Friday, March 27, 2009

In closing??


(As part of Rabett Run's Gerlich and Tscheuschner project, Eli has started drafting parts of a response, which we will gift wrap in Bozo paper and send to some unsuspecting journal, but certainly arXiv. This comes again from Chris Colose Way to go Chris. The Editorial Board expresses its thanks=:> Suggestions for changes and additions are welcome. It's a nice summary of the state of climate modeling. Perhaps this would go well in the Conclusion, or should it go in the Introduction)


FW?IW the idiocy du jour is that thermal energy is not heat. Thermal energy is heat. Joule showed that about 150 years ago


GCM’s are often referred to as General Circulation Models, which replicate from first principles the statistical description of the large-scale motions of the atmosphere and ocean. In modern times, where circulation is only one component in modeling exercises, GCM’s are more broadly defined as Global Climate Models.

Climate models range in complexity from basic energy-balance models where solutions can be worked out by hand, to very sophisticated models that make use of some of the fastest and most powerful computers available. There is a broad range of physics and parameterizations included in GCM’s. Processes must conserve energy, momentum, and mass for example. Most GCM’s make use of primitive equations (USCCP 2008) which is a simplified form of the equations of motion. Use is made of the fact that the atmosphere is thin in comparison to its horizontal extent. Small terms in the momentum equations are generally neglected.

Modern GCM’s have evolved tremendously over the decades following increased computing power and our understanding of the processes relevant to global climate. Improvements include increases in atmospheric resolution, height of the model top, sea ice dynamics, representation of atmospheric chemistry, improved cloud microphysical schemes, modeling of the terrestrial biosphere and vegetation interactions with climate, among other things (Schmidt et al 2006; Randall et al 2007). Many realistic factors of global climate emerge from the fundamental physics including ocean and atmospheric “modes” and oscillations, displacement of storm tracks and jet streams, heat transport mechanisms, and climate feedbacks as a response to warming (USCCP 2008). How well a model performs depends on what climate variable you are interested in (e.g., temperature, precipitation, sea level rise, humidity patterns), the statistics (e.g., trends, extremes, variability), as well as the spatial and temporal scales of interest (Knutti 2008a). Further, various models perform better for different questions than other models. Perhaps if Gerlich and Tscheuschner (2009) made their model criticisms too specific, they know it would be that much easier to invalidate.

Detection involves the processes whereby a change in climate can be identified against the background noise of natural variability, and Attribution allows one to assign causes to that change with some level of confidence. The ability to hindcast the time-evolution of the 20th century climate change (e.g. Meehl et al 2004) as well as realistically past climates (e.g. the Last Glacial Maximum) with standard radiative forcing and feedback concepts gives confidence in our understanding of the essential features governing global climate (Randall et al 2007; USCCP 2008). For example, the NASA GISS climate model was used to make a prediction of the global cooling that followed the 1991 Mt. Pinatubo volcanic eruption (Hansen et al 1992). The predicted global cooling as well as the recovery back to the ongoing global warming was well simulated. Successful climate prediction involves understanding how radiative transfer is affected with changes in the solar luminosity, planetary albedo, or changes in atmospheric chemistry. This is because the radiative balance of the planet serves to define the basic boundary conditions which constrain the global climate.

However, formal attribution involves comparing spatio-temporal patterns between observations and models, not the ability to simulate the amplitude of temperature change to a set of forcings (Knutti 2008b). There are many “fingerprints” of greenhouse-gas induced warming which include corresponding changes in the emission spectrum of longwave radiation (Harries et al 2001), stratospheric cooling, and decreases in the diurnal temperature gradient. These things have been both modeled and observed (Hegerl et al 2007). Anthropogenic causation as been detected in the world’s ocean heat content trends (Barnett et al 2001), atmospheric moisture content (Santer et al 2007), in the world’s biosphere (Rosenzweig et al 2008) and continues to provide a more consistent explanation of continental to global scale climate change than natural forcing alone. Despite their assertions, Gerlich and Tscheuschner (2009) have failed to show that this science is incorrect or in contradiction to known physics.

