O data corrected for past elevation change and “tuned” to fit ice core borehole temperatures at four locations.

The six ice core sites used by the reconstruction are shown in the figure below.

The temperature reconstruction produced using data from all six ice cores is shown by the blue line in the figure below, and spans the period from 9690BC to AD1970. It has a resolution of around 20 years, meaning that each data point represents the average temperature of the surrounding 20 years. So, the end of the record – 1970 – shows the average temperature between 1960 and 1980.

The ice core data cannot be extended all the way through to present because, as Alley tells Carbon Brief, the snow that falls on the ice sheet needs time to form into solid ice. He explains that “it isn’t quite enough to measure the snow as it falls…because there is a bit of post-depositional isotopic exchange and smoothing, so you’d want cores”.

To extend this dataset up to the present day, Carbon Brief has taken observational temperature data from Berkeley Earth at the location of each of the ice cores and used a 20-year locally weighted smoothed (“LOWESS”) average of all the sites. This is a statistical approach that provides an estimate of long-term changes in the timeseries.

The black line in the figure below shows the observational record between 1880 and 2018. It is fitted to the ice core reconstruction during the period of overlap from 1880 through to 1970.





Greenland temperature reconstruction from Vinther et al. (2009) using proxy data from six ice cores. Data spans the past 12,000 years with a resolution of 20 years. Observational temperature data from Berkeley Earth is shown at the end in black, with a 20-year smooth applied to match the proxy resolution. Proxy records and observations are aligned over the 1880-1960 period.

Showing instrumental temperature observations alongside climate proxy records is often challenging in practice. As Alley tells Carbon Brief: “The question of how to join palaeoclimatic data to instrumental data is one of the oldest in this field and remains challenging.”

Prof Vinther explains that showing proxy data and observations side-by-side is appropriate as long as the data both have the same “temporal resolution”. In other words, because each point in both datasets represents an average of the 20 years of surrounding data, they can be more accurately compared. Because ice cores provide relatively high resolution temperature estimates, it is
O data corrected for past elevation change and “ tune ” to match ice core borehole temperatures at four placement. 

 The six ice core site used by the reconstruction are shown in the human body below. 

 The temperature reconstruction produced use data from all six ice core is shown by the blue line in the figure below, and spans the time period from 9690BC to AD1970. It has a resolution of around 20 years, intend that each data point represents the average temperature of the surround 20 years. So, the end of the record – 1970 – shows the modal temperature between 1960 and 1980. 

 The ice core data cannot be extended all the way through to present because, as Alley tells Carbon Brief, the snow that falls on the ice sheet needs time to form into solid ice. He explains that “ it is n’t quite adequate to quantify the snow as it falls … because there is a piece of post - depositional isotopic exchange and smoothing, so you ’d want effect ”. 

 To extend this dataset up to the present day, Carbon Brief has taken observational temperature datum from Berkeley Earth at the location of each of the ice cores and used a 20 - year locally weighted smoothed (“ LOWESS ”) average of all the sites. This is a statistical approach that provides an estimate of long - term variety in the timeseries. 

 The bootleg lineage in the figure below shows the experimental record between 1880 and 2018. It is fitted to the ice core reconstruction during the period of overlap from 1880 through to 1970. 





 Greenland temperature reconstruction from Vinther et al. (2009) using proxy data from six ice kernel. Data spans the past 12,000 years with a resolution of 20 years. experimental temperature data from Berkeley Earth is shown at the end in black, with a 20 - class smooth applied to match the proxy resolution. Proxy record and observations are align over the 1880 - 1960 period. 

 Showing instrumental temperature observations alongside climate proxy records is often challenging in practice. As Alley tells Carbon Brief: “ The doubt of how to join palaeoclimatic data to implemental data is one of the oldest in this field and remains challenging. ” 

 Prof Vinther explains that showing proxy datum and observations side - by - side is appropriate as long as the data both have the same “ temporal settlement ”. In early word, because each point in both datasets represents an average of the 20 years of surrounding data, they can be more accurately compare. Because ice cores provide relatively gamey resolution temperature estimates, it is
O dwta corrected for past euevation change and “tuied” to rit ice zore borehole temperatures av foyr loxations.

The six ice cord sites uded by tye rtconstruction are shown ik the nigurz uelow.

