Although the database effort has maderemarkable progress in the year and a halfsince it was first proposed, it still has a longway to go. More than 450 tree-ring basedand at least 50 sediment-based fire recordshave been cited in the North Americanliterature, according to a 2002 proposal put

together by the database organizers.“Actually the biggest part of the task is to

get people to submit,” Professor Swetnamsaid. “There are some barriers that I thinkneed to be broken down. I think 99.9% offire research is funded with public money.People need to have the ethic that once theyhave published they should submit theirdata so they are really available to thepublic.”

The effort might be assisted by a recentlydeveloped policy of some prominentscientific journals. Science and Nature, forexample, both now require their authors tomake their raw data publicly available,either on the journals’ own websites or byposting them on another site, such as theIMPD.

Connie Woodhouse, an LTRR alumnuswho now works for NOAA’s PaleoclimatologyProgram and is the principal investigator forthe database work, agreed that it’s achallenge for researchers to find the time tosubmit data.

“We’re trying to tackle that in as manyways as we can,” Dr. Woodhouse said.

For example, NOAA recently sentHartman to the lab of one researcher toassist in the organization of many fire-historyfiles for submission to the database. Also,some funds will be available in April thatpotentially could be used to providegraduate student support to organize dataand metadata.

Efforts to make the database more“usable” may receive additional NOAAsupport in the future, Woodhouse indicated.

“NOAA is interested in finding ways thatclimate data can be useful, and since there’sa fire/climate relationship, this includesinformation about fire and climate,” sheexplained. “The intent is to try to connectthe paleodata to our modern data, and alsoto make our data more useful to forestmanagers and other land managers likethose at the BLM (Bureau of Land Manage-ment).”

With the cooperation of the U.S. ForestService, the database organizers plan tomake the database more “manager-friendly”

in the future by allowing web-users to zoomin and access maps of past fire occurrencebased on fire history data as well as modernfire records.

The interactions between fire andclimate are complex, and influenced byother factors as well, as previous research byDr. Swetnam and his students and colleagueshas highlighted.

Like the charcoal-layer researchers, theyhave related increased fire frequency toindependent records indicating drought.But they also found a relationship betweenarea burned and wetter-than-usualconditions a couple of years before big fireyears, which they attributed to a build-up offuel from unsustainable lush growth. Firesuppression in U.S. forests during the lastcentury also has limited the surface fires thatclear out the small trees and logs that areconsidered “fuels” in firefighter parlance.

Arrows point to dated fire scars in the sampled stump of a giantsequoia that died in the 1950s. The information helped reconstruct thefire history of the Giant Forest, Sequoia National Park. The scarswere created by low intensity surface fires that burned near the base ofthis tree during the indicated dates.

“We may be seeing the fuel dambursting,” Swetnam said. “We’ve had dryyears before in the 20th Century, but wehaven’t had fires this big. The 2002 fireseason broke all records.”

Swetnam and others are eager to have asCONTINUED ON PAGE 6


‘Medieval Warm Period’Pales by ModernStandards• By Melanie Lenart

So these three guys walk into a bar.They sit down and one of them ordersa bottle of wine. Then the bartender

says, “Good thing you lads waited until nowto place your order. We haven’t hadhomegrown wine in this region for centuries,until now.”

Admittedly, this is no joke. But neither isit a joke that the mild climate required forvineyard production had eluded Englandsince Medieval times, until the globalwarming of recent decades.

Did global temperatures during the so-called Medieval Warm Period rival themodern warming, which many scientistsbelieve stems from the release of greenhousegases into the atmosphere? That’s a questionProfessor Malcolm Hughes and colleaguescontinue to challenge, using tree rings and avariety of other natural archives.

Professors Hughes, a dendroclimatologistwith the Laboratory of Tree-Ring Research,addressed this question in an Oct. 17

commentary in the prestigious journalScience, written with colleagues RaymondBradley of the University of Massachusettsand Henry Diaz of the National Oceanicand Atmospheric Administration.Dendroclimatology is the science ofinterpreting climatic variation from tree-ringrecords.

