And a link to the referenced paper: http://link.springer.com/article/10.1007%2Fs00382-013-1761-5
"Until now, climate model intercomparison has focused primarily on annual and global averages of various quantities or on specific components, not on how well the general dynamics in the models compare to each other. In order to address how well models agree when it comes to the dynamics they generate, we have adopted a new approach based on climate networks. We have considered 28 pre-industrial control runs as well as 70 20th-century forced runs from 23 climate models and have constructed networks for the 500 hPa, surface air temperature (SAT), sea level pressure (SLP), and precipitation fields for each run. We then employed a widely used algorithm to derive the community structure in these networks. Communities separate “nodes” in the network sharing similar dynamics. It has been shown that these communities, or sub-systems, in the climate system are associated with major climate modes and physics of the atmosphere (Tsonis AA, Swanson KL, Wang G, J Clim 21: 2990–3001 in 2008; Tsonis AA, Wang G, Swanson KL, Rodrigues F, da Fontura Costa L, Clim Dyn, 37: 933–940 in 2011; Steinhaeuser K, Ganguly AR, Chawla NV, Clim Dyn 39: 889–895 in 2012). Once the community structure for all runs is derived, we use a pattern matching statistic to obtain a measure of how well any two models agree with each other. We find that, with the possible exception of the 500 hPa field, consistency for the SAT, SLP, and precipitation fields is questionable. More importantly, none of the models comes close to the community structure of the actual observations (reality). This is a significant finding especially for the temperature and precipitation fields, as these are the fields widely used to produce future projections in time and in space." Best wishes, Simon ________________________________________________ Simon Driscoll Atmospheric, Oceanic and Planetary Physics Department of Physics University of Oxford Office: +44 (0) 1865 272930 Mobile: +44 (0) 7935314940 http://www2.physics.ox.ac.uk/contacts/people/driscoll ________________________________ From: [email protected] [[email protected]] on behalf of Simon Driscoll [[email protected]] Sent: 01 August 2013 19:06 To: [email protected] Subject: [geo] Geoengineering carries unknown consequences The physicists out there may have already seen this short article: http://www.physicstoday.org/resource/1/phtoad/v66/i8/p8_s3 (also copied down below) which may be of interest to group members. Best wishes, Simon +++ I read with interest David Kramer’s piece on geoengineering (Physics Today, February 2013, page 17<http://dx.doi.org/10.1063/PT.3.1878>). I must say, I am more alarmed by what the geoengineers in his report are proposing than by the climate changes that are taking place. I believe geoengineers are removed from scientific reality. They ignore the fact that the climate system and its components—clouds, hurricanes, and so forth—are highly nonlinear and thus very sensitive to the initial conditions and to changes in the parameters. Nevertheless, one could study the system’s response in a probabilistic way when certain parameters are changed or when we introduce fluctuations, if the relationships among all the components are known exactly. And here lies the whole problem with geoengineering. The formulation of the climate system and its components is only approximately known. More than 30 climate models are floating around in the climate community, and their predictions about general dynamics simply don’t agree with each other. In a recent publication,1<http://www.physicstoday.org/resource/1/phtoad/v66/i8/p8_s3#c1> we considered 98 control and forced climate simulations from 23 climate models and examined their similarity in four different fields (upper-level flow, sea-level pressure, surface air temperature, and precipitation). We found that except for the upper-level flow, the agreement between the models is not good. Moreover, none of the models compares well with actual observations. One person in the Physics Today story said that geoengineering may result in changes in various weather patterns, but nobody knows what the changes are going to be and how they will affect the climate system. If the warming in the Arctic is a big event to mitigate, then it will require a significant “geoengineering” effort. To me, that means significant changes will occur elsewhere. Who can say whether those changes will be less serious than those taking place now? How can geoengineers talk about modifying clouds and albedo when clouds are represented in the climate models as mostly linear parameterizations? Kramer’s report did not mention hurricanes, but geoengineers also propose to dissipate them. Hurricanes are unique in the climate system because they represent major self-organization. As physicists well know, self-organization occurs in dissipative systems in which energy is not conserved but instead is exchanged with the environment. Hurricanes involve huge amounts of energy. Scientists have little idea how the atmosphere and the ocean will be affected if that energy is not allowed to be exchanged. I would not have a problem with geoengineering if the physics and dynamics of the climate system were well known. Climate scientists have a good idea of the large-scale flow of ocean currents, but detailed measurements are not available. They know the basic physics of cloud formation and its thermodynamics but do not fully understand detailed cloud microphysics or the complex connections between climate and ecosystems. And with complex nonlinear systems, details are important. So we need to make an effort to improve our understanding of our climate system and its components before we try to operate on it. We can engineer a car or a plane because we know the underlying physics of motion, combustion, and flight, and we understand the role of every component. Can geoengineers say the same about climate? ________________________________________________ Simon Driscoll Atmospheric, Oceanic and Planetary Physics Department of Physics University of Oxford Office: +44 (0) 1865 272930 Mobile: +44 (0) 7935314940 http://www2.physics.ox.ac.uk/contacts/people/driscoll -- 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/groups/opt_out. -- 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/groups/opt_out.
