[Dean's World] Aziz P: some admissions of error

[notify at powerblogs.com]

Posted by Aziz P:
some admissions of error
http://www.deanesmay.com/posts/1149083240.shtml


   In my recent post on Gore getting smeared (again) for his global
   warming advocacy, I made some statements that were incorrect in the
   comment thread and would like to acknowleddge them (and thank Jody and
   Casey in particular).

   First, I claimed that the output of a star drops off with the fourth
   power of distance. This is, as Casey points out, incorrect - as a
   simple review of basic geometry would suggest, if you define the
   surface area of increasing radius spheres, and postulate that the
   energy over that surface is to remains a constant, then it must be a
   inverse-squared law.

   My error was in confusing from my flawed memory the luminance relation
   with distance, with the luminance relation with temperature. In fact
   the output of a star varies with the fourth power to its blackbody
   temperature:

     l ~ ÏT^4

   where for a perfect black body, Ï = 5.67 Ã 10^-8 W m^-2 K^-4 (the
   so-called Stefan-Boltzmann constant).

   Also, Jody provided a link to information I had not seen before that
   indicates that the [1]power output of the sun is indeed variable. From
   that article:

     "Historical records of solar activity indicate that solar radiation
     has been increasing since the late 19th century. If a trend,
     comparable to the one found in this study, persisted throughout the
     20th century, it would have provided a significant component of the
     global warming the Intergovernmental Panel on Climate Change
     reports to have occurred over the past 100 years," he said.

   It is important to note the very big "If" in the quote above, for the
   purposes of trying to relate solar output to global warming. Again,
   given the absolute neccessity of keeping all these factors in proper
   account, and also making sure predictions fit to past observations,
   there is no substitute for computer modeling, despite what the skeptic
   Mr Gray claims.

   BTW, RealClimate had a piece discussing the [2]warming "trend"
   observed on Mars that I think is fair and rigorous. The RC folks also
   discuss the relevance of solar output in the following posts:

   [3]Did the Sun hit record highs over the last few decades?

   [4]The lure of solar forcing

   [5]A critique on Veizerâs Celestial Climate Driver

   Read them and draw your own conclusions.

   FWIW, Casey also takes me to task for my incredulity at dismissing
   computer models, and asks why models can't take 1950's data and
   predict 1975 weather. The answer however is that climate and weather
   are not the same thing. I respect Casey's fact-checking on luminosity
   above but the sheer idiocy of Gray's skepticism for computer models is
   indeed a credibility-shredding position. On this point, you need to
   learn more about what climate models are for. Predicting weather is
   decidedly NOT the point.

   And finally, I am sorry for the poor state of political wrangling in
   the HIV-AIDS debate, but rejecting the validity of peer review and the
   basic mechanism of how science works in this country as a result is an
   extreme cynic's perspective which I don't share. If HIV-AIDS is one
   anecdote, then my own field (medical physics) is the opposite and
   equal one. So I am still not even remotely sympathetic to cries of
   government bias and funding problems claimed by the skeptics. That's a
   cop-out - when you lose the debate on the facts, cry conspiracy.

   Thanks, guys, for keeping me honest.

References

   1. http://www.nasa.gov/centers/goddard/news/topstory/2003/0313irradiance.html
   2. http://www.realclimate.org/index.php/archives/2005/10/global-warming-on-mars/
   3. http://www.realclimate.org/index.php?p=180
   4. http://www.realclimate.org/index.php?p=171
   5. http://www.realclimate.org/index.php?p=153