Their perspective piece cited a variety ofresearch using tree rings and other proxyrecords to estimate that at the height of the“Medieval Warm Period,” between about1000 and 1200 A.D, the NorthernHemisphere’s mean temperature appears tohave been identical to that of the moderntime frame of 1901-1970. In both cases,this would be about 0.6 degrees Fahrenheitcooler than the Northern Hemisphere’smean temperature of the past 30 years.

This contrasts with a few recentdeclarations in the journals that themedieval climate was warmer, or at least notdetectably different, than today’s climate. In

one notorious case, the authors countedrecords of droughts and floods as well ashigher temperatures in any 50-year periodbetween 900 to 1300 A.D. as evidence of a“Medieval Warm Period” that was warmerthan today’s climate.

The claims “might seem innocuous,” Dr.Hughes and his colleagues wrote in theirperspective. “But for those opposed toaction on global warming, it has become acause célèbre: If it was warmer in medievaltime than it is today, it could not have beendue to fossil fuel consumption.”

Dr. Hughes has spent much of his careergrappling with such climate questions. In1994, he and Dr. Diaz argued in a ClimaticChange article that there were warmings andcoolings at different times, in differentseasons, in various regions around theworld.

“This does not constitute compellingevidence for a global ‘Medieval WarmPeriod,’” they concluded.

“The issue of synchroneity brings us rightback to (LTRR founder) Andrew Douglassand dating—the importance of getting theyears right,” Hughes added later during aninterview in his University of Arizona office.An analysis done for the Science pieceshowed that the only major cluster of 30-year warm events registered by two dozenproxy records of temperature over the pastmillennium falls in the 20th Century.

Mean Northern Hemisphere temperaturewas higher during the late 20th Century thanat any other time during the past millen-nium, Hughes reported in 1998 and 1999in papers co-authored with Dr. Bradley andlead author Michael Mann of the Universityof Virginia. They based their conclusions ona multivariate statistical approach thatproduced one temperature timeline thatcombined results from tree-ring chronolo-gies with other annual-scale proxy records,such as ice cores and corals.

When the instrumental record wassuperimposed on their timeline, it showedan accelerated warming since the mid-1970s with annual mean temperatures inthe 1990s that surpassed those recorded forthe past 1,000 years.

Their work was cited by many, includingthe Intergovernmental Panel on ClimateChange (IPCC), as providing evidence that

An Issue ofSynchroneity

The warmest 30-year periods in 23 reconstructed temperature records based on treerings, ice cores, lake cores, cave deposits, and historical documents were plotted byRaymond Bradley, Malcolm Hughes and Henry Diaz. Timelines are shown inwhite. Color intensifies as more than one 30-year warm period lines up in time.

Timelines extend through1970, so the intensificationin global warming thatstarted in 1976 is notcaptured in this image. Evenso, more records showed theirmaximum in the 20thCentury than in medievaltimes. For more details onthese records, see the Oct. 17issue of Science.

Figure excerpted with permission fromScience 302: 404-405. Copyright 2003AAAS and adapted by Martin Munro


humans have contributed to a globalwarming through greenhouse gas produc-tion. Since then, close to a dozen otherresearchers have published similar results.The IPCC and others have used the findingsto make a case for curbing greenhouse gasemissions from industry and automobiles.

While Professor Hughes recognizes thepolitical implications of his research, heconsiders them secondary to getting to thetruth of the matter.

“Our job as scientists is to address thescientific questions,” he maintains.

To that end, the research trio of Mann,Bradley and Hughes continues to push theirfamous timeline backward and forward andtest its veracity, with assistance from others,including LTRR Research Associates FenbiaoNi and Kurt Kipfmueller. The proxy recordsused for their earlier papers typically begannear or after 1000 A.D., and most of therecords ended around 1980, well before aseries of record-breaking years in the 1990s.

