Unusually, I’m in complete agreement with a recent headline on the Wall Street Journal op-ed page:
“The Climate Science Isn’t Settled”
The article below is the same mix of innuendo and misrepresentation that its author normally writes, but the headline is correct. The WSJ seems to think that the headline is some terribly important pronouncement that in some way undercuts the scientific consensus on climate change but they are simply using an old rhetorical ‘trick’.
The phrase “the science is settled” is associated almost 100% with contrarian comments on climate and is usually a paraphrase of what ‘some scientists’ are supposed to have said. The reality is that it depends very much on what you are talking about and I have never heard any scientist say this in any general context – at a recent meeting I was at, someone claimed that this had been said by the participants and he was roundly shouted down by the assembled experts.
The reason why no scientist has said this is because they know full well that knowledge about science is not binary – science isn’t either settled or not settled. This is a false and misleading dichotomy. Instead, we know things with varying degrees of confidence – for instance, conservation of energy is pretty well accepted, as is the theory of gravity (despite continuing interest in what happens at very small scales or very high energies) , while the exact nature of dark matter is still unclear. The forced binary distinction implicit in the phrase is designed to misleadingly relegate anything about which there is still uncertainty to the category of completely unknown. i.e. that since we don’t know everything, we know nothing.
In the climate field, there are a number of issues which are no longer subject to fundamental debate in the community. The existence of the greenhouse effect, the increase in CO2 (and other GHGs) over the last hundred years and its human cause, and the fact the planet warmed significantly over the 20th Century are not much in doubt. IPCC described these factors as ‘virtually certain’ or ‘unequivocal’. The attribution of the warming over the last 50 years to human activity is also pretty well established – that is ‘highly likely’ and the anticipation that further warming will continue as CO2 levels continue to rise is a well supported conclusion. To the extent that anyone has said that the scientific debate is over, this is what they are referring to. In answer to colloquial questions like “Is anthropogenic warming real?”, the answer is yes with high confidence.
But no scientists would be scientists if they thought there was nothing left to find out. Think of the science as a large building, with foundations reaching back to the 19th Century and a whole edifice of knowledge built upon them. The community spends most of its time trying to add a brick here or a brick there and slowly adding to the construction. The idea that the ‘science is settled’ is equivalent to stating that the building is complete and that nothing further can be added. Obviously that is false – new bricks (and windows and decoration and interior designs) are being added and argued about all the time. However, while the science may not be settled, we can still tell what kind of building we have and what the overall picture looks like. Arguments over whether a single brick should be blue or yellow don’t change the building from a skyscraper to a mud hut.
The IPCC reports should be required reading for anyone who thinks that scientists think that the ‘science is settled’ – the vast array of uncertainties that are discussed and dissected puts that notion to bed immediately. But what we do have are reasons for concern. As Mike Hulme recently wrote:
[S]cience has clearly revealed that humans are influencing global climate and will continue to do so, but we don’t know the full scale of the risks involved, nor how rapidly they will evolve, nor indeed—with clear insight—the relative roles of all the forcing agents involved at different scales.
…
The central battlegrounds on which we need to fight out the policy implications of climate change concern matters of risk management, of valuation, and political ideology. We must move the locus of public argumentation here not because the science has somehow been “done” or “is settled”; science will never be either of these things, although it can offer powerful forms of knowledge not available in other ways. It is a false hope to expect science to dispel the fog of uncertainty so that it finally becomes clear exactly what the future holds and what role humans have in causing it.
Dealing with the future always involves dealing with uncertainty – and this is as true with climate as it is with the economy. Science has led to a great deal of well-supported concern that increasing emissions of CO2 (in particular) are posing a substantial risk to human society. Playing rhetorical games in the face of this, while momentarily satisfying for blog commenters, is no answer at all to the real issues we face.
#496
while it should be easy enough to produce them – my question was specifically about whether the climate models actually do produce them.
if are produced by the climate models we should be able to learn more about their mechanics.
if they are never produced automatically from the climate models – why not?
“You have confirmed what I said. Neither you nor anyone else among the warmers knows what elements of natural variation have caused the flat trend since 1998.”
And you don’t know what’s caused the warming for the last 150 years.
“if they are never produced automatically from the climate models – why not?”
I think you are confusing ‘models’ with ‘model outputs’.
A climate model is a tool. It does not, of itself, do anything (a screwdriver needs a screw to function)
Climate models require inputs. These inputs (when used to model future climate) are scenarios. Google “SRES” for the IPCC report on the scenarios used in the TAR.
The ‘outputs’ depend on the scenarios. So if you were to stick in a scenario where solar forcing changed, the outputs would show the impact of that. If you were to put in a scenario where there is more volcanic activity, the model outputs change. (This has been done)
Of course, one can model solar changes in combination with GHG changes, aerosol changes and volcanos. I’m no modeller, but I assume this has been done.
I don’t know whether anyone has ever run models that look at long-term variations in solar forcing. (The sort that cause ice ages). The models /I/ am interested in are those of the next 100 years or so, because that is what impacts on human activity.
But your question is basically misapplied, because (so far as I understand) the sorts of event that cause significant global climate changes are not in the model, but could be in the /input/ to the model.
Does that answer your question?
Ray Ladbury (#491)says:
“J. Patterson, What you are failing to take into account is the fact that we have very good measurements of temperature over the past ~130 years, while resolution is more limited in the ice core data.”
Resolution can’t be an issue. The hypothesis in question is that positive feedback via increased CO2 concentration accounts for both the rapidity (i.e slope) and magnitude of observed temperature swings in the ice core data. The data is more than adequate to delineate these large scale effects, they are after all the primary signal, and has the advantage due to its time span of _spectral_ resolution which is what is required here. Using standard Sys Id techniques to derive the blackbox model parameters and forcing functions from the data, both the slope and magnitude of the observed temperature swings can be easily accounted for without positive feedback. Tools also exist to detect the presence of positive feedback in the derived forcing function. Such an analysis reveals nothing detectable.
I should also note (in reference to your comment on the modern record), that the rule of thumb is that you need a record length at least twice (and preferably 5x) as long as the time constant you are trying to detect. It the atmospheric time constant of emitted CO2 is only 65 years we wouldn’t be having this conversation.
“It is rather doubtful that Sys. Id. could discern the feedbacks given the noise in the data.”
Again, the hand wavers claim the mechanism in question is responsible for the primary swing. If the positive feedback effect is that subtle, how can it be the driving force in AWG?
“There are about 10 separate lines of evidence constraining CO2 sensitivity. All favor a value around 3 degrees per doubling. All preclude a sensitivity below 2 degrees per doubling. Thus, while there are some uncertainties in individual feedbacks, the net result is well measured.”
In non-linear system analysis it is odd to speak of sensitivities in this way. Sensitivities in such systems must by definition change dramatically over the limit cycle (and fall below unity during limiting else the system output grows with out bound). If your speaking here of the net effect on the output of doubling the CO2, well that is question begging of the first order.
Speaking of limiting, those who hold to the positive feedback theory must of necessity hold that a limiting mechanism exists (else we’d have cooked long ago). If such a mechanism exists, the ice record reveals that it occurs at a temperature 1-2C above our current levels. If you believe as such, what would preclude the same limiting mechanism for limiting the effect of AWG to similar benign levels?
“Resolution can’t be an issue.”
Why?
It’s not like the ice cores are hermetically sealed and chemically 100% inert over thousands (or hundreds of thousands) of years.
If it were, the medical industry wouldn’t have bothered with all those expensive metal containers of strange alloys…
J. Patterson, of course a limiting mechanism exists. However, we aren’t anywhere near that point–as demonstrated by the paleoclimate data (particularly the PETM). The issue is whether the algorithm works with very noisy data–data where the noise at any given time may be larger than the signal. Moreover, the data are not just noisy, but autocorrelated.
http://tamino.wordpress.com/2009/12/15/how-long/
There is a reason why we look for climatic signatures on timescales of 30 years or longer.
#503
If the models are a reasonably accurate representation of the climate then they should model all the significant driving forces.
Having build the models and let them run on their own I would have thought their output would show similar events that have happened the in the past climate. The Little Ice Age is one such event.
A model of Jupiter’s atmosphere would not be very convincing if it never produced something like a giant red spot.
A failure to produce any Little Ice Age ‘events’ could indicate that the model is not complete enough.
