dikranmarsupial says:
August 17, 2018 at 6:56 am
angech wrote “ECS can only ever come out as it is programmed in. ”
This is just grade A bullshit. If I were a Magrathean and built a replica Earth (as indeed they did), it would have the same ECS as the real Earth because it is an emergent property of the physics governing climate (and the position of the planet in the solar system and the distribution of land masses etc.), not because the Magratheans “programmed it in”. It doesn’t make any difference whether you simulate that physics on a computer (supposing you could do so with infinite spatial and temporal resolution) or whether you simulated them using a replica Earth.
It is the constant stream of this kind of bullshit (and angech is not the only one) that means I am giving up on commenting on blogs, probably permanently. As a scientist, I feel a pressure to respond to this sort of incorrect assertion about science, but at the same time I know it is a complete waste of my time because angech (an others like him) will continue to spread the same bullshit elsewhere or here in a later thread, or move on to some other topic of bullshit. Thus I can’t enjoy just having a reasonable discussion here on a topic I find interesting without being bothered by bullshitters every time (and I mean every time). It appears I should probably stop reading blogs as well. Well done angech.
dikranmarsupial says:
August 17, 2018 at 7:00 am
I should add, it is very easy to show that ECS is not programmed in to climate models. If this were possible, then climate skeptics would just take the code for an existing GCM and twiddle with the parameters etc. until they got a GCM that explains past climate with a low ECS. The trouble is that can’t be done without using parameter values that are either inconsistent with physics or with experiment. Of course this is something that has been pointed out repeatedly over the years. Still waiting.
angech says:
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August 17, 2018 at 10:03 am
angech wrote “ECS can only ever come out as it is programmed in. ”This is just grade A bullshit.”
One could look at 1000 papers like this. They show that ECS outcome, high or low, is very dependent on what initial parameters are put in.
Re examining the Relationship between Climate Sensitivity and the Southern
Hemisphere Radiation Budget in CMIP Models JOHN T. FASULLO
National Center for Atmospheric Research, Boulder, Colorado 8 January 2015
models with the highest values of ECS strongly reduce low-level marine clouds in most regions of the subtropics as CO2 increases, whereas models with the lowest values of ECS actually increase low-level marine clouds in some subtropical regions
The trade-off between a better representation of present-day Southern Ocean or subtropical shortwave CRE in these subsets of models points to choices made in the model development process, rather than robust physical processes. [1]
Consequently, we find no clear physical reason to expect a linkage between subtropical cloud biases and the correlations between ECS and present-day biases over the Southern Ocean.
Instead, the linkage between subtropical and mid-latitude cloud properties is likely an artifact of choices made in model parameterization and tuning [2]
Identifying large model biases in fields physically linked to climate feedbacks remains a promising path for improving models and for potentially narrowing their spread in ECS.[3]
when the correlation between ECS and a present-day climate property arises from a systematic model bias rather than from a real physical process, its utility becomes
questionable [4]
angech says:
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August 17, 2018 at 10:22 am
…and Then There’s Physics says:
angech, You’re just doubling down now. ECS is an emergent property of models.
From RealClimate “Each of these numbers is an ’emergent’ property of the climate system – i.e. something that is affected by many different processes and interactions, and isn’t simply derived just based on knowledge of a small-scale process”
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“The wording is one issue that I am immediately defeated on. Of course anything that comes out of running a computer program can be said to emerge from it. ” I had this discussion at Lucia’s two years ago with no success. The word emergent is used by many including those promoting the ECS from models view as being an unknown that emerges from the model results. That is it could not be predicted beforehand and yet would fall somewhere in the predicted range.”
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I feel helpless at this, caught in a paradox. Either we can discuss ideas and be allowed to be wrong but have it explained [I don’t mind being castigated for not understanding] or we can choose to dismiss contradictory views out of hand. Science depends on being explainable. To just say something is emergent means we cannot explain it. In which case what is the point of developing a computer model in the first place if the answer was unprovable?
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The wording is one issue that I am immediately defeated on.
Joshua.
Sorry about the circles.
Very well put.
“two people can have viewpoints that are mutually exclusive, where both are right”
Godel?
“In this case, we could say that ECS is the function specific inputs chosen by coders, and as such, those coders determine the final value by making choices among specific inputs. Or, we could say that the coders are putting in values that represent our best understanding of physics, and that ECS emerges as an output. Essentially, those views are incompatible, and yet I think both are true.”
You can say both those things.
Some people do.
“You can get anything you like out of a model. If you set it up with scientifically based suppositions about the physics of clouds, based on the existing evidence, and reflective of a scientifically quantified range of uncertainty, they will produce an ECS output range, which likewise reflects a quantified range of uncertainty. This will at some point in the future be modified with scientific improvements.”
is fine.
Note ECS may well be 3 or 4 and better provable and models in the future will, in their arcane way, be the best way of determining it. They must be in the ball park probably inside the bases.
Just they are striking out on the nature pitches.
“You can get anything you like out of a model depending on what you put into it” would be the best interpretation of what I was saying, which I think should be evident yet English is such difficult beast.
“You can only get out of a model what you put into it” is what people here are hearing me say.
Both statements are the same yet mutually contradictory.
Perhaps Willard could explain how this is allowed to happen.
Or ATTP could do a post.