Eli has always been impressed by Myanna Lahsen's take on physicists
they think they know everything, because they’re smart. What they don’t understand is that yes, it is true, actually meteorology is a branch of physics. And so you take a physicist, like me, and you can sit him down, and in 2 or 3 years, they could learn meteorology. But physicists confuse being smart and having the ability to learn everything with actually knowing stuff!and by way Watts, excerpted by Tallbloke, via a comment at Open Mind, comes another example, one Robert Brown, PhD, at Duke who offers up a BOE to showcase another argument from personal incredulity.
As some noble prize winners, he gets the wrong answer for the right reason. We have all gone through the trivial exercise of balancing the solar input against radiative loss from an Earth without an atmosphere, which shows that without greenhouse gases the temperature of the Earth would be a uniform 255 K, about 33 K colder than it is on average. Brown asks what would happen if the surface temperature was not uniform, without realizing that Arthur Smith provided the answer, it would be a lot colder. If you account for day/night differences, the change of temperature with latitude and such, 33K is a lower limit for the greenhouse effect if you insist on radiative balance. To cut a long story there short, assumption of a uniform surface temperature UNDERESTIMATES the effect of greenhouse gases on surface temperature. To return to the first paragraph, DECREASING the temperature at which the Earth's atmosphere radiates to space by increasing greenhouse gases, requires that the surface temperature INCREASE in order to restore radiative balance. Brown clearly was not on the distribution list.
The point is that as temperatures increase, the rate at which the Earth loses heat goes strictly up, all things being equal. Hot bodies lose heat (to radiation) much faster than cold bodies due to Stefan-Boltzmann’s T^4 straight up; then anything that increases the inhomogeneity of the temperature distribution around the (increased) mean tends to increase it further still. Note well that the former scales like:
P' being the radiated power.
P’/P = 1 + 4 dT/T + …straight up! (This assumes T’ = T + dT, with dT << T the warming.)
At the high end of the IPCC doom scale, a temperature increase of 5.6C is 5.6/280 \approx 0.02. That increases the rate of Stefan-Boltzmann radiative power loss by a factor of 0.08 or nearly 10%. I would argue that this is absurd — there is basically no way in hell doubling CO_2 (to a concentration that is still < 0.1%) is going to alter the radiative energy balance of the Earth by 10%.Well, Eli leaves it to the reader to decide whether a 6 K temperature change is reasonable for CO2, greenhouse forcing doubling, without getting into the issue of why Brown chooses 6K rather than the generally agreed on 2-3 K (so that is only a 2- 3% change), please don't spit the cherry pits out on the linoleum or the window, this is a high class blog, but even without going much further, how unreasonable is that 2-3 K change if the greenhouse effect accounts for more than 33 K of surface warming, which it does. Still dear bunnies, there is more.
The statement that "The point is that as temperatures increase, the rate at which the Earth loses heat goes strictly up, all things being equal." is where the good Doctor Brown goes serious GIGO. It is correct that the rate at which the Earth's SURFACE loses heat goes strictly up, but the surface is NOT where most of the thermal IR is emitted to space.
That is rather high up in the atmosphere, which can be seen by comparing the emission to space with the Planck distribution of thermal emission from the surface for example, but there are plenty of accurate measurements and models.
The point at which the emission curve matches a blackbody curve tells you the temperature of the effective altitude at which emission is occurring to space. Raising the greenhouse gas concentration raises the level at which the emission to space occurs to a colder level, and thus one where emission is slower. To make up for that the surface has to warm in order to push more energy through the open window directly into space.
Pass the mole hammer please.