[mikewonders]

The problem is wider than merely the total water content of the atmosphere,[...]

Absolutely.  But after this many years of debate and complexity, learned helplessness leads many wanting to imagine there's a tool in the box that can fix everything and solve debate by assumptions.  Unfortunately that's a very dangerous assumption.  I had hoped others here might help break down those complexities but it seems that may have been my first mistake.

[mikewonders]

It's a Christmas Miracle!
Mikewonders has got Petrochemicals and me to agree on something.

Miracle indeed.  Mikewonders didn't do that.  You two made the same wrong assumptions all on your own, albeit I may have brought that into the light.  Didn't I read here recently "Consensus doesn't equal fact?"   By the way, two wrongs don't make a right either.  Repeating the same assumption also won't lead to new or confirming discovery.  Sorry, "fail".

Maybe a simple thought experiment ... Why did Santa ask Rudolf to guide his slay?  Because, even that fat benevolent, cookie munching Goodfellow understood that increased water vapor, fog or otherwise, makes it harder to see?  Why?  Random redirection of photons.  Just as driving in a fog with your brights on reflects more light back at the driver and less light emanates in the direction forward, (read as greenhouse reflection). 

Hmmm, let's think about that...  Thicker troposphere, increased water vapor volume / density gradient, (increased green house effect) deeper increased density of reflectivity, increased amplification of CO2 reflection (force amplification)... Increased total oceanic volume, larger heat sink, greater surface area reflectivity...

I'm sure standing wave harmonic will land outside the limited scope of analysis here too.

Yeah, surely all that is wrong simply for a desire to hold a line of embarrassing oversight out of view.  If Santa thought like you two, he'd have shot Rudolf, ate him for dinner, and installed and high compression big block in his sleigh.   

You might also believe that CO2 increase leads temperature increase assuming causation...  You might struggle with correlations of increased global precipitation having a higher degree of correlation with temperature rise too.

You must not have children or grand children... If you're wrong, they may not be able to have children themselves one day.  Ignoring the truth is a pretty large assumption to wager the risk of your own descendants, unless of course that's not high priority.

At least the two of you found something in common, you're in good company...  You both rely on gross comparison leading to incorrect assumptions and believe repeating it in unison will establish fact from which to disparage others efforts to actually find further facts. 

It's like the old couple stranded on their roof top during a flood.  They stubbornly refused two boats and a helicopter to save them, chanting in unison "God will save us".   When they drowned and ended up before God they asked "Why did you not save us?"  God responded... "I sent you two boats and helicopter, what more did you want?"

Ho, Ho, Ho. 

[Bored chemist]

the currently fashionable consensus only discusses (at considerable expense to the taxpayer) the color of the mahout's turban.

I see what you mean.
We know the CO2 concentration is significantly higher than it was (and we know why) but some people are intent on discussing the water concentration which we know is pretty much the same (It's currently cold + misty outside; C and near 100 % RH which means the atmospheric moisture concentration is exactly the same as any other time when it was 3C and misty.)

[Bored chemist]

You two made the same wrong assumptions

What assumptions?

[alancalverd]

The primary assumption of fashionable "climate science" is that carbon dioxide is a significant forcing greenhouse gas at concentrations above 300 ppm.

The secondary assumption is that reducing the output of anthropogenic CO2 will have a significant effect on world climate.

The third assumption is that it is essential and inevitable to double the human population by the end of the century.

The fourth assumption is that all these people can be fed and watered on a decreasing area of farmland, along with a decreasing number of sea fish, and that we can actually grow more plants with a lower temperature and less CO2.

The fifth assumption is that they will all be happy with their current standard of living (assuming 4 is true) and will not demand any increase in artificial power (currently about 1.5 kW per capita worldwide, about 5 kW in the UK - which represents a reasonable aspiration) all of which can be harvested from the sun.

Looks more like religion than science to me. I'm sure BC doesn't subscribe to such nonsense.

[Bored chemist]

Only the first two of those are even plausible candidates for being an assumption.
Let's see you provide any evidence that anyone is making the...

...assumption is that it is essential and inevitable to double the human population by the end of the century.

Particularly the "essential" bit.

[alancalverd]

If it wasn't considered essential to increase the population, why do we spend so much money and effort on fertility treatments, neonatal medicine, and elder care? Child support benefits? Why do governments worry about falling populations? How can property developers make a profit if there's nobody to live in their shoddy new houses? Who will buy the next generation of iphones? Economics is all about increasing supply and demand.

[Bored chemist]

If it wasn't considered essential to increase the population, why do we spend so much money and effort on fertility treatments, neonatal medicine, and elder care?

The "We" who do that are the rich West. Our birth rate is less than our death rate.

How can property developers make a profit if there's nobody to live in their shoddy new houses?

As you say, the houses are shoddy. So they won't last a a generation.
So the new ones will be bought by those whose current ones are falling apart.

Economics is...

... now learning, slowly.
Perhaps you should  join it.

[alancalverd]

The "We" who do that are the rich West. Our birth rate is less than our death rate.

