cc: jean-claude.duplessy@cfr.cnrs-gif.fr, ll@dmi.min.dk date: Thu, 21 Nov 1996 17:46:17 +0001 from: Gerbrand Komen subject: past climate data, Abisko, 1 - 3 September 1997 to: bengtsson@dkrz.de, p.jones@uea.ac.uk Dear Lennart, Phil Below you find the next iteration in our workshop description. I suppose all have a chance to react by e-mail. Anyway, Lennart and I agreed that - Lennart would seek formal commitment from the organizing comittee members in the next few days - we would send out the invitation to participants in early December Best regards, Gerbrand Komen Proposal for a Euroclivar workshop on Past Climate Data Rationale Climate modellers concerned with understanding the physics behind low frequency variability and predictability of climate and for the detection of anthropogenic climate change are in a desperate need of better observational data. The situation is serious. Global 3-dimensional data for the atmosphere exist essentially only available for the last 18 years, for the oceans they are mainly restricted to the upper ocean only. Data for other aspects of the climate system; deep ocean, atmospheric chemistry, biochemical cycles, land ices are still only patchy. Surface data for temperature and pressure can at best be broadly reconstructed (essentially populated areas only) until the middle of the last century. Before that we have mainly only indirect observations, which by different techniques can be interpreted into geophysical quantities. We have now wonderful new potential possibilities to use models to bring all these sparse data together in a systematic way and the modellers and the Paleo "detectives" must now work closely together. Two actions are required: 1. To establish a comprehensive global climate observing system. (At least we must provide data for future generations) 2. To provide the best possible available data set of past data. The first of these two actions will be handled by GCOS. This work is well in hand and a special international committee (WMO, ICSU and UNEP) is presently developing such a concept. Euroclivar wants to stimulate work on - and with - past data. To this end a 3-day workshop will be organized as laid out below. 1. Long term objective To provide the best possible climate data of the past and to use these for the validation of climate models and an assessment of (natural) climate change. 2. Meeting products * A proposal for making (by whom?) data (what data?) better available (how?) * A plan of action for the validation of climate models and an assessment of (natural) climate change (to the extend possible). 3. Types of past data Climate data can conveniently be divided in four different groups; (i) 3-dim atmospheric global data 1979-1995, level 2 and 3, (ii) 3-dim Northern Hemisphere 1950-1995, level 2 and 3, (iii) Surface data 1750-1995 ("200+"), level 2, (iv) Paleo-data for the last 2000 years, level 1 and 2. [level 1 = indirect information; level 2 = geophysical parameters; level 3 = gridded data] Data set (i) is expected to be provided by the ECMWF re-analysis (ERA) project. The Euroclivar workshop will concentrate on (ii), (iii) and (iv). Assimilation of (mainly) Northern Hemispheric upper air data 1950(47?)-1995(98) is possible to achieve within the next two-three years. NMC has made a first start, but the result will be model dependent so at least another data set is needed. ECMWF is a perfect candidate, they have the technical expertise and they can also work reasonably well with external groups. The assimilation should of course be global and it will be interesting to see how well we can reconstruct/constrain the circulation in the tropics and for the Southern Hemisphere. For instrumental data (the last 200 years or so - principally surface) a distinction is made between * monthly data. These are needed for detection and validation. Much is available already. There are temperature and precipitation data sets available on a 5 by 5 grid-box basis. * data on a daily basis. At the moment it is not clear what is/might be available from (eg) ECSN. For Proxy (Paleoclimatic) data distinction is made between * Paleoclimatic time series (Year by year reconstructions of for example summer temperature or summer precipitation totals or possibly annual/wate- ryear values). The key aspect here is time series available for a number of locations from around the world from trees, corals, ice cores and varves. * Spatial patterns of change for periods in the paleo past (ie 6K , 9K and 18K years ago). This sort of data is needed for the PMIP intercomparisons, which can be thought of as validation - but only of spatial patterns. For detection/assessment the time series aspects are the ones that are most relevant. 4. Format of the meeting Three day meeting First Day: * Presentations (key) of instrumental and different kinds of proxy data. * Availability of the data - formats etc for inclusion in a data base. * What sort of analyses can be done between these data and model output with respect to validation/detection Second Day (Break into small groups) * Reanalysis * Last 200 years * Modern data where daily timescale available * Proxy - the last 2000 years * Spatial proxy - PMIP uses Third Day: Report Writing / Final Presentations 5. Organizing committee Bengtsson, Duplessy, Laursen, Jones, ECMWF (via Burridge), ECSN (via Orfila) Wibjoern Karlen (Stockholm) Organizing committee members should be willing to prepare strawman texts, e.g. re-reanalysis (ECMWF) 3d, 1950 - now (Bengtsson) 200+ (Jones) paleo (Duplessy) validation of climate models and an assessment of (natural) climate change (statistician + modeller [Simon Tett (HC, UKMO) and/or Gabi Hegerl (MPI, Hamburg]). 6. Place and venue: Abisko, Sweden, 1 - 3 September 1997 7. Participants Invited, 10 - 15 people: Bengtsson, Duplessy, Jones, Karlen, Laursen, ECMWF, ECSN, ICPO Further 1) Input from currently funded EC projects von Storch (Millennia) Jouzel (Ice core project - Antarctica + Claus Hammer re GRIP) European Coral worker (Patzold, Bremen) Other Instrumental people (eg Folland/Parker HC UKMO, Brazil, CZ Rep, Povl Frich from DMI re the NACD efforts in N.Europe) 2) The following non-Europeans: Francis Zwiers (Canada), Raymond Bradley (Dept Geosciences, Un. Mass.) and Tom Karl (NCDC Asheville,USA). Gerbrand Komen KNMI, P.O. Box 201 phone : + 31 30 2206 676 3730 AE De Bilt fax : + 31 30 2210 407 The Netherlands email : komen@knmi.nl http://www.knmi.nl/KLIMAAT/OCEAAN (see also http://www.knmi.nl/euroclivar )