“We’ve got a lot more records now thatcome out to the late 1990s,” ProfessorHughes said, adding that preliminary resultsindicate the warming trend registered by theinstrumental record is reflected in thenatural archives.

“Also, we’ll be able to do a better job ofthe last millennium, maybe go back anotherfew centuries,” he explained. “We’ll see howfar back we can go before error explodes.”

Potential error, a statistical measure ofvariation, increases as the number ofindividual records contributing to a timelineshrinks.

Another statistical concern involvesaccounting for variations that are related to

something other than climate. For instance,annual rings tend to be smaller when a treeis old because of growth trends, whileannual ice core layers tend to be smallerwhen the ice is old because of compaction.

The method used to “standardize” thedata to remove these non-climatic trendscan be controversial, however. ProfessorHughes noted that the research team istesting different methods of standardizingthe data, including age banding, to makesure the observed climatic trends transcendthe type of standardization applied.

Age banding involves lumping timelinesfrom similar-aged individual trees togetherbefore applying the statistical maneuvers thatremove the typical decline in ring width thatoccurs as a tree ages and becomes moremassive. Some researchers recommend thisapproach, developed by Keith Briffa ofEngland’s University of East Anglia, whentrying to distinguish climate trends for atimescale longer than the life of the averagetree in the record.

Even when considering all these issuescarefully, however, creating a temperaturetimeline of the past millennium poseschallenges because it requires working inpreviously uncharted territory.

“Until 20 or 30 years ago, studies of pastclimate were pretty much the province ofgeologists and oceanographers,” Hughesexplained. “They were working on bigchanges—large-scale changes in boundaryconditions of the climate system. When achange is that big, where the whole Earth ismoving in one direction, you can capture itin a few records.”

Climate records derived from ocean

sediment cores, for example, tend toconsistently show the ups and downs ofglobal temperature during the large-scaleice ages and interglacial periods of the last 2million years.

“We’re starting from the other end inregard to time,” he continued. “We’reaccustomed to working with small globalchanges and large local ones.”

“The issue of synchroneity brings us right back toAndrew Douglass and dating—the importance ofgetting the years right.”

–Malcolm Hughes

A temperature reconstruction by MichaelMann, Raymond Bradley and MalcolmHughes shows the recent period of warmingin the northern hemisphere followed adownward trend. The record, based on treerings, ice cores, coral reefs, and sediments, waspublished in the March 15, 1999, issue ofGeophysical Research Letters.Graphic adaptation of the timeline was done by Martin Munro.

Tree-ring records, for example, excel atdetecting temperature or precipitationchanges at the scale of the mountain orwatershed where the trees live. Often theselocal changes can be related to larger scalepatterns of atmospheric circulation.

“A change of that size is not big enoughto make every place change at the sametime,” Professor Hughes said, adding, “Thequestion of the slow change of the lastmillennium falls right between these twoways of looking at climate.”

Even so, there is evidence beyond thesetypes of proxy records that the climatewarming occurring in modern timesexceeds any occurring in the past millen-nium and more, he said. For instance, icecore records confirm that tropical glaciersin Kilimanjaro and the Andes have remainedat below-freezing temperatures forthousands of years.

“Some of those places are not stayingfrozen now,” Hughes reminded. “The ice ismelting and disappearing. That strikes meas being evidence that something ischanging, at least at 6,000 meters and up inthe tropical latitudes.”


Further Talesof the Bristlecone Pine

•By Linah AbabnehGraduate student

Fire HistoryCONTINUED FROM PAGE 3

I t is surprising what trees canreveal about their growthconditions. The science of tree-

ring analysis, called dendrochronol-ogy, provides a unique tool forbetter understanding environmentalchanges that affect the growthpatterns of trees.

A number of Laboratory of Tree-Ring Research scientists haveexplored the growth patterns of veryold bristlecone pines (BCP), aconifer found at higher elevations inthe Great Basin and RockyMountains.

