Over Confidence in the National Climate Assessment

[Jack Hays]

When scientists become advocates, advocacy is presented as science. Here Judith Curry raises some serious questions about the 4th National Climate Assessment Report (NCA4).

National Climate Assessment: A crisis of epistemic overconfidence

Posted on January 2, 2019 by curryja | 15 comments
by Judith Curry
“You can say I don’t believe in gravity. But if you step off the cliff you are going down. So we can say I don’t believe climate is changing, but it is based on science.” – Katherine Hayhoe, co-author of the 4th National Climate Assessment Report.
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". . . I am fairly familiar with half of these scientists (a few of them I have a great deal of respect for), somewhat familiar with another 25%, and unfamiliar with the rest. I looked these up to see which of them were the paleoclimate experts. There are only two authors (Kopp and LeGrande) that appear to have any expertise in paleoclimate, albeit on topics that don’t directly relate to the Key Finding. This is in contrast to an entire chapter in the IPCC AR5 being devoted to paleoclimate, with substantial expertise among the authors.
A pretty big lapse, not having an expert on your author team related to one of 6 key findings. This isn’t to say that a non-expert can’t do a good job of assessing this topic with a sufficient level of effort. However the level of effort here didn’t seem to extend to reading the IPCC AR5 Chapter 5, particularly section 5.3.5.2.
Why wasn’t this caught by the reviewers? The NCA4 advertises an extensive in house and external review process, including the National Academies.
I took some heat for my Report On Sea Level Rise and Climate Change, since it had only a single author and wasn’t peer reviewed. Well, the NCA provides a good example of how multiple authors and peer review is no panacea for providing a useful assessment report. . . .
The most disturbing point here is that overconfidence seems to ‘pay’ in terms of influence of an individual in political debates about science. There doesn’t seem to be much downside for the individuals/groups to eventually being proven wrong. So scientific overconfidence seems to be a victimless crime, with the only ‘victim’ being science itself and then the public who has to live with inappropriate decisions based on this overconfident information
So what are the implications of all this for understanding overconfidence in the IPCC and particularly the NCA? Cognitive biases in the context of an institutionalized consensus building process have arguably resulted in the consensus becoming increasingly confirmed in a self-reinforcing way, with ever growing confidence. The ‘merchants of doubt’ meme has motivated activist scientists (as well as the institutions that support and assess climate science) to downplay uncertainty and overhype confidence in the interests of motivating action on mitigation. . . ."

 

[Rogue Valley]

Oh Geez

:inandout:

 

[Taylor]

Anyone ever met someone who believed they wouldn't fall if they stepped off of a cliff? Yeah, me neither.

 

[Jack Hays]

Oh Geez

:inandout:

Your point would be?

 

[Jack Hays]

This will multiply her readership many times.

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[h=1]National Climate Assessment: A crisis of epistemic overconfidence[/h][FONT=&quot]Reposted trom Judith Curry’s Climate Etc. Posted on January 2, 2019 by curryja by Judith Curry “You can say I don’t believe in gravity. But if you step off the cliff you are going down. So we can say I don’t believe climate is changing, but it is based on science.” – Katherine Hayhoe, co-author…
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[Jack Hays]

So much for that load of BS.


Reassessing the RCPs

Posted on January 28, 2019 by curryja | 24 comments
by Kevin Murphy
A response to: “Is RCP8.5 an impossible scenario?”. This post demonstrates that RCP8.5 is so highly improbable that it should be dismissed from consideration, and thereby draws into question the validity of RCP8.5-based assertions such as those made in the Fourth National Climate Assessment from the U.S. Global Change Research Program.
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. . . AR5 does not provide probability assignments for any of the RCPs, and yet many impact assessments utilize RCP8.5 to declare consequences of inaction. For example, while RCP4.5 and RCP8.5 are utilized for the Fourth National Climate Assessment (NCA4), the majority of its assertions are based in RCP8.5. The NCA4 states, “RCP8.5 implies a future with continued high emissions growth, whereas the other RCPs represent different pathways of mitigating emissions.” (Executive Summary, p.7). The reader is left with the impression that, although “high” is not defined, it is the present state of things and RCP8.5 delineates how it will grow higher. Further, the statement portrays the other RCPs as mitigation scenarios that are not being acted upon. Therefore, RCP8.5 has been portrayed as the “business as usual” scenario, and impact assessments continue to spread this falsehood.
This article employs some quantitative analysis and the original RCP documentation to demonstrate how the use of RCP8.5 is misleadingly wrong and a lower, narrower range of future CO2 atmospheric concentrations can be identified.

 

[AtlantaAdonis]

So the scientists don't know if we're doomed in 20 years or 25. Big deal.

 

[longview]

So much for that load of BS.


Reassessing the RCPs

[FONT=&]Posted on January 28, 2019 by curryja | 24 comments[/FONT]
by Kevin Murphy
A response to: “Is RCP8.5 an impossible scenario?”. This post demonstrates that RCP8.5 is so highly improbable that it should be dismissed from consideration, and thereby draws into question the validity of RCP8.5-based assertions such as those made in the Fourth National Climate Assessment from the U.S. Global Change Research Program.
Continue reading →

. . . AR5 does not provide probability assignments for any of the RCPs, and yet many impact assessments utilize RCP8.5 to declare consequences of inaction. For example, while RCP4.5 and RCP8.5 are utilized for the Fourth National Climate Assessment (NCA4), the majority of its assertions are based in RCP8.5. The NCA4 states, “RCP8.5 implies a future with continued high emissions growth, whereas the other RCPs represent different pathways of mitigating emissions.” (Executive Summary, p.7). The reader is left with the impression that, although “high” is not defined, it is the present state of things and RCP8.5 delineates how it will grow higher. Further, the statement portrays the other RCPs as mitigation scenarios that are not being acted upon. Therefore, RCP8.5 has been portrayed as the “business as usual” scenario, and impact assessments continue to spread this falsehood.
This article employs some quantitative analysis and the original RCP documentation to demonstrate how the use of RCP8.5 is misleadingly wrong and a lower, narrower range of future CO2 atmospheric concentrations can be identified.

I always saw RCP8.5 as an upper limit boundary condition for the equation, never meant to be a real scenario.
The effort need to get an additional 532 ppm of CO2 into the atmosphere in the next 81 years, is likely beyond human capability,
as it represents a rate of growth of 6.5 ppm per year, more than double the highest years growth seen so far.

 

[longview]

So the scientists don't know if we're doomed in 20 years or 25. Big deal.

I think it is only politicians who throw out such numbers, and I do not think any scientists say we are doomed.

 

[Jack Hays]

So the scientists don't know if we're doomed in 20 years or 25. Big deal.

Not doomed at all.

 

[gfm7175]

So the scientists don't know if we're doomed in 20 years or 25. Big deal.

But what about "world renowned scientist" Alexandria Ocasio-Cortez claiming that we're doomed in 12 years???


First, global warming needs to be defined in a non-circular way... Have at it.