Well this topic is going to generate a plethora of responses.

I will be brief here:

1. IT is useful to look back at the history of the evolution of the IPCC process and associated models.  The entity does evolve and the models are much better thanthey were a decade ago.   So I do believe that the IPCC process does make scientific progress.

2. As commented above, there are lots and lots of groups running lots and lots of models so statistics of various models can soon be developed.

3. The role of feedbacks will always be the major model uncertainty as well as the biggest source of systematics.   Clouds are complicated.  Scattering is hard; deep sea transport of thermal energy remains largely unknown.

4.  My major scientific concern with the whole modeling process is that it does not adequately handle and model the "noise" in the climate system.  This, of course, is why the problem is difficult.  The Earth is complicated.

I believe that before the use of a GCM or RCM you have to evaluate the performance of the models against observed data in order to identify biases in the mean values or variability. Then you can apply a bias-correction method, but in any case you have to assume that the bias will remain constant during the projected period of time  (typically the 21st century). Examples of corrections can be found in Vidal and Wade (2009). Regarding scenarios, you have 4 options available with different characteristics. However, you can try to build your own scenarios easily just taking into account the past variability of a variable and then proposing that, for example, in 2050 you will experience a 25% increase in mean values and a decrease of 30% in variability. You can try a variety of future conditions and then overlap the results with projections of population growth or land use change.

Article A multimodel assessment of future climatological droughts in...

You can see how good are the IPCC models in simulating the prominent modes/drivers of climate variability in this study:

Article Revisiting the Indian summer monsoon-ENSO links in the IPCC ...

Hi Morteza,

Evidently, a lot of criticism exists with respect to the output of GCM's. I leave aside the RCM's since most of the RCM's are forced with the output of GCM's anyhow. There are alternatives to the output of IPCC results, but the scenrario's (which are a set of input boundary conditions for a GCM) are quite relevant according to me. It is according to me preferable to use the IPCC scenario's, exactly for the sake of GCM validation and comparison after simulations have been run with these standard IPCC scenario's as input for a GCM.. The alternative would be a jungle of incomparable climate outputs. The climatology community will in that case have even more headaches, to compare and interpret results based on a mumbo jumbo of input scenario's. As a rule of thumb, when a physical model gets rubbish as an input, even more rubbish will be generated as output.

Another issue is that users of GCM outputs, generally are not climatologists. Hence, they don't feel very confident when using these more or less 'magic box' outputs. To come to grips with the basics of climate modeling it is best, but a hard remedy, to get a grip on the meaning of the different climate outputs of different GCM's forced with the common good IPCC scenario's. To enable this several universities have developed more simplified GCM's for teaching purposes. They are not as accurate as the more professionally developed GCM's, but they have the advantage that a student can runthem on his or here laptop and start learning about the fundamental processes determining our climate.  Hence, one can do some systems analysis oneself. I can assure you that this will give more confidence, but you will need the courage to take the learning curve as well. Eternal learning is the destiny of a good scientist, hence, when climate is a core in ones research activities, I would suggest to step on the learning curve, by Googling yourself a simplified GCM, which you can run on your laptop. There is plenty of choice.

Cheers,

Frank

An interesting saying: everybody believes data except for the data analysts; nobody believes models except for the modelers themselves.   

Well this topic is going to generate a plethora of responses.

I will be brief here:

1. IT is useful to look back at the history of the evolution of the IPCC process and associated models.  The entity does evolve and the models are much better thanthey were a decade ago.   So I do believe that the IPCC process does make scientific progress.

2. As commented above, there are lots and lots of groups running lots and lots of models so statistics of various models can soon be developed.

3. The role of feedbacks will always be the major model uncertainty as well as the biggest source of systematics.   Clouds are complicated.  Scattering is hard; deep sea transport of thermal energy remains largely unknown.

4.  My major scientific concern with the whole modeling process is that it does not adequately handle and model the "noise" in the climate system.  This, of course, is why the problem is difficult.  The Earth is complicated.

