Wednesday, October 28, 2009

Misnomer of the century: "the Greenhouse Effect"

The Greenhouse Effect is one of those things that no one disputes, right? You know, the reason that the Earth is warmer than it should be is because of the fact that energy from the sun warms the planet but that "greenhouse gases" (such as water vapour, methane and CO2) trap the heat reflected from the surface—and so the planet is warmed.

No one disputes that, right? It's established science, yes?

Er... No.
One thing we can get out of the way immediately is that it doesn’t work in the same way as a greenhouse. There used to be a theory, dating back to Joseph Fourier in 1824, that visible radiation could enter through the transparent glass, but because glass is opaque to infrared, when it is re-emitted it gets trapped. Fourier proposed that gases in the atmosphere could act the same way. This theory was proved wrong for actual greenhouses in 1909 by Professor Wood of John Hopkins University. An experiment comparing a pane of glass to a pane of crystallised rock salt (Sodium Chloride) which is totally transparent to infrared found no difference in temperature. In fact, greenhouses work by preventing convection, a mechanism that is of course impossible to freely floating CO2.

The above paragraph is taken from PaAnnoyed's superb post at Counting Cats, which helpfully clarifies the physics of the so-called Greenhouse Effect: it's worth reading the whole post, but I'll present a quick summary.

Some of you might remember that, a few weeks ago, I published a piece pointing out that the approximate mass of Earth's atmosphere is...
... about five quadrillion (5x1015) tonnes, three quarters of which is within about 11 km (6.8 mi; 36,000 ft) of the surface.

This is, you will not be surprised to know, because I was researching the greenhouse gas effect myself: alas, a lack of time meant that I hadn't got around the writing the post—and now I have no need to do so.

So, if the Greenhouse Effect has nothing to do with greenhouses, then why is the Earth warmer than it should be? And why is the mass of the atmosphere relevant? Simples...
What keeps the layer at 10 km so cold? –54 C is far below the –24 C we expect on energy-balance grounds, so it can’t be by radiating to space. And the fact that there is a straight line all the way down to the ground suggests that whatever the mechanism is, it’s the same one that keeps the surface at +14 C. Straight lines don’t happen by accident.

I won’t keep you in suspense any longer. The answer is pressure. Because of the weight of air, the pressure at the surface is greater than it is higher up. This means that if air moves up and down, the pressure changes, and the air expands or is compressed. And when air is compressed its temperature increases.

Air is driven to circulate up and down by convection. As it rises, it expands and its temperature drops. As it descends, it is compressed and its temperature rises. This maintains a constant temperature gradient of about 6 C/km. (It would be bigger, but evaporation of water carries heat upwards too, which somewhat counteracts the effect.)

No heat passes in to or out of the air to effect this change. It is solely an effect of the changing pressure. (If you really want to know, the compression does ‘work’ on the gas, which increases its internal energy. It doesn’t come from any flow of heat or radiation.)

This temperature gradient is called the adiabatic lapse rate, and is an absolutely standard bit of physics.

Is that all clear? Good. Now, let's move onto the second part...
When we look at the Earth in infrared wavelengths, we see it merrily glowing away, like a coal ember, radiating all the heat it has absorbed from the sun. But unlike the view in visible light, where we can clearly see the surface, in infrared the atmosphere is fuzzy and opaque. It is full of water vapour, and a few other trace gases, that fog our view of the surface. And so when we ask what temperature the surface of the Earth should radiate at, the surface we see isn’t solid ground, but this fuzzy layer high up in the air. And therefore, it is this surface that settles down to –24 C, to radiate exactly the right amount of heat away.

It is about 4 km up, and held at –24 C by the heat rising from below balancing radiation directly to space. Below it, compression increases the temperature. Above it, decompression lowers it. The actual mechanism and explanation for the Greenhouse Effect is in fact pressure. To be specific, it is the pressure difference between the surface and the average altitude from which heat radiates to outer space. Moreover, it is the exact same mechanism by which the upper atmosphere is cooled to –54 C, and there is no way you can explain a massive cooling by heat being in any sense “trapped”.

Heat is not trapped by absorption by CO2. That is Wrong, Wrong, Wrong! Such trapping does go on, but it has no long-term effect on the temperature because the adiabatic lapse rate has overriding control. You can even theoretically get a greenhouse effect with no greenhouse gases at all! All you need is some high altitude cloud to radiate heat to space.

So, given that the standard Greenhouse Effect model is... well... let's call it "simplified" rather than "a colossal pack of lies", why are people still banging on about CO2 trapping warm the heat?

