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Assessment of modelling uncertainties in long-term climate and sea- level change projections

More:  Institutes 
Original title: Bepaling van onzekerheden in modelprojecties van het klimaat en het zeeniveau op lange termijn
Parent project: Science for a Sustainable Development, more
Reference no: SD/CS/01A
Acronym: ASTER
Period: December 2005 till January 2010
Status: Completed

Institutes (4)  Top 
  • Université Catholique de Louvain; Earth and Life Institute; Centre de recherche sur la Terre et le Climat Georges Lemaître (TECLIM), more, co-ordinator
  • Université de Liège; Faculté des Sciences; Département d'Astrophysique, Géophysique et Océanographie; Laboratoire de physique atmosphérique et planétaire (LPAP), more, partner
  • Vrije Universiteit Brussel; Faculteit Wetenschappen & Bio-ingenieurswetenschappen; Vakgroep Geografie; Onderzoeksgroep Fysische Geografie (FARD), more, partner
  • Belgian Science Policy (BELSPO), more, sponsor


Policymakers are facing a wide range of possible scenarios for long-term climate and sea level evolutions without knowing precisely why they differ and how reliable they are. Two factors explain this wide estimated range: uncertainties in the future anthropogenic emissions of greenhouse gases and aerosols, and uncertainties in the understanding and modelling of the processes that influence climate. Under these circumstances, it is difficult to know which decision should be taken to avoid the most dramatic effects of climate change. However, decisions should be taken in a very near future because we could possibly pass some threshold that would lead to irreversible changes.

Project description


The overall objective of ASTER is to identify a range of possible climate and sea level change scenarios over the next three millennia that are coherent with the past evolution of the Earth system in order to get some insight on uncertainties in the modelling process and to understand the causes of this range of projections.


We will vary some key physical parameters of LOVECLIM, a global three-dimensional Earth system model of intermediate complexity, within their range of uncertainty in order to construct about 30 different model versions resulting in contrasted climate, sea level and CO2 atmospheric concentration responses to changes in forcing. This approach has been chosen because it is cheap in term of computer time and because, using a restricted number of model versions will allow a better knowledge of the characteristics of each version. For each set of parameter values, three types of experiments will be conducted, i.e. a long control experiment under pre-industrial conditions, a freshwater hosing experiment to assess the stability of the North Atlantic meridional overturning circulation and an experiment in which the CO2 concentration will be quadrupled to have a clear and strong climate signal.
The selected model versions, which should all yield a reasonable control climate, will then be utilized to carry out transient experiments over the Holocene, with a particular focus on the period around 8200 year before present, i.e. at a time of an abrupt climate change event, and the last millennium. In a last step, we will select the model versions that show the best agreement with the available reconstructions of past climates and tracer distributions, and we will employ them to perform climate and sea level change projections over the next three millennia under various CO2 emission scenarios.

Interactions between the different partners

Each partner (UCL, VUB and ULg) carries out model improvements in his/her field of expertise in order to build a basic ‘ASTER’ model. UCL will develop an automatic procedure for set-up of the simulation and post-processing of the results and will design a test of the ability of the models to simulate specific climate situations.
The partners choose together the parameters of the model that will be at the base of the various versions, on the basis of result of three types of experiments (long pre-industrial equilibrium, quadrupling of the CO2 concentration, water hosing in the North Atlantic). VUB, ULg and UCL conduct the simulations specific to the project, i.e. 8200 year event, the Holocene and the last millennium, respectively. This work is distributed amongst the partners, but each partner performs the analyses related to his/her field of expertise for all the experiments. Regular meetings allow a thorough discussion of the results.

Link with international programmes

The objectives of ASTER perfectly meet those of the Global Change and Ecosystem Programme of the European Union’s Framework Programmes, the World Climate Research Programme (WCRP), in particular its core projects Climate and Cryosphere (CliC), Climate Variability and Predictability (CLIVAR), and Coordinated Observation

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