As readers will know, I have been thinking about the hullabaloo about CO2 and global warming and I quickly concluded that CO2 is no threat, won't do any significant warming (which would be good anyway), and is in fact 100% good for the planet. But someone said to me, if CO2 is no danger, that doesn't mean that humans are not causing a danger in some other way. Of course I agreed with this, because there are lots of things humans are doing wrongly and thereby causing terrible damage to our world (and the CO2 storm in a teacup is distracting us all from fixing those real problems).
My friend then went on, however, to propose that the danger was still global warming and that the mechanism was, instead of CO2 greenhouse warming, the mere fact that human technology gives off heat. All the power used by all the machines and transport and so on eventually ends up as waste heat. Maybe that is in itself enough to cause us serious warming trouble? So I did some calculations.
According to the laws of thermodynamics, the process of doing useful work must necessarily lose some of the energy from the fuel in the form of waste heat; and that heat, well, heats. In other words, because of the huge extra amount of useful work we do, we create excess heat that would not have been here otherwise, and that heat has to either be dissipated somehow, or else raise the temperature.
The factors that have caused the ice ages, as we saw, are primarily small changes in insolation (heating) by the Sun. The changes can happen because the Sun’s energy output changes or because of cyclic changes in the Earth’s orbit and inclination, etc., changing the amount of heat that actually arrives on the surface. Changes in the Earth’s orbit are believed to be the triggers for the onset of ice ages, and the changes in heating caused by those changes are thought to be quite small compared to the total power output of the Sun. This might lead us to suspect that human-caused changes in the amount of heat at the surface might indeed have a significant effect on the climate.
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