Well, because CO2 does have some minor effects.
Now supposedly, according to rather more complicated calculations, doubling CO2 levels in Earth’s atmosphere will raise the average altitude of emission about 150 m, which will therefore raise the pressure difference and hence the surface temperature about 1.1 C. If we raise CO2 by only 40%, surface temperature will go up about half that. So we had half a degree last century (an amount too small to reliably measure). We’ll have half a degree next century. And that’s all the standard Greenhouse Effect can give you.

As PaAnnoyed points out, to get any more than that requires that you factor in a whole bunch of other, less well understood effects—as well as a bunch of Chaotic modelling (which are, by their very nature, not closely understood or predicted).

And no, as PaAnnoyed also explains, Venus is not an example of "runaway global warming"—anyone who tells you that "Venus is what will happen to Earth" is either ignorant or lying. Or both.

As I said, you really need to go and read the whole post, but I do think that we can put to bed the whole concept of CO2 "trapping" heat. Further, I think that we really ought to stop talking about the "Greenhouse Effect" because, having come to mean what it does, it is entirely misleading.

In the meantime, Kerry McCarthy has put an inflammatory title to a post by Next Left that—quite reasonably—points out that many Tory bloggers (and some non-Tories, such as your humble Devil) are somewhat at odds with the stated policy of the Conservative front bench on the issue of climate change.

But the simple fact is that the Tory front bench is extraordinarily short of anyone with any kind of scientific credentials whatsoever. In fact, like the LibDim and NuLabour benches, the Tories' representatives are only really experts in how to steal money off the taxpayers of Britain.

The anthropogenic climate change hoax gives our irredeemably corrupt politicos ample excuse to do precisely that—are you surprised that they have wholeheartedly embraced this massive fraud?


UPDATE: Timmy has commented on this piece and what he says about the IPCC is quite correct: his error lies in ascribing certain motives to your humble Devil.
The result of which is that this explanation of atmospheric physics is not some great “gotcha” showing that the whole climate change set of prognostications is wrong.

Indeed. As I have said over there, I was not intending this as yet another proof that anthropogenic climate change is a colossal hoax—surely I have published enough of those by now.

No, what I intended to do was merely to educate: to show people that the Greenhouse Effect has nothing to do with greenhouses, and that CO2 does not affect the Earth's temperature in the way that most people think it does.

The desire to do so was inspired by reading a number of posts in which bloggers or MSM reporters stated something like "the Greenhouse Effect is not in dispute" or "everyone agrees that CO2 is a Greenhouse Gas" or "no one denies that CO2 traps heat in the atmosphere", and then proceeded to show that they didn't understand how the Greenhouse Effect actually operates.

So, as I said, this article was not supposed to be a "gotcha"—merely educational. After all, I doubt that they teach the truth in schools anymore...

26 comments:

JD said...

CARBON TAX IS THEFT - PLAIN AND SIMPLE.

http://www.facebook.com/group.php?gid=181254384531#/group.php?gid=181254384531&v=wall

Anonymous said...

Problem is most dummies I may mention GW to actually believe it.
Sheep are easily fleeced.
However as I am not a sheep.
I'm angry.
As for that ghastly tele advert with the demon thing over Bloody Trumpton or wherever the hell it is.
Shove it up your ass you thieving morons.
Willi-band is a theiving greedy little crook ,with a bloody rubber banana.
I FEEL A LITTLE BETTER NOW.
Hmmm hmm.
ps
If I looked north from my front garden 15000 years ago I would have seen a wall of ice 1000m high.
Of course the world is warming we have just come out of an ice age.
No Willi-band not the 3d cartoon film, an ice age, didn't they teach you that at school you moron.

Anonymous said...

Michael Hulme: Founding Director (2000-2007) of the Tyndall Centre for Climate Change Research says in his new book:

“The idea of climate change should be seen as an intellectual resource around which our collective and personal identities and projects can form and take shape. We need to ask not what we can do for climate change, but to ask what climate change can do for us.
……
Because the idea of climate change is so plastic, it can be deployed across many of our human projects and can serve many of our psychological, ethical, and spiritual needs.
…….
We will continue to create and tell new stories about climate change and mobilize them in support of our projects.
…….
These myths transcend the scientific categories of ‘true’ and ‘false’”

http://algorelied.com/?p=3011


AND, from the draft Copenhagen Treaty:


"To avoid dangerous climate change and build climate resilience, the way society is structured will need to change fundamentally – from investment patterns to development programs. This cannot be accomplished by a fragmented set of existing institutions."

http://www.docstoc.com/docs/12736932/A-Copenhagen-Climate-Treaty-Version-10-A-Pr...

You're right that the science does not support the theory of AGW, but it's not really about science, is it?

Global governance - coming to your neighbourhood soon!