The real world temperature rise does appear to have stopped/slowed down/reversed (take your pick of these). The models did not predict this so how reliable are they really even in the short term?
Ray Ladbury: “of course a limiting mechanism exists. However, we aren’t anywhere near that point–as demonstrated by the paleoclimate data (particularly the PETM).”
One would presume the period covered by Vostok would be more relevant to todays climate system and as I mentioned, the peak anomaly is only 1.5-2 degrees C above todays level.
“The issue is whether the algorithm works with very noisy data–data where the noise at any given time may be larger than the signal.”
If by noisy, you natural stochastic variation captured in the data, the noisier the better. It is from the spectral shaping of this background noise that the algorithms extract the system model parameters. If instead you mean to imply that the data itself contains errors that exceed the primary signal, then of course the entire field of paleoclimatology is a sham. Fortunately this is not the case. Fourier analysis of this data reveals amazingly thin spectral lines at all of the Milankovitch frequencies which speaks to the integrity of the data and the accuracy of the time scale adjustments that have been made.
Ray Ladbury: “of course a limiting mechanism exists. However, we aren’t anywhere near that point–as demonstrated by the paleoclimate data (particularly the PETM).”
One would presume the period covered by Vostok would be more relevant to todays climate system and as I mentioned, the peak anomaly is only 1.5-2 degrees C above todays level.
“The issue is whether the algorithm works with very noisy data–data where the noise at any given time may be larger than the signal.”
If by noisy, you mean natural stochastic variation captured in the data, the noisier the better. It is from the spectral shaping of this background noise that the algorithms extract the system model parameters. If instead you mean to imply that the data itself contains errors that exceed the primary signal, then of course the entire field of paleoclimatology is a sham. Fortunately this is not the case. Fourier analysis of this data reveals amazingly thin spectral lines at all of the Milankovitch frequencies which speaks to the integrity of the data and the accuracy of the time scale adjustments that have been made.
J. Patterson, if it were easy to “shape” the background, it would be easier to draw conclusions about the signal–that is not the case. And by “noise” I do not mean errors. There are many different factors that contribute to the “noise”. What makes CO2 stand out is its nature as a long-lived, well mixed greenhouse gas–long persistence and global effect. I rather doubt that the techniques you are offering would tell us much more than that.
Phil C. says “The real world temperature rise does appear to have stopped/slowed down/reversed (take your pick of these). The models did not predict this so how reliable are they really even in the short term?”
Um, actually they do.
https://www.realclimate.org/index.php/archives/2008/05/what-the-ipcc-models-really-say/
“One would presume the period covered by Vostok would be more relevant to todays climate system”
Why would one do that?
“If the models are a reasonably accurate representation of the climate then they should model all the significant driving forces.”
They do.
And for the timescale of centuries, the change in orbitals is not significant. Hence left out.
For paleoclimate research, millions of years, the change in orbital is significant and so is the change in solar output. Hence included.
Why do YOU believe (since you have no proof it IS belief) different?
“If the models are a reasonably accurate representation of the climate then they should model all the significant driving forces. ”
As pointed out, there is no significant trend in solar over the course of time that we are seeking to model.
If we were trying to model climate over the next 100,000 years, that would be a different question. We aren’t.
“Having build the models and let them run on their own I would have thought their output would show similar events that have happened the in the past climate. The Little Ice Age is one such event.”
Did the Little Ice Age actually exist? IPCC think not “Thus current evidence does not support globally synchronous periods of anomalous cold or warmth over this timeframe, and the conventional terms of “Little Ice Age” and “Medieval Warm Period” appear to have limited utility in describing trends in hemispheric or global mean temperature changes in past centuries… [Viewed] hemispherically, the “Little Ice Age” can only be considered as a modest cooling of the Northern Hemisphere during this period of less than 1°C relative to late 20th century levels”
“A model of Jupiter’s atmosphere would not be very convincing if it never produced something like a giant red spot.”
We aren’t, in case you noticed, modelling that.
“A failure to produce any Little Ice Age ‘events’ could indicate that the model is not complete enough.”
Are you suggesting that the models would need to sucessfully replicate observed results in order for us to have confidence in it?
Oh good. They do.
http://bartonpaullevenson.com/ModelsReliable.html
“The real world temperature rise does appear to have stopped/slowed down/reversed (take your pick of these).”
