tag:blogger.com,1999:blog-9959776.post1262526191411910294..comments2024-02-15T04:42:41.606+00:00Comments on James' Empty Blog: BlueSkiesResearch.org.uk: Project ICAD and UKCP09James Annanhttp://www.blogger.com/profile/04318741813895533700noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-9959776.post-47464931965070568172015-01-06T09:48:41.300+00:002015-01-06T09:48:41.300+00:00Yes, I also don't get the point of that commen...Yes, I also don't get the point of that comment about paying attention to other models. As for PPEs, tweets such as <a href="https://twitter.com/mat_collins/status/527036132694175744" rel="nofollow">this one</a>James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-42519779958106151562014-12-22T19:18:03.515+00:002014-12-22T19:18:03.515+00:00Your reply and further review of the 2004 open day...Your reply and further review of the 2004 open day has convinced me that my earlier comment was badly conceived and worded and that my memory was also faulty (certainly regarding date and probably more than just date).<br /><br />'Scatter gun approach' certainly does sound like a response to belief in over-tuned and too similar models.<br /><br />I think I would like to know more of the context to <br /><br />“A major strength of the Met Office Hadley Centre’s reputation is its unified model and the inclusion of other models can raise awkward questions about why don’t we pay more attention to the American, Canadian, French, or Swiss models?” (Met Office Climate Scientist 12 – Interview).<br /><br />as that seems a little strange to me.<br /><br />Also what give rise to "is the Hadley Centre’s apparent continuing preference for PPEs"?<br /><br />crandleshttps://www.blogger.com/profile/15181530527401007161noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-75711895785681524642014-12-22T16:49:02.073+00:002014-12-22T16:49:02.073+00:00James,
though not directly relevant to the PPE/MM...James,<br /><br />though not directly relevant to the PPE/MME choice, it's also interesting to look a little further back, to UKCIP98 and UKCIP02.<br /><br />These were each based based on single models (HadCM2 for UKCIP98, and a HadCM3/HadAM3H/HadRM3 linkup for UKCIP02).<br /><br />Though they both used an MME to give some context for the single-model projections (e.g. figures 36, 38, 48 of UKCIP98 compared HadCM2 with CGCM1, ECHAM4 and GFDL-R15; while a larger MME was available by the time of UKCIP02, which compare HadCM3 with eight other GCMs in figure 28), nevertheless the main projections were based on those single models.<br /><br />And this nicely highlighted the problem with using single models (though arguably we couldn't have done much else at the time). Annual precipitation totals were projected to increase in UKCIP98 but that changed to a decrease in UKCIP02. Across this period there was a change in emphasis, shifting from concern with future flooding to concern with future drought, and there were shifts in funding that reflected this.<br /><br />I don't argue that these changes in emphasis/concern on flooding to drought were driven entirely by the UKCIP98/UKCIP02 projection differences (and in fact the differences aren't as large as they appear, since they both projected wetter winters and drier summers, and the sign of the annual precipitation change arises from relatively smaller differences in which of these competing changes dominated and whether spring/autumn changed much). But nevertheless there was an influence and when I discussed the projections with various users at the time, they asked what fundamental change in scientific understanding between 1998 and 2002 had led to a change from projecting a wetter future for the UK to a drier one.<br /><br />Of course, nothing fundamental had changed. This is just what can arise when you sample single models from a range of possible models, if that range spans zero change. A point that I, and others, made when reviewing UKCIP02 and making recommendations for what was needed from UKCP08 (as it was originally, before becoming UKCP09). The gist was that whatever concept the new scenarios would adopt, they should reflect the gradually changing nature of modelling/understanding -- when a new model (like HadCM3) came along, it should subtly nudge the distribution of UK climate projections rather than cause a flip from one thing to another.<br /><br />By ~2004 it was both possible and necessary to do better at characterising projection uncertainty and including this in the main projections rather than as somewhat separate comparison.<br /><br />As well as the scientific issues that you mention, James, about whether a predominantly PPE or MME approach is preferred, there was also a practical one: if new simulations were needed then it would be more difficult to commission them from multiple climate modelling centres than from just one. I suppose this practical advantage favoured a Hadley Centre PPE approach.<br /><br />TimTim Osbornhttps://www.blogger.com/profile/11164890325617313780noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-88817363206994294152014-12-22T13:30:50.050+00:002014-12-22T13:30:50.050+00:00Thanks, I think it's a little different to hop...Thanks, I think it's a little different to hope for other groups to do similap PPEs and compare results, versus my claim that the ensemble of (tuned) CMIP models is already pretty good. From what I remember (which may be a bit partial and bised of course, it was 10y ago) CPDN members were generally at the forefront of claims that the CMIP models were over-tuned and too similar...James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-56503439986986653272014-12-20T21:08:52.473+00:002014-12-20T21:08:52.473+00:00At the July 2004 climateprediction.net open day, I...At the July 2004 climateprediction.net open day, I gained the impression that they really wanted other models to be done because a MME would better capture the range of uncertainty than their PPE. <br /><br />Managed to go back to July 2004 presentation and found a slide saying<br /><br />-What are we doing, physically?<br />-Ideally, we’d take an unbiased sample of all viable climate models, but we can’t do that<br />-Best we can do is take this scatter-gun approach<br />-Repeat with other models<br /><br />http://web.archive.org/web/20070412055038/http://www.climateprediction.net/science/pubs/openday/davef_plansfornextyear.pdf<br /><br />Of course a presentation is not really arguing the point in the peer reviewed literature.<br /><br /><br /><br />Don't know if you want to correct double words like "(the critics argued argued)" and "actually our our series".crandleshttps://www.blogger.com/profile/15181530527401007161noreply@blogger.com