Dim Sun Anyone?

[tomclarke]

And here is a direct answer to Simon's point. As I have said - the robustness of the GCMs attribution of warming to CO2 comes from the fcat that they are physics-based, otherwise, looking at correlations, the picture is just too complex:

# colin Aldridge Says:
17 December 2008 at 5:00 PM

I have seen a couple of papers, admittedly only in the blogosphere, which try and model the bit between climate change and weather based on AMO ENSO and CO2. These attempts give much better fits than ENSO plus C02 alone and suggest the CO2 component is nearer 0.7c for a doubling which is below the low end of IPCC by quite a lot.

Do you have a view on this Gavin. The obvious criticism is that given enough variables you can get anything to fit anything but its clear there are “natural variations at work” which are more than noise and CO2 signal

[Response: The main issue is that in the real world many things trended up in the 20th Century - sulphate aerosols, CO2, black carbon, maybe even solar for the earlier part at least. Therefore any correlation analysis will conflate these things and so you can get any one of them you like to explain all the trend. None of these correlation methods of climate attribution are robust especially if they use just the global mean surface temperature - which is why physics-based methods are generally preferred. There are some analyses that are worse than others though - for instance using a trend+AMO to match the N. Hemisphere temperatures is simply correlating the temperature with itself. Not much predictability there. Similarly, correlating T against CO2 and expecting the coefficient to give the equilibrium response is just foolish. - gavin]

[tomclarke]

For those interested in following the AGW issues - there are roughly 400 comments on the last 100 years of temperature trends and what they do or don't mean - I have quoted a few above. Of the 400 probably 100 are worth reading.

http://www.realclimate.org/index.php/ar ... -and-spin/

If anyone can find me a skeptical web-site with a similar list of comments with as wide a range of informed opinion I will be happy to read it too... But check out the sets of comments before you make assumptions.

Tom

[TallDave]

In answer to this question. I am not a "believer". My initial position is one of more trust in the scientific process of peer review and debate than you. It is not that individual scientists are great - but when many different people are all contributing different ideas, the best win over time. And GCMs have had time.

That wasn't the question, but OK, let's look at that. Do you know what the track record is for expert predictions? (Hint: forecasting scientists have studied this issue.)

When I look at the evidence now my problem is that this is complex science. The simple-minded blog rebuttals do not stand scrutiny.

Bullhooey. The AGW claims don't stand scrutiny. The anti-AGW claims stand up considerably better. And remember, a theory is disproven by a single confirmed contrary observation.

Equally, I can't rule out completely that all the pro-AGW scientists are somehow deluded / in collusion and getting it wrong.

What about the anti-AGW scientists? Why is it more likely they're deluded, in collusion, or getting it wrong? Because there's not as many of them?

Like most AGW believers, you often don't seem to fully understand the scientific process and why skepticism is the rule and not the exception.

Also, as best I can tell, you didn't answer the question. How many years of a flat/cooling trend would convince you AGW is probably wrong?

[TallDave]

None of these correlation methods of climate attribution are robust especially if they use just the global mean surface temperature - which is why physics-based methods are generally preferred.

Even by Gavin's low standards this is a very bad argument. The physical modelling is so weak as to be laughable; the unknowns in water vapor feedback alone are enough to make predictive reliability a joke. Just this week we found out the Atlantic conveyor GCMs all use doesn't actually exist.

As I have said - the robustness of the GCMs attribution of warming to CO2 comes from the fcat that they are physics-based,

That's only because it's easier to play with physical factors. You can just keep adding more and more of them and adjusting their impact till you get what you want, unlike correlations, which are inconveniently fixed and finite.

Want to bet a well-funded team of anti-AGW scientists couldn't put together a GCM that predicted no rise in temperature?

[tomclarke]

Talldave -

Your first sentence is a contradiction. IF they are phsics-based models then they don't assume their conclusions, and they are sound.

Your second one is possible. But whether or no climate models are weak is I think not something you can know without considerable investigation.

