Dear Alistair and others, Apart from the vagaries of turbulence at the trailing edge of airfoils, half full pots on the water on the stove and river flows?
Perhaps it is a metaphor. Water can’t get out of the gravity well unless you add energy on the stove top and it bounces out? Airplanes need laminar flow at the leading edge to fly and that’s why it is important not to walk all over the wing? But a metaphor for what? I know that global warming is involved somewhere but I can’t quite make the connection. I did quote the passage from Tim Palmer – although I assumed it was newer. You know what they say about assumptions. See Palmer’s newer proposal for stochastic models using observable PDF’s. Probably a better approach but I wonder if there is enough data for PDF”S for all possible phase spaces? Chaotic planets? ‘Although the numerical simulations all indicate chaos in planetary orbits, in a qualitative sense the planetary orbits are stable—because the planets remain near their present orbits—over the lifetime of the sun. However, the presence of chaos implies that there is a finite limit to how accurately the positions of the planets can be predicted over long times. Of all of the planets, Mercury's orbit appears to exhibit changes of the largest magnitude in orbital eccentricity and inclination. Fortunately, effects on its surface climate system through solar insolation variation, are found also to be small.’ http://www.pnas.org/content/98/22/12342.full So climate is chaotic and is therefore theoretically determinant. I’m sure I said that. I also said the weight of scientific opinion – not simply Palmer, but Hurrell, the NRC Committee on Abrupt Climate Change, the IPCC, Tsonis, Broecker, McWilliams (quoted below) amongst those I have mentioned and quoted – I could list many more. I know the explanation given at realclimate: the ‘climate of a model can be easily defined in terms of the limit of the statistics of the model output as the integration time tends to infinity, under prescribed boundary conditions. This limit is well-defined for all climate models. However, the real world is slightly messier to deal with. The real climate system varies on all time scales, from daily weather, through annual, multi-year and decadal (ENSO), Milankovitch, glacial-interglacial cycles, plate tectonics and continental configurations, right up to the ultimate death of the Sun. The average temperature, and all other details of the climate system, will vary substantially depending on the time scale used. So how can we talk meaningfully about “the climate” and “climate change”? Well, although there are interesting scientific questions to ask across all the different time scales, the directly policy-relevant portion is on the multi-decadal and centennial time scale. It is quite clear that the pertubation that we are currently imposing is already large, and will be substantially larger, by up to an order of magnitude, than any plausible natural variability over this time scale. So for the policy- relevant issues, we generally focus on the physical atmosphere-ocean system, sometimes with coupled carbon-vegetation system, and treat the major ice sheets, orbital parameters and planetary topography (and I might add solar irradiance - RIE) as fixed boundary conditions. It’s an approximation, but a pretty good one.’ There are fundamental problems with cloud parameters (see Palle at the BBSO in the link provided), in the solar boundary constraint (solar irradiance in the models is either constant or flucuates in 11 years cycles around a constant mean - solar activity peaked last century in a thousand year high) and in tuning. The latter in that there is another process adding to the temperature rise between 1976 and 1998. That is - much of the warming was from ocean processes (eg Swanson and Tsonis, Latif) that are probably related to cloud changes. There are fundamental problems with idea of slow evolution of climate over this century – eg Tsonis shows the potential for abrupt climate shift at decadal timescales - the NRC gives examples of abrupt change at decadal scales. Here’s another view of the problem – perhaps one that is a little more nuanced, is peer reviewed and is less of an undergraduate level blog. ‘Sensitive dependence and structural instability are humbling twin properties for chaotic dynamical systems, indicating limits about which kinds of questions are theoretically answerable. They echo other famous limitations on scientist’s expectations, namely the undecidability of some propsitions within axiomatic mathematical systems (Godel’s theorem) and the uncomputability of some algorithms due to excessive size of the calculation.’ http://www.pnas.org/content/104/21/8709.full.pdf+html Although there are climate models their veracity has not been demonstrated – they are best described as plausible. The only reasonable confirmation is in comparison with an untuned reality. It's not looking real good at the moment. You guys are just making things up as you go. To what purpose? I wan't to learn - I wan't real discussion and debate - not this play school stuff. Research - show me the science - don't bother me with glib trivialities. Cheers Robert On Feb 1, 7:32 am, Alastair <[email protected]> wrote: > On Jan 31, 4:19 am, Robert Indigo Ellison > > <[email protected]> wrote: > >http://www.newscientist.com/article/mg12416903.900-a-weather-eye-on-u... > > Thanks for that link, but it is a bit out of date - 1988. > > > The changing story – from ‘weather averages’ to determining ‘the shape > > and position of the whole climate attractor’. The latter is the > > average strange climate attractor maybe? I'm amused but I don’t like > > his chances considering that weather models become wildly inaccurate > > after 7 days at most. This article is a bit of a scramble - similar > > to Hurrels blurb - to preserve jobs, funds and face in unanticipated > > chaos. > > Weather averages describe the orbits of the strange attractor. If it > alters, then you get new averages and a climate change. > > > You guys ready to give in yet and admit that climate is chaotic? > > Because really the weight of scientific opinion is against you. > > Tim Palmer is not scientific opinion. Gavin Schmidt takes the opposite > view. But IMHO Tim not Gavin is correct. > > If climate is chaotic then it is deterministic, so we can predict what > will happen, but not with the precision of weather. But we do not > need that precision for climate. We don't need to know what the > weather in London will be in four days time. We need to know what the > climate will be in Europe in 10/100 years time. > > The orbits of the planets are chaotic, but we can still predict there > positions a hundred years hence. > > Cheers, Alastair. -- You received this message because you are subscribed to the Google Groups Global Change ("globalchange") newsgroup. Global Change is a public, moderated venue for discussion of science, technology, economics and policy dimensions of global environmental change. Posts will be admitted to the list if and only if any moderator finds the submission to be constructive and/or interesting, on topic, and not gratuitously rude. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/globalchange
