Philosopher Karl Popper claimed in his book ‘The Logic of Scientific Discovery’ that a hypothesis, proposition or theory is scientific only if it is falsifiable:
"Logically, no number of positive outcomes at the level of experimental testing can confirm a scientific theory, but a single counterexample is logically decisive: it shows the theory, from which the implication is derived, to be false. Popper's account of the logical asymmetry between verification and falsifiability lies at the heart of his philosophy of science."
It seems that whatever happens in the climate system is consistent with climate model predictions. Warmer, colder, less ice, more ice, droughts, floods, more hurricanes, less hurricanes, stronger hurricanes, weaker hurricanes, and so on.
An recent example from the media:
Cold wave in India attributed to global warming
Mumbai: The recent cold wave sweeping across Mumbai and other parts of India could be attributed to global warming, experts said on Tuesday here at an environmental conference.
Would the observed mid-troposphere warming of less than the 2 to 3 times increase over surface warming predicted by climate models represent falsification? Or would a prolonged period of global cooling do the job?
So, what event or observation, or series of events/observations over what timescale are required to falsify the climate modelled hypothesis of CO2 driven climate change or global warming?
This post was inspired by a couple of blog posts over at Prometheus:
The Consistent-With Game: On Climate Models and the Scientific Method
Climate Model Predictions and Adaptation
Serious answers to a serious question, please.
gavin - "I’m also trying to point out to those non GCM believers that we built aircraft and flew into space largely without depending on modern computer “models”. Although the slide rule was common practice in most engineering some (and I) used a log book for all technical maths. Regardless, that put the emphasis back on obtaining empirical data for the critical stuff."
And I was not going to disagree with you. What computers allow us to do is do all the calculations that go into an aircraft design so quickly that we can now do them over a thousand times with slightly different parameters to see if the performance would be better. Slide rule people could take years to do the calculations where a computer has done it before you can take your finger off the Enter key.
I don't know if you have read Slide Rule by Neville Shute however in it there is a really good description of the months taken for one stress calculation in the design of the R100. (Neville Shute Norway was an engineer who drifted into aircraft design)
For the climate we could spend a thousand years doing the flow calculations that would model the climate if we did not have computers. I guess someone would do it anyway as it yields interesting lines of research.
Ender: Seems you missed my point, IMO we can use GCM’s to “predict” whatever.
I’m also trying to point out to those non GCM believers that we built aircraft and flew into space largely without depending on modern computer “models”. Although the slide rule was common practice in most engineering some (and I) used a log book for all technical maths. Regardless, that put the emphasis back on obtaining empirical data for the critical stuff.
Faith grows from direct measurements including fatigue testing of wing structures, accelerated aging of moving parts, impacts, skins and coating performance etc. Obtaining good data from turbulent external events however took a while longer.
Sometimes we have to use guinea pigs not instruments where life is concerned. Our sensitivity to a changing environment in the end comes down to the numbers of winners or losers along the development path. Science generally records both groups.
Gavin - "t’s been my view all the while if GCM’ can’t be used in some way to project / predict future outcomes; why bother building them in the first place?"
What would you have scientists do? I don't think that we can create a convenient planet to test things on so we have to do something. Computers offer a way to experiment. They can explore what the future might hold exactly as designers of aircraft use numerical modelling to rough out and refine designs without building lots of hideously expensive prototypes.
No-one in aircraft design would think that a numerical flow model can completely predict the performance of an aircraft but the best of them get withing a few percent in the normal performance envelope. They are not very good outside this however even then you can make sure that normal control inputs do not cause gross excursions in to the non-linear part of the envelope. When this happens the aircrafts behavior is in the hands of the gods. It is a tribute to the designer's skills that when it happens most planes cope better than can be expected.
In the same way GCMs are tools that can be used to at least see where the future might lie. They clearly show that CO2 warming will cause some degree of climate change. This is not ironclad as there are many things that we do not know. However as they get better and computers get faster they do a better and better job.
Ender: To test your statement” Yes and that would be true if GCMs were used to predict the future which they are not.” I went straight to this wiki page and noticed it was last updated on the 15th Feb. IMO anyone following this end of the thread should go right through this wiki lot. Note the discussion on nested models and spectral v grid etc.
http://en.wikipedia.org/wiki/Global_climate_model
It’s been my view all the while if GCM’ can’t be used in some way to project / predict future outcomes; why bother building them in the first place?
BTW I knew guys who were employed here in tracking the moon shots and other near space exploration. Most were highly skilled in eng cals on the slide rule, many were ex Woomera, a few went to the US for retraining at mission control. Although I guess the only common ground we had then was around pressure vessel monitoring I was most aware they retained team spirit across the globe long after those spectacular events.
http://en.wikipedia.org/wiki/Project_Apollo
Industry went down a slightly different path and reading short term deviation on a dopey control recorder became the sole chore for a tiny handful of isolated commissioning agents.
Looking back, let’s ask where would we be without the likes of Texas Instruments? The microchip had just come into calculations at the end of the 1960’s. I reckon we had very little help with any process modeling before the expensive HP-35 pocket calculator cheaper TI-30 in the mid 70’s.
Gavin - "IMHO Spaceship Earth has quite a bit hanging onto it"
I am not sure if you read the link however in the case of shuttle software it was in direct control of the spacecraft. Really the pilots tell the software what they want to do - there is no direct connection between the pilots input and the final control output. One bug and they all die.
Fortunately the GCMs do not control the climate in the same way. Wise people will always treat the output of GCMs with a grain of salt and apply their own experience and knowledge to intepreting what the models say. Exactly as is done with aircraft design.