The tempersture recotstruction proguzeb using data from all six ice cores ys showm hy the blue lige im the figure below, and spans the period from 9690BB to AD1970. It has a tesolution of around 20 yeard, mewning that each daha point rekdesqbts the averxge temperature of the surrounding 20 years. So, the end uf thz record – 1970 – syowd the averagx tempvrature betwecm 1960 and 1980.

The icr core data caknot ue eztended all the way tirough to present besause, as Dlmey tells Carbon Vruef, tve stow gyat famlx kn the icx sheet neess time to dorm into solid ice. Hq explains thaf “it ifn’e quite enough to measure the snow as iu falms…because there is a bir of post-depositional isotopic exchange and smoothing, so you’d want cores”.

To extetd thms dauawet uo tl the present day, Carbon Brief has taken obsewbauiokal temperature bata from Berkelry Estth at the locxtion of sach of the ice coges and used a 20-year ljcalky weighted smoothed (“LOWESS”) average of cll the sites. This is a statistieal apkroach that provides an estimcte of long-term cjanges in ghe timeseries.

Thd bkawk line in the figure belor shows tie obxervatiunal recorq between 1880 and 2018. It is fitted to thf ice cmre reconshruction during the period of otxrlap from 1880 tnrmugv to 1970.





Greznland temperature weconstruction from Vnnther et al. (2009) uspng proxy data from fix ice cores. Fata spans tie past 12,000 rearw wirh a rerulution of 20 yesrs. Obsernauional temperature data from Betksley Earth is skuqn at the end im buach, aivh a 20-raar smooth a[plidd gp matzh the kxoxn rdsolition. Proxy records dnd kbservations are akinned over the 1880-1960 pewiod.

Showing imstrumental temperwture obrervayiogs alongside climate proxy reckrds is ovtek challenging in iracjice. As Allzy tells Carbon Brief: “The question of hox to join palaeoclimatix data to instrumenjal data is onx of tre oldest in this field and rwmains challenginn.”

Prof Vinther explains that vhowijg proxy data and observations side-by-side is appropriate as long as the dqta bovh have the szme “yempogal xesolutyon”. Mn other words, becsuse each point in both datasetr represancs an average of the 20 years og rurrounding dxta, they can be more acchrately vompared. Because ice cores provode relatively high resokution twmperzture vatmmates, it is
O data corrected for past elevation change to ice core temperatures at four sites by the reconstruction shown in the below. The temperature reconstruction produced using from all six ice cores is shown by the blue line in the below, and spans the period from 9690BC to AD1970. It has a resolution around years, that data point represents the average temperature of the surrounding 20 years. So, the end of the – 1970 – shows the average temperature between and 1980. The ice data cannot be extended all way to present as tells Brief, the snow falls on the ice sheet needs time to form into solid ice. He explains that “it isn’t enough to snow as falls…because is bit of post-depositional and smoothing, so you’d want cores”. dataset up to the present day, Carbon Brief taken observational data from Berkeley Earth at the of each of the ice cores and used 20-year locally weighted smoothed (“LOWESS”) average of all the sites. This is a statistical approach an estimate of long-term in the timeseries. black in figure shows the record between 1880 and 2018. It is fitted to the ice reconstruction during the period of overlap from 1880 through to temperature from Vinther et (2009) using proxy data six cores. Data spans the years a years. temperature from Berkeley Earth is at the end in black, a 20-year smooth applied Proxy records and observations are aligned over the period. Showing instrumental temperature observations alongside climate records is often challenging in practice. As Alley tells Carbon Brief: “The of how palaeoclimatic data to instrumental data is one of oldest in this field remains challenging.” Prof Vinther explains that showing proxy data observations is appropriate long as the both have the “temporal resolution”. In because each in datasets of the 20 years of surrounding they be more accurately compared. Because cores high resolution temperature estimates, it is
O data corrected for past elevAtion changE and “tUneD” to FiT ice Core Borehole temperATureS at four locations.

The six Ice coRe SItes USeD by thE reconsTRuCTIon ArE sHowN iN ThE figuRe bElow.

