Sunday, 7 June 2020

"How I bamboozled a generation of scientists"

Guest post by James Hansen.
In the 1970s, I made up my mind that rising CO2 levels were the cause of rising temperatures. Nobody really knew whether this was cause-and-effect (and if so, which causes which); correlation (a third factor causes both); pure coincidence; or just one of those things we'll never be able to explain - maybe these warmer phases come every thousand years or so (Roman warm period, Mediæval warm period, Modern warm period...), but I decided to stake my career on it.

I didn't have much evidence - at the top of page 1, column 2, I clearly stated "The major difficulty in accepting this theory has been the absence of observed warming coincident with the historic increase. In fact, the temperature in the Northern Hemisphere decreased by about 0.5C between 1940 and 1970; a time of rapid CO2 buildup." (my children call this a 'spoiler'; my grandchildren call this a 'clue bat'), so I twisted the facts to fit my logic. I did a Diagonal Comparison, reversed cause and effect and then covered my tracks a bit by using technical jargon.

There is of course a Greenhouse Effect. Broadly speaking, all else being equal, the thicker the atmosphere, the warmer the hard surface will be. The atmosphere is like a blanket. It warms up and cools down slowly, it keeps the hard surface a bit cooler by day time and a lot warmer by night. Surely people can work this out intuitively? What the atmosphere's constituent gases are is pretty irrelevant, all that really matters is their specific heat capacity (which is not much different for nitrogen, oxygen or CO2 - see below). Ozone is a special case (that actually does have an effect). But 'Greenhouse effect' is neat shorthand, so I hijacked the term and made up my own explanation for it.

Luckily, CO2 levels and temperatures have continued rising since my 1981 essay, so everybody heralds me as a visionary genius and assumes that my logic was sound. I'm really surprised that nobody ever noticed the sleights of hand, not even those we deride as Climate Skeptics or dismiss as Science Deniers who are out to debunk it all.

Nonetheless, like any great showman at the end of his career, I now want to tell the world how I did it (not least because regular commenter Dinero posted a link to my original essay here, and our blog host saw straight through it and will blow the gaff if I don't do it first).

Start with some basic physics and maths

As any physicist knows, you can calculate the expected temperature of the visible surface of a planet by working out the average amount of solar radiation each m2 gets from the Sun (over the planet's day); deducting the amount that is reflected back to space; dividing that by the Stefan-Boltzmann Constant (5.67/10^8); taking the fourth root of the result; and that's your temperature in degrees K.

Here are the workings:

The Stefan-Boltzmann Constant is derived from observation and trial and error; you can tweak the figure for albedo a bit (nobody knows the exact values) and so of course it all stacks up and is a good match for measured temperatures.

Don't forget that we take (white) cloud cover into account when calculating how much radiation is reflected straight back to space, so the end-result of our calculations is the expected temperature of the cloud cover (to the extent that the planet has cloud cover) at that altitude (i.e. the altitude of the visible surface)...

- The altitude of the visible surface of Venus is 65 km, the mid-point of the cloud cover, which is between 50km and 80 km altitude.
- The average altitude of the visible surface of Earth is 5 km altitude. Earth's visible surface is two-thirds cloud cover, mainly in the upper half of the atmosphere - effective altitude 7.5 km - and one-third hard surface or open ocean - altitude zero - so the overall weighted average altitude of the visible surface is at an altitude of approx. 5 km.
- The average altitude of the visible surface of Mars is 1 km. Mars has very little cloud cover, but there are dust storms. On average, the visible surface is barely above the hard surface, call it 1 km for sake of argument.

Of course, simply referring to this as "the expected temperature of the visible surface, be that cloud cover or hard surface, at the average altitude of the visible surface" would have made the next logical leap too transparent, so I used the term "effective temperature" instead, a term whose meaning is not immediately obvious.

Trick 1 - the Diagonal Comparison

Having shown that I can plug numbers into equations and get the right answer, I then did a Diagonal Comparison. I compared the temperature of the visible surface (at a high altitude, now referred to as "effective temperature") with the actual measured hard surface temperature (at zero altitude) and called the difference 'The Greenhouse Effect', which I explained with the hand wave "the excess... is the greenhouse effect of gases and clouds".

