HR: 1340h
AN: GC43A-0952    [Abstracts]
TI: Improving Probabilistic Rainfall Projections for Australia
AU: * Smith, I
EM: ian.smith@csiro.au
AF: CSIRO, PBN 1, Aspendale, VIC 3195, Australia
AB: One of the aims of developing new climate projections for Australia is to better address the requirements of stakeholders - particularly those who require less uncertainty and/or probabilistic information to work with. Recent projections differ from those issued previously, but there are two risks that need addressing. If the uncertainty is only narrowed slightly, then this may not satisfy some stakeholder requirements. Furthermore, if the differences between old and new projections are not large, then this could be construed as evidence that the problem has been solved (as much as it can be), and that further work in this area is not justified. Here we argue that it is possible to derive more reliable and less uncertain information about the future which may avoid these risks. One of the important steps in developing projections is deciding how to weight various model results. This is a controversial topic and there are a range of opinions, both here and overseas, on how make sense of a large number of results, some of which are often contradictory. Some argue for no weighting – on the grounds that a large number of results represent a real sample of possible outcomes and should not be tampered with. On the other hand, there are compelling reasons to downgrade, if not entirely dismiss, some model results based on their failure to satisfy some obviously necessary criteria. Current techniques already dismiss some model results and weight others, so the problem becomes one of deciding how to do this in a more consistent fashion, and investigating whether this makes a difference. We show how a critical approach to model performance can result in severe weighting of models and that this leads to significantly different projections for the Murray Darling Basin region. These are characterised by a shift in the probabilities towards much drier conditions.
DE: 3337 Global climate models (1626, 4928)
DE: 4928 Global climate models (1626, 3337)
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting