Thursday, August 24, 2006

Inconvenient truths

"The glaciers are melting!" Well, of course they are. That's what glaciers do.

"No, no, Greenland's glaciers are melting, and it's global warming!!" Well, yes they have been shrinking ... for at least a hundred years. And guess what: "the biggest reduction was observed between 1964 and 1985." During that period I think you'll find the world was slightly cooling. Hmmm.

"And, and, snowfall in Antarctica is increasing/decreasing/showing clear signs of global warming!!" Well, no. Not true either. In fact, "There were no statistically significant trends in snowfall accumulation over the past five decades, including recent years for which global mean temperatures have been warmest."

Next!

LINKS: Greenland's glaciers have been shrinking for 100 years: study - Breitbart.Com
Overall Antarctic snowfall hasn't changed in 50 years - National Science Foundation

RELATED: Science, Global Warming

9 Comments:

Blogger Andrew said...

Peter, I accept that it is entirely possible that your stance on global warming is correct. Do you accept the possibility that you may also be wrong, and that global warming is something that may have disastrous outcomes in the future.

I am not so sure either way, but I believe that entertaining the possibility of global warming is not a bad thing.

You seem so sure about something that just isn't your field of expertise.

8/24/2006 10:41:00 am  
Blogger PC said...

I'm simply reporting the evidence as I see it, Andrew.

I'm sure you're aware that since it is impossible to prove a negative, the onus of proof is always on those making a claim -- in this case then the onus of proof is those who making the claim that man-made global warming exists, and the inconvenient truth about much of the evidence adduced to date is that it has been less than stellar.

8/24/2006 11:27:00 am  
Blogger Andrew said...

Given that the data generated by research into global warming is observational at best, absolute proof for the existence of man-made global warming is not possible either. Even experimentally this isn't possible to proof (see the use of p-values in a lot of science). As for plausible evidence, I agree with you, it may not be all that convincing ... yet. But who knows what future research will tell us. I am not making any bets on this one yet. The immense number of variables and interactions between variables involved in something like man-made global warming in dizzyingly complex. For that reason I am cautious about accepting AND rejecting the possibility of global warming. And even if it is happening, we don’t actually know if that has positive or negative effects for us.

However, that was not my point. You seem very very sure that man-made global warming isn't happening, and never seem to accept that it may be possible. I just asked you if you thought it was possible.

Personally I don't believe in the existence of a god or a metaphysical soul. However, I would never claim that they don't exist.

8/24/2006 01:28:00 pm  
Blogger PC said...

But the onus of proof is always and must be on those making a positive claim, on those who say that so-and-so exists or so-and-so is happening.

It's just not possible to prove a negative, but it is possible to look at a claim about, say, glaciers melting in Greenland and say, "Nah, that's wrong."

You see, any claim that's made without evidence to support it is not a 'conditional' claim, it's simply an arbitrary pronouncement with no more claim to truth than claims about there being fairies at the bottom of the garden, or green spiders on the far side of Mars.

"Who knows what future research will tell us"? Who knows. All we have is current evidence. All we ever have is current evidence. And outside continually-revised computer modelling, there is no present evidence for man-made global warming, which makes any claims for its existence as arbitrary as claims about fairies in the garden, spiders on Mars, and the previously fashionable claims about man-made Global Cooling.

8/24/2006 02:57:00 pm  
Blogger Andrew said...

Yes, and those that make those claims are trying to get the evidence. I also think it is good that people challenge those findings. In fact, that is extremely important. I also support the existence of organisations like the Climate Science Coalition.

However, I sometimes wonder if your views on some issues can ever be changed. My point was that we can never prove man-made global warming, and that the best evidence we can possibly generate using observational research, will never be good enough for some people.

Example:
We can't prove that smoking causes lung cancer. It would be nice to try and find some experimental evidence for this, but we can't ethically conduct such studies. Therefore we rely on correlational research.

The fact there is a relationship between smoking and lung cancer, and that non-smokers just don't get lung cancer (yes there may be one or two exceptions), on the face of it seems pretty convincing. However, the problem with that is that there is always some other possible explanation for the link between smoking and lung cancer. That is, people who take up smoking are different from those who don't, and it is that personality variable that may actually be responsible for the cancer. It is improbable, but possible. It took a very very long time for tobacco companies to publicly accept that smoking probably does cause lung cancer in some people. However, there is no proof.

Now given your desire to provoke, and knowing that you smoke, you probably don't believe the conspiracy theory that smoking causes cancer.

If that is so, I give up.

However, if not and you are willing to accept that global warming is a possibility, if you are provided with the evidence, maybe you could provide some idea of what, in your view, convincing evidence is.

8/24/2006 06:33:00 pm  
Anonymous Falafulu Fisi said...

Andrew said...
[My point was that we can never prove man-made global warming, and that the best evidence we can possibly generate using observational research, will never be good enough for some people.]

