Saturday, 23 April 2022

Out of the frying pan... into the Greenhouse Effect

As is well known, if the sun is shining brightly enough, you can leave a frying pan in the sun and then fry an egg on it. This works because aluminium (and many other metals) have low emissivity.

And as we also know, if an object is absorbing solar radiation, it will warm up until it is emitting the same amount of radiation energy (ignoring other forms of heat transfer, like conduction etc).

If an object (the frying pan) has low emissivity, then for a given temperature, it is emitting less radiation than another object at the same temperature with higher or 100% emissivity (a 'blackbody'). But the amount of radiation absorbed, and hence emitted, is fixed, so the frying pan reaches a higher temperature (than the ground around it) before it reaches a steady-state temperature where solar radiation absorbed = radiation emitted.

So on a hot sunny day, ground-level air temp might be 'only' 30 degrees C, but the frying pan is more than 100 degrees C, hot enough to fry an egg. Key thing to note is that ground and pan are emitting a similar amount of radiation. Which is why you have to calibrate an IR thermometer to take the emissivity of the object into account - if you don't, it will tell you that the ground and the pan are a similar temperature.

[OK, I have glossed over the fact that pans are shiny and therefore reflect more, and absorb less, radiation, which would make them cooler than their surroundings, all things being equal. But all things are not equal and the lower emissivity outweighs the albedo effect.]

I doubt any Physics Denier looks at the hot frying pan and concludes that, because the frying pan's actual temperature is greater than the hypothetical temperature it would be if it were a 'blackbody' with 100% emissivity, this must be an example of the Greenhouse Effect.
-------------------------------
But this is the best (and basically only) evidence they have that there is a 33 degree Greenhouse Effect in the first place - they just compare actual temperature of oceans and land with hypothetical surface temperature of a planet with a uniform surface, all at the same temperature and with 100% emissivity. This is like saying that clouds, oceans and land are a) all at the same temperature and b) have 100% emissivity. Neither a) nor b) is correct, it would be fairer to say a) and b) are deliberately misleading assumptions. (Cooler clouds are missing from the first part of the comparison, this is a key part of the deceit).

There's a handy overview of cloud properties here. Note that typical or average cloud emissivity is given as 0.7. If you pick sensible estimates for typical or average cloud-top altitude, then you know how much warmer it is at sea level than at the cloud-tops (this relationship is fixed by the gravito-thermal effect), then you can work out total radiation emitted to space by clouds and cloud-free oceans/land respectively (oceans/land beneath clouds can't emit radiation directly to space, the clouds absorb, reflect and re-emit it). Take a weighted average and hey presto, the overall radiation being emitted spacewards is the same as incoming solar.

Therefore, no radiation is being blocked or absorbed by 'Greenhouse Gases'; there is no 'Greenhouse Effect' (unless you see clouds as acting like the roof of a greenhouse, which I suppose they do) and there is nothing left to explain away.

When I did the workings, I calculated that clouds emit about 47% of the total radiation reaching space, the 'official' estimate of "cloud amount weighted by the cloud IR emissivity" is 50%, so I'm not far off and I suspect the 50% is rounded.

And of course, clouds are nebulous. Nobody will ever know what the exact thickness; altitude; temperature; emissivity; or radiation being emitted by any particular cloud or cloud-top at any particular moment are. How many measurements would you have to make to have a fair picture of the global average over a year? Dunno, even though it wouldn't be that difficult with enough weather balloons and satellites.

But it's easy enough choosing reasonable mid-points of ranges of estimates to get sensible answers, and until these time wasters dedicate a bit of time and effort on doing actual observations of all these variables (and proving me wildly wrong), I will assume that they simply don't want to know (and they can't).

32 comments:

A K Haart said...

I do like the frying pan illustration. A huge number of people must notice a similar effect on their car bodywork or a patio which can become too hot to walk on in bare feet.

Mark Wadsworth said...

AKH, or cars, they're made of metal. Or our metal sink under a South facing window, which gets much hotter than the counter top. A patio gets hot, but nowhere hot enough to fry an egg.

johnd2008 said...

My white car has a black, carbon fibre roof. When I bought it I worried that it would get the car too hot, but in fact the car is cooler than my previous car which was red. Speaking of the greenhouse effect, my house has a Sunroom on the west side and can reach temperatures of over 40 degrees on sunny days. It is also useful in warming the living room even on overcast days in the winter.

Bayard said...

"A patio gets hot, but nowhere hot enough to fry an egg."

A slate roof can get hot enough to take the skin off your hand, so I suspect a slate patio, or any other black stone, would get similarly hot.