None of ’em. Within the S/N it is rising as quickly as before.
“The models did not predict this so how reliable are they really even in the short term?”
Did they not?
Do you know what the error bars on the model outputs are? Does the temperature fall within the error bars?
Do climate models predict steady temperature rises, or does the output vary from year to year like the real world?
Incidentally phil c, if you are /really/ interested in climate models, you can take a look at the actual output of them.
The control run from HadGEM (or any other model) should give you an idea of what sort of year-to-year fluctuations you see from a climate model
http://www.mad.zmaw.de/IPCC_DDC/html/SRES_AR4/index.html
514
“Did the Little Ice Age actually exist? IPCC think not “Thus current evidence does not support globally synchronous periods of anomalous cold or warmth over this timeframe, and the conventional terms of “Little Ice Age” and “Medieval Warm Period” appear to have limited utility in describing trends in hemispheric or global mean temperature changes in past centuries… [Viewed] hemispherically, the “Little Ice Age” can only be considered as a modest cooling of the Northern Hemisphere during this period of less than 1°C relative to late 20th century levels”
this “modest” cooling lead to very modest freezing on the thames in the centre of London. This allowed very modest ‘ice fairs’ to take place each year.
The Little Ice Age is a well known historical fact but as the Peer Reviewed tree rings etc. prove it never happened then I guess we’ll just have to deny it really happened.
Ray Ladbury: “if it were easy to “shape” the background, it would be easier to draw conclusions about the signal–that is not the case.”
This is incoherent. Spectral shaping of necessity occurs as the forcing signals pass through the system processes (in this case the system = the global climate). This is basic transfer function theory.
“And by “noise” I do not mean errors. There are many different factors that contribute to the “noise”. What makes CO2 stand out is its nature as a long-lived, well mixed greenhouse gas–long persistence and global effect.”
All the easier its global effect, if any, can be characterized via Sys Id techniques.
#514
““A model of Jupiter’s atmosphere would not be very convincing if it never produced something like a giant red spot.”
We aren’t, in case you noticed, modelling that.”
My point was that an Earth Climate model that never produced a “Litte Ice Age” or “Medieval Warm Period” would not be too convincing either. But now the IPCC have said these never happened, I’m relieved to know the models are much more accurate.
How much do we really know?…
We are basing this on what we know now. There is a whole universe out there. What effect does this have on our climate and weather. Do we even know? Its like saying is there life out there? And how many people have seen UFOs.
The real questions are:
Are you taking a van-pool or carpool to work?
Are you turning off all your lights as soon as possible?
Are you recycling all you can?
This is from an American. You know the biggest consumer of energy in the world.
What are the little things being done. How many jets were taken to Copenhagen?
How many limousines were used there? People talk, but how many are doing?
I believe that there is as much cause from the universe as there is from humans,
but we just haven’t figured it all out yet. That’s because we as humans just don’t
know very thing yet. So if we do as much as we can and try and figure the rest out,
I think we will be just fine. Of course just the opinion of one man.
Re: Comment 493 by Silk – thankyou for your response. However HIV/AIDS, gravity and Einstein’s theorems are able to be tested against the behaviour of the real world, in real time, whereas you’d think the theory of anthropogenic global warming can’t be tested, except by waiting and seeing what happens. Computer modelling cannot – surely – duplicate the complexity of the entire earth and all its systems. It’s an entirely different ball game to identifying the modus operandi of one virus, or the laws of gravity – with them, you can sit down, figure out what should happen in scenarios x,y or z and then go an implement scenarios x, y or z to test the predictive efficacy of the theory. You guys can’t do that. So I’m trying to find the parts of your work which are testable and easily reproducible. Please bear in mind here that I am a trained historian, not a scientist, and I have no idea of the maths or statistics you work with, which are clearly very complicated. Now, you asked: “Do you have any idea how much a climate model which WORKED and which could disprove climate change would be worth?” To me, that’s an odd question because we don’t need a *model* which works – we have the real thing – we have planet earth! It works! It coheres! It hangs together and chugs along beautifully as far as I can see… but now that you mention it, if it would be worth billions to have a model that could demonstrate that everything’s fine – is there anyone who’s tried to build one?