It's like a green grocer telling you that potatoes are more expensive than tomatoes, because 5 lbs of potatoes costs $1.50, but 1 lb of tomatoes only costs $1. You might fall for that one, but my table below is like me telling you that potatoes are more expensive than tomatoes because 1 ton of potatoes costs $600 and 1 lb of tomatoes costs $1.

Luckily, most people just stop reading here. They put 2 and 2 together to make 507. The atmosphere of Venus is 95% CO2, so my followers talk about "the runaway Greenhouse Effect" and sound plausible. In truth, if you follows the basic maths and physics outlined below, 2 plus 2 still makes 4. There's no geometric effect, and not even a logarithmic effect (Heaven only knows why the Skeptics set off on that road).

Some more basic physics and maths

Having established the expected temperature at a certain altitude, it's not difficult to estimate the temperature of the hard surface and to get your estimate to match up to measured temperatures.

The atmosphere gets cooler the higher up you go; which is another way of saying that it gets warmer as you descend to ground level. This is the lapse rate (which we insiders call 'adiabatic lapse rate' to sound clever). The lapse rate is actually easy to work out. You just have to understand that the kinetic energy (heat) in air lower down is converted to potential energy as it rises (and vice versa); heat is 'used' to lift the air, which gives it more potential energy (and vice versa as it descends). You calculate the lapse rate as gravity ÷ specific heat capacity of the air.

How to work out the lapse rate:

[What tickles me here is that I openly admitted that water vapour and clouds reduce the lapse rate by one-third. To quote from my 1981 essay "The [moist] lapse rate is less than the [predicted] value because of latent heat release by condensation as moist air rises and cools". That part is actually true - moist air releases heat as it cools - but I explained it so briefly that most people would either not understand it or ignore it

Now that my followers have been forced to admit that the effect of CO2 must be far lower than they want it to be, they are falling back on the Positive Feedback effect of water vapour (and ignoring the inevitable clouds, which more than cancel it out).]

Finally, you estimate the expected hard surface temperature. You start with the estimated effective temperature from above; multiply the lapse rate by the altitude of the visible surface; and add them together. Stands to reason - the thicker the atmosphere (and lower the hard surface is relative to the cloud cover), the higher the temperature at the hard surface. Not even the most hardened Skeptic or Denier disagrees on this; it's common sense. The end results are very close to measured temperatures (unsurprisingly, because you can tweak all the variables a bit):

Once you know how and why the hard surface temperature arises, the 507 K on Venus doesn't seem nearly so scary, does it? That's why I had to do the Diagonal Comparison instead and pull 507 K straight out of nowhere to shock people.

Trick 2 - reversing cause and effect

Of course, using the proper chain of logic and cause and effect (as above) would have given the game away, so I reversed the logic and swapped cause and effect - I had to show that a higher hard surface temperature led to less radiation going into space (seriously, I'm surprised anybody fell for this).

To quote from my 1981 essay again, "The mean surface temperature [on Earth] is 288 K. The excess ['effective temperature' less hard surface temperature] is the greenhouse effect of gases and clouds, which cause the mean radiating level to be above the surface... the atmospheric composition of Mars, Earth and Venus lead to mean radiating levels of about 1 km, 6 km and 70 km and lapse rates of 5 K/km, 5.5 K/km and 7 K/km*"

(* the current agreed values differ slightly, but I deserve credit for being pretty close).

You note that this is where I circle back to "greenhouse... gases" out of nowhere, adding the vague phrase "the atmospheric composition", even though the entire trail of physics so far clearly shows that the only thing that matters is their specific heat capacity and hence the lapse rate.

The lapse rate on Earth is slap bang in the middle of the lapse rates on Venus or Mars, even though "the atmospheric composition" on Earth is completely different to that on Venus or Mars. So more gullible readers must have assumed that the atmospheric composition on Earth is similar to that on Venus or Mars, even though I never actually said that, did I?