Brew Wales said...

Seem to remember about 20 years ago at uni being told that the largest CO2 contributers were volcanoes. Obviously today this is not taught or even researched, those bstads at the Benfield Centre for Hazard Research know that preaching scare stories makes funding come in.

Anonymous said...

Thanks for this piece.
I would suggest reading the entire original article though. This is not a criticism but just a suggestion for anyone like myself who has a limited and rusty knowledge of thermodynamics.

Jack Savage said...

Excellent post. Keep them coming. We only have a few more days to save our money from the rent-seekers at Copenhagen!

Henry Crun said...

The greenhouse effect so beloved of the global warmmongers is a complete work of fiction.

According to the second law of thermodynamics, the greenhouse effect is impossible in a planetary system such as ours.

Tim Worstall said...

"Now supposedly, according to rather more complicated calculations, doubling CO2 levels in Earth’s atmosphere will raise the average altitude of emission about 150 m, which will therefore raise the pressure difference and hence the surface temperature about 1.1 C. If we raise CO2 by only 40%, surface temperature will go up about half that. So we had half a degree last century (an amount too small to reliably measure). We’ll have half a degree next century. And that’s all the standard Greenhouse Effect can give you."

Quite true. And it's also actually what the IPC reports themselves say.

No, really, they do.

The direct effect of CO2 concentration rises is minimal and we don't really care all that much about them.

The whole of the rest of the structure is built upon: what are the feedbacks? We know very well that there are positive feedbacks (say, tundra melting and releasing further CO2 and or methane)and we know very well that there are negative feedbacks (say, higher plant growth and thus more carbon sequestered in soil).

The real point of the IPCC reports and of all of those computer models is in trying to work out what the net balance of those feedbacks are. And truth to be told, we don't really know all that well.

But CO2 rises leading to temperature rises directly? Yes, the IPCC comes to very much the same conclusion as Pa Annoyed above.

No, really, they do.

commentor said...

That second law of thermodynamics is great. It also disproves evolution, ISTR.

Now, please excuse me. I need to go to the local 12 Foot Tall Lizard Centre, to have my brain implant battery replaced.

Dave said...

The real danger is extreme cold, not extreme heat. There's a great article over at Numberwatch (it's a bit hard to find but is well worth the effort.
He postulates this- if we have a period of extreme cold with no wind, the margin of supply over demand shrinks to nil. All it would require is for a catastophic failure in the network- a transformer failure, or ice bringing down power lines, for switches to be turned off and whole communities left without electricity. No electricity means no gas central heating, no fuel pumps, no supermarkets, and your own freezer going belly up. No power, no heat, no fuel, no food. And the windfarms producing nothing.
I fear the worst this winter.

Hamish said...

Doesn't this mean that chemicals like methane and CFCs which absorb lots of IR and which we're always told are infinitely more dangerous than the dreaded CO2, actually aren't?

Looks like I can eat all the cow I want and that cunt Stern can fuck off and drown in a lentil filled grain silo.

Mark Hodson said...

"I won’t keep you in suspense any longer. The answer is pressure. Because of the weight of air, the pressure at the surface is greater than it is higher up. This means that if air moves up and down, the pressure changes, and the air expands or is compressed. And when air is compressed its temperature increases.

Air is driven to circulate up and down by convection. As it rises, it expands and its temperature drops. As it descends, it is compressed and its temperature rises. This maintains a constant temperature gradient of about 6 C/km. (It would be bigger, but evaporation of water carries heat upwards too, which somewhat counteracts the effect.)"

So why are the oceans not warmer at the bottom than at the top?

The pressure increase/m is lots (? ten times?) higher in water...

Hoddy

Anonymous Coward said...

@MH

I think because water doesn't get hotter the more you compress it - is that right? The more you heat water, the more dense it becomes, and so dense water can't be particularly hot.

bella gerens said...

Mark:

So why are the oceans not warmer at the bottom than at the top?

They are. At least during part of the year. You don't find icebergs in the Mariana Trench.

Pogo said...

"Hoddy"...

In answer to your question, it's basically that "water is bloody odd stuff". For a kick-off it's virtually incompressible so it's not going to obey the gas equations that show why air etc gets hotter when compressed (why you can burn your fingers on a bicycle pump if you're a tad overenthusiatic), and secondly it's at its densest at about 4C (pure water, not sure and too lazy to look for the figures for seawater) which is why, as Bella says, the coldest bit is part-way up the column.

HTH.

Roue le Jour said...

"This theory was proved wrong for actual greenhouses in 1909 by Professor Wood of John Hopkins University."