Now, the CRU guys – you may find that the whole thing ends up as a boon to yoru cause in the sense that it has focussed many people’s attention, including mine, for the first time on really trying to understand what’s going on with AGW. It has quite simply been in the too-hard basket for me thus far in my life to really try to get to grips with. I don’t yet know whether I think they did something wrong, but lots of traditional scientists think they may have, so I need to try and find out what I think. That’s why I’m here. Now, what do I seek that RealClimate doesn’t provide? – I notice many responses from scientists here which are very testy. I know you’re smart and you’ve given your lives to doing this work, but please endeavour to be patient with people who come looking – intellectually clobbering people won’t endear you to them. Patient explanations will. Finally may I ask you a concrete physics-based question – one glaring anomoly I’ve found in AGW accounts and skeptic accounts of atmosphere is the level of past CO2 in the atmosphere… this site says (somewhere) that CO2 is higher now than it’s been for the past 250,000 years; whereas many scientists in traditional areas like geology (e.g. at this site – http://www.geocraft.com/WVFossils/Articles1.html)say CO2 is the lowest it’s been for 500,000 years. Measuring past CO2 is supposed to be the easy bit – so why such discrepancies between the sciences? That is the question I am currently trying to answer for myself, I’d be grateful for any pointers you can give. Many thanks, Catherine.
[Response: CO2 is very definitely higher than it has been for 800,000 years. Probably higher than it’s been in ~2.5 million years, and possibly will get higher than it has been for ~20 million years. The IPCC reports are helpful here (last panel) and here. – gavin]
Oh, another question, I was reading an atmosphere site which said that if global temperatures are rising, then it’s the satellite measurements of atmospheric temperature about 5kms up, halfway through the troposphere, which will be of most interest, because this is where the greatest concentration of CO2 is found, and hence the greatest trapping of heat will occur at that point – is that correct in your understanding? Many thanks, Catherine.
[Response: Not very close I’m afraid. See our discussions about tropical tropospheric trends for more info. – gavin]
Phil C.
You’re really confused, by accident I hope.
Nobody questions there were _European_ event that, in Eurocentric records, is recorded as a “little Ice Age” event and “Medieval warm period.”
The IPCC documents include the records and research done on sites elsewhere in the world — these were not global events.
The Europeans had a lot of funny ideas about how they were the entire world and what happened there was all that mattered. You should look beyond that limited nomenclature.
Hello Catherine– If you’d like, I’d happy to be of some help.
CO2 concentration is the highest it has been in at least 800,000 years (see Luthi et al’s paper which I discussed here). There is no disagreement about this in the scientific community. “geocraft.com” rarely has anything coherent to say about this subject, and I would advise against using it as a resource. After you go beyond the ice core record, assessing past CO2 concentrations becomes a bit dicier, although I think we can say with some confidence that you can extend the above statement out to at least several million years. Just as important, the rate of change of CO2 concentration is extremely unusual.
Hat tip to MapleLeaf over at Deltoid for this:
“… posted at The Air Vent on 12 November 2009. Jeff Id says at one point “so let’s have a little fun with the team”. You can read the full post at: …
noconsensus.wordpress.com/2009/11/12/no-warming-for-fifteen-years/ ”
(Tamino has dealt with this stuff recently.)
“this “modest” cooling lead to very modest freezing on the thames in the centre of London. This allowed very modest ‘ice fairs’ to take place each year.”
Well, in addition to modest warming since 1800, there were also a number of changes to the Thames, including embankments and London bridge changes, such that even if temperature were to return to those colder periods it is unlikely that a frost-fair could occur with the current river configuration.
Hank Roberts: “Nobody questions there were _European_ event that, in Eurocentric records, is recorded as a “little Ice Age” event and “Medieval warm period.””
I think there are researchers who suggest that the “event” was more widespread than just Europe.
http://www.sciencemag.org/cgi/content/short/324/5923/78
It seems like so much of the debate over the models is dealing with is warming happening now and is it caused by CO2 by humans. And that given CO2 will continue to rise that temperatures will also increase.
That said, I actually have a question about modeling for the future. Was reading up on your blog postings and it seems that you don’t have any describing exactly how you account in the models for human forcing of the climate over time.
