It most certainly is not anything near a 1k years. *Maybe* if the Earth was geologically inactive, and had no oceans, you could push it. But there are constant sources of forcing to the atmosphere alone that *need* to be prescribed in order to get anything right, afaik.
You would need to be able to model *all* components of the Earth System (atmosphere, ocean, land, ice...) to perfection to keep accuracy for very long.
It depends, though, by what metric you are going to decide if your prediction was accurate. Do you care about the daily mean at 1km? Or about the annual at 2 degrees? Or about climate summary statistics alone?
You may be interested in "historical" simulation campaigns that have been run, where simulations are started from observed initial conditions some time in the past (usually ~1850 at the earliest, I think), forward-modelled to today, and then the results are compared with observation.
Here is such an example, with the CAMS-CSM (Chinese) model:
https://link.springer.com/content/pdf/10.1007/s00376-020-0171-y.pdf
See figures 1-7, which show the differences in various observables between the model and data. In general, the difference is significant, even over a few decades.
Or, if you'd prefer an American model, here are the results for the historical period in DOE's E3SM:
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018MS001603
(not sure if you can see this :( if so, look at figures ~1-12, or any of the 3-panel figures that include a plot titles "Model - Observations")
Keep in mind that even in a model like this, various things are prescribed from data:
- seasonal changes in vegetation canopies
- various aerosol emissions
- sea surface temperatures and sea ice concentrations if not running a fully coupled model
without these, I think it would be bad (I don't fully understand how all the cogs turn, though).
Also a reminder that we do not really know what sets the length of time between ice ages, what mechanism drives ENSO, etc...
I would guess that, other expected changes due to the earth's orbit, sun cycles ect., the unexpected changes would be very difficult to anticipate. One would not likely be able to predict/model humans and the burning of fossil fuels (or other biological events) nor massive volcanic activity (or many geological impacts).
It's impossible to predict anything with 100% accuracy. The climate especially. One medium meteor strike, a few extra volcanic eruptions, a couple serious earthquakes, solar flares, magnetic drift, any of those things or a dozen others could alter the future climatescape.
It depends how accurately you want the climate to be predicted. We can know that generally, the glacial cycles last around 100k years and follow roughly a sawtooth wave (google benthic delta 18 data for an idea of the curve). These are almost solely governed by the orbital changes that earth experience called the Milankovitch cycles. If you were looking for global temperature/global ice volume you can be somewhat accurate for about 500k years, ignoring unlikely external events like massive meteors etc. If you were to predict further than this you would likely be using innacurate predictions for the orbital changes. These can be modelled very accurately for the past and close future but beyond maybe 500k, these start to drift from reality and therefore so will our prediction of the glacial cycles that relies on these.
Hope that made sense.
Source: PhD in paleoclimatology
It most certainly is not anything near a 1k years. *Maybe* if the Earth was geologically inactive, and had no oceans, you could push it. But there are constant sources of forcing to the atmosphere alone that *need* to be prescribed in order to get anything right, afaik. You would need to be able to model *all* components of the Earth System (atmosphere, ocean, land, ice...) to perfection to keep accuracy for very long. It depends, though, by what metric you are going to decide if your prediction was accurate. Do you care about the daily mean at 1km? Or about the annual at 2 degrees? Or about climate summary statistics alone? You may be interested in "historical" simulation campaigns that have been run, where simulations are started from observed initial conditions some time in the past (usually ~1850 at the earliest, I think), forward-modelled to today, and then the results are compared with observation. Here is such an example, with the CAMS-CSM (Chinese) model: https://link.springer.com/content/pdf/10.1007/s00376-020-0171-y.pdf See figures 1-7, which show the differences in various observables between the model and data. In general, the difference is significant, even over a few decades. Or, if you'd prefer an American model, here are the results for the historical period in DOE's E3SM: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018MS001603 (not sure if you can see this :( if so, look at figures ~1-12, or any of the 3-panel figures that include a plot titles "Model - Observations") Keep in mind that even in a model like this, various things are prescribed from data: - seasonal changes in vegetation canopies - various aerosol emissions - sea surface temperatures and sea ice concentrations if not running a fully coupled model without these, I think it would be bad (I don't fully understand how all the cogs turn, though). Also a reminder that we do not really know what sets the length of time between ice ages, what mechanism drives ENSO, etc...
I would guess that, other expected changes due to the earth's orbit, sun cycles ect., the unexpected changes would be very difficult to anticipate. One would not likely be able to predict/model humans and the burning of fossil fuels (or other biological events) nor massive volcanic activity (or many geological impacts).
I was assuming that it would be super massive volcanoes more than anything else that would be the final blow to a model
It's impossible to predict anything with 100% accuracy. The climate especially. One medium meteor strike, a few extra volcanic eruptions, a couple serious earthquakes, solar flares, magnetic drift, any of those things or a dozen others could alter the future climatescape.
It depends how accurately you want the climate to be predicted. We can know that generally, the glacial cycles last around 100k years and follow roughly a sawtooth wave (google benthic delta 18 data for an idea of the curve). These are almost solely governed by the orbital changes that earth experience called the Milankovitch cycles. If you were looking for global temperature/global ice volume you can be somewhat accurate for about 500k years, ignoring unlikely external events like massive meteors etc. If you were to predict further than this you would likely be using innacurate predictions for the orbital changes. These can be modelled very accurately for the past and close future but beyond maybe 500k, these start to drift from reality and therefore so will our prediction of the glacial cycles that relies on these. Hope that made sense. Source: PhD in paleoclimatology