Let diSg/dt = SR be the annual internal production of entropy by the global biota, and deSjB/dt = SjB, j = S,P,H,A be the flows of entropy from jth subsystem into biota, then the rate of its entropy change is dVd/ = (¿SB + SpB + ¿H
Here we make a very important assumption: although we do not know what the specific entropy of living matter is, we can still speak about the change of entropy. For instance, the value of (— TB-AS) can be interpreted as an ability of a living system to perform the work, which in turn can be measured. This ability is named 'exergy'.
For the Earth's surface, using the data given above, deCTG/dt0.586 W K—1 m—2. Since the area of globe is 5.1 x 1014m2, deSG/dt« (—0.586 WK—1m—2)(5.1 x 1014) (3.15 x 107) =—9.41 x 1021J K—1 yr—1.
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