domenica 26 giugno 2011

Strawmen's raising @AGW

La recente risposta di Mike Mann agli attacchi perpetrati a suo tempo da Richard Muller nell'ambito di un'intervista pubblicata un mese fa su Scientific American, è lo spunto per un veloce stream di pensiero dedicato ad una ampiamente non esaustiva raccolta di fallacie da "uomo di paglia" nell'ambito della deriva e dell'associato travisamento dello scetticismo più profondo (quello dei Neinsager ambientali per default) da parte della piccola minoranza attiva in questo ambito (aka "denialism d'ufficio" e terrapiattismo ante litteram) sul tema del GW.

Il post vuole essere poco argomentato e approfondito e con alcuni semplici rimandi sottoforma di keywords: a parlare il quoting e - per approfondire alla fine - la relativa link di rimando a fine post. Per rendere più fluide le citazioni, ho deciso di togliere i riferimenti bibliografici.
In realtà chi segue MS (e la galassia della blogosfera, ma anche la letteratura ufficiale) sa già benissimo di cosa sto parlando e le argomentazioni di supporto abbondano.


#Basics, incertezze, presunti benefici del GW, media e par condicio
The greenhouse theory has been studied carefully, and it has been successfully tested by observations of the Earth's radiation and also the climate of our sister planets, Mars and Venus. Furthermore, we know from observations that the concentration of these greenhouse gases has been steadily rising in this century. There can be no questioning that fact. So why is there a controversy over the idea that there is a possibly a global warming already taking place, and that it should accelerate in the decades ahead if mankind continues on its present course? First, there is good justification for the view that there are just too many interacting factors involved in the extraordinarily complex system that determines our climate, and that we can never hope to understand all those interactions. (...) no action should be taken until the scientists come to better agreement. (...) A second motivation for resisting the temptation to take such action is the notion, being advanced in some quarters with considerable vehemence, that a global warming will be beneficial to the world as a whole, and we should do nothing to slow it down. (...) In the past year or two the media have reported the statements of a small cadre of scientists who disagree with the conclusions of the majority of those who are doing research on the climate system.
#Sensitività climatica, modelli e incertezze
We have already pointed out that the climate system modelers (...) express reservations about their ability to simulate reality on their computers. In doing so they are simply behaving as responsible scientists, who know that hardly any theory can be said to be absolutely correct. Yet the five or so most advanced climate models, developed over a period of many years by top notch teams, have all come to essentially the same conclusion: The global average surface temperature would probably rise by about 2 to 5 K if the greenhouse gas concentration were maintained at double the pre-Industrial Revolution level, which for carbon dioxide was 270 to 280 parts per million (ppmv). (...) Since the greenhouse gas will increase gradually up to that point, there will be a lag of several decades, due in large part to the large heat capacity of the oceans of the world.
(...) some still express doubts that there has already been a long-term warming due to the greenhouse effect (...). It is not significant, they sometimes say. (...) But the probability of the signal being real (not just a product of random noise) is greater than 98%. (...)  So some of the more cautious policy makers who are listening to our debate can, at least for the time being, cite the IPCC report and argue that they have another ten years or so to wait before remedial action will be justified by “unequivocal” evidence.
#Effetto UHI
However, even if this bias exists at urban climate observing stations on land in other parts of the world, it can hardly have an influence on the COADS marine temperature record. Thus, the combined global surface temperature record, shown in Fig. 1, must be accurate enough to demonstrate a real warming trend, and the urban heat island effect on the land stations is considered to have less than a 0.05 K effect on the average.
#GW finito, global cooling?
The point is simply that one cannot demonstrate a 100-year trend by looking at a 10-year segment of the record, particularly when there is so much natural fluctuation in the record.
#Rilevamenti satellitari e validità per i trend
The oxygen emission measured by the satellite instrument actually comes from a region of the atmosphere extending from near the ground up to the tropopause, and it may sometimes include part of the lower stratosphere. (…) Thus, the temperature of a very deep portion of the atmosphere is being sampled, and the upper part of this layer is expected theoretically to show a cooling trend rather than warming. This fact suggests that such microwave observations may not be suitable for monitoring the year-to-year progression of the greenhouse effect, during which the warming should occur mainly in the lower part of the troposphere.
#Is it the sun, stupid?
However, no long-term trend is evidenced unless the progressively important greenhouse effect is also introduced as a third-forcing function. (...) Finally, satellite observations have revealed that the magnitude of total solar radiation changes on time scales of a solar cycle or longer is too small to have a measurable effect on the global temperature.
#Feedbacks negativi ed effetto Gaia
It thus appears that the critics of currently accepted assessments of climate change are going to have to continue their search for some powerful and credible (but hitherto overlooked) negative feedback mechanism that will greatly reduce the apparent sensitivity of the earth’s climate system to an increase of the greenhouse gases.
#Il problema delle nuvole
Over the past 30 years the tropics have gotten warmer, especially over the oceans, and in this period high clouds in the tropics (Ci and Cb) have increased, while lower and middle clouds (Cu and St) have decreased. Both of these trends in cloudiness contribute to a positive feedback, or warming. 

Vi suona come un dejà-entendu familiare di recente origine? È forse una sorta di variante del noto blog di John Cook?

In realtà, tutto quel che ho quotato deriva da un seminale paper pubblicato esattamente 20 anni fa sul BAMS e scritto da quel "dissidente eretico" che risponde al nome di William Kellog.
Nessuna parentela con i famosi cornflakes:  classe 1917, morto a Boulder il 12 dicembre di 4 anni fa a 90 anni, fu invece uno dei più grandi pionieri della scienza del clima del secondo dopoguerra, insieme ad una manciata di altri grandi (potremmo qui velocemente ricordare Jacob Bjerknes, Richard Goody, Harry Van Loon, Suki Manabe, Jo' Smagorinsky, Ed Lorenz, Roger Revelle, Hans Suess, John Mike Wallace, Wally Broecker, Hans Oeschger, Paul Crutzen, Veerabhadran Ramanathan, Stephen Schneider, Hermann Flohn, Klaus Hasselmann, ovviamente Jim Hansen... ma farei torto a molti altri non menzionandoli: ci tornerò con un post dedicato).

Consiglio una lettura accurata di questo lavoro. Da notare anche una cosa: Kellog cita uno dei primi tentativi di discredito del mainstream scientifico sull'AGW da parte del GMI mediante un testo pubblicato nel 1989 e scritto da personaggi ben noti la cui strategia ideologica è stata più volte spiegata ad es. da Naomi Oreskes (vedi ad es. quiqui).

2 commenti:

  1. E così dopo vent'anni ci ritroviamo ancora a confutare la solita disinformazione... E tra altri venti? Non oso pensarci...

  2. Già. Magari fra 20 non ce ne sarà più neanche bisogno. Ma forse vedo il bicchiere mezzo...