date: Tue, 14 Feb 2006 08:28:03 +0100 from: Pål Svensson subject: RE: SUMMER TEMPERATURE VARIABILITY IN CENTRAL SCANDINAVIA DURING to: "Keith Briffa" Hi back Thanks for taking time to answer. My feeling is that the greatest contributor to worldwide temperature changes is the variation in solar influx on earth. You have both long and short timed circles. I am sure that you have taken all that into account, but I found this article today showing that not everybody does. http://sciencenow.sciencemag.org/cgi/content/full/2006/213/1 Best Paal -----Original Message----- From: Keith Briffa [mailto:k.briffa@uea.ac.uk] Sent: 10 February 2006 14:57 To: Pål Svensson Subject: Re: SUMMER TEMPERATURE VARIABILITY IN CENTRAL SCANDINAVIA DURING THE LAST 3600 YEARS Hi Paal the quick answer is that we do wish to longer timescales - but this analysis tried to capture the spatial extent of warming over the whole Hemisphere - so we have to compromise between as wide a coverage as possible but going back as far as possible. Hence we settled on a compromise between coverage and length. Other analyses based on much fewer series do however indicate that these findings are probably still relevant for a longer period, though at present not based on sufficient coverage to justify publication. Cheers Keith At 13:24 10/02/2006, you wrote: >Hi Keith > >The article below was published today in a >norwegian newspaper saying that todays global >warming is the worst in the last 1200 years. > >My question is why just the last 1200 years? Why >don't you take the last 3.600 years? > >Best regards > >Paal Svensson > >Global oppvarming verre enn på 1.200 år >NTB <mailto:dn.no@dn.no> >Været er varmere over hele verden i dag enn i noen annen periode på 1.200 år. >Det heter det i en artikkel i tidsskriftet Science. >Studien har undersøkt endringer i årringer, >fossiler og iskjerner fra 14 steder på den >nordlige halvkule for å fastslå hvordan >temperaturendringene har artet seg siden året 800. > >Uvanlig høye temperaturer >Forskerne kom frem til at det 20. århundre >utmerket seg med uvanlig høye temperaturer. Den >nåværende varme perioden som ble innledet mot >slutten av det 20. århundret, er den lengste og >mest utbredte perioden med unormale temperaturer >siden det 9. århundret, skriver Timothy Osborn >og Keith Briffa ved East Anglia-universitetet i artikkelen. > >For å undersøke om varmeperioden er i >overensstemmelse med naturlige >temperatursvingninger, sammenlignet de den med >andre perioder i de siste 1.200 årene. > >Årringer >For å fastlegge klimasvingningene så forskerne >på årringene til gran- og furutrær i >Skandinavia, Sibir og Nord-Amerika, der brede >årringer indikerer varme år, og de undersøkte >kjerner som er boret ut av innlandsisen på >Grønland som viser hvilke år som er varmere enn andre. > >De benyttet seg også av kilder som dagbøker og >andre nedskrevne øyenvitneskildringer fra >middelalderen om uvanlige fenomener som >gjenfrosne kanaler i Belgia og Nederland. > >SUMMER TEMPERATURE VARIABILITY IN CENTRAL >SCANDINAVIA DURING THE LAST 3600 YEARS >HANS W. LINDERHOLM1, > >AND BJÖRN E. GUNNARSON > >ABSTRACT. A Scots pine (Pinus sylvestris L.) >tree-ring width chronology from Jämtland, in the >central Scandinavian Mountains, built from >living and sub-fossil wood, covering the period >1632 BC to AD 2002, with a minor gap during AD >887-907, is presented. This is the first >multi-millennial tree-ring chronology from the >central parts of Fennoscandia. Pine growth in >this tree line environment is mainly limited by >summer temperatures, and hence the record can be >viewed as a temperature proxy. Using the >regional curve standardization (RCS) technique, >pine-growth variability on short and long time >scales was retained and subsequently summer >(June-August) temperatures were reconstructed >yielding information on temperature variability >during the last 3600 years. Several periods with >anomalously warm or cold summers were found: >450-550 BC (warm), AD 300-400 (cold), AD >900-1000 (the Medieval Warm Period, warm) and AD >1550-1900 (Little Ice Age, cold). The coldest >period was encountered in the fourth century AD >and the warmest period 450 to 550 BC. However, >the magnitude of these anomalies is uncertain >since the replication of trees in the Jämtland >record is low during those periods. The >twentieth century warming does not stand out as >an anomalous feature in the last 3600 years. Two >multi-millennial tree-ring chronologies from >Swedish and Finnish Lapland, which have >previously been used as summer temperature >proxies, agree well with the Jämtland record, >indicating that the latter is a good proxy of >local, but also regional, summer temperature variability. -- Professor Keith Briffa, Climatic Research Unit University of East Anglia Norwich, NR4 7TJ, U.K. Phone: +44-1603-593909 Fax: +44-1603-507784 http://www.cru.uea.ac.uk/cru/people/briffa/