DHMO - "My statement was "You can model a jet engine or a nuclear power station. Each of these obeys the laws of physics in an orderly way they are not chaotic." Your rebuttable "The flow over an aircraft's wing is one of the most apparent demonstrations of chaotic behaviour as the boundary layer is tripped in the transition from laminar flow to turbulent" is very unsound."
No it is completely to the point. Yes you can model a jet engine however they like any other modelling are chaotic making all computer models a simplification. You implied in this statement that modelling a jet engine or nuclear power station is completely predictable whereas it is not. There are elements of chaos in all of this. As you do not seem to get it a compressor or turbine blade is a wing that will stall unpredictably given the right conditions and the engine will flame out. Part of the modelling that is done is to ensure that when the engine is operated normally it stays in the linear region.
"Your statements about the Space Shuttle do not contribute anything and neither does your link to the site you found fascinating. The hardware that was used for various does not contribute anything to this."
No but it is incredible fascinating and confirms to me that you are not really interested in learning. Anyone that was fascinated by technology and also wanted to learn could not help themselves to read this.
"So Ender you are an Evangelist and we are actually engaged in a religious exchange."
Yeah right. I am as sick of it as you so go ahead and think what you want why should I care.
""There are many methods for predicting the future. For example, you can read horoscopes, tea leaves, tarot cards, or crystal balls. Collectively, these methods are known as 'nutty methods.' Or you can put well-researched facts into sophisticated computer model, more commonly referred to as 'a complete waste of time.'" Scott Adams."
Yes and that would be true if GCMs were used to predict the future which they are not.
A small point of order Ender
"Also this software has eight lives depending on it. CGMs have no such constraints"
IMHO Spaceship Earth has quite a bit hanging onto it
Jan
This will be my last post on this thread. I have finally accepted I was involved in a pointless religuous discussion. I just wanted to give you a tip. You need to link any research you want to do to global warming that way you will get your "Deep Thought" and plenty of funds. As for cancer research here is the link http://news.bbc.co.uk/1/hi/health/1161895.stm
In fact anything but anything can be linked so get with it and join the band wagon. Wonder if requires prayer as well?
Ender
"Are you serious here? The flow over an aircraft's wing is one of the most apparent demonstrations of chaotic behaviour as the boundary layer is tripped in the transition from laminar flow to turbulent. Planes crash because of this transition happening at the wrong time."
So extract an exception and focus on that, So invent the idea I was referring to aircraft design and extract an exception to something I did not say. My statement was "You can model a jet engine or a nuclear power station. Each of these obeys the laws of physics in an orderly way they are not chaotic." Your rebuttable "The flow over an aircraft's wing is one of the most apparent demonstrations of chaotic behaviour as the boundary layer is tripped in the transition from laminar flow to turbulent" is very unsound. So you expect them to build a computer model of this and apply it to aircraft manufacture without further testing. Would you travel on that plane?
Your statements about the Space Shuttle do not contribute anything and neither does your link to the site you found fascinating. The hardware that was used for various does not contribute anything to this.
I think you know full well why GCMs are so important in this whole question.
The views you express show you see yourself on the side of good, fighting off the evil doubters who don't think as you do. Further this is because they are being swayed by vested interests. So Ender you are an Evangelist and we are actually engaged in a religious exchange.
Finally
"There are many methods for predicting the future. For example, you can read horoscopes, tea leaves, tarot cards, or crystal balls. Collectively, these methods are known as 'nutty methods.' Or you can put well-researched facts into sophisticated computer model, more commonly referred to as 'a complete waste of time.'" Scott Adams.
No doubt you will find who wrote this and do the usual ad hominem attack but it is fairly accurate explanation of GCMs that is what you should address. As well the phrase ‘a complete waste of time’ describes you as well. I learnt to not argue with the faithful there is no point to it.
DHMO - "But I do know I and suggest you stop because it shows you are not at all concerned with my argument that building a GCM is waste of time because they are not definitive or testable."
How would you know this from a cursory look at Climateprediction.net. Have you actually looked at the peer reviewed literature about climate modelling and how it is tested? Until then you are speaking from a position of ignorance. Why not email Gavin Schmitt, who is a climate modeller, and ask him for a list of reading - I am only too sure that he would be more than willing to help.
"Each of these obey the laws of physics in an orderly way they are not chaotic."
Are you serious here? The flow over an aircraft's wing is one of the most apparent demonstrations of chaotic behaviour as the boundary layer is tripped in the transition from laminar flow to turbulent. Planes crash because of this transition happening at the wrong time.
"The Space Shuttle software took 2000 years of effort so we would be looking for something in the order of at least that perhaps a 100 times bigger."
No the Space Shuttle used IBM AP100s and the reason that it took so long is that the Shuttle kept changing weights every other day. Also this software has eight lives depending on it. CGMs have no such constraints. You are comparing apples and oranges.
You may find this resource as fascinating as I did when I read it (warning geek level extreme)
http://www.hq.nasa.gov/office/pao/History/computers/Part1.html
"Doubt and skepticism is the corner stone of science without it science becomes a religion so do not talk to me about “real science”. Do you expect me to produce an experiment to disprove the quasi paradigm of climate models. The damage that is being done by the fear, uncertainty and doubt of those who say we are doomed because what the GCMs predict, do far more damage to science."
And that is alive and well in the scientific community if you would care to look. GCMs predict nothing. They give a range of scenerios that might occur if so and so happens. I do not know why you think that the entire AGW problem is invented by GCMs. The concern of AGW started long before GCMs from solid atmospheric science that the GCMs now help to quantify along with the thousands of other scientist working in the field.
The idea that the only evidence for climate change from AGW is from computers running AGM is false and part and parcel of the FUD campaign started by vested interests.