turtlehurricane Posted March 12, 2012 Share Posted March 12, 2012 Who does numerical simulations of hurricanes using student programmers? Probably every institution that simulates hurricanes. How else would people become good programmers in their field. Link to comment Share on other sites More sharing options...
WeatherRusty Posted March 12, 2012 Share Posted March 12, 2012 A simple way to think of chaos is many nonlinear terms feeding back on each other, so if you change one thing the result is something you can't predict to an extent. Climate sensitivity is merely approximating the result of changing one thing in the system, and is derived directly out of an already incorrect climate model. Climate models have no nonlinear terms, period. Nonlinear terms are intractable for numerical models. So it's a very weak first approximation of climate chaos, and I'm sure no one who makes such estimates claims that climate sensitivity values bound true chaos in any way. Yes, equilibrium climate sensitivity is the system's final response to a change of 1.2C in temperature. 1.2C is the Planck Response given at radiative equilibrium by a doubling of CO2. This is therefore the minimum increase in global temperature to be expected according to physics alone. How much higher it goes is a function of climate sensitivity. Link to comment Share on other sites More sharing options...
turtlehurricane Posted March 12, 2012 Share Posted March 12, 2012 Yes, equilibrium climate sensitivity is the system's final response to a change of 1.2C in temperature. 1.2C is the Planck Response given at radiative equilibrium by a doubling of CO2. This is therefore the minimum increase in global temperature to be expected according to physics alone. How much higher it goes is a function of climate sensitivity. This doesn't account for biological activity, man (besides the CO2 part),changes in ocean circulation, nor things like clouds. The net result of the feedbacks can't just be assumed to be +. Link to comment Share on other sites More sharing options...
TerryM Posted March 12, 2012 Share Posted March 12, 2012 How else would people become good programmers in their field. Programming is not black-smithing - we didn't learn in an apprentice program. If anyone is interested, climate simulations, as well as other computer programs, even those that use very rudimentary mathematical structures such as FORTH, regularly and easily handle non-linear equations. Anyone who has done any programming would be aware of this. I'm really beginning to doubt your sincerity. Link to comment Share on other sites More sharing options...
LocoAko Posted March 12, 2012 Share Posted March 12, 2012 Who does numerical simulations of hurricanes using student programmers? At the graduate level, probably everyone. Graduate students, assuming they are RAs, are often part of teams that publish and do real research. I'm a little confused as to why you're confused. I can't speak for TH or his knowledge but this is common. Link to comment Share on other sites More sharing options...
turtlehurricane Posted March 12, 2012 Share Posted March 12, 2012 How else would people become good programmers in their field. Programming is not black-smithing - we didn't learn in an apprentice program. If anyone is interested, climate simulations, as well as other computer programs, even those that use very rudimentary mathematical structures such as FORTH, regularly and easily handle non-linear equations. Anyone who has done any programming would be aware of this. I'm really beginning to doubt your sincerity. You would have a nobel prize if you showed the world your exact solution to non-linear numerical programming. It doesn't exist, there are only approximations. Doubting my sincerity based on me stating a universal truth at this point in time is fairly annoying. Link to comment Share on other sites More sharing options...
Mallow Posted March 12, 2012 Share Posted March 12, 2012 A simple way to think of chaos is many nonlinear terms feeding back on each other, so if you change one thing the result is something you can't predict to an extent. Climate sensitivity is merely approximating the result of changing one thing in the system, and is derived directly out of an already incorrect climate model. Climate models have no nonlinear terms, period. Nonlinear terms are intractable for numerical models. So it's a very weak first approximation of climate chaos, and I'm sure no one who makes such estimates claims that climate sensitivity values bound true chaos in any way. This doesn't make sense. You're arguing on one hand that feedbacks are a source of "nonlinearity", and on the other hand you're talking about "nonlinear terms" in climate models. The former is treating linearity in the context of a response to a forcing, whereas the latter is treating linearity in the context of numerical approximations of physical equations. The two are not interchangeable. You can have a completely "linear" model (in the sense of how the physics is calculated) that still simulates many physical feedbacks and therefore produces nonlinear results. Link to comment Share on other sites More sharing options...