In a 1984 paper, ValmoreLaMarche, Donald Graybill, HaroldFritts and Martin Rose described anincrease in tree-ring widths of BCPssince 1850. Because their studyinvolved older trees, they encoun-tered BCPs that had lost portions oftheir bark, leaving the woodunderneath (sapwood) exposed anddead, a condition known as “strip-bark.” Although a part of thetree is dead it still lives and maintains growth every year.

LaMarche, et al., however, did not address the strip-barkphenomenon, but focused on the increase in tree-ring widths inthese strip-bark trees, attributing it to increased atmosphericcarbon dioxide, which has doubled since 1850, and called itthe “carbon fertilization theory.”

A subsequent paper written in 1995 by Donald Graybill andSherwood Idso proposed a different theory. After conductingsimilar studies of the same BCPs, Graybill’s and Idso’s findingssuggested a possible correlation between the observed increasein tree-ring width and the existence of strip bark in older trees.

My research follows from theprevious two studies but includes asignificantly higher number of oldBCPs. Furthermore, I am analyzingvariability in tree-ring widths ofBCPs, specifically the observedincrease in tree-ring widths and thephysiological condition of the tree(strip-bark vs. full bark) in relationto soil type (dolomite and sand-stone) and difference in elevationover a defined period of time.

The study of the effect of onefactor at a time, i.e. bark condition,soil type, and elevation, allows me tobetter assess Graybill’s and Idso’stheory of a relationship betweentree-ring widths and strip bark inolder trees. Assessment of LaMarcheand colleagues’ proposed carbonfertilization theory would requirefurther research.

The preliminary results of myresearch indicate that elevation and

soil type have different effects on the BCPs’ growth. In addition,it seems that moisture levels in different soils may have an impacton the growth pattern. For example, dolomite and sandstone,the soil types in my research, have different moisture levels. I amalso finding differences in tree-ring widths that relate todifferences in elevation. More conclusions are still to be drawn,as the final stages of research are progressing.

This work is being accomplished by the generous support ofthe University of California, San Diego and Davis, Sigma Xi, andMary DeDecker Grants, as well as the Laboratory of Tree-RingResearch’s Agnese N. Haury Fellowship Fund and the BristleconePine Student Endowment.

much data as possible to work with as they tease out the effects ofclimate—and climate change—from that of fuel build-up. Otherresearch at the LTRR and elsewhere has documented an increase inNorthern Hemisphere temperature since about the mid-1970s. (Seerelated story on page 4.)

“There may be increasing signs that what we’re seeing is reallyclimate-driven. That debate is really warming up,” Swetnam said.“But it’s too early to say whether the warming is causing regionalfire changes.”

The director likened the development of the paleofire databaseto that of the International Tree-Ring Data Base. The ITRDB was setup, also on a NOAA website, following a 1974 meeting in Tucsonthat set the tone for tree-ring research on climate for decades tocome.

“That’s been extremely successful. Different scientists workingat different institutions around the world could link arms,” he said.“The same thing could be done for fire history through theIMPD.”

Phot

o co

urte

sy o

f W

ally

Woo

lfend

en


I n August of this year, the department lostan old friend—the Berkowitz Apartment

building, better known to people associatedwith the Laboratory of Tree-Ring Research forthe last 30 years as the “White House.”

It served faithfully by providing much-needed space variously for faculty, staff,researchers, graduate students, and storage,including the departmental library.Our humble introduction to theWhite House was through rental ofone of its four units around 1972when it was privately owned.

By 1975, the LTRR was occupyingthree of the four units, and not longthereafter the University owned it and LTRRhad the whole enchilada, driven in largepart by the rapidly expanding researchprograms of Professors Hal Fritts, ChuckStockton and Val LaMarche. The new space

BEHIND THE WOODSHED

By Steve LeavittAn irreverent microanatomical view of life at the LTRR

demanded furnishings, some of which werepurchased new, and others of which werehand-me-downs from the Optical SciencesAnnex and the Administration Building.