I think that observational research is the norm of scientific investigations. However in todays environment, we are heavily rely on computer models to stretch our imaginations to domains that it is impossible to do experimentally. When you step, into the unknown using the model, then you come up with different possibilities of outcome. If the model is formed by wrong assumptions, then wrong outcome or conclusions will come out as a result. This happens all the time. When it happens, it is either improved or refuted by other researchers when they publish their peer review work. Climate modeling is a complex systems phenomena and it should be treated as such using the appropriate model.

Andrew said...
[However, if not and you are willing to accept that global warming is a possibility, if you are provided with the evidence, maybe you could provide some idea of what, in your view, convincing evidence is.]

In my view , I have accepted that global warming is a possibility, but based on some papers I have read relating to the global-warming debate, I am not convinced that it is happening. I have dug deep into the mathematical modeling those pro-warming group have used and I am alarmed at many defects in the type of algorithms they used (perhaps, they were not aware of more recent robust ones available). For example, I have dug deep into the paper for 'hockey-stick' by Prof. Mann, et al where the Kyoto was based on, and I can see some improper techniques being used.

"Global-scale temperature patterns and climate forcing over the past centuries."
http://www.geo.umass.edu/faculty/bradley/mann1998.pdf

First is the use of PCA (Principal Component Analysis), which is a linear method that is inappropriated for non-linear data as weather.

Second, his paper is vaque about the transfer functions for AR (Auto-Regression) process. He mentioned AR but never gave any transfer function (ratio of the output to the input variable).

Third, he never clearly described how he dealt with missing data. The data collected from the period described in his paper had missing data and to run an analysis such as that, you first have to pre-process the data to take out outliers , where there was no clear description if he did or did not. If the outliers are not taken out it will have an influence in the outcome. If you run analysis on the unclean data, then you expect a huge error that might be caused by outliers present or missing values present. I had communicated with Professor Schneider of Caltech (Calfornia Institute of Technology) recently after I have read his paper which was published in 2001 in the Journal of Climate to see if Prof. Mann et al did use any 'missing-data-fill-in' algorithm such as 'Expectation-Maximisation' (EM) or not. His reply was that he tried to communicate with Prof. Mann but was given vague answer to whether they (Mann et al) used such algorithm at all. In his view that it was not used at all. Now, anyone can just infer what kind of results if the analysis didn't use any 'missing-data-fill-in' algorithm as EM. Of course tha

"Analysis of incomplete climate data: Estimation of mean values and covariance matrices and imputation of missing values"
http://www.gps.caltech.edu/~tapio/papers/imputation.pdf


Fourth, there was never any mention regarding the de-noising of the data. This is a standard procedure in signal processing prior to formal spectral analysis. If noise is not removed, then obviously the results is going to be skewed.

As seeing all those steps I have listed above, I concluded that the analysis was incomplete and I can infer that the results was not convincing.

8/24/2006 07:49:00 pm  
Blogger PC said...

Andrew, you said: "Yes, and those that make those claims are trying to get the evidence."

But how can you make a claim before you have the evidence? What truth value does any claim have when made prior to the collection of evidence. If the claim fits with already-known evidence and integrates many of them, then such a claim would be the basis of a very good hypothesis that could then go on to be tested.

But if on the other hand the claim itself is pretty much all the evidence -- such as my claim that there are green spiders on Mars -- then my claim is just arbitrary, and in the realm of knowledge it's out.

"However, I sometimes wonder if your views on some issues can ever be changed."

Oh, of course they can, but it requires evidence and sound reasoning. Just as it does with everybody else. :-)

"My point was that we can never prove man-made global warming, and that the best evidence we can possibly generate using observational research, will never be good enough for some people."

Well, if it exists, of course you can prove it. You certainly can't if it doesn't, however.

As you're saying about smoking and lung cancer, as yet (as I understand it) there's been no direct causal link found between smoking and lung cancer that might explain, for instance, why nine people will smoke like trains and be cancer-free, and one will have the occasional social puff and spend the last years of their life on an inhaler.

But even without such direct causal link being found, the overwhelming preponderance of the evidence shows that the risk to regular smokers of getting lung cancer is several orders of magnitude above what it is for non-smokers.

So there is overwhelming evidence for the claim, despite the lack of a known causal link. The evidence does suggest however that one will be found eventually.

"Now given your desire to provoke, and knowing that you smoke, you probably don't believe the conspiracy theory that smoking causes cancer."

Well, as I address the latter point in my comments above, I wonder what evidence you have for me being a smoker? ;^)

8/25/2006 11:55:00 am  
Anonymous Falafulu Fisi said...

PC said...
[Well, as I address the latter point in my comments above, I wonder what evidence you have for me being a smoker?]

I think Andrew means the occasional 'Port Royal' rollies that you pinch from Patrick to have a puff.

8/25/2006 12:50:00 pm  
Blogger Chefen said...

The smoking thing is a red-herring. In that case even if you have no idea of the link you have literally millions upon millions of trials conducted... all those smokers. You can slice and dice them to control for many factors and come to the conclusion that smoking is the most likely factor.

With global warming however there is only one trial and you are in the middle of it being conducted. Hence the reliance on incomplete models and extremely dodgy historical proxy methods.

The difference is very important.

8/26/2006 02:40:00 am  

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