turtlehurricane Posted March 12, 2012 Share Posted March 12, 2012 This doesn't make sense. You're arguing on one hand that feedbacks are a source of "nonlinearity", and on the other hand you're talking about "nonlinear terms" in climate models. The former is treating linearity in the context of a response to a forcing, whereas the latter is treating linearity in the context of numerical approximations of physical equations. The two are not interchangeable. You can have a completely "linear" model (in the sense of how the physics is calculated) that still simulates many physical feedbacks and therefore produces nonlinear results. Weatherusty was talking about climate sensitivity which is generally derived from numerical models. And yes, but the terms are still linear instead of nonlinear. Link to comment Share on other sites More sharing options...
Mallow Posted March 12, 2012 Share Posted March 12, 2012 How else would people become good programmers in their field. Programming is not black-smithing - we didn't learn in an apprentice program. If anyone is interested, climate simulations, as well as other computer programs, even those that use very rudimentary mathematical structures such as FORTH, regularly and easily handle non-linear equations. Anyone who has done any programming would be aware of this. I'm really beginning to doubt your sincerity. I believe Turtle is mostly talking about "linearization", where you separate the variables into mean and perturbation values, assume perturbations are small compared to the mean, and treat the product of perturbations as if it's small enough to ignore. This is done to save computational power, which is not to say it cannot be done without such simplifications... just that it is computationally expensive. Link to comment Share on other sites More sharing options...
turtlehurricane Posted March 12, 2012 Share Posted March 12, 2012 I believe Turtle is mostly talking about "linearization", where you separate the variables into mean and perturbation values, assume perturbations are small compared to the mean, and treat the product of perturbations as if it's small enough to ignore. This is done to save computational power, which is not to say it cannot be done without such simplifications... just that it is computationally expensive. The point remains though that it is simply impossible to have an exact numerical solution for a prognostic model with nonlinear terms. Link to comment Share on other sites More sharing options...
Mallow Posted March 12, 2012 Share Posted March 12, 2012 Weatherusty was talking about climate sensitivity which is generally derived from numerical models. And yes, but the terms are still linear instead of nonlinear. But whether or not the terms in the physical equations are linearized does not impact whether the results can be non-linearly dependent on changes in variable magnitudes. The point is, you can still simulate "nonlinear" results with "linear" equations. In other words, just because equations are linearized does not preclude you from drawing conclusions about climate sensitivity... there's no physical or mathematical basis for such an argument. Link to comment Share on other sites More sharing options...
turtlehurricane Posted March 12, 2012 Share Posted March 12, 2012 But whether or not the terms in the physical equations are linearized does not impact whether the results can be non-linearly dependent on changes in variable magnitudes. The point is, you can still simulate "nonlinear" results with "linear" equations. In other words, just because equations are linearized does not preclude you from drawing conclusions about climate sensitivity... there's no physical or mathematical basis for such an argument. The basis for the argument is that your results are only correct assuming your nonlinear terms are being correctly approximated by the linear terms used instead. Automatically this fails, and who knows by how much. Link to comment Share on other sites More sharing options...
WeatherRusty Posted March 12, 2012 Share Posted March 12, 2012 This doesn't account for biological activity, man (besides the CO2 part),changes in ocean circulation, nor things like clouds. The net result of the feedbacks can't just be assumed to be +. Sure it does. The range given by estimates of climate sensitivity is a measure of all feedbacks. Climate sensitivity is the net of all the feedback you mention and more as determined by past climate change in response to understood perturbations such as the transitions into and out of ice ages in response to orbital cycles, volcanic eruptions such as Mt. Pinatubo, and yes, computer modeling. Link to comment Share on other sites More sharing options...
turtlehurricane Posted March 12, 2012 Share Posted March 12, 2012 Sure it does. The range given by estimates of climate sensitivity is a measure of all feedbacks. Climate sensitivity is the net of all the feedback you mention and more as determined by past climate change in response to understood perturbations such as the transitions into and out of ice ages in response to orbital cycles, volcanic eruptions such as Mt. Pinatubo, and yes, computer modeling. It depends on which model you pulled your number from, and still it is only an approximation. Link to comment Share on other sites More sharing options...
