Is the Earth a
Super Organism?
Positive and Negative Feedback
 courtesy of avlxyz on flickr
courtesy hairy_jack on flickr
Push the tape, it will roll back
"Negative Feedback"

Push the tape when on top of the mug, rolls away and falls off
"Positive Feedback"
Sledging brother and sister
Example of Positive Feedback:
North Pole Ice
Data and Vizualisation Courtesy NSIDC  http://nsidc.org/data/virtual_globes/
Negative Feedback: CO2 and Forest expansion
More CO2 leads to
Expansion of forest
Living things stay the same
(homeostasis)
Your body keeps the same temperature
Sweats if you get hot
Shivers if you get cold
Like the tape in the mug
So life is a negative feedback system
So Is Earth a Super Organism?
For:
Your body = cells, not all human!
'Planet You'
Earth's climate has negative feedback loops Trees and Carbon Dioxide
like Homeostasis 




Against:
Earth also has positive feedback loops
Ice and Water temperature
Not like homeostasis
Earth doesn't reproduce (as far as we know)


Final Point about Systems

Folded paper, push will push back, pull will pull back.  + or - feedback?
Pull too much and will rip, system is 'broken'.
Remembering homeostasis in humans....


More Detail 
located by 'i'
throughout
i
More detail on the polar ice effect on climate here: 
http://www.realclimate.org/index.php/archives/2006/12/not-just-ice-albedo/

The ice doesn't just act as a reflector of sunlinght, it also acts as an insulating lid preventing the earth from losing heat from the sea.

Amongst other positive feedback systems affecting the climate are: Methane clathrates that could put methane back in the atmosphere (a global warming gas) and melting permafrost in the polar regions.  When the permafrost melts it releases frozen vegetation which then rots again releasing methane.
i
The negative feedback of the forests is a carbon dioxide 'sink' keeping CO2 levels in check.  Other important sinks are the shells of diatoms in the oceans.  These are made of calcium carbonate which traps CO2 in their shells.  When they die, if they manage to sink to the ocean floor without dying they trap CO2 in sediments on the ocean floor.

Further details and discussions of the ocean 'sink' actually failing and becoming a source here http://bit.ly/4dkIY
Homeostasis explained in greater detail here:
http://en.wikipedia.org/wiki/Homeostasis

Not all life maintains its own temperature, cold blooded creatures such as snakes do not and there is a play off between them being sluggish in the cold and not having to use food energy to maintain their body temperature. 


i
i
This argument is underpinned by the Gaia theory, which proposes that the earth is alive.  

http://en.wikipedia.org/wiki/Gaia_philosophy

40 years old the theory is still controversial and is a lot more detailed than discussed here.  My conclusion that the earth is not alive is basically supporting the 'weak Gaia hypothesis' which has many simularities with 'Earth System Science'. 

The concept that the earth has past a tipping point and we are moving towards a new climatic state is the topic of James Lovelock's latest book, 'Gaia's revenge'.  The new state is not attractive, far from being 'a bit warmer' it will probably involve more frequent violent weather events, amd the eventual flooding of low land (Bangladesh, Florida, Norfolk Broads).  These changes may be so large as to threaten civilization itself.

However, I'm not convinced there is strong evidence that we have past the necessary tipping points, we don't understand the earth's climate well enough to do that.  What is certain is that we are putting ourselves in danger of approaching one. 

i
Q]
If Earth is warmer, more water evaporates from ocean making clouds more likely.  Will this be positive or negative feedback?
Clouds
A]
Actually it could be positive or negative.  Clouds block the sun which would represent negative feedback, however, they also keep the planet warm as they are a greenhouse gas (frosty winter nights tend to be clear)

Scientists are unclear which is the more important effect.
Blocks sun => -ve
Greenhouse gas => +ve
(frosty clear nights)
If we apply the idea of systems breaking to homeostasis in humans what do we get? 
Q]
Systems Breaking Applied
to Human Homeostasis?
A]

You'd die.  

E.g. If you were in desert despite sweating you'd die.  
Negative feedback systems on earth may be protecting us, keeping CO2 from rising too far
Tipping Point
Earth will get a new climate with 
- - Extreme weather (droughts)
- - Higher sea level (flood Norfolk  Broads)
key to avoiding climate change is to understand those systems.