Having admitted that water vapour and clouds reduce the lapse rate by one-third, the more discerning reader should have been able to work out that even if we had 95% CO2 in our atmosphere, the lapse rate would be 9.807 m/s2 ÷ 0.846 J/K/kg = 11.6 K/km, reduced by one-third for water vapour and clouds = 7.7 K/km. The visible surface would still be 255 K at 5 km altitude, so the hard surface temperature would increase to 255 K plus 5 km x 7.7 K/km = 293 K, that's an upper limit of 5 K 'global warming' resulting from CO2 concentrations going up from 400 ppm to 950,000 ppm.

Having fooled people with the "runaway Greenhouse Effect on Venus due to CO2", nobody expected to see me admit that there's nothing to worry about.

If you read my essay properly, you'll see that I started with the temperature of the hard surface and subtracted a lapse rate* to arrive at the temperature at the altitude of the visible surface, which in real life is the first thing you work out, not the last. The figures 1 km, 5 km and 70 km are our starting points for the calculations, not the end results! In the US, we call this "arse backwards", I believe you Brits call it "arse over tit".

* It's nonsense to work out a lapse rate the way I did, by dividing the altitude of the visible surface by the difference in temperature between hard surface and visible surface. You can work out the lapse rate independently (see above) and then you multiply that by the altitude, etc. On either side of The Pond, that's called a circular calculation and Excel will give you an error message.

It's like a green grocer saying, "Well, 5 lbs of potatoes cost $1.50, so the price for 1 lb must be 30c", when in fact, he decides the price per lb first; you tell him how many lbs you want to buy; and then he works out the total price in $.

Covering my tracks

I referred to the altitude of the visible surface (i.e. the cloud cover, which anybody can understand) as "mean radiating level" and/or "the flux-weighted mean altitude of the emission to space". Why use an easily understandable concept if an impenetrable one will do?

I started the section headed Greenhouse Effect as follows "The effective radiating temperature of [a planet] is determined by the need for infrared emission from the planet to balance absorbed solar radiation". I then gave the long version of the equation for working out the temperature of the cloud cover based on solar radiation coming in (easier to understand) and said it was the equation for working out the temperature of the layer which radiates to space (conceptually more difficult to understand, although the two equations are the same, you just reverse cause and effect).

Well of course the temperature of the layer that absorbs radiation is the same as the temperature of the layer than emits radiation - it's the same layer! But it distracted people from the fact that I had wasted two whole columns explaining how to work out backwards how high the cloud cover is (to the extent that a planet has a cloud cover), which is easy, you just measure it!

In practice, most of the cloud cover is most of the top half of the troposphere, on Earth as it is on Venus (the dust clouds on Mars are more at surface level). I admitted as much in page 2, column 3: "Study of Venus suggests that some clouds occur at a fixed temperature. The Venus cloud tops, which are the primary radiator to space; are at [the altitude of] 70 km, where the [actual measured temperature = the expected temperature]". .

So really, I wasted two whole columns saying that "the cloud cover is at 70 km because the cloud cover is at 70 km". But I had the good sense to squeeze in some pseudo-scientific babble in between and/or gamble on nobody reading that far.

You don't believe me?

Now I've explained how I did it, just re-read page 1, column 3 and page 2, column 1 of my 1981 essay and see if you can spot how I papered over the cracks:

(copy that URL into your browser, I'm too old for hyperlinks).

Please don't kick yourselves too hard, a whole generation of scientists and 'activists' fell for it as well!

With best wishes,

James Hansen

PS, if you have any questions, please write to me at:
James Hansen
c/o Climate Science, Awareness and Solutions
Earth Institute, Columbia University
475 Riverside Dr. Ste 401-O
New York, NY 10015


Bayard said...

It's amazing how really quite famous scientists do this. They get seduced away from the Scientific Method, i.e. testing the Theory to destruction and start believing the Theory (their Theory) to be The Truth. They then start to scrabble around for facts to fit the theory, rather than the other way around, as Conan Doyle warned, via Sherlock Holmes, "It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts."

Mark Wadsworth said...

B, see also "nuclear fusion" and "Dark Matter". But those are intellectual curiosities, we waste taxpayers' money on them, but the futile search for them doesn't destroy livelihoods.

Bayard said...