Yet they were still happily teaching it to me in school fifty years later. I remember it clearly. I also remember thinking, so why does the Nissen hut get so bloody hot, then?

James Higham said...

There is an equal and opposite amount of science also pointing to the warming. It is by no means established and in fact is quite confusing. I could choose my scientists to make out a case either way.

There are only two certainties. One is that the Gore led pollies are using it to enslave us and the other is that time will tell on the science itself.

Anonymous said...

It is all very very complicated stuff, every aspect of climate science is pretty much guess work.
For example: The C02 molecule has two modes of vibration at which it can absorb IR radiation.
No one can be sure if the atmosphere had or will have enough C02 to entirely notch out both of those two frequencies...
What about common sense observation. Its getting colder and the ice caps are growing while C02 is increasing...

Anonymous said...

'So why are the oceans not warmer at the bottom than at the top?'
Could it be something to do with the physical properties of gases and liquids...
Liquids and solids are very much better conductors of heat than gases. The heat generated by the compression of the water at the lower depths would quickly be dissipated.
Gas are poor conductors and can only loose heat through convection.

g1lgam3sh said...

Apropos of toss all...still...

http://www.dailyexpress.co.uk/posts/view/137032/Blogger-whose-abuse-forced-a-council-to-quit#at

Pavlov's Cat said...

I actually used this post today to put the record straight on the Greenhouse Effect being taught as fact at university. Much thanks, DK.

The Hobbs End Martian said...

Wattsupwiththat recently posted links to the Glenn Beck interview of Lord Christopher Monckton regarding the Copenhagen Treaty.

listed here

In Video 7 Lord Chris destroys AGW, he refers to the work of Prof Richard Lindzen; Beyond models - using physics to assess climate sensitivity, attribution, and the relevance of both to alarm. the pdf is available here (1.2 MB)

Pa Annoyed said...

DK,

Many thanks! Your article is much appreciated.

And you're exactly right about this not being intended as a 'gotcha' about IPCC science - as I was at pains to point out, this is the official 'climate science' version. It is meant to be educational, to act as a base for discussion.

But it was intended as a 'gotcha' about:
a) every single one of those media articles that explains the effect wrongly;
b) all those patronising AGW-activists who says the physics is simple or trivial, and sceptics must be ignorant or anti-science to doubt it, and yet evidently doesn't understand it themselves;
c) all those scientists who do know better but fail to object to or correct the ubiquitous appearance of the wrong explanation in the media with so much as a hundredth of the energy that they devote to any sceptical arguments or errors;
d) all those scientists and pundits who have pontificated to the public on the importance of understanding global warming but who have failed to explain any of this previously.

And some or all of those categories do indeed include scientists and others apparently speaking as members or representatives of the IPCC. Gotcha, indeed.

I will also note that some prominent sceptics have occasionally used the "trapped IR" version too. (I don't take sides when it comes to the science.) I hope this will improve matters - I hope/expect sceptics will be more likely to pay attention.

I plan at some point in the future to be looking at some of the flaws and assumptions in the argument. But we need to set the groundwork first.

Anonymous said...

MH,

You can't compress a liquid - that is why hydraulics work so efficiently. The increase in pressure on water only changes the temperature at which it will change to a gas.

Brian H said...

As Gerlich and Tscheuschner are at pains to demonstrate, there is no such thing as “radiative balance”. Only energy balance. Some of the energy coming in from the Sun ends up as work (expended energy causing motion or chemical change, for example.) What do you think causes the wind to blow, the currents to flow, and plants to grow? All of that absorbs (uses) energy which does NOT get radiated back into space, nor does it end up as hot air.

Also the 33° Greenhouse effect etc. is totally bogus. “(c) the frequently mentioned difference of 33°C is a meaningless number, calculated wrongly” etc. http://arxiv.org/pdf/0707.1161v4 To be simplistic, the greybody temp climatology uses is the 4th root of the average insolation, but it should use the average of the 4th roots of the local insolations. That yields a greybody temp of -129°C, not -18°C.

And so on. The IPCC papers and models are riddled with fundamental errors of that sort. Pure computer-game garbage.

Brian H said...

Runawaylessness

The postulate of positive feedback in the system (i.e., that water vapor multiplies the effect of CO2, which raises air and ocean temperatures driving even more CO2 and H2O into the atmosphere, and so on) has been disproven soundly in thorough experimentation ... by Planet Earth. The geological record shows that every combination of low and high CO2 (slightly lower than present up to 20X current numbers) and high and low temperature (from tropical poles to ice sheets nearly to the equator) has been tried, at great length, and no "runaway" has occurred. The minute range of values we're now experiencing and playing with thus has no more chance of causing runaway than spitting in the ocean has of causing a tsunami.