Mark Wadsworth said...

JB, my cars with black vinyl soft tops get insanely hot in the sun (when the roof's up), so hot that the stereo stops working in one of them and the seats are unbearable. But not egg frying hot.

I think your patio is just the actual greenhouse effect, i.e. air can't cool by convection.

B, slates too, but hot enough to fry an egg on? Apparently slate has emissivity 70% to 80%, so the extra temp is probably largely due to low albedo (nearly black) and partly due to < 100% emissivity.

Bayard said...

M, Dunno, but it's sunny today, so I will put out a piece of slate in the sun and see how hot it gets.

Mark Wadsworth said...

B, put out lots of different things and see which gets hottest.

Bayard said...

I was prompted to look up "Emissivity" in Wikipedia, where there was a link to this paper https://www.acs.org/content/acs/en/climatescience/atmosphericwarming/climatsensitivity.html which, as far as I can see, shows that if you assume that greenhouse gases cause the greenhouse effect you can prove that the greenhouse effect is casued by greenhouse gases.

Mark Wadsworth said...

B, yup, they are playing the usual game when calculating the 255 and then making up numbers.

Mark Wadsworth said...

B, I can tell you where the lies are:

Lie #1 "In the absence of greenhouse gases in the atmosphere, ε would be unity"

Emissivity of oceans/land is quite high, 96%, but not 100% (unity).
Emissivity of clouds (two-thirds of surface as seen from space) is average 70%.

Lie 2 "for Tp ≈ 288 Κ"

(Where Tp = temperature of surface)

The 'surface', as far as absorbing radiation from or emitting radiation to space is concerned, is two-thirds clouds, avg temp 255K (coincidentally) and one-third oceans-land, avg temp 288K.

So basically,

i) clouds exist when scaling down the 342W/m2 incoming solar to 239 W/m2 incoming solar - the higher albedo of clouds increases avg albedo from 0.1 to 0.3, so knock 30% off the 342. Clouds are considered part of the absorbing surface, but

ii) clouds do no exist when looking at outgoing radiation, they only look at the radiation from the warmer sea level surface. Of course some of it is missing if you measure it from space! It is reflected, absorbed, re-emitted downwards by the clouds.

They kick off with two Big Fat Lies, therefore any conclusions are not worth the paper they are written on.

Mark Wadsworth said...

B, it has taken me two years more or less to the day to actually unpick every last Warmenist lie.

I've had lots of false starts and been sent off in the wrong direction too many times because I took their crap for granted, once you understand one layer of crap, it takes you a while to realise that the conclusions are wrong... you can then attack the layer of crap beneath that, but I think that this is now the end of the line, the base layer, the fount of all misinformation.

Those are the two Big Fat Lies (previous comment) that underpin it all, if you understand these basics, you know that the rest is a pyramid of piffle.

Bayard said...

This might amuse you, from the Wikipedia article on albedo:

"Black carbon[edit]
Another albedo-related effect on the climate is from black carbon particles. The size of this effect is difficult to quantify: the Intergovernmental Panel on Climate Change estimates that the global mean radiative forcing for black carbon aerosols from fossil fuels is +0.2 W m−2, with a range +0.1 to +0.4 W m−2.[40] Black carbon is a bigger cause of the melting of the polar ice cap in the Arctic than carbon dioxide due to its effect on the albedo.[41][failed verification]"

Mark Wadsworth said...

B, Dirty snow melts quicker. Fine. That is a different effect, seems plausible and is widely accepted as true.

This has bugger all to do with completely made up 33 degree greenhouse effect. And "radiative forcing" does not exist, it is a made up concept.

ontheotherhand said...

Their advantage is the simplicity of the phrase 'greenhouse effect'. Joe public didn't need to understand convection, radiation, emissivity. They just imagine, "Oh, it heats up like a greenhouse"

This stuff is not intuitive. e.g. a white t-shirt will keep you cooler in the sun, but a black outfit enables your body to radiate more at night.

What name can we give the lapse rate and the gravito-thermal effect? I suggest "the bike pump effect"

Lola said...

OK. We all agree that the alarmists are lying, but why are they lying? And why do others like governments compound in the lies?

Mark Wadsworth said...

OTOH, once you have delved as far down as I have, the gravito-thermal effect is a side show.

The point is the 288K is not a relevant comparison and the 255K is deliberately and maliciously understated. The 33 is a made up number and meaningless. I could subtract your height in feet from your shoe size and say that this is the likely number of O levels you have.