I don't regard the search for a viable fusion reactor as a waste of money, it's peanuts compared to what the world spends on armaments, whilst professing not to intend to use them. More importantly, it hasn't morphed into a pseudo-religion. AGW and Christianity share the similarity that they are showing you the truth, and if you do not accept the truth, you will die (OK, with Christianity, the "eternal life" promised isn't actually here on Earth, but the concept is the same.)

Mark Wadsworth said...

B, if fusion works, that would be great. But it's always ten years into the future.

One thing you missed of your AGW/Christianity similarities list was the Spanish Inquisition. Any scientist or TV presenter who dares question The Truth loses their job and funding.

Lola said...

Policy based evidence making, I think it's called. Or 'what's my prejudice?'. 'Ooo look - 'evidence'/'reasons'.

Mark Wadsworth said...

L, I've decided on the title of my book: "The Greenhouse Effect: How NASA bamboozled a generation of scientists". It will basically be the above blog post with extra chapters explaining the real physics behind it, interspersed with excerpts from his reverse logic.

Lola said...

MW. You can self publish easily with Print on Demand. I'll chip a few quid for the costs if it would be useful?

Mark Wadsworth said...

L, ta, this has taken me a good month of slog so far. So there's no urgency, I'm only half way there.

Mark Wadsworth said...

Actually, two months, most of lock down so far.

Lola said...

MW - how very diligent. I've been teaching myself to turn threads on my between keeping my business afloat.

Mark Wadsworth said...

L, you're making your own custom bolts? Cool - do they work?

Lola said...

L. I am making various components that need a thread. For example a 5 1/4 inch long 3/8th inch diameter shaft to carry the accelerator pedal on the pedal box and that needs threading at each end - and my 3/8 24 tpi threading die was old and tired.

And yes, 'of course' they work...:-) Can't thread metric though. Mines an Imperial lathe.

Dinero said...

You need to cover the mean radiating level being made higher in altitude by the infra red opacity of the atmosphere. ie CO2 causing the height at which the effective temperature occurs to be higher. You have called it the cloud cover level. Climatologists call it the mean radiating level. For a warmer atmosphere from absorbed infra red, the higher atmosphere is warmer - and so working downwards from the higher altitude of the effective temperature, as you do in your calculations, the surface is hotter.

This is the exert from the Hansen paper, which could be badly worded making its meaning unclear.

The excess, Ts - T0 , is the greenhouse effect of gases and clouds,
which cause the mean radiating level to be above the surface. "

If you add the words , - caused by -

The excess, Ts - T0 , is *caused by* the greenhouse effect of gases and clouds, which cause the mean radiating level to be above the surface.

It then describes the effect and tallys with meaning of the next sentence,

" An estimate of the greenhouse warming is
Ts ~ Te + rH
where H is the flux-weighted mean altitude of the emission to space and r is the mean temperature gradient (lapse rate) between the surface and H."

That equation with Ts ~ Te + rH includes your lapse rate and working down from the mean altitude of the emission to space , but importantly has a variable H. And that tallys with what I have read elsewhere.

Mark Wadsworth said...

Din "You need to cover the mean radiating level being made higher in altitude by the infra red opacity of the atmosphere. ie CO2 causing the height at which the effective temperature occurs to be higher. You have called it the cloud cover level."

But there's no evidence for it, he admits as much.

Or else why can you so easily reconcile surface temp on Venus, Earth and Mars without making ANY ADJUSTMENT WHATSOEVER for this magical 'back radiation' or 'radiative forcing' and all the other made up expressions?

If there such magical things, then surely they would show up on Venus? It's got 1,000,000 kg of CO2/m2. On Earth it's 6 kg/m2. If you can't get a signal from 1,000,000 then you sure as heck won't get any from 6 kg, or 8 kg or 10 kg.

The cloud cover can't go any higher - it's already as high as it can go. So the 'mean radiating level' can't go any higher either.

Dinero said...

The Cloud cover level is your idea. Climatologists call it the mean radiating level.

You are making it too complicated.
If the atmosphere is warmer then the height at which the effective temperature occurs is a higher altitude. Then working down to the surface lapse rate multiplied by km you get a warmer surface.

Mark Wadsworth said...