I not working on models directly, buy usually compare my own results with their outputs and also bibliography.

If yo check the draft of last IPCC5 available in the main IPCC web site, you will be realize how the models have been used perhaps, let me say, in not the proper way. Compare the Figures of global temperature evolution at stations (I know, a global mean serie is....) and suggested by models, and then compare the final form in which these data have been presented in the AR5....

Climate models, as any model, are only SIMPLIFICATION of REAL WORLD, no more. Better or worse, but in any case simplification, and their results some times are imposible to check with empirical data simply because we have no data in this area (desert, high latitude, high altitude) so many results apparently non-controversial are only hypothesis, or in the worst case speculations imposible to contrast. 

I suggest some references about how models have produce highly differences (particularly in high troposphere, but not only) and how they have been understood. There are only a minor number of the amount of literature, basically focussed on how models have not predicted the upper temperature, why models not predicted the present hiatus of temperature, and how models have not predicted minimum temperature at the surface .

Parker D (2011) Recent land surface air temperature trends assessed using the 20th Century Reanalysis. Journal of Geophysical Research 116 D20125, doi:10.1029/2011JD016438.

Cohen JL, Furtado JC, Barlow M, Alexeev VA, Cherry JE 2013 Asymmetric seasonal temperature trends. Geophysical Research Letter 39: L04705, DOI: 10.1029/2011GL050582.

Kaufmann, R. K., H. Kauppi, M. L. Mann, and J. H. Stock, (2011), Reconciling anthropogenic climate change with observed temperature 1998–2008, Proc. Nat. Acad. Sci., doi: 10.1073/pnas.1102467108.

Christy JR, Norris WB, McNider RT (2009) Surface Temperature Variations in East Africa and Possible Causes. Journal of Climate 22, 3342-3356.

Douglas DH, Pearson BD, Singer SF, Knappernberger PC, Michaels PJ (2004) Disparity of thropospheric and surface temperature trends; new evidences. Geophysical Research Letter 31, L13207, doi:10.1029/2004GL020212.

Klotzbach PJ, Pielke RA Sr, Pielke RA Jr, Christy JR, McNider RT (2009) An alternative explanation for differential temperature trends at the surface and the lower troposphere. Journal of Geophysical Research 114, D21102, doi:10.1029/2009JD011841.

I do not deny models, I only ask for a proper interpretation of their outputs (they do not produce laws, they produce hypothesis)

Best wishes

C

Any type of model primarily depends on input quality data. Once the climate data are not  accurate than any model can give greater error.

I am studing the Arctic Sea ice and the CEMIP5 future projections show a Very large scatter..Therefor i use the CO2 as proxy for a driver for ice  extent and worked out the relationship between th CO2 and the ice extent,see Johannessen 2008 Decreacing Arctic Sea ice mirrors increacing CO2  on decadal  time svale.AOSL Volume 1,published by IIAP,CAS,2008.Recentlly  I have workd out a similar relationship between the CO2 and the September Ice extent and aske at what CO2 values will the

September ic

Sorry,some of my sentences dissapeare,Here I continue

Recently I have worked out a similiar relationship between the CO2 and the  September ice extent for the last 100 years and then asked the question at what value of CO2 will the September ice  dissapear and the answer is 500ppmv.if we continue at the current rate this will be 40 years from now,perhaps to simpel calculation?

I give the sea ice data as an exercise in my scientific programming class.  The figure below shows the data which

a) reveals the scatter indeed is significant

b) offers two fits, both with equal chi^2 minimum values; obviously the future clearly is different if the non-linear acceleration trend represents the right physics.  Personally, I believe that it does because a lot of this is threshold effects and once you cross the threshold it becomes harder to build back up the sea ice, thus continuing the acceleration.

I believe a single platform for all the global models, and CMIP5/IPCC is one of them. But their coarse resolution can not fill the gap of inaccuracy against observations. Individual model needs to chip-away their caveats with time and then we can expect a better and reliable forecast. These many runs (Multi experiments, time frequency range, ensembles and variables..etc) are possible  with CMIP5 kind of efforts only.

when you think Van Kooten has a "high critical scientific manner" to explain, you have not studied his CV: he is an economist NOT a climatologist.