Clouds are higher up and cooler. if asked, refer to the 'lapse rate' (the existence of which nobody disputes) and for the few hard core Physics Deniers, explain the GT effect and point out that it exists in all atmospheres etc.

L, why? Emperor's New Clothes. Pol's are too lazy to spend two years looking into it as extensively as I have.

ontheotherhand said...

Lola, they probably do not think that they are lying. People look for information that confirms what they have already decided. The logic of their aims doesn't add up though. Let's say that they are right that the temperature of the earth should not change. Should we spend our economy trying to cool the earth to pre-industrial temperatures? Does it matter whether humans or something else like the sun is to blame? How do we know if it's worth doing something about it? The answer is to do cost/benefit analysis, but that just shows certain costs now for small uncertain benefits in the future. Should we all be poorer now, (and reduce our economic capacity to research, adapt if necessary, as well as help humans in the present with things like clean water, education, disease). Their solution seems to be bigger government, compulsion, and censorship (BBC 'the science is decided)

Mark Wadsworth said...

OTOH

"cost/benefit analysis"

Costs = infinite, as whatever they try won't work.

Benefits = zero, as whatever they try won't work.

At least, there's only fabricated evidence for any of this.

Lola said...

OTOH / MW
isn't all that rather the point made by Nick Stern? And that the best he could do was to say, 'well, as best as I can estimate add this Carbon Tax to everything and let markets sort it out'?

Mark Wadsworth said...

L, ignoring all this globular warming doolally, I am (in principle) thoroughly in favour of taxes on 'fossil fuels', it's like land value tax... for raw materials, road use, pollution and also discourages imports from despicable regimes like Russia, Saudi, Iran etc.

Some of the Greenie solutions make good sense either way. Some of them are complete self-harming bollocks.

ontheotherhand said...

If he is right that C02 is damaging, then it is an economic externality whereby those who damage others do not currently pay, and a carbon tax equal to the damage would help. But... if there is damage, how much does it cost? When does it cost? What 'discount rate' do you use to bring the cost back to today's value? So if we are pretty unsure about the damage, and it is decades away, then the discount rate is high and the present value of the cost is tiny. That is partly why they argue that we only have few years left. The Stern report in 2006 forecast huge costs by 2035 to justify urgent costly actions.

Bayard said...

"but why are they lying? And why do others like governments compound in the lies?"

It's the power of religion. Alarmism is a quasi-religion and thousands of years of history show how effective religion is in getting people to do things that governments want. As to the Alarmist, they are after the ego-boost of being Right. (see A.E. van Vogt's Theory of the Right Man)

Bayard said...

"But all things are not equal and the lower emissivity outweighs the albedo effect."

But would not that mean that a white car (high albedo, low emissivity), would be hotter than a black one (low albedo, high emissivity)?

Mark Wadsworth said...

OTOH, where's the evidence that Co2 is damaging? I see none.

B, L, yes, it's a kind of religion, hence the pilgrimages where youth groups walked on foot from [somewhere] to Glasgow COP thingy. St Greta loves playing the martyr and suffering for the cause, like sailing across the Atlantic (instead of not bloody going in the first place, which has zero impact on environment). Buy a Tesla and thou shalt be redeemed!! Wankers.

B, apparently, painted metal has similar emissivity to bare metal. But those are two unknowns and other stuff to take into account. In summary, I don't know.

Unknown said...

In re emissivity I recall reading somewhere that matt black radiators are better at warming the house than glossy white ones.= 'cos they 'radiate' better. Or have I mis-remembered? And even I haven't is that relevant?

Mark Wadsworth said...

U, people used to say that. My dad painted his radiators Matt black. Turns out it's nonsense.

Bayard said...

Mark, U, some manufacturers list a higher output from a white towel rail than a chrome one of the same size. You could also check the output of a dark grey radiator compared to a white one. AFAICR, it's the same.

Lola said...

FYI Unknown = Lola (still got google issues....)

Mark Wadsworth said...

L, yes, after a decade, I can recognise your comments :-)

ontheotherhand said...

Perhaps black radiators worked better when they were the fat old 'radiators' from the early days of central heating. You only see them in really old houses or schools. Modern ones should perhaps be convectors. Lots of surface area created by being long and thin with a zig zag of metal sandwiched between two.

Doonhamer said...

Any one who has sat on an unrecessed screw head on a wooden sauna bench knows the effect.

Mark Wadsworth said...

Dh, that is actually a slightly different effect, has similar result but has to do with metal being better heat conductor than wood and the fact that wood is porous, so part of what you are sitting on is just air. But ta anyway.