Re: [Phys-l] Climate skeptic convinced by data. Was: Re: Mike Mann _The hockey

[Brian Blais <bblais@bryant.edu>]

On Feb 18, 2012, at 17:12 PM, John Denker wrote:

> 2) There is no serious doubt that atmospheric CO2 has recently increased.
>
> 3) There is no serious doubt that the increase in CO2 is anthropogenic.
> The isotope signature gives it away.

I'm ok with these (2) and (3).  


> 1) There is no serious doubt that the recent increase in temperature is 
> unprecedented over the last 1000 or 2000 years.

this part (1) is where I disagree.  How do we know that it is unprecedented in the past 1000-2000 years?  from proxy data.  From everything I have seen, there is serious doubt on this, on several grounds:

a) there is a systematic downplaying of the uncertainties.  I've looked at the data myself, and have found the variability to be startlingly high.

b) the methods that are made to downplay the uncertainties seem to be both sensitive to a very small subset of the proxy data set, and also seem to pick out "hockey-stick" shapes out of noise.  combined with a general lack of openness with the data and methods, this calls into question the confidence in the analysis

c) we know that some of the proxy reconstructions predict *opposite* trends for 1/3 of the time period where we *know* the actual temperature.  this divergence problem, which may perhaps have a reasonably solution, call into question the validity of the reconstructions during the times where we don't have independent confirmation.

d) the models are tuned to this temperature profile.  so, if the proxy data are wrong, or the temperature reconstructions from them are wrong, then the models will be wrong.  It won't matter if all the models agree, or that they agree with the proxy data (to which they are tuned). 

e) there is at least some evidence that it was warmer at some point during the last 2000 years, which would certainly call into question all of the claims.  I am not saying I am necessarily convinced by this evidence entirely, but with the stakes as high as they are, this needs to be handled very carefully.

> 4) There is no serious doubt that item (3) explains item (2). Since item (2)
> in turn explains item (1), this means that the warming is anthropogenic.

well, actually it is not true that your item (2) necessarily explains your item (1): it depends on the feedbacks in the system, which are only now being measured independently.  If, for example, there are strong negative feedbacks in the system then (2) won't lead to (1).  Are we confident in our understanding of these feedbacks? not even close.

Although I think it is *plausible* that we are causing at least *some* of the warming observed, I am not convinced that we are responsible for *all* of it (although that is possible) and I am not confident that it is unprecedented in the past 2000 years.  I definitely don't trust the proxy data, and thus the models (garbage in = garbage out).  I'd love to be convinced otherwise, but I haven't seen this addressed well in the climate community.  The "Climategate" emails, and the descriptions written over at climateaudit.org, seem to indicate a tendency to tribalism and closed procedures in the climate community, and to Michael Mann's group in particular.  I like Dr Muller's Berkeley Earth Surface Temperature project...the same needs to be done for proxy data, so everything is out on the table.  Perhaps when we have an open process we can actually determine the truth from the fiction.

I think the attitude of "global warming is a settled issue" is contrary to science, and to the obvious uncertainties that even a cursory look at the actual data shows.


			bb

-- 
Brian Blais
bblais@bryant.edu
http://web.bryant.edu/~bblais
http://brianblais.wordpress.com/