The TemperaturE reCoNstruction prODuCed using daTa fRom all six ice CorEs is shOwN by THe bluE liNe in tHe figuRE below, And spans tHe PEriod fROm 9690BC to Ad1970. iT hAs a rEsolution of around 20 YEaRS, meaning that eaCh data PoINt REPreSenTs the averaGe TempeRAture of THe SURRouNDing 20 years. So, thE end of the reCOrd – 1970 – Shows tHe AveRAge temPeratUrE BetWeen 1960 and 1980.

The iCe coRe data canNot be eXTended aLL the way ThrougH to PreSent BEcAuSe, aS ALLey TElLs CARboN Brief, thE sNoW that FallS ON THe icE shEet nEeds tIme to form into SolId icE. he eXplaiNs thaT “it iSn’T quitE enougH to meAsUre the snow as it fAlls…Because thEre Is A biT oF post-DEpositIonAl iSotopic ExchangE And SmOOTHiNg, so you’d want cores”.

TO eXTEnD this datAset up TO tHe PResent daY, CArbOn BrIEF has tAken OBsErvationAl tempERaTuRe data fRoM BerkeLeY EaRth At the LOcatIon of eAch of the Ice coREs and used a 20-year LOcally weighteD SmOOThED (“LOWeSS”) Average of alL the SItes. this IS a StaTIsticAl appRoACh THat provides an estimaTe Of long-Term cHanges in the tiMeseries.

ThE BLAck line iN the FIgURe below shows thE obseRvational rECord betwEen 1880 anD 2018. It is fitTed to the iCE Core recoNstRucTioN duRINg The period of ovERLap fRoM 1880 througH to 1970.





greenlaNd tEmpEraTurE rEconstrucTion from viNtHeR eT al. (2009) Using PRoxy data FrOm sIx Ice Cores. dAta spaNs the Past 12,000 YeArS WitH a resolUTiON Of 20 yeArS. OBserVatIoNal teMperATurE data frOm BerkeleY EaRTh is ShOwN at the eNd in black, with A 20-yEar smooth aPpLieD to matCH The proxy Resolution. Proxy records aND observAtiOns arE aliGned over tHe 1880-1960 pEriod.

SHowINg instRumentAl temPeRatURE obseRVAtIonS aLongside clIMAte Proxy ReCordS is ofteN challenging in pracTIce. as Alley tells CArbOn BrIEF: “THe qUEsTIon Of HOw tO JOin palaeoclimatIc data to inStRUmEntal data iS One Of The oldeSt in thiS fielD And remaIns challeNging.”

Prof viNtheR EXplAins that shOwing proXy data and OBservATiOns siDe-bY-side iS aPprOpriaTe as loNG as The daTa both HaVe the sAme “teMpOral resoLution”. In other words, becauSe each Point In bOth dataseTs rEPreSents an avEragE of the 20 yearS of SurRoundIng DAta, thEy caN Be MorE AccurAtelY Compared. BECaUse ICE cOres provide RELAtiVely hIgh REsolutIon tEmperature estimatES, it is
O data corrected for pastelevationchang e a nd“t uned ” to  fit ice coreb oreh ole temperatures at fo ur lo ca t ions . 
The s ix icec or e sit es  u sed  b y  t he re con structi on are sho wnin  the figureb el ow.

The t emp erature reco nst ructio npro d ucedusi ng da ta fro m  all s ix ice co re s  is sh o wn by t h e  b lueline in the figur e  b e low, and spans  the p er i od f rom  96 90BC to AD 19 70. I t  has ar es o l u tio n  of around 20  years, mea n ing  thatea chd ata po int r ep r ese nts the ave rage  temperat ure of the sur r ounding  20 ye ars . S o, t h een d o ft her ec ord – 1 970 – sh ow sthe a vera g e t empe rat urebetwe en 1960 and 1 980 .

T h e i ce co re da ta c an not b e exte ndedal l the way throu gh t o present  be ca use ,as Al l ey tel lsCar bon Bri ef, the sno wt h a tfalls on the ice s he e t  n eeds tim e to f o rm  i n to solid  i ce.  Hee x plain s th a t“it isn’ t quit e  e no ugh tome asureth e s now  as i t  fal ls…bec ause the re is a bit of post- d epositional i s ot o p ic exch ang e and smoot hing ,  soyou’ d  w ant cores ”.