In the intro of the book, free on the web, he mentions that he started to study climate change during a sabbatical in 2009-2010. What can he have learnt in a SINGLE year to write e a critical book on the complete climatological aspects of Climate Change, published in 2012?

I strongly advice you to go to the original work, the 2013 IPCC-report, written by hundreds of climatologists

I have my own aproach, it quite diverges from the rest

https://www.researchgate.net/profile/Dimis_Poulos

As mentioned by Harry, many parts of the book are available through Google Books. Page 96 is here: https://books.google.co.uk/books?hl=en&lr=&id=XrIJpobiVZsC&oi=fnd&pg=PR5&dq=Cornelis+Van+Kooten&ots=-NbjsqpJ9S&sig=HvP5yUB3Ea36yC_2pqeUkFnF6rU&redir_esc=y#v=snippet&q=political%20expediency&f=false

Reading the full excerpt it can be seen that the scientists are being criticised for not engaging with the politician Al Gore, and that is regarded by van Kooten as a political act!

invalid, I have writen and documented and detailed described that, and discovered the mechanisms involved on climate variability

https://www.researchgate.net/profile/Dimis_Poulos

HOW VALID ARE CLIMATE MODELS

Climate models are mathematical representations of the interactions between the atmosphere, oceans, land surface, ice – and the sun. This is a complex issue. Climate Models or GCM's RCM's or LCM's are developed to estimate Climate trends rather not events.

For example, a GCM can tell you it will be cold in winter, but it can’t tell you what the temperature will be on a specific day except when downscaled to a RCM or LCM. The accuracy of these models is much higher – they get real close to weather forecasting on the long-term. It is waiting for both to touch each other ;-)

Climate trends are weather events, averaged out over a longer period of time and secondly they are not estimated with Numerical models and Supercomputers like the one in ECMWF, which predicts WEATHER up to about a week GCM's and RCM's usually require at least a year and when trends are needed they go up to a period of 10 to 30 years. Trends are important because they eliminate - or "smooth out" - single events that may be extreme, but occur quite very seldomly (statistically speaking). Clearly GCM's DO NOT predict Earthquakes and when these happen in the ocean you get Tsunami's, which can be devastating.

They do not predict volcanic eruptions which do influence climate on the long-term as well. Just to be clear about this. They do not predict how much aerosols will absorb or reflect (depending on their albedo)  incoming solar radiation. Hence intrinsically, GCM's, RCM's and LCM's are valid only under certain boundary conditions which describe the uncertainty of the models. The larger the time horizon, the larger the uncertainty. That's exactly the same with meteo predicitions, very accurate when predicting on daily basis, but much less when the prediction period is a week. A meteo model cannot predict the meteo a month ahead (yet).

Climate models have to be tested to find out if they work. We can’t wait for 30 years to see if a model is any good or not. In general this type of models (GCM's) are tested against the past, against what we know has happened with climate (by measurements). If a model can correctly predict trends from a starting point somewhere in the past, we could expect it to predict with reasonable certainty what might happen in the future. We call this the validation of the model. Whether it is a climate model or a meteo model or a pollution model, the principle is the same.

So all models are first validated in a process called hindcasting. A test is performed whether the GCM model used to predict future global climate can accurately map past climate changes. If it gets the past right, then we can assume that the physical backbone of the model is trustworthy. Validating models against existing instrumental records like CO2, is a known approach, but not enough. all measured variables should be used to validate a GCM.  All known forcings should explain temperature variations in the hind casting validation, prior applying the model to estimate a rise in temperature over thirty years from now.

Models which have been running for a sufficient time, have also been proved to make more  accurate predictions. For example, the eruption of Mt. Pinatubo allowed modellers to validate  the accuracy of models by using the aerosol data from the eruption in the GCM. Aerosols from eruptions (or atomic explosions on atols in the Pacific for that matter during the sixties) can circle in the stratosphere during years and years and slowly disperse (hence also radioactive aerosols with nuclear explosions).

