2011-02-21 14:03:08John McLean Miscalculation


Thought you might be interested in another McLean rant that seems to have its basic physics that he claims to know so much about all wrong.


Here he is claiming 1m of seawater has the same heat capacity of 3300m of atmosphere.

A few calculations seem to prove that the heat capacity he claims is out by a factor of 855. But it is a while since I did tertiary physics so I wouldn't mind a cross check.

Values for specific heat capacity Cp

Air: 1.0035 J/(g*K)

fresh Water: 4.1813 J/(g*K)

The density of air at  sea level and at 15°C according to ISA (International Standard Atmosphere), air has a density of approximately 1.22521 kg/m3.

At 3300m it is about 72% of sea level, basically linear reduction with height. So in the first 3300m density is an average 86% of SL or 1053.5 kg/m3.

1m of Seawater; density is 1025kg/m3, specific heat capacity 3993 J /kg/K @20 degrees.

                    water      air

SL  density/m3      1025        1.22521

density factor          1           .86

av/density kg/m3    1025           1.0535  

height                  1       3300

actual kg           1025        3663   

kj/kg/K             3993        1003.5

kj/K for "x"amount 

depth (m)            Kj/K of this mass       Ratio      

   1.225 0.86      3300  1057  1004  1060887     0.259 of water 1025 

       1025  1     1025  3993  4092825     3.857926    of air


            seawater @20C     1025kg/m3                                

In other words the first 3300m of atmosphere has a bit more than a quarter of the heat capacity of 1m of water.

So McLeans conclusions as to relative heat capacities of atmospheric air to water are out by a factor of 3300/3.857926 or 855.

He can’t even claim a decimal point error with any more conviction than the rest of his bodgy unqualified theories.

Alan Flint