tag:blogger.com,1999:blog-9959776.post112269477123582886..comments2024-02-15T04:42:41.606+00:00Comments on James' Empty Blog: Emissions ScenariosJames Annanhttp://www.blogger.com/profile/04318741813895533700noreply@blogger.comBlogger8125tag:blogger.com,1999:blog-9959776.post-1153153290445527652006-07-17T17:21:00.000+01:002006-07-17T17:21:00.000+01:00You write, regarding the IPCC TAR projections, "Ye...You write, regarding the IPCC TAR projections, "Yes, I think they were (scientifically) valid..." <BR/><BR/>So does that mean you think they were falsifiable? Or do you think falsifiability is not necessary for a projection to be scientifically valid?<BR/><BR/>If you think the IPCC TAR projections were falsifiable, what future events do you think would show the IPCC TAR projections to be false? Note that the IPCC TAR *explicitly* states that, "Scenarios are images of the future or alternative futures. They are neither predictions nor forecasts." How can any future event falsify the IPCC TAR projections if they are explicitly NOT "predictions" or "forecasts"?<BR/><BR/>You then write, "For your followup about falsifiability, I will do some of my own 'teaching a man to fish' by asking you whether a forecast that says '70% chance of rain' tomorrow is falsifiable. Or even 'my next coin toss has a 50% chance of turning up heads'."<BR/><BR/>Here are my answers to your questions: <BR/><BR/>1) If a weather forecaster says there is a 70% of rain tomorrow, and it doesn't rain tomorrow, I would say there is a 70% chance the forecaster was wrong. So I'd say such a weather forecast is falsifiable.<BR/><BR/>2) I don't think a prediction of 50/50 chance of landing on heads for a single coin toss is falsifiable. However, a prediction of a 50/50 chance of landing on heads for 1000 coin tosses is falsifiable.<BR/><BR/>But I hope we can get back to my questions, since you were the one who asked for opinions on why the IPCC TAR scenarios weren't being updated in AR4. In your opinion, what future events would falsify the IPCC TAR projections…especially given the fact that they are explicitly NOT predictions or forecasts of the future?<BR/><BR/>Oh, that leads me to another question...have you read any of the "Limits to Growth" series of books (e.g., “Beyond the Limits,” or “Limits to Growth: The 30-year Update”)?markbahnerhttps://www.blogger.com/profile/01039587157589669954noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-1153114613488440662006-07-17T06:36:00.000+01:002006-07-17T06:36:00.000+01:00Well, the first part of 1 is repeated in 2, so I w...Well, the first part of 1 is repeated in 2, so I will start with its second half:<BR/><BR/>1. I do think that the scenarios should be updated, although as long as they are carefully used and interpreted, they are probably good enough. That puts quite a responsibility on climate scientists who are not experts in economics though.<BR/><BR/>2. Yes, I think they were valid - not necessarily perfect - at that time (or at least, when written - clearly some aspects are bound to date rapidly, and the SRES were actually produced several years prior to 2001).<BR/><BR/>For your followup about falsifiability, I will do some of my own "teaching a man to fish" by asking you whether a forecast that says "70% chance of rain" tomorrow is falsifiable. Or even "my next coin toss has a 50% chance of turning up heads".James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-1153096830784214512006-07-17T01:40:00.000+01:002006-07-17T01:40:00.000+01:001. OK, so the questions are whether the IPCC TAR...1. OK, so the questions are whether the IPCC TAR analysis was scientifically valid in 2001, and whether the changes have been significant enough since then.<BR/><BR/>2. Let's not try to guess what the authors were thinking. I was asking you whether *you* think the IPCC TAR projections were scientifically valid when they were published in 2001. <BR/><BR/>For example, are the IPCC TAR projections falsifiable? And is it necessary for the projections to be falsifiable in order to be scientifically valid?markbahnerhttps://www.blogger.com/profile/01039587157589669954noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-1153026704929373862006-07-16T06:11:00.000+01:002006-07-16T06:11:00.000+01:001. Yes, it's obvious enough that this would be tru...1. Yes, it's obvious enough that this would be true, but it is also obvious that this is a hypothetical question. The issue is whether the updating would lead to significant enough changes to make it worth the effort, not whether new scenarios would be exactly the same as the existing ones (which no-one would argue to be the case).<BR/><BR/>2. I'm not an economist, but clearly there was a significant bunch of economists (ie SRES authors) who thought so at the time (or, more precisely, thought so at the time they were writing the scenarios, which was probably several years prior to 2001). It still seems rather limited to predicate all scenarios on the hypothesis that no mitigation takes place, but if that's what they were asked to do...James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-1152998118657675022006-07-15T22:15:00.000+01:002006-07-15T22:15:00.000+01:00James,I was looking for other information when I c...James,<BR/><BR/>I was looking for other information when I came across this post.<BR/><BR/>You write, "I don't know why the scenarios were designed to exclude any mitigation effects, and it makes the decision to not update them seem rather unfortunate, but perhaps someone will have a good explanation."<BR/><BR/>I have a very good explanation. But it seems hard to believe you can't puzzle through to what the explanation is. So on the "Teach a man to fish..." theory, I'll give you a hand.<BR/><BR/>1) Would you agree that there is no reason to update the projections from IPCC TAR (issued in 2001) if they still (as of 2006) represent a scientifically valid assessment of future events?<BR/><BR/>2) Do you think the projections in the IPCC TAR were a scientifically valid assessment of future events when it was issued in 2001?<BR/><BR/>HTH,<BR/>Markmarkbahnerhttps://www.blogger.com/profile/01039587157589669954noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-1123046164891214392005-08-03T06:16:00.000+01:002005-08-03T06:16:00.000+01:00Roger,I would certainly agree that there is quite ...Roger,<BR/><BR/>I would certainly agree that there is quite a disconnect between what we predict (eg global or perhaps regional average temperature, largely cos we can) and what an end-user might want at the local (even national) level if they wanted to adapt.<BR/><BR/>OTOH it is clear that many warnings of environmental risk or damage do not rely on explicit predictions, at least in the somewhat limited sense in which you use the term. That seems to be a closer analogue to where we are in climate prediction, compared to (say) the skill and detail of weather forecasting.<BR/><BR/>Anyway, any rational decision-making process must rely on some estimate of how different decisions will influence the likely outcomes (ie predictions). I don't see this as an alternative to divining, just a generalisation of it.James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-1122953061552648612005-08-02T04:24:00.000+01:002005-08-02T04:24:00.000+01:00Yes, nice post. Of course, an alternative to all ...Yes, nice post. Of course, an alternative to all of this divining might be to ask "What future do we want? (and who is we?)" and then ask "How do we get there?" Have a look at this discussion:<BR/><BR/>R.A. Pielke Jr., Sarewitz, D. and R. Byerly Jr., 2000: Decision Making and the Future of Nature: Understanding and Using Predictions. Chapter 18 in Sarewitz, D., R.A. Pielke Jr., and R. Byerly Jr., (eds.), Prediction: Science Decision Making and the Future of Nature. Island press: Washington, DC.<BR/>http://sciencepolicy.colorado.edu/admin/publication_files/resourse-73-2000.06.pdfAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-9959776.post-1122758369702500892005-07-30T22:19:00.000+01:002005-07-30T22:19:00.000+01:00Nice post. Thanks.Nice post. Thanks.William M. Connolleyhttps://www.blogger.com/profile/05836299130680534926noreply@blogger.com