Barnett, T. P., Pierce, D. W., and Schnur, R., 2001: Detection of anthropogenic climate change in the world's oceans, Science , 292, 270-274

Climate Models: An Assessment of Strengths and Limitations. A Report by the U.S. Climate Change Science Program, [Kunkel, K.E., Miller, R.L, Tokmakian, R.T., Zhang, M.H., (Authors)]. U.S. Department of Energy, Washington DC, USA

Hansen, J., A. Lacis, R. Ruedy, and Mki. Sato, 1992: Potential climate impact of Mount Pinatubo eruption. Geophys. Res. Lett., 19, 215-218, doi:10.1029/91GL02788

Harries, J. E., H. E. Brindley, P. J. Sagoo, and R. J. Bantges, 2001: Increases in greenhouse forcing inferred from the outgoing longwave radiation spectra of the Earth in 1970 and 1997. Nature, 410, 355-357

Hegerl, G.C., F. W. Zwiers, P. Braconnot, N.P. Gillett, Y. Luo, J.A. Marengo Orsini, N. Nicholls, J.E. Penner and P.A. Stott, 2007: Understanding and Attributing Climate Change. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA

Knutti, R., 2008: Should we believe model predictions of future climate change? Triennial Issue Earth Science of Philosophical Transactions of the Royal Society A, 366, 4647-4664

Knutti, R., 2008: Why are climate models reproducing the observed global surface warming so well? Geophysical Research Letters, 35, L18704, doi:10.1029/2008GL034932

Meehl, G.A., W.M. Washington, C.M. Ammann, J.M. Arblaster, T.M.L. Wigley and C. Tebaldi, 2004: Combinations of Natural and Anthropogenic Forcings in Twentieth-Century Climate. J. Climate, 17, 3721-3727

Randall, D.A., R.A. Wood, S. Bony, R. Colman, T. Fichefet, J. Fyfe, V. Kattsov, A. Pitman, J. Shukla, J. Srinivasan, R.J. Stouffer, A. Sumi and K.E. Taylor, 2007: Climate Models and Their Evaluation. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA

Schmidt, G.A., R. Ruedy, J.E. Hansen, I. Aleinov, N. Bell, M. Bauer, S. Bauer, B. Cairns, V. Canuto, Y. Cheng, A. Del Genio, G. Faluvegi, A.D. Friend, T.M. Hall, Y. Hu, M. Kelley, N.Y. Kiang, D. Koch, A.A. Lacis, J. Lerner, K.K. Lo, R.L. Miller, L. Nazarenko, V. Oinas, Ja. Perlwitz, Ju. Perlwitz, D. Rind, A. Romanou, G.L. Rosenzweig, C., D. Karoly, M. Vicarelli, P. Neofotis, Q. Wu, G. Casassa, A. Menzel, T.L. Root, N. Estrella, B. Seguin, P. Tryjanowski, C. Liu, S. Rawlins, and A. Imeson, 2008: Attributing physical and biological impacts to anthropogenic climate change. Nature, 453, 353-357

Russell, Mki. Sato, D.T. Shindell, P.H. Stone, S. Sun, N. Tausnev, D. Thresher, and M.-S. Yao, 2006: Present day atmospheric simulations using GISS ModelE: Comparison to in-situ, satellite and reanalysis data. J. Climate, 19, 153-192

Santer, B. D, C. Mears, F. J. Wentz, K. E. Taylor, P. J. Gleckler, T. M. L. Wigley, T. P. Barnett, J. S. Boyle, W. Bruggemann, N. P. Gillett, S. A. Klein, G. A. Meehl, T. Nozawa, D. W. Pierce, P. A. Stott, W. M. Washington, M. F. Wehner, 2007: Identification of human-induced changes in atmospheric moisture content. Proc. Natl. Acad. Sci., 104, 15248-15253

Comments?

12 comments:

chriscolose said...

//"as well as realistically past climates (e.g. the Last Glacial Maximum) with standard radiative forcing"//

It sounds like I missed a word in there some where, in between "realistically" and "past."

trading computers said...

very interesing...

Bob said...

Can I ask a set of sort-of-related questions? I will try anyway, im just throwing some stuff around trying to see if I understand it correctly or whether I don't (so please say if something I say below is very wrong)

Take a theoretical planet absorbing 300wm-2 solar energy with an atmosphere of only nitrogen.

I would expect =all= the outgoing radiation to be emitted from the surface in that case. So the surface is emitting 300wm-2 and as a result the surface temperature would have to be 270K.

