tag:blogger.com,1999:blog-9959776.post113706915432091868..comments2024-02-15T04:42:41.606+00:00Comments on James' Empty Blog: Probability, prediction and verification I: UncertaintyJames Annanhttp://www.blogger.com/profile/04318741813895533700noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-9959776.post-1137304795264702482006-01-15T05:59:00.000+00:002006-01-15T05:59:00.000+00:00But Lumo,You just admitted that different forecast...But Lumo,<BR/><BR/>You just admitted that different forecasters could give different probabilities of rain (and they frequently do). So of course the weather forecast depends on "model-dependent, and subjective effects". And weather prediction uncertainty is not an aleatory uncertainty in any case, given that the atmospheric dynamics are deterministic. How can you possibly hope to treat today's forecast in a frequentist manner? Tomorrow's forecast is a physically distinct problem, not a replicate of today. Yet weather forecasting is an example of predictive science at its best - there's no shying away from reality, and the results prove their value on a daily basis. <I>You</I> may choose to only use the forecast as a "rough estimate", but many others whose livelihoods depend on it (such as farmers, energy companies) make directly quantitative interpretations of the probabilistic forecasts, and would be foolish not to do so.<BR/><BR/>Outside of mathematics, we never "know" the answers to any questions, without acknowledging some uncertainty in our answer. How old is the universe, BTW? The Earth? Are these intrinsically unscientific questions?<BR/><BR/>Brian,<BR/><BR/>Without knowing the odds, you can't give a frequentist answer (and even if you do a frequentist experiment, you can only approximate the odds - so no-one can ever tell that a coin really is unbiased, except when this is given as a premise in mathematical problems). I don't think the people you are trying to debate with are worried about such philosophical problems, they are simply denialists who refuse to examine or acknowledge the inconsistency of their own positions...James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-1137294409224670752006-01-15T03:06:00.000+00:002006-01-15T03:06:00.000+00:00I only use the "chances of rain" as a very rough e...I only use the "chances of rain" as a very rough estimate to see whether someone who has looked at the situation much more quantitatively - and with the help of computers - thinks about the weather tomorrow. It is about a subjective feeling of someone who may be trusted more than myself in this particular question.<BR/><BR/>It is just an argument that affects the question whether I will take an umbrella to Seattle tomorrow - still undecided, by the way. ;-) If they told me whether it will be raining above the campus on Monday morning and evening instead of the number 50%, it would be more useful. ;-)<BR/><BR/>The precise value of these "chances" has absolutely no meaning, and a different weather forecaster with different models would surely give you different figures.<BR/><BR/>The numbers are only quantitatively meaningful to the extent that they can be defined as frequentist probabilities (and experimentally verified) - which is partly possible in the weather once you define the ensemble of situations more accurately. The trade-off is completely clear: either you allow uncontrollable, model-dependent, and subjective effects influence your estimates, and then your numbers are not science. Or you keep things scientific, but then you are forced to admit that you simply don't know the answers to many questions instead of generating random figures representing "chance".<BR/><BR/>Best<BR/>LubosLuboš Motlhttps://www.blogger.com/profile/17487263983247488359noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-1137285856695387972006-01-15T00:44:00.000+00:002006-01-15T00:44:00.000+00:00Would you say there's a difference between defined...Would you say there's a difference between defined and undefined aleatory uncertainty? A fair coin toss is irreducibly random, but has defined 50:50 odds. Contrast that to a computer program that will use some unknown random process to choose between the words "warmer" or "cooler", but you don't know what the odds allocation will be between the two words.<BR/><BR/>I think this is the heart of the argument for people who say there's no reason to believe in anthro global warming AND say that 2:1 betting odds, offered to them against it getting colder in 10 years, is meaningless.<BR/><BR/>I doubt they really believe it, or else they'd also reject 20:1 odds, and I expect they'd jump all over those odds (like I would). It's still their argument though.Brianhttps://www.blogger.com/profile/09301230860904555513noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-1137218770575598602006-01-14T06:06:00.000+00:002006-01-14T06:06:00.000+00:00Thanks Steve,I've no plans for C&L, but we'll see ...Thanks Steve,<BR/><BR/>I've no plans for C&L, but we'll see how things go. It seems to me that the main content of their paper was basically valid, but they dressed it up in sceptical-sounding sentences (somewhat tangential to, and exaggerating the impact of, the science itself) for effect. The RC post tried to over-reach and turned into a bit of a train wreck IMO.James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-1137195814834759252006-01-13T23:43:00.000+00:002006-01-13T23:43:00.000+00:00Thanks, James, that was nicely written. Will you ...Thanks, James, that was nicely written. Will you be getting to the Cohn and Lins paper as part of this? As you probably know, it's been the subject of a multitude of even more childish rants (back-handed compliment to Lubos!) over at you-know-where.Anonymousnoreply@blogger.com