By 1984, however, LTRR Acting DirectorBill Robinson was actively seeking newspace for the lab and wondered if it couldbe found in time for us to “abandon the(White House) before it abandons us.” Bythat time, door and window security issuesand termite problems were alreadyrecognized, and not long thereafterproblems emerged with the ailing roof,floors and climate control (evaporativecooler and furnace). Estimates within thelast two years indicate it would have cost$50,000 to $100,000 for repairs necessaryto bring it up to standards, which mostagree would be the epitome of throwinglarge-denomination bills down the fleamarket rat-hole coin toss.

The White House had been living onborrowed time. Its fate was further sealedover the last 15 years as this little island ofsqualor was encroached on by constructionof the shiny new Recreation Center, parkinglots, and a Parking and Transportation fieldcompound.

The proud and mighty building did notgo down without a fight, and it held out fora surprising number of nanoseconds againstthe onslaught of incessant blows by thewrecking ball (actually big shovel). Theresult was never in doubt, however, like theinevitable outcome to the overconfidentyoung man impressing his girlfriend byaccepting the barker’s challenge at a flea

market elephant-wrestling promotion.Yes, the White House seemingly had its

insurmountable problems, but there werestartlingly few complaints by the actualoccupants. Now it can be revealed that thebenign outward appearance of that buildingbelied its ostentatious amenities, of whichour brethren departments throughout theegalitarian University of Arizona can onlydream.

For example, the White House had anunderground parking garage with free valetparking for all faculty and staff. For thosewho chose to walk or ride bikes, there wereshowers with gold-plated fixtures andredwood hot tubs in the basement.

The attic had a fully stocked faculty clubto encourage recreation, camaraderie andinformal interactions. Its revolving rooftoprestaurant provided spectacular panoramicviews of the city over the course of eachgourmet meal and looked down on thelowly stadium skyboxes.

Campus planning might do well to take apage or two from these White Houseamenities, but then again, some may not beworth perpetuating. I never did take a likingto the White House complaint desk to whichI was referred many times, and for thatmatter, why was I seemingly always the onlyone to be directed to the whine cellar?

Come to think of it, my brusquetreatment at that dump at times can only becompared to that given a health inspector atthe flea market gravy and pie buffet.

The Walls ComeTumbling Down


Laboratory of Tree-Ring ResearchPO Box 210058Tucson, AZ 85721-0058

CHANGE SERVICE REQUESTED

NON-PROFIT ORG.U.S. POSTAGE

PAIDTUCSON, ARIZONA

PERMIT NO. 190

LTRR’s HirschboeckWins Teaching Award

LTRR Associate Professor KatherineHirschboeck won the prestigious 2003Provost General Education Teaching Awardfor her innovative methods in teachingnatural science courses.

As a pioneer and leader in innovativeteaching methods and use of new teachingtechnologies, Hirschboeck is known forimplementing programs that use collabora-tive group learning; immediate feedback inexaminations; and student/peer evaluationtools.

“Her exemplary teaching, her dedicationto her students, and her university-wideinfluence as a role model for generaleducation curriculum development,

innovation and assessment are compellingreasons to grant her this award,” wrotePlanetary Sciences Professor Harold Larsonin his letter of nomination, one of manysent to the selection committee.

About 500 faculty and administratorsattended the awards ceremony to honorDr. Hirschboeck and the seven other facultymembers who received teaching awardsfor the year.

During the 2001-02 University-wideGeneral Education Committee “BestPractices for Improving Student Learning”retreat, Hirschboeck’s presentation wasrecognized as the “Best of Show” in termsof its organization, completeness andadherence to all of UA’s general educationguidelines and requirements.

Hirschboeck’s teaching team(above) strategizes on how toteach 150 students to plot,crossdate and test hypothesesusing tree-ring samples. Atleft, students carry out theplanned exercise in class.

Dr. Hirschboeck sits with one of manysmall groups formed to facilitate discussionin her “Introduction to Global Change”class.

fire records go online medieval vs. modern warmth

Documents