Comment by nabla9 | Hacker News Reader

Comment by nabla9 | Hacker News Reader

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>This profound mathematical understanding seems to be broadly lacking, and it makes people grant wildly excessive credence to unverified models.

3d General circulation models and basic energy balance models are verified against range of temperatures, pressures, and atmospheric conditions in the Earth, Mars, Jupiter and Venus. The same model used for exoplanets is used to model paleo-Mars, paleo-Venus, and Titan. If the model is somehow completely wrong outside known limits, so is the parent model that is used in the Earth Climate change studies. The models work just fine at this level of required accuracy. You put parameters that describe the Earth, Mars or Venus into the and you get good description of atmosphere and climate in Venus and Mars that matches observations.

We don't have to model specific planets to get interesting information. In generally the interest is to model different categories of the planets and discover how their environments vary when we vary the parameters. It's possible to say something generic about tidally locked planets and their climate. This is what these simulations do.

GISS modelE GCM https://www.giss.nasa.gov/tools/modelE/

ROCKE-3D version of GISS modelE GCM https://www.giss.nasa.gov/projects/astrobio/

Thank you for providing these links. Some people, especially on HN, seem to be surprised how far GCM modeling for exoplanets has gone.

Besides the examples you mention, research groups are now doing data assimilation for Mars (https://www2.physics.ox.ac.uk/research/geophysical-fluid-dyn...; https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/201...).

Other groups are testing and improving models for Jupiter and Saturn, as you mention, based on various remote sensing observations. (For Saturn, see: https://theoryofclimate.sciencesconf.org/conference/theoryof...).

All of these cases have allowed modelers to observationally test their models and model physics against non-Earth conditions. This work has been going on for a decade now, but it somehow has not reached the technically-aware audience.

The case of tidally-locked planets is another step beyond the above solar-system planets. Thank you for the references you supplied, in your original comment, on GCMs for this case.

I think Jerf's point is that for systems that complex, it is more sane to expect that we will be off by a lot. Remember that weather casting is frequently wrong in your own city.

I enjoy modeling, and I think it's useful, interesting as well as respectable work. But a little humility would in science is always a good things.

I don't think this is a good take. Firstly, we're discussing climate, not weather, which is easier to predict than chaotic swirling fluids. Secondly, if we were basing a practical decision off this information, then we should apply some kind of higher threshold, but this research is essentially a discussion piece and it seems pretty plausible that this might be the case on some worlds.

Regardless, it's more useful to point to particular areas of uncertainty than to point to a general miasma of uncertainty around climate modeling as though nothing can be learned. It doesn't really move any conversations forward.

Weather forecasting (short term details) may be wrong, but climate modeling (long term trends) is generally correct.

Just because we can't predict when an individual hurricane will occur doesn't mean that we can't predict "hurricane season".

Climate modelling on Earth generally refers to the scale of tens or hundreds of years, not to billions of years. Our climate model for the next few billion years is essentially "Eventually the sun will turn into a red giant". And we live here.

edit: Apparently it's not even certain whether the Sun will engulf the Earth or not!

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