When the models successfully predict the climatic response after an eruption, we can assume that the physics is well conceived and that the validation of the model is successful. Models also correctly predict other effects subsequently confirmed by observation, including a larger warming in the Arctic and over Greenland, a higher warming during the night. GCM's may be conservative in their predictions. For example, here’s a graph of sea level rise as produced with a GCM from the IPCC.

 Observed sea level rise since 1970 from tide gauge data (red) and satellite measurements (blue) compared to model projections for 1990-2010 from the IPCC Third Assessment Report (grey band).  Sea level rises mainly as a result of melting land ice and thermal expansion of ocean water as temperature rises.  The observed sea level tracks the upper range of the IPCC projections pretty well.

Hence, Though GCM's have their limits like any physical model by the way, the trends they predict are pretty trustworthy and not to be thrown in the garbage can on the condition that the GCM HAS BEEN VALIDATED INTENSIVELY.

Frank

A nice description but I have a question and a comment

1. What do do you mean with ".. do not predict how much aerosols will absorb incoming solar radiation" is this in connection to volcanic eruptions? BTW these aerosols do not absorb radiation but reflect radiation

2. There is no climate response with resepct to volcanoes: the aerosol is gone in a few years

Hi Harry,

Concerning question 1, you know that some aerosols reflect light and others absorb it. That depends on their multiple scattering abedo. Black carbon aerosols absorb light, fine suspended loam reflects it. Of course the ratio betwen absorbtion and reflectance is a difficult issue, because it will be different according to the sources of the aerosols on Earth.

Ever read something about this issue? Would be interesting because radiative forcing would change accodingly (to a small extent). No? and hence Global Change? Yes?

Question 2. I show you the results from a detrended CO2 measurement series on Hawaii which is quite well correlated with volcanic eruptions in the Pacific at least, in the Ring of Fire! How do you explain the correlations with volcanic eruptions? You do know that, as a matter of fact, CO2 is the primary forcing molecule of Global Change! So? No effect of volcanic eruptions, I don't think so Harry.

It is a well knwon phenomenon. In the graph the correlation is not always consistent, but a lot of the eruptions leave their mark on ENSO occurences AND  detrended CO2 measurements at Hawaii which is located in the midst of the ENSO pathway through the Pacific! How about that?

CHeers,

Frank

Frank

ad 1. The role of aerosols in climate (change) has been one of my 2 main research objects for the last 25 years. As for the projections: there are very keen scientist working in this field fully aware of the absorptive character of soot and the reflective character of sulphate / nitrate and modelling the future effects

Olivier Boucher

Joyce Penner

Ulrike Lohmann

ad 2. what I meant was that climatologists tried to assess the radiative forcing produced and the lack in 0cean cooling but mention that the time frame is (too) short to give answers for thewater vapour feedback that determines the warming at doubling CO2

Thanks Harry,

No offence, but look at this mate:

http://earthobservatory.nasa.gov/Features/Aerosols/page3.php

and this,

http://www.nasa.gov/topics/earth/features/warming_aerosols.html

and this,

http://www.ucsusa.org/global_warming/science_and_impacts/science/aerosols-and-global-warming-faq.html#.VkQ8K-KbEQ0

Aerosols and Global Change? Do you have doubts about the phenomenon? What are the main conclusions of your research in this filed then? Do you have papers on the topic. I'd like to read them, it is always stimulating to read other peoples work.

I'll give you a nice aerosol model in return:.OPAC, BUT I chnged it! It now takes into account atmospheric humidity, which the original version does not. That makes a big difference at high humidities, for some of its outputs.

I can assure you that Olivier Boucher, Joyce Penner and Ulrike Lohmann are not the only ones studying the effects of aerosols! There is half of a remote sesing community working on that topic! But I am interested in their papers as well. If you have some references to them, that would be great.

