The main issue though with climate science, the elephant in the room, is not the infancy of the field. It's that any result is used as fact and that this is in turn used to drive policy.

Actually, this appears to be your main issue with climate science. If you think scientists are presenting it as fact, you're reading the wrong papers.

The man [is] projecting if he thinks multi body systems are a sum of their parts.

You didn't read it properly if you think that is all it was saying.

Try reading his article properly. It's not just that the underlying physics is well-tested and essentially regarded as scientifically true, it's also that it is very difficult to explain many observations if there are major issues with our understanding of climate science. The greenhouse effect being one of many examples.

If you don't like the things that you regard as climate policy, that's of course your choice. There are many things being done in the name of climate policy that I don't like either. Justifying that on the basis that you think our understanding of climate science is much weaker than it actually is, is also your choice, but would seem odd for someone who claims to have all this great expertise in science.

Micky,

It doesn't matter if you understand parts of a system really well if you don't understand others or understand how the system works when everything runs together.

I don't know why you think that they don't. Of course people study how the system works as a whole. Ray's article wasn't suggesting that all we have are some physical process that we understand well. What we have is a complex system in which the physical processes associated with the evolution of that system are generally well understood physical processes.

The whole premise of AGW requires fixed water vapour and clouds. That's in the IPCC definition of radiative forcing.

Did you mispeak here? This is NOT the definition of radiative forcing (IPCC or otherwise).

It may be varying due to an underlying process that you don't know about. And science says you have to assume this possibility - the Null Hypothesis - until you can eliminate it.

No, it doesn't. Science doesn't require any such thing. If it did, we'd never regard ourselves as understanding anything. Science does require that you test your ideas and try to show that you're wrong. It doesn't, however, require that you assume that there is something else and that you have to do so until it is eliminated. Have you tested your null hypothesis?

If we had better data on clouds then a lot of this could be resolved and we could move on to trying to determine what processes change surface temperature.

Except we do have lots of data on clouds. Yes, they are still the biggest uncertainty. However, a cloud feedback that is very different to what we currently expect would be difficult to reconcile with paleo-climate and with the basic greenhouse effect.

Ken,

how do you define palaeoclimate? What time interval does it cover and how precisely are the temperastures and palaeo CO2 levels determined?

Paul,
I don't know if you can see this, but I'm referring to this kind of thing (Knutti & Hegerl 2008). If you look at paleo studies of ECS, you get a likely range (66%) of about 2-4C and a very likely range (90%) of about 1-5C - these are eyeballed, but I think they're about right. If cloud feedbacks are very different to what we currently think (somewhere between slightly below 0 and about 1 W/m^2/K, IIRC) then it becomes increasingly difficult to explain this. The same even applies to the instrumental-based estimates.

Bear in ind that there was a recent paper that suggested that cloud feedbacks were more positive that we currently think and that ECS might be as high as 5.3C. That's also hard to reconcile with the other lines of evidence.

aTTP said:

"Ray's article wasn't suggesting that all we have are some physical process that we understand well. What we have is a complex system in which the physical processes associated with the evolution of that system are generally well understood physical processes."

That is a quite breathtaking distortion of a cleverly written article. The article strives very hard to give the impression that everything is understood. Uncertainties and unknowns are swept under the carpet. The author focuses on things that are well-known and settled by "experiment" and models. However, on closer look, the claims he makes are wishy-washy hand-wavy qualitative things - the behaviour of CO2 in labs, the behaviour of the troposphere v the stratosphere. Glacial melt (he doesn't mention the uncertainties there, that are not even close to being reolved by the latest IPCC report 10 years later). Nothing important.

Nothing very sciency there. More akin to the ramblings of Entropic Man.

It is all designed to give the impression that the whole system is well understood but he is not preapred to go into any detail. In passing he alludes to the need for a tropospheric hotspot but seems to suggest it will soon be found. I think he wrote it in 2006...we are still waiting, meanwhile we have been told by other sources that the heat has gone into the deep oceans by some unfathomable process. Does that impress you, aTTP? I remain rolling on the floor with laughter at the chutzpah of Pierrehumbert.

At the end of his article, he refers to some matters that are not fully understood, as if they are irrelevant or unimportant. Among them is the water vapour cycle that Dr Corbett has brought to the table. Pierrehumbert suggests that any uncertainties will soon be sorted out.... The question that occurs to me is what drugs he was on when he wrote that.

