And a follow up on the follow up to briefly note that we used a very simple model predictive control (i.e. relying on a simple dynamic model to make an initial estimate of the needed radiative forcing that can subsequently be corrected with feedback) in the paper Ken mentioned yesterday. (The focus of that paper was to introduce the idea that the goal of a geoengineering deployment need not be to keep things constant, but potentially just to slow the rate of change… to do so we used feedback and MPC to track a desired trajectory, though we didn’t use the MPC terminology.)
I think we’re gradually making small progress as a community on treating this as a design problem rather than turning down the sun and noting what happens, that is, we get to choose how much (solar) geoengineering to do and how to distribute that in space, in order to focus on particular objectives such as maintaining Arctic sea ice. doug From: [email protected] [mailto:[email protected]] On Behalf Of Ben Kravitz Sent: Thursday, February 05, 2015 11:42 AM To: [email protected] Subject: [geo] Re: Assessing the controllability of Arctic sea ice extent by sulfate aerosol geoengineering Hi everyone - Just to follow up on Ken's reply, there has actually been quite a bit of work on this topic (papers attached): D. G. MacMartin, B. Kravitz, D. W. Keith, and A. Jarvis (2014), Dynamics of the coupled human-climate system resulting from closed-loop control of solar geoengineering, Climate Dynamics, 43, 243-258, doi:10.1007/s00382-013-1822-9. B. Kravitz, D. G. MacMartin, D. T. Leedal, P. J. Rasch, and A. J. Jarvis (2014), Explicit feedback and the management of uncertainty in meeting climate objectives with solar geoengineering, Environmental Research Letters, 9, 044006, doi:10.1088/1748-9326/9/4/044006. S. R. Weller and B. P. Schulz, Geoengineering via solar radiation management as a feedback control problem: Controller design for disturbance rejection. (I think this is a white paper, but if someone finds a better citation, please correct me.) I think there is a lot of potential for using control theory in geoengineering research, or in basic climate research for that matter. I would consider this a wide open field right now. Putting controllers in climate models can be applied to many different variables to achieve many different climate goals. In the attached MacMartin et al. and Kravitz et al., we applied simple proportional-integral control (explained in more detail in the two papers), where we used information from past years to calibrate the response of geoengineering. In the Weller and Schulz paper, they used a different method of control to do something similar. What I really like about Jackson et al. is that they used model predictive control - instead of just using information from past years, they also ran a simple predictive model after every year and used that information to guide their controller as well. As Andrew said, a very clever approach. The important thing to note in these papers is the use of two separate models: a control design model and a real world proxy. This mimics how control on SRM might actually work in the real world (assuming such a thing were actually doable in the real world and that SRM would work in a similar way to how the models say it would). One would effectively get as many climate model simulations as one wanted, but there is only one Earth, so it's very important to "get it right" in the real world proxy the first time. Best, Ben -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout.
