Observations represent the truth, models…

In the last year during a larger meeting I had made a comment, which let a lot of attendees shake their head and others just smile. The statement was:

“Observations represent the truth, models the state of our understanding.”

Like I have said before, on the first sight it is of cause rubbish that observations have anything to do with the truth. Indeed, truth is a great word with many different meanings and implications. In the context above “truth” (which anyhow should always set between quotation marks) describes the possible best estimation of the real world by the current available technology in real case situations. When I personally write things up, I usually use a measurement operator to make this clear that observations are never able to describe the full reality. How much effort observers might put at it (and they usually do an amazing job), the real physical state of a physical system can only be approximated. Continue reading

Drawing a line between models and observations

In my last post I showed that observations are models as well.  But when this is the case, why do we distinguish between these two kinds of data the way we do? Why is everyone so keen on observations, when they are just another model output?

The reason can be found usually in their different structure. The amount of modelling, which is applied to an observation to still be called observation should usually be very basic. Coming from the atmospheric sciences myself, the border between the two worlds can often be drawn in the type of the data. Generally the observations in that field are point data, often in situ data, which are irregular in time and space. In contrast to this, model data is usually very regular and sometimes high-dimensional.

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All observations are models

Doing statistics between the two worlds of observations and model results lead often to the assumption that both are completely different things. There are the observations, where real people moved into the field, drilled, dug and measured and delivered the pure truth of the world we want to describe. In contrast to this, the clean laboratory of a computer, which takes all our knowledge and creates a virtual world. This world need not necessary have something to do with its real counterpart, but at least it delivers us nice information and visualisation. But this contrast between the dirty observations and the clean models is usually only something, which exists in our heads, in reality they are much more connected to each other.

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