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“there are two views on Bayesian probability that interpret the probability concept in different ways. According to the objectivist view, the rules of Bayesian statistics can be justified by requirements of rationality and consistency and interpreted as an extension of logic. According to the subjectivist view, probability quantifies a “personal belief”.
In probability theory and statistics, Bayes’ theorem (alternatively Bayes’ law or Bayes’ rule) describes the probability of an event, based on prior knowledge of conditions that might be related to the event.
The sequential use of Bayes’ formula: when more data become available, calculate the posterior distribution using Bayes’ formula; subsequently, the posterior distribution becomes the next prior.
ATTP says rightly “The idea then is that you can combine the different lines of evidence, and use Bayesian inference, to determine a range for the ECS.””
dikranmarsupial says: November 30, 2016 at 4:06 pm
“The real problem with objective Bayes (in this particular case) is that we do have prior knowledge, and we need to include it into our analysis if we want to be objective in the sense of maximizing correspondence to observed reality. However doing this in an objective (in the sense of “not influenced by…”) manner is rather difficult, but that is not a good reason for ignoring the prior knowledge.”
No problem if following the method above
Thorsten Mauritsen says: November 30, 2016 at 9:18 am
“the less careful reader is easily lead to believe that the study has actually constrained ECS”.
The whole purpose is to develop a method to actually constrain the ECS
Victor Venema says: November 30, 2016 at 1:09 pm
“Fully agree with James Annan. There is no such thing as an “objective” Bayesian method.”
It is possible, though your view would count against it in an objective Bayesian method.
dikranmarsupial says: November 30, 2016 at 4:17 pm
ATTP “Why would one not take advantage of that aspect of Bayesian inference?
The place where “uninformative” priors are really useful is in expressing the knowledge that there is some quantity that you know don’t know anything about, so the effect of that uncertainty is properly accounted for in the uncertainty in the conclusions of the analysis”
-A prior event is either informative or uninformative.
If uninformative it is irrelevant.
It has no place in any assessment and it is not an uncertainty.
Prior events on the other hand are full of uncertainty and are very important to Bayesian assessment. They have to be included and as new information comes to light clarifying the uncertainty a new, more rigorous and tighter ECS range can be established.
Despite ATTP and yourself refusing to consider impossible a priors the Bayesian approach handles this with no fuss.They do not matter.
Take a negative ECS or a 20C positive ECS. Apply the concept. No past evidence of either? scrub them and add in a positive ECS 0.1 and a high ECS 12 C . Still not possible move up into the real ranges. Will it be 3C?
Who knows but the method if used by Nic or Stevens, Sherwood, Bony and Webb does not care about the starting point. Every bit of informative evidence improves the prior towards the right range]. As Dikran says “an objective method that incorporates the laws of physics, observations of paleoclimate and modern observations is needed”
This is scientific practical and another bit of the puzzle. embrace it. Point out to Nic which bits you feel he has missed out and incorporate them as well. If you do not like his ratings that very salient observation often made to me by Mosher springs to mind. Do the work yourself.
JCH says: March 31, 2017 at 10:38 pm “To me, the very most important thing is… who was the first person to speculate that 2017 has the stuff to become the 4th warmest year in a row?”
A tautology really. A bit like those guys who continually predict that the stock market is going to crash and then are right, heroes once every twenty years. Except no-one is happy with them. Let me guess, one of them would be JCH.Please do not send out a prize.
“I do think that we should avoid attacking those who present alternative views;”‘
“I’m certainly in favor of criticizing what others say when it’s clear that what they’re presenting is not consistent with the best evidence available today.”
Criticizing is different to attacking but not always perceived the correct way by those on the end of the criticism.
I would love to engage with and dissent from JCH on his view that 2017 will be the warmest on record.There are several caveats, which record, which medium air or ocean, but I have learned from past experience in a warming world not to be too sanguine. The moment one commits to these notions is the moment one loses. So I will watch with interest and hope the outcome of this year and remind JCH, if he is wrong, next year here perhaps? Or appear and get shellacked. My very modest and wrong observation would be that given the fall in ocean temperature from 2015/2016 there would have to be a marked El Nino to have any hope at all of this year coming within a cooee of 206 or 2015.