Comments on: Responses to Gavin Schmidt, Part 2

By: barry

barry — Sun, 23 Nov 2008 05:27:00 +0000

Warren wrote: "Since when has direct comparison of forecast models against observation and measurement been the wrong way to validate or invalidate the forecast or model?"

Since never. But this is a completely false interpretation of Schmidt's statement.

"Instead, the anti-model crowd focuses on the minor issues that crop up every now and again in real-time data processing hoping that, by proxy, they'll find a problem with the models."

The "minor issues that crop up every now and again in real-time data processing" are not robust "observation and measurement", obviously.

By: Bart

Bart — Thu, 20 Nov 2008 07:35:43 +0000

Jennifer said: "Again, they don't assume positive feedback. Positive feedback is required to match the observations."

That is to say, it is the only thing the researchers could think of that allowed them to match the observations. This is an argument from ignorance, a classic logical fallacy.

"The climate system is not 'long-term stable' - in fact, instability, in the form of sudden state changes, is the defining characteristic of the long term climate record."

Sudden changes can occur from internal instability, or from external forcing. This is petitio principii or begging the question, another classic logical fallacy.

By: Giovanni

Giovanni — Thu, 20 Nov 2008 03:48:02 +0000

Ah, Gavin Schmidt, Dr. Hansens own little water carrier. Word of caution… whenever you read or even argue with Gavin keep in mind the following: He is an expert in what I like to call “baffle them with bull shit” and he uses it quite frequently.

By: CarbonFever

CarbonFever — Fri, 14 Nov 2008 14:13:30 +0000

Jennifer -
I don't see where anyone is saying it is impossible to model a chaotic system. However, by definition chaotic systems are extremely sensitive to initial conditions - model inputs in this case. The point is that the "data" produced by the model will vary wildly depending on the inputs. The models are doomed to fail. I think the comparisons of model output to real data is proving that point. The models are worse than useless.

By: Jennifer

Jennifer — Fri, 14 Nov 2008 14:00:35 +0000

What you haven’t yet told me is the trends that you’ve calculated, for 1994-present. The data sets from which I got the numbers I quoted are:

RSS: http://www.remss.com/data/msu/monthly_time_series/RSS_Monthly_MSU_AMSU_Channel_TLS_Anomalies_Land_and_Ocean_v03_2.txt
UAH: http://vortex.nsstc.uah.edu/data/msu/t4/uahncdc.ls

By: An Inquirer

An Inquirer — Fri, 14 Nov 2008 12:12:53 +0000

Jennifer: I am sure that it is an innocent oversight. I have given you a website that is typical of data sources I use; you have not given me your source — and typically you readily provide websites. It would be convenient if I could post those stratospheric temperature graphs in the comment section (Maybe Warren Meyer could post them?) because they quite clearly show wiggles since 1994 but no downward trend.

By: Jennifer

Jennifer — Fri, 14 Nov 2008 00:28:24 +0000

An Inquirer: rather than just eyeballing, can you tell me what trend you derive from the data? Because from 1994-present, I calculate a trend of -0.032 K/decade from UAH and -0.028K/decade from RSS. I cannot see how you could even describe the trend as flat, let alone slightly positive.

It seems clear to me that the reason the drop after the volcanic eruptions is greater than the preceding rise is simply that the volcanic effect is superimposed on a downward linear trend. I see no statistical justification for describing the stratospheric temperature trend as a step function, and there is no possible physical mechanism that could produce one, that I can think of. Do you think otherwise?

By: An Inquirer

An Inquirer — Thu, 13 Nov 2008 21:34:42 +0000

Jennifer,
Well, it appears that we are looking at the same graph, but we are having different reference points. We have this understanding in common, stratospheric temperatures are now generally lower than they were in 1978. You seem to say that it has been a consistent trend. When I look at the graph, I see it being flat since 1994. Yes, there is a big difference whether you add 18 months on the beginning -- because stratospheric temperatures were much higher 18 months earlier, perhaps due to volcanic activity. I see an anomaly of around -0.5 for the three measures in 1994, and now they are around -0.2 in the Hadley site. I am not offering any scientific explanation why stratopheric temperatures dropped by more than they rise following the last two or three volcanoes. I am just pointing out that is what the graph shows. We have not had a major volcano the last 1.5 (or so) decades and stratospheric temperatures have been flat to slightly positive. (And yes, you have a valid point that stratopheric temperatures cannot have consistently fallen by more than volcanic-induced increases throughout history without some positive trends in between.)

By: An Inquirer

An Inquirer — Thu, 13 Nov 2008 19:44:01 +0000

Regarding Hansen 1988, I need to lean a little more toward Jennifer's current position than what the skeptics are saying on this blog. There are other GHGs which heavily influenced the outcome of Hansons 1988 forecast. We have covered these issues repeatedly on this blog, so I will not repeat them all. But here are a few highlights:
1. Hansen did himself no favor or credibility by inserting written statements that seem to contradict what he actually did.
2. By labeling Scenario A the Business as Usual scenario and by carrying that Scenario far into the future, Hansen created a situation where readers can easily get the impression that Scenario A is one that deserves focus.
3. There are other GHGs in Hanson's model that make it legitimate to claim that overall inputs do not match Scenario A, but something lower.
4. Hanson's testimony to Congress occurred a year after the Montreal Protocol, so questions could be raised whether a business-as-usual scenario should have reflected that Protocol. However, Hanson certainly was working on his model before the Protocol; yet the outcome of the Protocol was quite well known ahead of time. Therefore, different views on this issues are certainly understandable.
5. Given actual developments of inputs, I do not see how you can get below Scenario B.
6. At least one AGW pessimist has said that Hanson 1988 model is no longer relevant (indeed, apparently it can no longer be compiled and run) because models have improved in the last 20 years. Of course, that begs the question whether we should rely on today's models or models that will be developed 20 years from now.

By: Industry Insider

Industry Insider — Thu, 13 Nov 2008 18:46:24 +0000

“Jennifer,” your identity is clear enough for those of us who have followed these discussions for a long time. I am sincerely glad you have returned, and I will continue to be civil/friendly toward you as I have always been.