onsdag 29 juli 2009
Global Climate Modeling: Fate of Humanity?
Policies to control climate change must be based on global climate models which are mathematical models of the circulation of the atmosphere and the ocean of our planet in the form of the Navier-Stokes equations of fluid flow plus thermodynamics with various energy sources, referred to as General Circulation Models GCM.
Recently G8-leaders have decided to put a limit to global warming of 2C.
The key question is the reliability/accuracy GCM. Since GCM is based on computational solution of the Navier-Stokes equations, also referred to as Computational Fluid Dynamics CFD, it is of interest to investigate what is state-of-the-art of CFD.
The areodynamics of flight is governed by the Navier-Stokes equations, and one may ask if today CFD allows computational modeling of the take-off of a jumbo-jet, for example. The answer is a disappointing NO: We have to wait 50 years before computers are powerful enough! Says the state-of-the-art expert Parviz Moin.
Of course you ask: If we cannot computationally model the flight of an airplane, how can we expect to model the immensely much more complicated system of the the global climate?
Or maybe more is possible than what state-of-the-art says, see Fear of Flying and Why It Is Possible to Fly.
Maybe it is possible to predict global climate with better Navier-Stokes solvers, which can be used today on existing computers. Waiting 50 years for the predictions may not be very meaningful, like waiting one week to get the prediction of tomorrows weather.
As concerns the state-of-the-art of CFD and fluid mechanics in general, see the Interview with Editors of Journal of Fluid Mechanics JFM.
Since the fate of humanity critically depends on the reliability and accuracy of computational global climate modeling, it would seem that no efforts should be spared to bring forward the best possible competence in this area. It does not seem to be represented by JFM, which poses a serious problem since JFM is supposed to be the leading journal of fluid mechanics. What can be done? But who cares? Do you?