Thread: bbc inacuracies
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Old September 17th 17, 07:38 PM posted to uk.tech.digital-tv
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Default bbc inacuracies

On Sun, 17 Sep 2017 17:44:00 +0100, Chris Hogg wrote:

But water vapour is continually being recycled, mainly be evaporation
from the oceans.
[...]
Water
vapour is present in the atmosphere at roughly 100 times greater
concentration than CO2, depending on air temperature and altitude. To
claim that CO2 is the all-important greenhouse gas is perverse.
[...]
It's main relevance is as an
amplifier for increases in temperature caused by CO2, methane, etc. So
the real problem is these other gases with long atmospheric lifetimes
- take care of them and the water vapour will look after itself.


The rate of evaporation of water increases with higher temperature,
and decreases with lower temperature, thus the water vapour acts as an
amplification factor on *changes* in temperature caused by other
things. In a stable climate, average water vapour content of the
atmosphere will be stable, so is not a significant factor. It's chief
significance therefore is to amplify *change*. Which was my point and
probably why the original programme didn't see any necessity to
mention it.

The role of water vapour, and in particular the role of clouds in
influencing global temperatures, is poorly understood. Is cloud cover
increased by a warmer climate, and if so does that reflect IR
radiation back out of the atmosphere and prevent it reaching the
surface, or does it act as a blanket, holding the heat in?


We know enough to know that both these things happen, but that the
latter is more significant than the former. The run-away greenhouse
effect on Venus tells us that. The planet is about the same size as
Earth, but is closer to the sun, so gets more heat directly from the
sun. Despite the planet being completely covered in cloud, so much
heat enters the atmosphere that all the surface water on the planet
exists only as water vapour in the atmosphere, and in fact the
temperature at the planet's surface is hot enough to melt lead.

It is one of the several weaknesses in the AGW
hypothesis.


Exactly as I thought, there was a political motivation all along.
There is no weakness of any significance.

I didn't see the program, but, given the above, it doesn't sound to me
as though water vapour was necessarily relevant to the point being
made by the programme.


It was only a short clip, but it was unbalanced. The best part was the
gun-cotton igniting.


If it was a short clip, then it's hardly surprising that the role of
water vapour as a complicating amplification factor was omitted.
probably in the interests of clarity. Nothing wrong with that.
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