In article <43CEB68B.B6581F95@eagle.ca>,
G. R. L. Cowan wrote:
> "H. E. Taylor" included:
>>
>> The solar constant as measured by satellite is ~1365 watts/m^2.
>>
>>
>> At the bottom of the atmosphere this is attenuated to ~350 watts/m^2.
>
> Earth's surface area is four * pi * r_equatorial * r_polar.
> Its projected area as seen from the sun is pi * r_equatorial * r_polar ,
> exactly a quarter as much, and that, not atmospheric attenuation,
> is I think the source of the 350 W/m^2.
>
> Attenuation brings surface insolation annual averages lower than that:
> according to my CRC, p. F-202, to 290 W/m^2 at 30°N, 240 W/m^2 at 45°N.
> This does not include the effects of clouds.
>
>> 8) Humans use approximately 12*10^12 watts of energy per year.
>
> Just watts, not watts per year.
>
Okay. Thanks for the corrections. I am in muddle through mode.
However the question of NPP compared to human energy usage remains.
On another page van der Pluijm states that about 0.023% of the sun's energy
is captured by photosynthesis. Which would mean:
0.023/100 * (1.7*10^17) watts ==> 39.1 * 10^12 watts.
Which compares well with Hubbert's value of 40*10^12 watts.
The van der Pluijm page is at:
This number breaks down to respiration and net primary production.
If we take the Kling's values for GPP & NPP, we can calculate NPP.
GPP = 5.83 x 10^6 cal m-2 yr-1
NPP = 4.95 x 10^6 cal m-2 yr- 1
NPP/GPP = 4.95/5.83 = 0.849
NPP = 0.849 * 40*10^12 ==> 33.96 * 10^12 watts
Some part of this NPP will be in the oceans and basically inaccessible.
Again using Kling's figures [Table 1], we can calculate the
power required for terrestrial NPP at:
(132.1/224.5) * (33.96*10^12) watts ==> 19.96 * 10^12 watts.
[The Kling page was earlier URL'ed.]
Do you see a problem with these calculations?
-het
PS
Roger, the screwy thing about the units in this inquiry is
that NPP [GPP & R] are given in units of kcal/m^2/yr
or petagrams, which is a reflection that it is a conversion
from sunlight to plant material.
--
"Education is an admirable thing. But it is well to remember from
time to time that nothing that is worth knowing can be taught."
-Oscar Wilde
Name your Poison: http://www.autobahn.mb.ca/~het/catastrophes.html
H.E. Taylor http://www.autobahn.mb.ca/~het/
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