Nothing inconsistent with what Sr Corbett wrote but a lot that appears to me to be dissembling and prevarication. Is he just dissembling or is he lying in order to get people to change their ways?

All in all, just another of those articles that led most people to avoid Real Climate.

All in all, just another of those articles that led most people to avoid Real Climate.

That you've avoided RealClimate is pretty obvious.

Micky,
Okay, I see what the problem is. You said

The whole premise of AGW requires fixed water vapour and clouds. That's in the IPCC definition of radiative forcing.

This not true. What is true is that a radiative forcing is a change (external) that produces a TOA imbalance and is defined as the TOA imbalance prior to any feedback responses, such as water vapour, lapse rate, clouds, that act to return the system to equilibrium. Changes in water vapour, lapse rate and clouds are regarded as feedbacks, not forcings. This does not mean that AGW requires fixed water vapour or clouds (and, in fact, if you read Ray's article you will note that he says this explicitly). You really should familiarise yourself with the details a little more. As I said, maybe spend some time actually talking to some experts, rather than simply assuming that you somehow have sufficient expertise yourself. Of course, if you want to continue what you're doing, that's also fine.

Ken your whole argument is based on assuming that natural variation cannot explain changes in temperature which seems odd considering we don't know how all the natural processes work especially on different timescales.

No, this isn't my whole argument.

Micky,

Saying that water processes are a feedback is a theoretical construct that has been applied to modelling. It forces CO2 to drive change them water to react. Again an assertion. Do we know this?

To within the limits of modern physics, yes. It is possibly regarded as one of the most robust aspects of this topic.

Micky,
Read Steven Sherwood's post here. Also, we're not yet in equilibrium so we wouldn't expect to yet see the full water vapour feedback response.

ATTP if you take a forensic attitude, much of what is posted on Real Climate comes across as special pleading, selective quoting or, if the Potsdam Institute is involved, deception. The site gives the air of being deceptive. It is designed to wipe out debate and uncertainty. As a result, it creates distrust. As a rhetorical construct, it has failed massively.

Ken,

I think this is the crux of the issue for me. The estimates of climate sensitivity based on both the modern and palaeo records cover a wide range and allow for a water-vapour/cloud feedback that could be negative or positive. We are limited with the quality of the data we have. This is not a criticism of any of the studies. Most are very sophisticated but recovering palaeodata is difficult, time consuming, and expensive largely because of the complexity of the proxy systems and their susceptibility to post-depositional changes which are not well constrained. So we have a short modern record where the small magnitude of changes makes accurate estimate of sensitivity difficult, or we have a palaeo record where we see much larger changes but the error bars on our estimates of both Delta T and Delta pCO2 are correspondingly large. Somewhere within this we have the role that water vapour and clouds are playing.

If climate sensitivity lies at the lower margin of estimates, say 1 degree C then the development of the climate in the future will be very different than if it lies closer to the middle of the range, or at the farthest flung regions of some modellers dreams.

Paul,

If climate sensitivity lies at the lower margin of estimates, say 1 degree C then the development of the climate in the future will be very different than if it lies closer to the middle of the range, or at the farthest flung regions of some modellers dreams.

Of course. However, if the 90% range is around 1-5C, then that means about a 5% chance of it being 1C or less, AND a 5% chance of it being 5C or higher. One problem with it being 1C or less, is that we've already warmed by about 1C and still have a planetary energy imbalance. This is really hard to reconcile with natural variability being responsible for lots of warming. There are a number of arguments for this, but one is simply that how have we warmed by about 1C and still and still not be in equilibrium if ECS is 1C or less (remember thayt on terms of forcings, we're not yet 2/3 of the way to doubling CO2)?

Similarly it is very hard to reconcile things with an ECS of 5C or more. If it were this high, why have we only warmed by 1C.

Also, if you talk with those who work on this, they're pretty convinced that - in the absence of clouds - the ECS is greater than 2C. There is (despite what you might read here) a great deal of confidence about the non-cloud feedbacks. Clouds could bring it down, but current work suggests it is small and positive. That's why most would put ECS at somewhere between 2C and 3C. Also, bear in mind that ECS is defined in terms of fast feedbacks only. There are slow feedbacks (permafrost release, albedo changes due to reductions in ice cover) that almost certainly produce an ESS that exceeds the ECS.

