Bruce, Sawzaw

I was intrigued by the idea that the direct heat from all our power stations will eventually warm the atmosphere even without worrying about C02. As a chemistry/physics guy I like these little puzzles!

So I dug out a few numbers to see.

The total power output of all the world's power stations is 4000GW. (1GW is a billion watts, or 1 billion joules per second)

So if all that power was converted to heat and it all went into the atmosphere, then in a year the heat output would be

1 billion X 365 X 24 X 3600 or 1.26 E^20 joules (thats 1.26 followed by 18 zero's!)

But the energy needed to raise 1g of air by 1 degree C is 1.012 Joules, and there are about 5.36 E^15 tonnes of air in the atmosphere. So the heat needed to raise the whole atmosphere by 1 degree (its heat capacity) is about 5.42 E^21 Joules (1.012 X 1 million to get from grams to tonnes, and multiply by the weight in tonnes).

So I reckon the heat from all the world's power stations in a year would raise the temperature of the atmosphere by at most 0.023 degrees - thats at least 10 times less than the predicted carbon dioxide related warming. You can double it by 2030 if you can believe the various projections for the increased energy demands by then. And in practice the warming would be less than my quick calculation as much of the residual heat from power stations goes into the sea not the air, and the sea has a much higher heat capacity than the atmosphere.

Sawzaw, your comment at 6.24pm above that you are in favour of 'solar, wing, hydro, nuclear energy, anything that does not pollute' I think is still valid. I think I agree with Bruce about the need for sensible adaptive measures as well - there are quite sensible people who buy/build houses on flood-plains and then complain when they get wet every winter!

hope this is clear and not too 'lecturing' :)

KP