Mallow Posted March 12, 2012 Share Posted March 12, 2012 The point remains though that it is simply impossible to have an exact numerical solution for a prognostic model with nonlinear terms. I don't think I agree with this. From a Lagrangian perspective, your heat equation would not have any nonlinear terms, but from an Eulerian perspective with background flow it would (due to advection). Does the fact that you have used solely geometry to "make" your terms nonlinear mean you can't solve the heat equation exactly now? I could be off base here, so I hope someone will correct me if I'm wrong. Link to comment Share on other sites More sharing options...
Mallow Posted March 12, 2012 Share Posted March 12, 2012 The basis for the argument is that your results are only correct assuming your nonlinear terms are being correctly approximated by the linear terms used instead. Automatically this fails, and who knows by how much. That's what scale analysis is for. It's pretty clear that the order of magnitude of the nonlinear terms is much smaller than the order of magnitude of the linear terms. And that's why I brought up chaos earlier. In the weather world, these tiny, essentially random "errors" will cause solutions at any given time down the line to diverge greatly, due to the chaotic nature of atmospheric eddies and smaller-scale features. In the climate world, that's not the case, since you're interested in looking at long-term trends (which are not influenced by the placement of an eddy at time t) rather than instantaneous values (which are). Link to comment Share on other sites More sharing options...
TerryM Posted March 12, 2012 Share Posted March 12, 2012 I believe Turtle is mostly talking about "linearization", where you separate the variables into mean and perturbation values, assume perturbations are small compared to the mean, and treat the product of perturbations as if it's small enough to ignore. This is done to save computational power, which is not to say it cannot be done without such simplifications... just that it is computationally expensive. I assume TH is attempting to refer to equations requiring a finite # of iterations to approximate a result. I thought it was interesting that he never mentioned imaginary numbers (basis of chaos), nor did he distinguish highly iterated instances from nonlinearities such as 2nd degree polynomials whose solutions are sophomoric. To claim that climate models don't use anything but linearity is belied every time one sees a graph with a curved line. Link to comment Share on other sites More sharing options...
WeatherRusty Posted March 12, 2012 Share Posted March 12, 2012 Climate sensitivity is determined by various means, not just models. Climate sensitivity from models The first estimates of climate sensitivity came from climate models. In the 1979 Charney report, two models from Suki Manabe and Jim Hansen estimated a sensitivity range between 1.5 to 4.5°C. Forest 2002 uses a fingerprinting approach on modern temperature records and finds a range 1.4 to 7.7°C. Knutti 2005 uses modelling (entering different sensitivities then comparing to seasonal responses) to find a climate sensitivity range 1.5 to 6.5°C - with 3 to 3.5 most likely Hegerl 2006 looks at paleontological data over the past 6 centuries to calculates a range 1.5 to 6.2°C. Annan 2006 combines results from a variety of independent methods to narrow climate sensitivity to around 2.5 to 3.5°C. Royer 2007 examines temperature response to CO2 over the past 420 million years and determines climate sensitivity cannot be lower than 1.5°C (with a best fit of 2.8°C). Climate sensitivity from empirical observations There have been a number of studies that calculate climate sensitivity directly from empirical observations, independent of models. Lorius 1990 examined Vostok ice core data and calculates a range of 3 to 4°C. Hoffert 1992 reconstructs two paleoclimate records (one colder, one warmer) to yield a range 1.4 to 3.2°C. Hansen 1993 looks at the last 20,000 years when the last ice age ended and empirically calculates a climate sensitivity of 3 ± 1°C. Gregory 2002 used observations of ocean heat uptake to calculate a minimum climate sensitivity of 1.5. Chylek 2007 examines the period from the Last Glacial Maximum to Holocene transition. They calculate a climate sensitivy range of 1.3°C and 2.3°C. Tung 2007 performs statistical analysis on 20th century temperature response to the solar cycle to calculate a range 2.3 to 4.1°C. Bender 2010 looks at the climate response to the 1991 Mount Pinatubo eruption to constrain climate sensitivity to 1.7 to 4.1°C. Link to comment Share on other sites More sharing options...
