Population vs Ice Cap, H20 Content

By etrigan - Last updated: Tuesday, September 1, 2009 - Save & Share - Leave a Comment

Occasionally, to give myself some science/math challenge (beyond the “last page of Make magazine”:http://makezine.com/aha/), I like to attack a multidisciplinary problem that is (a) completely inappropriate for a man of my education, and (b) has probably already been done by someone with the appropriate education.

A recent “Believe it or not” cartoon led me to data that: of the fresh water in the world only 0.3 percent is surface water which I verified(?) at Wikipedia.com along with the fact that “two-thirds of [fresh water] is frozen in glaciers”:http://en.wikipedia.org/wiki/Freshwater, I started to wonder about how much water the human race contains and where, in relation, that water is (or is going to come from). I wonder about the noise made that the polar ice caps are melting, and I wonder how the volumes and ratios of population growth and polar ice cap melting align, since the water in a living body is stably “trapped” in itself and therefore removed from the global cycle of water circulation.

The pertinent data I _can_ come up with is that the “human body is about 60% water in adult males and 55% in adult females”:http://en.wikipedia.org/wiki/Body_water, that the “sex ratio is commonly assumed to be 105 boys to 100 girls”:http://en.wikipedia.org/wiki/Sex_ratio but “the current world wide sex ratio at birth is 107 boys to 100 girls”:http://en.wikipedia.org/wiki/Sex_ratio. Also, I found data on “world population history”:http://en.wikipedia.org/wiki/World_population#Population_figures that I can use to calculate the amount of H2O mass “trapped” in humans. To get conservative figures, I assumed that the average human mass is 60 kg and applied the 100/105 ratio.

                 1800    1850    1900    1950     1999    2050      2150

World Pop.         978   1,262   1,650   2,521    5,978   8,909     9,746
F. Water        15,743  20,315  26,561  40,582   96,231  143,413  156,887 
M. Water        18,033  23,270  30,424  46,485  110,228  164,273  179,707 
Total H2O       33,777  43,585  56,985  87,067  206,460  307,686  336,594 
Delta H2O                  29%     31%     53%      137%     49%       9%

(population in “millions”; mass in Mg)

So I can show the amount of water in humans is currently over 307 metric tons, and the change in that amount over the last 5 decades is an increase of 50%.

I’ve found charts about the _rate_ change in the polar ice caps, but I can’t find anything with actual numbers. Anyone know what that is? or does anyone have arguments about my approach?

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