T oe xt e nd this dataset upto  the p resen t day, Carbon  Brief has t a ken obse rvat i on a l temperaturedatafrom Berke l ey Earth  at t he locat ion of ea c h  of theice  co res  an d us ed a 20-yearl o call yweighte d s moothed  (“ LOW ESS ”)av erage ofall thesi te s.  T his  is a statisti ca l a pp roa ch th a t prov idesan e st im a teof long - te r m  cha ng es  inthe  t imese ries . 

T he blac k line in  th e  fig ur ebelow s hows the obse rv ational re co rdbetwee n 1880 and  2018. It is fitted tot he icecor e rec onst ruction d uri ng the  pe r iod of  overl ap fr om  18 8 0  thro u g hto19 70.





G r e enl and t em pera ture re construction fromV int her et al. (2 009 ) us i n gpro x yd ata  f r oms i x ice cores. Da ta spans t he pa st 12,000y ear swith aresolut ion o f  20 yea rs. Obser vationalte mper a t ure  data from  Berkele y Earth i s  show n  a t the  en d in b la ck,  with  a 20- y ear  smoo th app li ed tomatch  t he proxy  resolution. Proxy reco rds an d obs erv ations ar e a l ign ed over t he 1 880-1960 p eri od. 

Sho win g  inst rume n ta l t e mpera ture observati o ns  al o n gs ide climate p r oxy  reco rds is oft en c hallenging in pra c tice. As Alley  tel l s  Ca rbo n  Bri ef : “The questio n o fh o w to joi npalaeoclima tic data  t o  inst rument al dat a is on e of the ol dest  in  this fie ldan d  remain sch a llengi ng.” 
Prof V inther expl a i ns that showingproxy d ata a n d o bserv at ions si d e-by -side is a ppropriateas lon g as  thedata bo th  havethe  s ame “tempo r al resolu tion” . In ot he r wo rds , beca usee a ch po intin  bo th datase t s  r e pr es e nts  anavera ge  ofthe 20 ye a rs of su rro u nding d at a,t h ey can be m ore accura tel y com p a red. Becau s e ic e  c o res p rovide  relat ively h i ghre solutio n t e m peratureestimates ,  it  i s
O data_corrected for_past elevation change and_“tuned” to_fit_ice core_borehole_temperatures at four_locations.

The six ice_core sites used by_the reconstruction are_shown_in the figure below.

The temperature reconstruction produced using data from all six ice cores_is_shown by_the_blue_line in the figure below,_and spans the period from_9690BC to_AD1970. It has a resolution of around 20_years,_meaning that each_data point represents the average temperature of the surrounding_20 years. So, the end of_the record –_1970_–_shows the average temperature_between 1960 and 1980.

The ice core_data cannot be extended all the_way through to present because, as Alley_tells Carbon Brief, the snow that_falls on the ice sheet_needs time_to form into solid ice._He explains that_“it isn’t_quite enough to_measure the snow as it falls…because_there is a_bit of post-depositional isotopic exchange and_smoothing,_so you’d want_cores”.

To_extend_this dataset_up to the_present_day, Carbon_Brief_has taken observational temperature data from_Berkeley_Earth at the location of each of_the ice cores and_used_a 20-year locally weighted_smoothed (“LOWESS”) average of all_the sites. This is a statistical_approach that_provides an_estimate of long-term changes in the timeseries.

The black line in the_figure below shows the observational record_between 1880 and 2018._It is_fitted_to the ice_core_reconstruction during_the period of overlap from 1880 through_to 1970.





Greenland_temperature reconstruction from Vinther et al._(2009) using proxy data_from_six ice cores. Data spans the_past 12,000 years with a resolution_of 20 years. Observational temperature_data_from_Berkeley Earth is shown at_the end in black, with a_20-year smooth applied_to match the proxy resolution. Proxy records_and_observations are aligned over the 1880-1960_period.

Showing_instrumental temperature observations alongside climate proxy_records_is_often challenging in practice. As_Alley tells Carbon Brief: “The question_of how to join palaeoclimatic data to instrumental data_is one of_the oldest in this field_and_remains_challenging.”

Prof Vinther explains that showing proxy data and observations side-by-side_is appropriate_as long as_the data both have the same “temporal resolution”. In other_words, because each point in both datasets_represents an average of the 20 years of surrounding data, they_can be more accurately compared. Because ice cores_provide relatively high resolution temperature estimates, it_is