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Akria · 04-01-2007, 06:09 PM

Quote:

Originally Posted by Besoeker

Quote:

Originally Posted by Akria

Has anyone else seen that advert for some TV programme or other stating that a rise of two degrees Celsius would cause mass extinction in the oceans? That may or may not be true - I'm not an expert on the matter - but they strategically neglected to mention one thing: the energy required to do it.
I'm an amateur physicist, so I spotted it

.
1. One litre of water, I believe, takes 4,200 joules to have a rise in temperature of one degree Celsius.
2. 1,408,700,000 cubic kilometres is about 1.4087 × 10^21 litres, or 14,087,000,000,000,000,000,000,000
3. Now, we know that 4.2 kilojoules are needed to raise one litre of water by one degrees Celsius. Therefore, the total energy required to heat the entire volume of water on the Earth is equal to 1,408,700,000,000,000,000,000 times 4.2 kJ.
This will give us the amount of energy needed in kilojoules.
So let's do it: 1,408,700,000,000,000,000,000 times 4.2: 5,916,540,000,000,000,000,000 kilojoules.
Almost six thousand million billion kilojoules. Times that by a thousand to get the answer in joules.
And that's to raise the temperature of all the world's water by one degrees Celsius. Double the answer to raise it by two.
Bottom line: it's not gonna happen soon. The energy needed is too great.

Akria

Over what time period?

Hmmmm?
What do you mean exactly?
Let us suppose that each litre of water in the world absorbs about half a kilojoule of energy per day, a very large estimate.
That would take 8.4 days.
Now, as I said, this is a very large estimate. Extremely large, in fact.
I would hazard a guess that it would be a tiny fraction of a joule per day, mainly because we have to consider the idea that any energy absorbed by the water will not only be lost through the normal methods (conduction and radiation to surroundings and convection currents to the colder air) but will also be expended through the things the water does and through both the breaking of waves against the coast and water currents.
Then you must consider that the weather varies, especially out at sea: on colder, cloudier days, as they so often seem to be at sea, particularly in the Atlantic, less energy from the Sun will be absorbed.
I believe that global warming is a real phenomenon being hastened by the actions of humanity, and I agree that it is a real problem that we need to do something about. However, I disagree with the idea that the oceans are going to be warmed by two degrees Celsius before marine life capable of surviving the change evolves.

Akria