I understand the difference between climate and weather as you have outlined on this site, so my question is regarding the climate models the IPCC uses in order to predict the climate change effects by year 2100.
As you have stated in previous blog posts it seems the following are used to create these models:
“…deal with radiative transfer, the circulation of the atmosphere and oceans, the physics of moist convection and cloud formation, sea ice, soil moisture and the like. They contain our best current understanding for how the physical processes interact (for instance, how evaporation depends on the wind and surface temperature, or how clouds depend on the humidity and vertical motion) while conserving basic quantities like energy, mass and momentum. These estimates are based on physical theories and empirical observations made around the world.”
Seems more than understandable; you are taking the information known about these forces and running models against them to determine if they are accurate and as you also noted:
“And are those predictions in different cases then tested against observations again and again to either validate those models or generate ideas for potential improvements? Yes, again.”
Fair enough, but the climate is also being effected by human actions and output of CO2.
So, here’s my questions: How to you account for the human forcing of CO2 over time then? It’s been noted that the standard is just to double CO2 for the models, but then I saw this:
http://en.wikipedia.org/wiki/Special_Report_on_Emissions_Scenarios
But what are the underlying assumptions behind the various tiers and their subsets? For example subset in A1 “A1B – A balanced emphasis on all energy sources.” What qualifies as a “balanced emphasis”? Is it a total number of pounds of C02 emitted in one group versus another? What is that actual number if that’s how it’s calculated? And if so, HOW is that number calculated, by an assumption on population growth?
Do you account in the models for the probability of huge technological improvements that could have large effects on human CO2 output?
Any other nature forces (I understand aerosols are accounted for in the models) or disasters that could effect the human race, and thus the output levels of CO2?
If so, where can I read about how those probabilities are incorporated into the models?
It just seems like there are wide variables in terms of the future output CO2 and thus impossible to calculate to a high degree of certainty.
Don, of course — but not global ones that match the European records, which is what the guy above was upset about, claiming the IPCC had done away with something he believed was global.
By the way, did you click the link at the bottom of the page, where it says “Cited by” this paper?
http://www.sciencemag.org/cgi/content/abstract/326/5957/1256
> Catherine Jameson says:
> I was reading an atmosphere site
Care to cite the source? It’s always interesting and sometimes helpful to be able to read the original. I tried searching on words from your posting and found a few sites but nothing that seemed likely to be your source.
Don Shor says: 15 December 2009 at 10:03 PM
“I think there are researchers who suggest that the “event” was more widespread than just Europe.”
Careful scrutiny of the entire article suggests reorganization of thermal energy, not a global net change. Interesting that the notorious Mann cited the piece (http://www.sciencemag.org/cgi/content/full/326/5957/1256), using it along with other findings to better understand global surface temperatures during the medieval period:
“…Global temperatures are known to have varied over the past 1500 years, but the spatial patterns have remained poorly defined. We used a global climate proxy network to reconstruct surface temperature patterns over this interval. The Medieval period is found to display warmth that matches or exceeds that of the past decade in some regions, but which falls well below recent levels globally…”
I suppose this means Trouet and coauthors are part of the Global Conspiracy. In fact, Mann’s use of the term “network” to describe the proxy methodology could well be a slip of the tongue, the smoking gun giving away the whole conspiracy show. Right?
522
Is it surprising that I am confused over the Little Ice Age?
First it’s an established fact of history.
The IPCC reduce it to ‘modest cooling’
and it was localised to Northern Europe
except some people claim it was more global.
Whatever it was, the LIA coincided with the Maunder Minimum which could be a coincidence and as some indicators show the Sun may be sunspot free in 2015 we may have the opportunity to find out soon.
I accept the layout of the Thames has changed but with the amount of cold necessary to freeze the Thames in central London circa 1770 we may have to relocate the ice-fairs to say, the Serpentine in Hyde Park.
