cc: "Pittock,Barrie" , nleary@earth.usgcrp.gov, shs@stanford.edu, "Pittock,Barrie" , lindam@ucar.edu, m.hulme@uea.ac.uk, djgriggs@meto.gov.uk, meehl@ncar.ucar.edu, "Whetton, Peter" , tkarl@ncdc.noaa.gov, m.manning@niwa.cri.nz, shs@stanford.edu date: Mon, 23 Oct 2000 22:46:31 +1100 from: "Jones, Roger" subject: RE: Table 3-10: a third version and some other considerations to: 'Timothy Carter' Dear Tim, Well done to get all this down in the rush! And all - The 3rd version sits best with my point of view and I agree with the star changes suggested so far. WGII really has to stress the importance of climate extremes in impact, V and A analysis and cannot be seen to endorse by default a structure that cannot pass on confidences in phenomena (or create scenarios!) until they have been represented in GCMs. One can still take information from Table 3-10, regional means for P and E from climate models, and artificial or historical variability and create valid scenarios in a better form than a GCM can represent directly. If confidences can be used to prevent what Steve S. terms as type I analyses by avoiding 0/100% binary predictions - it is/is not happening - then both type I and type II errors are more likely to be avoided. Where this approach has not quite worked is in the representation of confidence in the science and probability - the two are a little mixed in the presentation and are likely to remain so for the moment. For instance, in the simple and complex recurrent extremes, there are three choices: increase, decrease and no change. Here, columns 2 and 3 are quantifying the confidence in one choice. By default this almost ends up as a probability, i.e. I read maximum temps as >95% likely to occur. Peak TC wind intensities may increase, they may not (this still makes it more likely than either no change or a decrease if they have equal probability). This becomes even a little more strained with the singular phenomena. Is a complete shutdown of the THC >95% not likely to happen this century? Or it could happen but we have very little confidence in the knowledge surrounding that possibility (ditto for the collapse of the WAIS). This is the reason why I think this scale is best used with the supplemental qualitative uncertainty terms in Moss and Schneider. However, further work has to be done on how to best represent confidences in terms of probabilities, particular where several competing alternatives may be present. Specific comments (quibbles really) Intense precipitation may not occur in some areas where significant rainfall decreases occur In the southern hemisphere projected mid/high latitude winter wet spells are >40°S (e.g. Tasmania, southern S. America). 20-40°S may experience reduced winter/spring rains and mid latitude summer drought. Are the confidences given extended to regionality? Where you have used note e this works well. Hope these comments are useful. cheers Roger Dr. Roger Jones Climate Risk and Integrated Assessment Project Climate Impact Group CSIRO Atmospheric Research Private Bag No.1, Aspendale Victoria 3195 Australia Phone +61 3 9239 4555 Fax +61 3 9239 4688 Email roger.jones@dar.csiro.au Climate Change Impacts Network ccin_man@dar.csiro.au WWW http://www.dar.csiro.au/res/cm/impact.htm