Nor can I. As I have said we have different starting points. Without other knowledge I choose to trust the totality of scientists who work on this. I do this because their debate appears to be genuine and seek the truth, and what they say is generally more detailed and convincing then what the anti-AGM advocates say.

Over whether the GCMs are weak. If I do not accept other people's evidence to understand all the assumptions and cross-validations, reach my own estimate of where are the weakest links, how weak are they? It would take a lot of work.

I admit this. I do not see how it can be different for you - so your view that they are weak muct come from a different initial starting point.

[TallDave]

Your first sentence is a contradiction. IF they are phsics-based models then they don't assume their conclusions, and they are sound.

Sorry, I deleted that because it seemed confusing. But yes, they all assume CO2 levels are driving climate. They don't arrive at that position after eliminating every other possibility. Then they choose physical models that support that assumption.

Without other knowledge I choose to trust the totality of scientists who work on this.

You're a believer, in other words. I am a skeptic. I choose not to trust anyone, but rather try to evaluate the worthiness of their theory from a skeptical viewpoint.

Over whether the GCMs are weak. If I do not accept other people's evidence to understand all the assumptions and cross-validations, reach my own estimate of where are the weakest links, how weak are they? It would take a lot of work.

Fortunately, forecasting scientists have been studying the reliability of models for some time, and have done the work for us.

You still haven't told me how many years of a flat/cooling trend would cause you to view AGW skeptically.

[tomclarke]

What about the anti-AGW scientists? Why is it more likely they're deluded, in collusion, or getting it wrong? Because there's not as many of them?

For three reasons:

(1) some of them are just not approaching the problem with a careful scientific mind. They make simplistic assumptions, ignore evidence, etc. They are usually working outside their own field - eminent people who have come to climate science from a different background entirely and with what appears to be a prejudice.

(2) There are many fewer of them. If I choose between a few scientists having weird ideas or most doing this the few is more likely. On any scientific question there always are outliers (just as well).

(3) I have not read the published papers that justify the anti-AGM view. The arguments I hear are often meta-arguments, mostly based on character assasination. When I read real papers they do not convince:

G&A - treating GCMs as stochastoc models. This is absurd. they may be flawed physical models but they undoubtedly have strong physical evidence. there analysis is only relevant to stocastic models (their area of expertise is ecomomic models where there is no equivalent of physical causality and most theories are based on perilous assumptions).

Morner - seems very much an outlier and reading the rebuttals of his papers and his counter-rebuttals I know which is more convincing, and it is not him.

Let me turn this round Dave. What is your reason for preferring the arguments of the few anti-AGM scientists? Wre are not talking about the blog simplifications posted here - they are easily dismissed. we aretalking about the underlying scientific argument. Is it your judgement that the scientific weight of evidence (rather than blog arguments) is on the anti-agm side? Can you quote me papers, and have you read the commentray on the papers you quote to get both sides?

Do you maybe prefer the anti-AGW case because it has many fewer scientists, or more popular web sites?

[tomclarke]

That's only because it's easier to play with physical factors. You can just keep adding more and more of them and adjusting their impact till you get what you want, unlike correlations, which are inconveniently fixed and finite.

Want to bet a well-funded team of anti-AGW scientists couldn't put together a GCM that predicted no rise in temperature?

No. There are so many possible correlations with potential forcing parameters. If you allow stochastic theories you add enough parameters and the problem becomes underdetermined. This is what Simon incorrectly accuses AGMs of. It is certainly something to beware.

Physical theories can be cross-validated (or refured). Every step of the case can be tied down to some potentially calculable physical relationship. If the problem cannot be solved analytically it can be simulated or investigated empirically using data quite different from the GCM results.

Well-funded anti-AGM scientists? Are you telling me there is no money behind the anti-AGM case? There are powerful and rich interests behind it. Do they not fund research? If not, why not?