If the consensus IPCC view is that the Little Ice Age was only “localised modest cooling of only 1degree” then quite a few people (including me) would say the peer reviewed consensus is wrong on this topic.
phil c – This paper will be of interest to you. It shows the skill of regional climate modelling (which is more difficult than global modelling, for fairly obvious reasons) in predicting extreme weather events.
http://www.hydrology.org.uk/Publications/durham/bhs_07.pdf
Or you could do it yourself. See https://www.realclimate.org/index.php/archives/2008/11/faq-on-climate-models/#more-527
Also, you asked if people were doing work on running climate models long-term to see what comes out. Yes they have, and yes the are. See http://cmip-pcmdi.llnl.gov/index.html?submenuheader=0
I’ll leave the last word on the subject to the IPCC. Everything you could possibly want to know about climate modelling is contained therein, and in the references. You don’t need me to explain it to you.
If you /genuinely/ care about whether or not climate models are reliable, see http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter8.pdf
I draw your attention to FAQ 8.1 (particularly Figure 1). See also figure 9.5 in Chapter 9, which shows that models can distinguish between what would happen without manmade impacts, and what would happen with manmade impacts (and note which one is best preproduced!)
I’m signing off now. You’ve got all i know about climate models. If none of it satisfies you, as above, you can run your own model and see what happens.
“Re: Comment 493 by Silk – thankyou for your response. However HIV/AIDS, gravity and Einstein’s theorems are able to be tested against the behaviour of the real world, in real time, whereas you’d think the theory of anthropogenic global warming can’t be tested, except by waiting and seeing what happens.”
Er, no. There is no “theory of AWG”. What there is is a theory of how the climate responds to forcing.
And there are plenty of ways you can test the theory of how climate responds to forcing. You can look at recent temperature trends. You can look at paleoclimate data. You can see how the climate responds to perturbations like volcanic eruptions, and test your understanding against those. You can see how well your model replicates rainfall, etc. to see if it is reliable. And you can do detection and attribution studies.
We /already/ have enough data to understand how humans have impacted on climate change. There is no need to wait and see, because human impact on climate can be directly demonstrated.
“Computer modelling cannot – surely – duplicate the complexity of the entire earth and all its systems.”
Are you saying that, because the earth is a very complex system, we can’t model it and therefore we should give up? Because if you /are/ saying that, this discussion is utterly pointless and we can all go home now.
” It’s an entirely different ball game to identifying the modus operandi of one virus, or the laws of gravity – with them, you can sit down, figure out what should happen in scenarios x,y or z and then go an implement scenarios x, y or z to test the predictive efficacy of the theory.”
I have no idea about the relative difficulties of understanding viruses, so I don’t agree or disagree with this statement.
“You guys can’t do that.”
I’m not one of those ‘guys’, simply a member of the public.
“So I’m trying to find the parts of your work which are testable and easily reproducible. Please bear in mind here that I am a trained historian, not a scientist, and I have no idea of the maths or statistics you work with, which are clearly very complicated.”
You can test the following :
a) That CO2 and other GHGs in the atmosphere are manmade.
b) That an atmosphere of IR absorbers warms the planet (compare mean surface temperatue of moon to that of earth!)
c) That CO2 absorbs IR radiation, and that doubling the concentration of CO2 in the atmopshere would cause a forcing of X/W per sq metre of earth’s surface.
d) That paleoclimate shows the response of the atmosphere to changes in forcing equivalent to doubling CO2 to be around 3 degrees
e) That reconstructions of climate of the last 150 years or long are consistent with this.
All of those can be tested. If you can disprove any of them (and there’s a lot of evidence for all, so you can use that evidence, or new evidence, to test them) then our theory of how the climate works would have to be reconsidered.
“it would be worth billions to have a model that could demonstrate that everything’s fine – is there anyone who’s tried to build one?”
No one, so far as I know, has tried to build a model with the ‘output’ in mind (i.e. you don’t set out to prove global warming, you set out to get a model that has ‘skill’). There are lots of scientists out there, trying to build better and better models.
If Exxon, say, really really thought they could disprove climate change, and really really thought all the modellers were political and thus wouldn’t bring out a model that challenged AWG, they could easily employ their own modelers to produce alternative models.
Personally I believe its paranoia to think that climate models are somehow ‘biased’ to prove global warming. Not that I’m accusing you of this, of course. But if any skeptic wants to build a model, they can. These things are hardly secret.
