Radiative equilibrium is one of the foundation stones of radiative forcing theory. But it is not a law of physics, only a rather archaic and untested supposition found in climatology textbooks alone.Yes, really. If the Earth were to cool without radiating energy to some other part of the universe, or to warm without receiving additional energy from elsewhere, that would break a very basic law of physics: the law of Conservation of energy.
"For the Earth to neither warm or cool, the incoming radiation must balance the outgoing."
It’s best to regard radiant energy simply as a finite power source — indeed, that power is expressed as watts per square meter. An object is said to "cool" by radiating, yet this would seem to imply that restricting its radiation will make it get hotter and hotter. That’s the very premise of greenhouse theory, of course, that by disturbing outgoing radiance any magnitude of temperature gain is possible. But this is easy to test.This is complete codswallop, written by someone whose technical vocabulary exceeds his technical understanding. Stripped of the technobabble and trivia, the question posed, and then answered incorrectly, is "What happens if you put a light bulb in an enclosed environment and turn on the electricity?"
Confine a lightbulb inside an infrared barrier (like a globular mirror) and electrically feed one watt to it. After a while, will it be generating the heat of a thousand watt bulb? No.
When its temperature is consistent with the input, further heating stops.
The correct answer to that question is that the light bulb will radiate light and heat, any air in the environment will be heated by the bulb, then whatever enclosure you've put the light bulb in will start to heat up. At that point the whole system - light bulb, air and enclosure - starts to lose heat to the outside environment and reach a thermal equilibrium where the energy it loses is equal to the energy being put in. Turn off the electricity and it will cool down again.
It’s like water seeking its own level. Lacking any means to radiate to its surroundings the lightbulb ...The whole purpose of a light bulb is to radiate energy to its surroundings. That's what makes them useful. All that putting a lightbulb inside a reflective enclosure achieves is to make the surroundings smaller.
... merely gets as hot as a watt of power can make it, which is not much hotter than what it would be in the open. If not, we’d be able to generate incredible temperatures very cheaply. Just confine, wait, and release.See above.
Conservation of energy: it’s not just a phrase...Indeed not - it's a law of physics which Alan Siddons has misunderstood, at best.
The theory of radiative equilibrium arose early in the 19th century, before the laws of thermodynamics were understood.The truth of a scientific theory isn't determined by how old it is, bnut by how well it fits the observed facts. And it appears that the laws of thermodynamics aren't universally understood, even today.
From The Analytical Theory of Heat:Fourier got that exactly right - later developments in thermodynamics haven't changed that one iota.
The radiation of the sun in which the planet is incessantly plunged, penetrates the air, the earth, and the waters; its elements are divided, change direction in every way, and, penetrating the mass of the globe, would raise its temperature more and more, if the heat acquired were not exactly balanced by that which escapes in rays from all points of the surface and expands through the sky. — Joseph Fourier (1768-1830)
Update: more at Deltoid and Atmoz.