rockdoc123 wrote:The Navier-Stokes equations and the radiative transfer equations are based on first principles and not knob tuning and ad hoc approximations. Solving the radiative transfer equations for specific mixtures of gases and making simplifications based on this ........
Which is all good but completely misses the point that he made…..there are still unknowns or forcings that are known but are poorly contstrained.
Put up or shut up. List these unknown forcings. I dare you.
Not having a complete understanding of the impact of unknown unkowns is important and Gavin Schmidt gives a good example where the consensus of chemistry models that projected a slow decline in stratospheric ozone levels in the 1980s, but did not predict the emergence of the Antarctic ozone hole because they all lacked the equations that describe the chemistry that occurs on the surface of ice crystals in cold polar vortex conditions--an "unknown unknown" of the time.
The ozone hole and the radiative effect of CO2 are unrelated physical processes. The lack of a prediction of the ozone hole rested completely on the lack of the chemistry being represented in the models. CO2 is a dry gas and we do not need to worry about its chemistry, only about its production.
As dohboi has pointed out numerous times, Arhenius knew about the radiative effect of CO2 over a century ago. Before any climate model and before the side issue of the ozone hole. The radiative transfer equations came long before climate models. The claim that they are uncertain and that the effect of CO2 is obscure is a patent lie.
With respect to poorly constrained variables the IPCC itself has a fairly wide range on what they accept as equilibrium climate sensitivity (which they believe is due to poor understanding of cloud feedback) and a number of recent papers has increased the range of what that sensitivity might be.
I could care less what the IPCC consensus is because it is compromised by the lowest common denominator of having to accommodate countries were AGW denial is strong (e.g. Saudi Arabia). IPCC follows the philosophy of "if in doubt, leave out". They did this in the case of land ice melt and came to the "consensus" that sea level rise would be 0.5 meters based purely on thermal expansion of the oceans. In the latest round they have had to backpedal on this BS.
CO2 increase in and of itself (all things being equal) will have a negligible impact on temperature going forward, what drives the projections is climate sensitivity and with a wide range in that number you end up with a tremendous range in modeled projections.
Yet another rubbish claim designed to pull the wool over the eyes of non-experts (and you are one of them). CO2 is the primary greenhouse gas on Earth. Water vapour is slaved to the temperature by the Clausius-Clapeyron relation. Without CO2 the Earth would become an ice Hell. The salty oceans would freeze. Water is a very effective greenhouse "gas" but it is not a dry gas and is very efficiently removed by precipitation. N2 and O2 simply do not trap infrared radiation. Being a noble gas argon does not either. That leaves H2O vapour and trace gases such as CO2, CH4, N2O, NOx, O3 and HOx as the main components of the radiative budget of the atmosphere. Of these CO2 is the most important.
Feedbacks are not all well understood according to IPCC and numerous papers published as of late which means arriving at climate sensitivity from first principles rather than having to torture it out of empirical observations is difficult at best. Add to that the assumptions in each model run regarding values that are quite variable such as (and not limited to) precipitation, total cloudiness, cloud parameterization, meridional wind, aerosols and sea surface temperature and you have uncertainty which would be best handled through stochastic approaches.
Clearly you have no clue what you are talking about. The circulation is not prescribed or parameterized in GCMs. It is resolved. That is on of the main reasons why we run those models. Deniers love to harp about cloud physics in GCMs and claim it is all BS. Deniers are the ones spouting off BS. Cloud parameterizations give valid leading order behaviour to inputs since they are based on physics and not nose-picking. The only serious skeptic out there, Richard Lindzen, proposed all sorts of theories how clouds could offset warming by acting like IR valves or via positive albedo feedbacks. All of his theories have flopped. I respect him for think outside the box and actually doing science. I cannot respect rabid obfuscators and liars who claim all sorts of things about AGW none of which are based on scientific research.
Wow, what a complete and utter rubbish claim. The energetics of the ocean-atmosphere system are not some probabilistic projection based on "assumptions". They are deterministic and can be quantified with current knowledge based on first principles equations. The main problem is how to measure the energy content of the ocean-atmosphere system due to the sparsity of observations. But recent work has done a good job of identifying the heat accumulation in the oceans. That accumulation does not resemble any stochastic process whatsoever.
Well I think this is a massive over-simplification and flies in the face of what the IPCC has identified as uncertainties in models as well as what has been identified by a number of scientists who are currently spending much of their time working on how to quantify uncertainties in climate models and projections. You seem to suggest that there is zero uncertainty with respect to forcings or interaction of forcings but if that were the case why are there so many individual models in CMIP5? Why is there so much time being spent by researchers looking at variability in the models and how to constrain the results better? Richard Feynman probably captured this best by saying Scientific knowledge is a body of statements of varying degrees of certainty— some most unsure, some nearly sure, but none absolutely certain.”
You have not refuted anything I said. You just trot out an argument that because research is an ongoing process where various details are uncertain that the knowledge of the whole system is uncertain. You are changing the subject. Deniers claim that the ocean-atmosphere system is intrinsically uncertain like some stochastic process. This is BS. Your example does not support your uncertainty claim. The global integral of the equations governing the system removes the dynamics leaving only the radiative transfer and boundary conditions. Academics spend a lot of time looking at second order effects because they are academics and not business people who need to optimize revenues for some company and meet fixed deadlines.