Tom

[TallDave]

(1) some of them are just not approaching the problem with a careful scientific mind. They make simplistic assumptions, ignore evidence, etc. They are usually working outside their own field - eminent people who have come to climate science from a different background entirely and with what appears to be a prejudice

Shrug. I could say the same about the pro-AGW side. There's really no such thing as strict "climate science" anyway, it's a mishmash of other fields.

If I choose between a few scientists having weird ideas or most doing this the few is more likely

Most of the people who have lived on the Earth have believed it was flat. Should we settle the the matter by majority opinion?

G&A - treating GCMs as stochastoc models. This is absurd.

Not a valid criticism, as I've previously pointed out.

Wre are not talking about the blog simplifications posted here - they are easily dismissed.

Sure, gravity is easily dismissed too. But things still fall. I think it is easy to dismiss criticisms of a theory you've already decided you like. It's known as confirmation bias.

Do you maybe prefer the anti-AGW case because it has many fewer scientists, or more popular web sites?

Well, overall I prefer to be skeptical. It's a little philosophy called "science."

Of course, there are also the numerous distortions and unscientific behavior of people like Hansen and Gore, and the political arguments being made on the basis of the theory. That should always make one extra suspicious.

I've noticed you still haven't answered my question. A scientific theory MUST be falsifiable. How many years of flat/cooling temps would falsify AGW for you?

[tomclarke]

Fortunately, forecasting scientists have been studying the reliability of models for some time, and have done the work for us.

You still haven't told me how many years of a flat/cooling trend would cause you to view AGW skeptically.

Give me a break? We have rehashed the issue about G&A, stochstic vs physical models, etc. I think you are either quoting what others say, or avoiding the question. If you choose to deny that GCMs are physical models that is fair enough - but you know my case rests on the fact that tey are. So your argument which falls flat unless they are stochastic models like economic theories where opinion is all does not add to your case.

I do view AGW skeptically - both the pro and anti case. I don't believe you can define a flat trend! The global temperature variability is very high and you need a timescla eof 30 years, or preferably more, to establish a trend.

So given the past history I would say another 5 years? Unless the science gets better and the variations can be modelled physically (not stochastically). In that case the undelying trend could be disambiguated ffrom the physically modelled noise, and the trend would be more evident.

Did you read carefully my many quotes above about temperature trends? And have you read the 100 other comments? (I have not read all of them) they might help you to put this temperature trend idea in its place.

Tom

[TallDave]

There are powerful and rich interests behind it.

Name one, tell me what they've funded. Let's see a list of funding remotely comparable to what AGW gets. We can start with the $400M in the stimulus package.

Do they not fund research? If not, why not?

To prove a negative? Why bother anyway? A carbon tax only really hurts the poorest people. The big fossil fuel companies are more than happy to jump on board with higher fuel prices.

[TallDave]

If you choose to deny that GCMs are physical models that is fair enough - but you know my case rests on the fact that tey are. So your argument which falls flat unless they are stochastic models like economic theories where opinion is all does not add to your case

Sigh. They don't need to be stochastic models to be forecasts. Forecasting principles still apply. They apply to all predictive models.

[TallDave]

The global temperature variability is very high and you need a timescla eof 30 years, or preferably more, to establish a trend.

Do you realize what you're saying here? If AGW cannot be disproven, it is not even a scientific theory.

Additionally, it's a glaring contradiction to the "90% certainty" we're told for the IPCC predictions. It's absurd to say

1) we know almost for certain AGW is real and going to be very bad
but
2) we can't disprove AGW, possibly on any timescale, because the trends are so uncertain

[TallDave]

Re the forecasting scientists: it seems you've only read the RealClimate rebuttal, which gives a fairly silly argument. Essentially, they're saying "Well, our predictive model is physical, so we don't have to follow rules like these." But the actual report is quite damning for any predictive system, and it did not just address GCMs but also the impact studies.

[MSimon]

http://wattsupwiththat.com/2009/05/29/s ... falsified/