How much would 200 ZJ warm the top 700 meters of the oceans?
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Re: https://sealevel.info/how_fast_are_the_oceans_warming_sciencemag_2019-01-11_perspective_measured_excerpt01.png
and: https://twitter.com/LHaden_Climate/status/1523294438906220545
That graph shows estimated ocean heat content of the upper 700 meters
of ocean gaining about 200 ZJ (zetajoules) in about 35 years.
What do you think 200 ZJ (zetajoules) of warming means in terms
that normal people can comprehend, like average ocean temperature?
Total volume of water in the oceans:
1,338,000,000 cubic-km = 1.338 × 10^9 km³ = 1.338E9 km³
Volume of water in the upper 700 meters of the oceans:
360,000,000 km² × 0.7 km = 2.52 × 10^8 km³ = 2.52E8 km³
The density of seawater is about 1027 kg/m^3 and the specific heat is about 3850 J/(kg C).
So 2.52E8 km³ of seawater weighs:
(1.027 × 2.52) × 10^8 Gt = 2.588E8 Gt
1 Gt = 10^12 kg = 1E12 kg, so the top 700m of the world's seawater masses:
2.588 × 1E8 Gt × (1E12 kg/Gt) = 2.588E20 kg
So, let's calculate how much energy it would take to heat that
amount of water by 1°C.
You probably know that one calorie of energy will raise one gram
of fresh water by one degree Celsius. So 1000 cal will raise 1 kg
of water by 1°C. 1 cal = 4.184 J, so 4.184 × 10^3 J = 4.184E3 J
will raise 1 kg of water by 1°C.
Seawater has a slightly lower specific heat of 3.850E3 J / (kg °C).
So it would take 2.588E20 kg × 3.850E3 J/kg = 9.964E23 Joules
to raise the temperature of the top 700m of seawater by an
average of 1°C.
1 ZJ = 10^21 = 1E21 joules, so 200 ZJ = 2.0E23 joules
So 200 ZJ of energy should raise the top 700m average
temperature by (2.0E23 / 9.964E23) = 0.2007 °C, or about
1/5-th of a degree.
That's right, one-fifth of a degree, in 35 years.
Is that supposed to be frightening?