Nic Posted March 12, 2012 Share Posted March 12, 2012 http://www.ucar.edu/news/releases/2009/images/temps_2.jpg I do not like that chart he used in the article at all. He fails to acknowledge that some of the decreased cold records are increased warm records could be due to UHI especially around airports where a lot of the thermometers are, air traffic has increased and huge asphalt runways are built around the thermometer. Airport measurements cannot be that accurate there are airplanes flying around everywhere with exhaust. http://wattsupwiththat.com/2011/07/17/see-temps-rise-at-sea-tac/ http://wattsupwiththat.com/2010/07/07/new-temperature-record-at-bwi-atmospheric-or-asphaltic Link to comment Share on other sites More sharing options...
turtlehurricane Posted March 12, 2012 Share Posted March 12, 2012 I don't think I agree with this. From a Lagrangian perspective, your heat equation would not have any nonlinear terms, but from an Eulerian perspective with background flow it would (due to advection). Does the fact that you have used solely geometry to "make" your terms nonlinear mean you can't solve the heat equation exactly now? I could be off base here, so I hope someone will correct me if I'm wrong. Removing advection is removing the nonlinear term in that case. Do some research on this, I am 100% sure that nonlinear terms are mathematically intractable in numerical models. Link to comment Share on other sites More sharing options...
PhillipS Posted March 12, 2012 Share Posted March 12, 2012 http://www.ucar.edu/...ges/temps_2.jpg I do not like that chart he used in the article at all. He fails to acknowledge that some of the decreased cold records are increased warm records could be due to UHI especially around airports where a lot of the thermometers are, air traffic has increased and huge asphalt runways are built around the thermometer. Airport measurements cannot be that accurate there are airplanes flying around everywhere with exhaust. http://wattsupwithth...ise-at-sea-tac/ http://wattsupwithth...ic-or-asphaltic As you may have heard, the urban temperature records are adjusted for the heat island effect. The BEST project found that rural stations are actually indicating a slightly higher temperature trend - so airport temperatures are reliable. Believe it or not, the staff who take temperature measurements aren't stupid and they know how to do their jobs. You need to grasp a better strawman argument - the UHI one has been thoroughly debunked, and even Watts said he would accept the BEST project results. If you refuse to accept the validity of AGW, that's your perogative. But don't try to rationalize your denialism by blaming airplane exhausts. Link to comment Share on other sites More sharing options...
Nic Posted March 12, 2012 Share Posted March 12, 2012 As you may have heard, the urban temperature records are adjusted for the heat island effect. The BEST project found that rural stations are actually indicating a slightly higher temperature trend - so airport temperatures are reliable. Believe it or not, the staff who take temperature measurements aren't stupid and they know how to do their jobs. You need to grasp a better strawman argument - the UHI one has been thoroughly debunked, and even Watts said he would accept the BEST project results. If you refuse to accept the validity of AGW, that's your perogative. But don't try to rationalize your denialism by blaming airplane exhausts. I was just saying that it could have some effect, I was unaware of the BEST project but I am glad someone did it. I am not trying to deny a whole theory with that argument that would be just plain ridiculous. I am just questioning everything before I believe it. Link to comment Share on other sites More sharing options...
WEATHER53 Posted March 13, 2012 Share Posted March 13, 2012 I wonder if it is not a error to have so many values takes from cities that have gotten a lot bigger, more built up and populated over last 40 years. I wonder if tempertaures taken in a deep forest would be nearly as much higher in the same time period. Link to comment Share on other sites More sharing options...
PhillipS Posted March 13, 2012 Share Posted March 13, 2012 I was just saying that it could have some effect, I was unaware of the BEST project but I am glad someone did it. I am not trying to deny a whole theory with that argument that would be just plain ridiculous. I am just questioning everything before I believe it. I apologize if I responded too strongly - but your posting a repeatedly debunked theme (UHIs), and backing it up with, not one, but two links to WUWT gave you every appearance of being a denialist troll. WUWT is a flatly denialist site with no pretensions of being neutral. It is to science websites what Fox News is to serious investigative journalism. If you truly want to learn more about AGW there are many better sites to go to than WUWT. Or you can always use google scholar and look for recent peer-reviewed papers on whatever aspect of climate change you're wondering about. Link to comment Share on other sites More sharing options...
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