Sorry Harry to be so bold, but discussion stimulates and cleans up rusty concepts. That's why I try to shake the science tree as hard as possible. Maybe fruit(full) ideas come falling down;-).

One of me  credo's: Expect the unexpected!

Cheers,

Frank

Frank

First of all remote sensing and OPAC are NOT a projective science but a descriptive science what I mean is that it does not provide a "prediction" of coming aerosol influence.

The 3 researchers I mentioned are involved in modelling the current and future global aerosol burdens as well as their radicative properties. Of course the list is not exhaustive and there are others. However the 3 mentioned are authors of the aerosol/cloud chapter of AR5. Sure others there are also Shindell, Haywood Hansen

My work was/is on the radiative forcing of aerosol at the regional European scale

We were the first to experimentally show the importance of (ammonium) nitrate as a scattering aerosol component, as dod=cumneted in the TAR of IPCC

As for OPAC: this is not a predictive model but a descriptive model and by the way we worked for years on quantifying the hygroscopic growth of nitrate/sulphate(/soot) mixtures in a novel humidograph. By the way Pepijn Veefkind was the student performing those tests and the first to do remote sensing of aerosol above land in his thesis and now the leading expert of remote sensing at KNMI for OMI.

Apart from the direct aerosol effect we studied the indirect effect in our large cloud chamber coming up with numbers for the regional AIE in W-Europe.

As for publications they are all at my site here at RG

to name a few

https://www.researchgate.net/publication/233428112_The_impact_of_aerosols_on_regional_climate

https://www.researchgate.net/publication/239279617_Simulation_of_aerosol_optical_thickness_during_IMPACT_%28May_2008_The_Netherlands%29_with_ECHAM5HAM

https://www.researchgate.net/publication/233784136_Effect_of_aerosols_on_the_downward_shortwave_irradiances_at_the_surface_Measurements_versus_calculations_with_MODTRAN_4.1

https://www.researchgate.net/publication/29629243_The_nitrate_aerosol_field_oer_Europe_simulations_with_an_atmospheric_chemistry-transport_model_of_intermediate_complexity

https://www.researchgate.net/publication/233387117_Aerosol_Nitrate_the_New_Atmospheric_Cooling_Agent_in_Europe

https://www.researchgate.net/publication/232708062_Aerosols_a_matter_of_cooling_or_warming

Ulrike Lohman latest:

On the characteristics of aerosol indirect effect based on dynamic regimes in global climate models

Article in Atmospheric Chemistry and Physics 15(17):23683-23729 · September 2015 

Article The impact of aerosols on regional climate

Article Simulation of aerosol optical thickness during IMPACT (May 2...

Article Effect of aerosols on the downward shortwave irradiances at ...

Article The nitrate aerosol field over Europe: simulations with an a...

Conference Paper Aerosol Nitrate, the New Atmospheric Cooling Agent in Europe

Article Aerosols: a matter of cooling or warming

Harry,

Now you are talking!

I know Harry, that OPAC is just a rather simple simulation (or descriptive) model (intended for students), but it has its merits on the condition that it takes account of humidity on aerosol growth by condensation. The aerosol shape of course is strongly simplifified in OPAC,...a sphere :-/, and for sure the model does not predict - because that requires meticulous validation - but it simulates, which is evidently something entirely different.

Of course when water vapour condensation takes place on an aerosol or particle, then whatever the shape of that particle, when condensation increases it will get close to the shape of a sphere (or a droplet) I figger. Your humidigraph should have given outcome on that.

Thanks for the papers and references. I'll read them attentively and try to figger out based on your and your colleagues work, what you and your partners think about aerosols having an influence on Climate.

That's an honest question no?

CHeers,

Frank

Frank

Yes you are fair

I like to add one thing: aerosol particles in our region are spheres because of the presence of nitrate in the aerosol. This compound does not lose its accreted aerosol water when the air becomes very dry because its efflorescence RH is less than 10%.

Never too old to learn Harry!

Thanks,

Frank