If you believe that 11.38 is less than 9.43, you will probably believe anything. Admittedly that's just the UK figures, but I think you will find that the population of whatever you call the west has increased significantly over the last 20 years.

[Bored chemist]

I think the birth rate of 1.65 per woman is less than the death rate of (very close to) 2 per woman.

[alancalverd]

As you say, the houses are shoddy. So they won't last a a generation.
So the new ones will be bought by those whose current ones are falling apart.

That is approximately true in North America where the majority of dwellings are made of wood, with a design life of maybe 50 -  100 years, but the number of inhabited dwellings in the UK has increased by about 1% per year  every year this century.
To  the best of my knowledge, each new house built in the UK (principally brick) requires the emission of at least 80 tons of CO2 (2 bedroom terrace) and has a design life of 100 - 200 years.

[alancalverd]

I think the birth rate of 1.65 per woman is less than the death rate of (very close to) 2 per woman.

You really need to learn about life and statistics.

Half of those 1.65 children are female. Most women give birth around the age of 20, so within 60 years our average Eve has 1.65 + (1.65 x 0.825) + (1.65 x 0.825 x 0.413) = 3.57 living descendants, and is probably still alive herself.

[Bored chemist]

You need to learn about death and statistics.
If the women in a group have less than 2 children on average, the population of the group will fall in the long term.

We seem to have strayed somewhat from the topic.

If increased water in the air caused climate change, what caused the increased water in the air?

[alancalverd]

If the women in a group have less than 2 children on average, the population of the group will fall in the long term.

Then please explain where my arithmetic, based on your statistic of 1.65 children per woman, is wrong.

The figures of 11.38 births and 9.43 deaths per 1000 population in the UK for 2020 clearly show that the number of bodies in these islands increased, as it has done practically every year since the 1800s 

Your error is in assuming that the "group" is static when it is obviously dynamic. If every woman produces more than one child in her lifetime, and lives long enough to see her grandchildren, the population will increase. UK life expectancy nowadays includes grandchildren as a "given"  and great-grandchildren are well within the range of normal.

Population is a highly relevant matter.  If there is an anthropogenic element to undesirable climate change, it makes sense to limit the number of anthros causing the problem. If there isn't, we still need to determine what size population could be sustained at an acceptable standard of living  under likely predicted climatic conditions.

[alancalverd]

If increased water in the air caused climate change, what caused the increased water in the air?

Consider a very simple model: a block of ice with dry air above it. Sun shines on the ice and some water evaporates. Water is a greenhouse gas so the atmosphere above the ice gets warmer, so more water evaporates.

Only a climate change denier would think otherwise.

[wolfekeeper]

Yes, but positive feedback, below a certain amount, just acts as an amplifier. That's the point, water vapour amplifies the effects of increased CO2, because it's a really strong greenhouse gas in its own right. That makes the situation worse not better. While nobody is spraying large amounts of water into the atmosphere, humans are spraying large amounts of CO2. Which in turn causes more water vapour, which in turn causes more heating... it's a convergent series.

In fact, the whole thing is super complicated, there's clouds to consider, rain, snow, reflection from surfaces etc. etc.

Climatologists use computer models to predict the overall effects, and they can run the models with different levels of CO2 in them. They find that the CO2 makes the difference.

[alancalverd]

The historical data all shows the temperature graph leading the CO2 curve. And even if the opposite were true, there is no plausible mechanism for a cyclic, sudden doubling of CO2 concentration every 100,000 years.

Computer models can only model an observed correlation or an assumed hypothesis. If you assume that A causes B, and you generate a model based on that assumption, and adjust the parameters to fit recent observations, it will support your hypothesis. Problem is that it doesn't explain the historic result, and that makes it an unreliable precedent for future action.

While nobody is spraying large amounts of water into the atmosphere, humans are spraying large amounts of CO2.

2C₈H₁₈ + 25O₂ = 16CO₂ + 18H₂O

That's a lot of water vapor from the combustion of octane. And the more we use hydrogen-rich fossil fuels to replace coal, the more water we pump into the atmosphere. 

it's a convergent series.

Historically there is indeed a convergence because the temperature cycles over a fairly fixed range of 12 degrees. So what determines the limits? And why would they be any different now from then?  Sadly, lots of careers (including at least one good friend of mine) depend on the series diverging.

[Bored chemist]

Then please explain where my arithmetic, based on your statistic of 1.65 children per woman, is wrong.

You forgot to carry on long enough.

[Bored chemist]

Your error is in assuming that the "group" is static when it is obviously dynamic. If every woman produces more than one child in her lifetime, and lives long enough to see her grandchildren, the population will increase.

Imagine what would happen if all the children were boys and none was a girl.
(A well known quote attributed to Mark Twain might help here).

Now imagine that only half of the children were girls.
How many daughters must each woman have to maintain the number of women?
If only half of the children are daughters, how many children must each woman have in order to maintain the number of women?

(To make it easy, we can assume that they all grow up + have kid(s).)

[Bored chemist]

That's a lot of water vapor from the combustion of octane.

No.
It's a tiny amount of water, as I already  pointed out.
And, of course, most of it fell out of the sky before the next Winter was over.