Din, they call it "mean radiating level" to bamboozle people.

You have fallen for the pseudo-science, which has to be complicated or else people will see straight through it.

Hansen cheerfully admits that on Venus the "mean radiating level" is exactly the same altitude as the clouds (on average). It must be.

They invented the Diagonal Comparison.

The Achilles Heel of the Diagonal Comparison is that because there is no cloud cover on Mars, the "mean radiating level", the "cloud cover" and the "hard surface" are all at the same altitude - zero. Which is why they can't identify any big Greenhouse Effect, by definition.

But there is 150 kg/m2 CO2 on Mars and only 4 kg/m2 on Earth. So if there really is 33 K of "CO2 induced Greenhouse Effect" on Earth, surely there'd be quite a lot on Mars?

Oh dear, there isn't. Hoist by their own petard.

Mark Wadsworth said...

Din, try doing a proper comparison.

Imagine there were no clouds on Earth at all for a few days or weeks.
Albedo goes down from 0.3 to 0.15.
Solar radiation hitting surface goes up.
Temperatures at surface go up couple of degrees - say to 290 K.
Effective temperature now 267 K.
Now, subtract 'hard surface temperature' from 'effective temperature' = 23 K.
Has The (real) Greenhouse Effect gone down?
Of course not.
But using their crappy definition, the GH has fallen from 33 K to 23 K.
Therefore, defining the GH as ET minus HST is bollocks and always was, unless you calculate ET based on albedo of surface and ignore clouds (which sounds like bollock as well but probably isn't).

That 23 K is real GH based on thickness of atmosphere, 10,000 kg or atmosphere/m2 .

You can do the same for Venus (albedo 0.25 like Mars) and get ET 301 K, surface temp up a bit (745 K?), real GH = 445 K, based on 1,000,000 kg atmosphere/m2.

Set up your own spreadsheet and try it!!

Dinero said...

The Hansen paper has one model where the clouds move up due to the temperature.
I don't know about the figure for mars, but you say that earth mars and venus can be reconciled without any adjustment. That is not right, there is an adjustment made , the adjustment is the moving of the height where the effective temperature occurs upwards.
And that height is calculated using the composition of the atmosphere.
But you don't even need to go into that complexity, if you accept the postulate that CO2 absorbs and emits IR then the upper atmosphere is warmer and then following the lapse rate the surface is warmer.

Mark Wadsworth said...

... having quickly done the spreadsheet for V, E and M assuming all have albedo 0.25 and plotted an X-Y scatter for the three planets using logarithmic axes, we get a nearly straight line.

So like I said, like every sane person has been saying for centuries, it is only the thickness of the atmosphere that matters, not the constituent gases.

Dinero said...

A scatter plot of what. With what inputs.

Mark Wadsworth said...

Din, set up your own spreadsheet, reverse engineer mine, my columns are clearly labelled, much about with it, draw your own conclusions. Perhaps you will stumble across something that proves that It's All About The CO2.

So far I am struggling to find the slightest trace.

Mark Wadsworth said...

much = muck

Dinero said...
This comment has been removed by the author.
Mark Wadsworth said...

Din, nope.

Key to this is thickness of atmosphere (fixed). This is 99% of what you need to know.

Then amount of H2O or H2S4 vapour (fixed) and then finally how high clouds are (upper half of troposphere).

Those form clouds, which affect a) albedo and b) height of cloud cover or "mean radiating level".

My workings are based on Hansen's and control for all these variables.

If there are more clouds at higher levels, a) albedo goes up so effective temp goes down and b) altitude between them and surface goes up.

Higher albedo - lower effective temp. But higher altitude means that the extra K to be added to effective temp to find surface temp go up.

Those two effects pretty much cancel each other out.

But you have helped me pin down yet another contradiction inherent in 'climate science' that proves yet again what a load of horse shit it is.

Thanks, see next post.

Bayard said...

L, do you have a lathe where the cutter disengages automatically at the end of the thread, or do you have to do it manually? It was the latter when I learned to do it, keeps you on your toes.

Din, please don't call climate "scientists", climatologists. The former are the priests of the new religion, the latter are scientists who study the climate.