Re: [Phys-l] global temperatures

[Brian Whatcott <betwys1@sbcglobal.net>]

It's interesting to estimate the thermal time constant of the Earth. 
This would be
an important underlying trend line effect resulting from any significant 
change of solar heating.
As I recall, Kelvin did such an estimate, neglecting the effect of 
nuclear internal heating.
His estimate for the Earth's age amounted to a small number of million 
years, for it to cool to the present ambient.
I imagine that would place the terrestrial TTC at perhaps  200 kyr about....
I ask myself: if the Earth acted like a homogeneous body with a thermal 
time constant of 200 kyr,   and there was a step increase of say 5% in 
solar heating: then after ten years, what would be the expected increase 
in mean World temperature from say 4K through 288K?   Maybe (288K- 4K) * 
5% * 10/200000 = 0.7 milliK

We seem to be dealing with some change of rather larger magnitude. Then 
again, the
lowest 30,000 ft of atmosphere, and highest 1000 feet of Earth -  ground 
and sea are far from a uniform passive material.

Brian W



marx@phy.ilstu.edu wrote:
> Rick and others,
>
> There has been a flattening and perhaps a slight decline in global temperatures, depending on the 
> dataset you look at.  One could draw the conclusion that there is not a direct connection between 
> increased CO2 and global temperatures or that there are more parameters that need to be considered.  
> The modelers claim that the influence of the Sun is minimal.  However, it is curious that the flattening 
> and slight decrease are coming at a time when solar activity is at a century minimum.  
>
> In the late 90s and first few years of this decade, solar activity was at a long term high...
> http://news.bbc.co.uk/2/hi/science/nature/3869753.stm
>
> Check out the report from NASA this week...
> http://science.nasa.gov/headlines/y2009/01apr_deepsolarminimum.htm
>
>
>
> On 16 Mar 2009 at 14:43, Rick Tarara wrote:
>
>   
> > I noticed nobody has answered Bob's question about global temps over the 
> > last ten years.  I'm sure he knows, but I actually didn't.  So I Googled 
> > 'Global Temperature by year'.  I would suggest two quick looks....
> >
> > www.boston.com/bostonglobe/editorial_opinion/oped/articles/2008/01/06/br_r_r_where_did_global_warming_go/
> >
> > This one gives a typical newspaper (and GW skeptic) account, but
> >
> > http://www.cru.uea.ac.uk/cru/info/warming/
> >
> > is not from a skeptic and has an informative graph.
> >
> > The bottom line is that the temp hasn't really changed in the past 10 
> > years--it has been high, but that is the predominant trend that has been 
> > clear for some time now.  If anything the trend looks to be turning some 
> > (but too little data to be sure).  Now this flattening is during a time of a 
> > 4% CO-2 increase, but what is interesting to me is that the rate of increase 
> > from 1975 to 2000 is about the same as it was between 1915 and 1940, when 
> > the CO-2 concentrations weren't nearly what they were at the end of the 20th 
> > Century.
> >
> > These are, IMO, the types of data that should trigger some caution, at least 
> > some healthy skepticism concerning the model predictions.  Again, this is 
> > just SO complicated.  Is the leveling because of increased aerosols and 
> > Global dimming -- or is the global air quality better than earlier which 
> > makes a ten year leveling more mysterious?  What about the other natural 
> > drivers--the sun for example.  What's it been doing during this ten year 
> > period--has it cooled off enough to compensate for the greenhouse increases 
> > or is it pumping in more energy such that we would have expected continuing 
> > record setting temps (1998 is still the hottest--according to the graph and 
> > the Boston Globe story).  I would point to the last paragraph of the Globe 
> > story!  ;-)
> >
> > Rick
> >
> > ***************************
> > Richard W. Tarara