During the day heat would flow from the surface to the atmosphere and during the night it would flow in the other direction (in order to be in balance of 270K emitting 300wm-2)

Now what if the atmosphere was much thicker than Earth's? Would a surface pressure of 1000atm cause the surface to be warmer than 270K?

I don't see how it could, where would the energy be coming from? But at the same time I don't see how it can't because I thought immense pressure caused warmth? Isn't jupiters core hot because of pressure?

I tried to look this up but either my google skills are useless or nothing out there talks about pressure and planet surface temperatures (which I suspect is because I have made a funamentally incorrect assumption in a step above)

Thanks, and I look forward to the finished G&T response,

Bob

chriscolose said...

You'd actually get somewhat of a greenhouse effect in very dense atmospheres composed of just diatomic gases.

Anonymous said...

Following up on chriscolose's response: in dense gases you get "collision-induced absorption" - a pair of molecules can absorb a photon while they are close enough to be exerting forces on each other (you can think of the two colliding diatomic molecules as forming a very short lived polyatomic molecule.) This is a significant contribution to the opacity of the gas giants, I believe.

Robert P.

Bob said...

So what sort of densities are we talking about here to provide any significant warmth? I imagine it is insignificant for Earth, but is it an insignificant component of Venus's temperature?

Barton Paul Levenson said...

Jupiter's core, and the core of every planet, is hot because

1) the material that fell in to form it converted kinetic energy to thermal energy when it hit, and

2) planetary cores contain radioactive elements which produce heat when they decay.

There are exotic heat producers for specific planets. The jovian planets are still contracting and some heat comes from that, especially for Jupiter. In Saturn, "helium rainout" supplies some heating.

But pressure itself never generates temperature. Temperature can go up when pressure increases, but static pressure will not generate heat.

EliRabett said...

Last Eli looked (and deep down this is not his area of interest so this was a couple of years ago) there was still a hot debate about whether Jupiter had a core, in the sense of a solid phase. As the bunny recalls the hot idea was metallic hydrogen.

Chris Colose said...

Chris heard a good idea today from an anonymous GW skeptic...papers like this (e.g., G&T) are created by global warming proponents in an effort to make the skeptics look bad. Amusing theorem...

Barton Paul Levenson said...

I think a paper by Alan Boss a few years ago revised the size of Jupiter's rocky core down from the old estimate of 15 Earth masses to something in the range 3-10, but I believe they still consider one to be there, under the liquid metallic hydrogen needed to generate the magnetic field. There had to have been some non-volatiles in the planetesimals that fell together to form Jupiter, and the denser substances would have wound up at the core.

Joel said...

Chris,

Yeah...At first, I thought that the G&T paper could be an Alan Sokal-style hoax (http://en.wikipedia.org/wiki/Sokal_affair) until I learned more about Gerlich's previous pronouncements on AGW. And, in fact, I think one lesson from this whole affair is that Sokal shot "too low" when he just tried to perpetrate his hoax on a social science journal since one can apparently get similar physics gibberish published in an actual physics journal!

As an aside, I noticed that even Roy Spencer has posted something debunking some of G&T's points (although he doesn't mention them or their paper directly): http://www.drroyspencer.com/

Since Spencer has, on that blog, recently been defending the notion that much of the rise in CO2 might not be anthropogenic, it is interesting to see that the G&T arguments are even too bad for him to defend.

Duae Quartunciae said...

Just to be precise...

In modern thermodynamics, we tend to speak of "Heat", and "Internal Energy"; which are not quite the same thing.

"Internal Energy" includes that energy a body has by virtue of its temperature. "Heat" is reserved for energy in transit between bodies by virtue of a different in temperature. Both are energy terms, measured in the same units.

Hence, you can have 100 J of heat transferred into a heat sink; with the result that the internal energy of the heat sink increases by 100J. We don't say that the heat sink now has another 100J of heat.

You can confirm this usage with definitions of "Heat" at wikipedia, or physicsforums, or hyperphysics. Let's make sure the reply keeps to correct usage.

Hence to say "thermal energy" is "heat" is not really correct terminology. Heat is actually the TRANSFER of "thermal energy", or "thermal energy in transit". It's still measured in joules.

G&T's comments here are even worse; but in fixing it we want to be precise.