Final thing. If you consider the work on the carbon cycle, the expectation is that this is essentially irreversible on human timescales (absent some kind of techno-fix). So, yes, there is a chance that ECS could be low enough that the impacts will not be something we should really be thinking about addressing. If it isn't, however, we don't easily get to reverse what's already happened.

Perhaps a new thread should be opened where aTTP, Phil Clark, EM and Mickey Corbett can throw verbiage at each other. While it is of some interest to see totally different interpretations of the causes, scale and even existence " greenhouse effect " their discussion does not seem to add much illumination to the debate on the topic:-

Are Geological Paleo-Climate Records Relevant to The Climate Debate?

That would leave some space people like Paul Dennis, Paleoclimate Buff , Alan Kendall and others to engage in a useful ( and polite) exchange of views on t the relevance of the paleoclimate record to the interpretation of the very short period of modern obsevations.

Ken,

I think we might be in danger of going around in circles here. My understanding is that some of the more recent estimates based on the modern observational data suggest that the probability of a sensitivity as low as 1C is now rather higher than 5% with best estimates somewhere between 1.3 and 2C. This is not inconsisitent with some pal date either however I am sceptical of the utility of palaeodata in this context given the large errors. I do though need to revisit the Knutti and Hegerl paper and see exactly what they do say. From memory I think the bulk of their evidence is from the LGM. Not with standing this I think it is a stretch to place too much weight on extant palaeodata and that our best hope of constraining the climate sensitivity is with the instrumental record.

I'm not a big fan of the precautionary principle. The data does though seem to be pointing towards a lower climate sensitivity than first envisaged. This buys us more time to better understand the issues and optimise a societal response. I grant you that with time this picture may change but it hasn't as yet.

Mickey C: Yes but water vapour amplification hasn't been observed. 

Um, yes it has. Dessler et al 2008, Water-vapor climate feedback inferred from climate fluctuations

Abstract

Between 2003 and 2008, the global-average surface temperature of the Earth varied by 0.6°C. We analyze here the response of tropospheric water vapor to these variations. Height-resolved measurements of specific humidity (q) and relative humidity (RH) are obtained from NASA's satellite-borne Atmospheric Infrared Sounder (AIRS). Over most of the troposphere, q increased with increasing global-average surface temperature, although some regions showed the opposite response. RH increased in some regions and decreased in others, with the global average remaining nearly constant at most altitudes. The water-vapor feedback implied by these observations is strongly positive, with an average magnitude of lambda q = 2.04 W/m2/K, similar to that simulated by climate models. The magnitude is similar to that obtained if the atmosphere maintained constant RH everywhere.

From the conclusions:

The existence of a strong and positive water-vapor feedback means that projected business-as-usual greenhousegas emissions over the next century are virtually guaranteed to produce warming of several degrees Celsius. The only way that will not happen is if a strong, negative, and currently unknown feedback is discovered somewhere in our climate system.

http://onlinelibrary.wiley.com/doi/10.1002/2014JD022887/full

Paul,

My understanding is that some of the more recent estimates based on the modern observational data suggest that the probability of a sensitivity as low as 1C is now rather higher than 5% with best estimates somewhere between 1.3 and 2C.

No, not really. Consider the table here, from Lewis & Curry (2014). Look at the 5-95% ranges. In two cases, the bottom end of the range is 0.9C (which would mean slightly more than 5% chance of and ECS below 1C) but in two cases the bottom end of the range is 1C or higher. So, even these methods don't give much more than a 5% chance of an ECS of 1C or lower. Such a low ECS really is very unlikely.

Also, there's a question I've been trying to get Nic Lewis to answer. The TCR to ECS ratio for his best estimates are around 0.8. This seems a little too high, given that we have some idea of the heat capacity of the oceans and how long it will take to equilibrate. If this is too high, then it suggests that his TCR and ECS best estimates can't both be right. Maybe the TCR best estimate is too high. However, we've already warmed by about 1C, so it can't come down much. Alternatively, his ECS best estimate is too low, and we're heading back towards 2C.

The full forces of "real climate" will now come into play. Human rabbits, stoats, Rahmsdorf. Tobis, the SkS attack team, including Phil "the knob head" Clarke. Be warned.