[LINK] The End Is Nigh [Was: On the Day that you were born (UN

[David Boxall]

First, my apologies to the list. This is well off topic for Link. My 
change to the subject line was intended as a joke. I didn't expect it to 
carry on like this.

What follows is based on memories from the time of Carl Sagan (who died 
in 1996) and chemistry, which I haven't studied in more than a quarter 
of a century.

On 13/11/2011 9:47 AM, Jan Whitaker wrote:
> At 09:27 AM 13/11/2011, David Boxall wrote:
>> ... I guess that would make the most likely candidate HNO3.
>
> hmmm.... acid or nitrous oxide? Will we all be 'happier'? (think dentist)
> ...
Bear in mind that nitrous oxide isn't just happy gas. There was, for a 
while, a fashion for getting high by sniffing the contents of whipped 
cream bulbs (N20 is used because CO2 curdles cream). Too many people 
ended up with brain damage, so the fad fizzled. N2O is dangerous.

The chemistry's not simple; HNO3 isn't as stable as H2SO4, so we end up 
with complications as it decays and reforms at different levels in the 
atmosphere. I avoid using the term "acid" because, to behave in the ways 
we'd associate with that word, HNO3 requires water.
> ...
> The other question about this atmospheric change like Venus: was it a
> cataclysmic snap of the finger change or an evolutionary change? If
> the former, I think we are in deep trouble (assuming that is the
> ultimate greenhouse shift) because humans in current form would be
> here to experience it (a la the dinosaurs). If evolutionary (slower),
> then maybe the biological evolutionary change pace on Earth will
> match to a degree. In that case, humanity will be different as well
> and may be heading off to inhabitable planets via wormholes.
>
> Time scales matter.
> ...
Stretching the memory muscles here (and repeating a lot that most people 
already know):
 From the point at which evaporation first exceeds precipitation, the 
concentration of water vapour in the atmosphere begins to build. This is 
popularly known as a tipping point. On Venus, the trigger for change was 
massive volcanism. On Earth, it's us.

Nobody really knows where the tipping point lies, but it's generally 
accepted as somewhere beyond 2 degrees C above long-term averages (which 
we might have already exceeded) or 350ppm CO2 (which we have already 
exceeded). The energy output of the sun has risen over time so the past 
is not a reliable guide. We've also interfered with our atmospheric 
chemistry; remember the fuss a little chlorofluorocarbon caused?

Water vapour is a greenhouse gas so, as its atmospheric concentration 
increases, so does the greenhouse effect. The inevitable result is 
feedback and an accelerating greenhouse effect.

A millennium or so after the tipping point, there's no water left on the 
surface. Give it another hundred millennia or so and the atmosphere has 
stabilised to the dry HNO3 state mentioned previously. At that point, 
there's little if any subsurface moisture left.

Humanity would probably be extinct within a century of the tipping 
point. Well before that, we'd be eating each other. Before then society 
would have collapsed, leaving little prospect of technological salvation.

On 13/11/2011 11:23 AM, Kim Holburn wrote:
 > ...  If the global temperature rises 5 or 10 degrees it will probably 
wipe out our civilisation.  It probably won't wipe us out for a few more 
degrees.  It wouldn't wipe out life.  Not even close.
 > ...
Better minds than yours or mine are not so certain.

 > ...Microbial life can exist in a very wide range of temperatures and 
pressures, kilometres underground, almost any part of the ocean or 
atmosphere.
 > ...
Without liquid water?

 > ...
 > The risks we're taking, are with our society and comfort not with the 
earth.
 > ...
Better minds than yours or mine are not so certain.

On 13/11/2011 2:22 PM, Bernard Robertson-Dunn wrote:
 > On 12/11/2011 6:30 PM, Frank O'Connor wrote:
 >> In terms of the environmental debate, an increase of 5 to 10 degrees
 >> in the mean temperature of Earth would probably be good for life.
 >
 > IMHO.
 >
 > The climate science may be settled, ...
I've never heard any such thing from anyone suitably qualified. It's a 
straw-man assertion, employed by deniers. The best qualified are as 
close to consensus as science ever gets; that's as certain as we can be.

 > ...
 > Firstly, as far as I can tell, all the debate and modelling is concerned
 > with temperature. The real danger is not temperature, but energy. The
 > greenhouse effect traps energy, which results in increased temperature.
 > It will also show up as an increase in violent weather events. AFAIK,
 > the climate models do not model heat or other forms of energy (chemical,
 > kinetic, etc).
For public consumption temperature is a proxy for all forms of energy, 
much as CO2 is a proxy for all greenhouse gases. The models take account 
of all known forms.

 >
 > Secondly, the climate prediction models are linear. ...
The models are many things. It would be more accurate to say they're 
exponential. But not very accurate.

...
 > That doesn't mean I am suggesting climate change is not real and that we
 > should not worry about it. In fact the reverse. Policy makers should be
 > taking the "safety first" approach. But they are not. That's what
 > worries me.
 > ...
When the vast majority of the best qualified say we have a problem, 
won't any mentally and morally adequate adult support effective precautions?

On 13/11/2011 8:29 PM, Rachel Polanskis wrote:
 > ... the modern Judaeo-Christian technological Western life that we 
currently lead...
I'm thinking at a more basic level: life that relies on liquid water.

-- 
David Boxall                         | ignorance more frequently
                                     | begets confidence than does
http://david.boxall.id.au            | knowledge
                                     | --Charles Darwin (introduction
                                     |  to 'The Descent of Man' 1871)