You keep harping on this climate sensitivity issue as if it is some defining element of climate science:
1) Climate sensitivity F > delta where delta is a positive number greater than zero. Deniers go so far to claim that delta is zero or less than zero. Total BS.
2) F is almost a meaningless concept. It is trying to parametrize a complex process in terms of a bulk variable. So it is never right at any given point and any given time. One cannot derive F from the underlying equations. Real Climate shoots down the lowball estimates of F very effectively by pointing out the serious limitations of the two papers that underestimated it. For humanity the short term F which may be several times larger than the long term F is likely to be of critical interest. Deniers would like everyone to wast their time with getting this fuzzy metric "super precise" as if it makes any difference. A typical denier disruption ploy.
You clearly are denier since you make the above BS claim which is a mishmash of denier talking points. The CO2 levels are observed and the associated warming is determined by both observations and models. Simulations between 1850 and the modern period show good fidelity between models and observations.
First off I think you misunderstand what was being said. With regards to the range of IPCC projections CO2 is indeed a major "tuning knob" simply because each RCP (representative concentration pathway) represents a different projection with regards to CO2 contribution to the atmosphere going forward. The IPCC sees this as being one of the large uncertainties as to future climate.
You have utterly no idea what a climate model simulation is. CO2 is not a tuning knob it is a genuine input like the solar constant. Climate models do not simulate human industry, resource extraction and the burning of biomass and fossil fuels. Climate models deal with the impact of the chemical composition changes on the atmosphere. Recently they have been coupled to ocean models. Since the dynamical timescales and spatial resolution requirements are vastly different in these two systems the numerical challenges are significant.
You make the implicit claim that uncertainty in CO2 emissions from humans validates the drivel of the original poster. Yet more denier BS. Even if humans stopped CO2 emissions today the system is locked into at least 2 C of warming. Of course denier diversion will focus on the lack of total precision in the forecast for human CO2 emissions as some show stopper for evaluating the impact of historical to present day CO2 emissions. As if they are old news and not a monkey on humanity's back.
I will say that you and the rest of the deniers can sod off. The CO2 emissions vs global GDP correlation is incredibly tight based on all of the historical data. So technological evolution makes basically no impact on CO2 emissions. There is no way that CO2 emissions will stop unless the global GDP goes to zero. So this IPCC scenarios being "tuning" is beyond absurd. Go ahead and claim that CO2 emissions will become irrelevant in the future. But I bet you won't and instead prefer to deliberately mix up the "uncertainty" of the inputs with the uncertainty of the physical process being modeled.
Secondly the models have not done a very good job of prediction over the past several decades (presumably the impact of poorly constrained climate sensitivity). Looking at past temperatures and tweaking model parameters to give you an answer you want is hardly proof positive of anything. The models offer non-unique solutions, different combinations of variables and weightings can result in the same answer. But how good is the fidelity you speak of?
More of the broken "uncertainty" record mixed in with the tired lie about tuning. Runs between 1850 and 2005 have done a good job capturing the observed temperature change. I dare you to produce any evidence to the contrary.
As the IPPC stated in AR5Most simulations of the historical period do not reproduce the observed reduction in global mean surface warming trend over the last 10 to 15 years. There is medium confidence that the trend difference between models and observations during 1998–2012 is to a substantial degree caused by internal variability, with possible contributions from forcing error and some models overestimating the response to increasing greenhouse gas (GHG) forcing. Most, though not all, models overestimate the observed warming trend in the tropical troposphere over the last 30 years, and tend to underestimate the long-term lower stratospheric cooling trend.
Here we see why the IPCC is a politically tainted waste of time. It actually repeated the denier lie about some "hiatus" in the warming. Climate models are not weather models. They are not subjected to assimilation of observations to nudge them on the right trajectory in state space. Their objective is to consider the effect of the energy balance on where the weather trajectories will reside in state space. As such climate runs are done as ensembles and the trends away from the current climate are discerned from the changes that survive averaging of the ensemble members. Since CO2 and its slave H2O will have a direct impact on the temperature and the energy in the system it is not surprising that climate models find solutions (weather trajectories) that deviate beyond dynamical noise form the current state.
The so-called hiatus is a deliberate misinterpretation of the data. There was a surge in warming during the mid-1990s that petered out by the mid 2000s. So the temperature trend "flattened out" in the mid 1990s. But we have seen on this board plenty of evidence that the 2000s have been warmer than the 1990s. So this undulation on the temperature trend did not actually affect the long term trend.
The origin of the multi-year undulations are due to heat exchange between the oceans and the atmosphere. ENSO is not the only such exchange mode. There is a whole spectrum of them spanning a few years (ENSO) to decades (Pacific Decadal Oscillation). These are nonlinear oscillations that can change their frequency rather substantially. A climate simulation with a GCM is not going to capture such oscillations with the right timing even if the GCM is coupled to a full ocean model. As I mentioned already, climate simulations are free runs and not weather simulations. The objective is not to anchor them to daily weather observations. It is enough for them to capture the main physical processes.
The historical runs between 1850 and 2005 did a good job capturing the cooling during the 1950s through the 1970s associated with the global dimming effect of pollution. That they did not time the bogus "hiatus" right is a total non-issue.