http://www.motherjones.com/blue_marble_blog/arc...
The Southern Ocean is near it's tipping point for acidification. "Hellish results" predicted. Natational Academy of Science moved up tipping point by 30 years.

Written in December 2008

Re: http://www.motherjones.com/blue_marble_blog/arc...

The problem with most of these reports is that the models they are based on are far too simplistic to be at all meaningful.

Models of acidification of the ocean is based on a large number of assumptions such as:
* There are no other variables.
* The system model is well known. For example, the model might assume a linear relationship.

The major reason for these simplifications in these models is twofold:
1) We have very limited knowledge of natural processes and don't have a full appreciation for how they work.
2) Modelling is very hard and simplification is the only way we can make sense of anything.

Of course in the real world, these models very seldom stack up because these assumptions are ill founded. For example, as acidification kicks in, other processes start up, and the variables change.

Thus, when scientists make predictions from these models, they say things like: "If the current rate of acidification continues then we might see result xxx".

That's all very well except that the simplifications have stripped out any meaning from the exercise.

As an analogy: remember your high school physics... You'd have learnt a whole lot of things about momentum and acceleration and had to solve problems where you could assume that gravity is constant (it is not) or that there is no friction (there always is). Those simplifications are done because the calculations get too complicated when you add in friction and changing gravity. For example, consider a problem of a person jumping out of a plane. If you ignore friction, then it is a trivial calculation to figure out how fast the person is going when they hit the ground. Add in friction and you need to consider terminal velocity, their parachute and other real world factors. When you consider these other factors you see that it is perfectly possible for a person to jump out of a plane at 10,000 ft and survive.

In most cases, natural processes are self correcting. That is, balance is found between supply and demand. When an environment starts generating more of xxx, then processes that consume xxx tend to thrive thus reducing xxx. For example, in the case of CO2, plants love the stuff so increasing CO2 levels stimulates plant growth.

These factors are very difficult to understand, let along characterise and model, which is why they are typically left out.

Written in December 2008