“Now, the CRU guys – you may find that the whole thing ends up as a boon to yoru cause in the sense that it has focussed many people’s attention, including mine, for the first time on really trying to understand what’s going on with AGW. It has quite simply been in the too-hard basket for me thus far in my life to really try to get to grips with. I don’t yet know whether I think they did something wrong, but lots of traditional scientists think they may have, so I need to try and find out what I think. That’s why I’m here. Now, what do I seek that RealClimate doesn’t provide? – I notice many responses from scientists here which are very testy. I know you’re smart and you’ve given your lives to doing this work, but please endeavour to be patient with people who come looking – intellectually clobbering people won’t endear you to them. Patient explanations will.”
I’ve been here a while. Gavin et all are usually very polite (and certainly more polite than if I went to a deniers website and said “I am sorry, you are wrong. Please look at papers X, Y & Z”
Two things make them testy.
a) People asking basic questions that they could answer themselves by reading the FAQ, or clicking “Start here”
b) People who ask more difficult questions, are given the answer, and then ask the questions again. These so-called “trolls” are basically attention seekers and not interested in climate.
“Finally may I ask you a concrete physics-based question – one glaring anomoly I’ve found in AGW accounts and skeptic accounts of atmosphere is the level of past CO2 in the atmosphere… this site says (somewhere) that CO2 is higher now than it’s been for the past 250,000 years; whereas many scientists in traditional areas like geology (e.g. at this site – http://www.geocraft.com/WVFossils/Articles1.html)say CO2 is the lowest it’s been for 500,000 years. Measuring past CO2 is supposed to be the easy bit – so why such discrepancies between the sciences? That is the question I am currently trying to answer for myself, I’d be grateful for any pointers you can give. Many thanks, Catherine.”
This one is easy. See https://www.realclimate.org/index.php/archives/2005/11/650000-years-of-greenhouse-gas-concentrations/
Catherine – PS. This is a really good page. It shows you what climate sensitivity is from a variety of different sources, most of which are measured (and hence testable) http://www.skepticalscience.com/climate-change-little-ice-age-medieval-warm-period.htm
phil c, no one is saying the LIA didn’t happen. They’re saying it wasn’t global. Do you understand the difference?
#535
I understand the difference.
But it comes down to whether you believe the IPPC on this when there appears to be evidence that it actually was Global
I know Wikipedia is not peer reviewed however, http://en.wikipedia.org/wiki/Little_Ice_Age
RS,
I did the work to prove my point. Here it is:
http://BartonPaulLevenson.com/30Years.html
phil c “I understand the difference.
But it comes down to whether you believe the IPPC on this when there appears to be evidence that it actually was Global”
So you don’t know if the IPCC is right, so you assume they’re wrong?
Why?
And why is their version of wrong “the MWP was global” rather than “the MWP isn’t even there”, which are the two ways of being wrong from the IPCC reconstruction of the MWP: more MWP or less MWP.
538
I dont assume they are wrong – if they are saying it is localised and there is evidence that it is global then they could be wrong.
do you assume they are always right?
Re#527
First, “Eric” you probably need to chose a new name. eric is a regular contributor here and your’s will cause confusion.
“But what are the underlying assumptions behind the various tiers and their subsets? For example subset in A1 “A1B – A balanced emphasis on all energy sources.” What qualifies as a “balanced emphasis”? Is it a total number of pounds of C02 emitted in one group versus another?”
Read the SRES. It’s online.
“Do you account in the models for the probability of huge technological improvements that could have large effects on human CO2 output? ”
No model assumes fusion. The B1 model makes some assumptions about increasing efficiency leading to emissions reductions.
Critically, the IEA (who know more about energy than you, me or anyone else) have made estimates of what happens to emissions to 2030 and 2050, and it ain’t pretty. Without significant policy intervention, CO2 emissions double by 2050. The reason for this is simple – coal is the cheapest fuel there is, and without policy intervention, will remain so for a few decades. Once you build a coal fired power station, you run it for 30-40 years to get your money’s worth. And no, we aren’t running out of coal.
So, without a carbon price or carbon regulation, CO2 emissions will just keep going up, at least to 2030. By that point, it’s too late to avoid 450ppm, or probably even 550ppm.
“Any other nature forces (I understand aerosols are accounted for in the models) or disasters that could effect the human race, and thus the output levels of CO2?”
No. The base assumption is the human economy continues to grow. Why would that be a problem?
“It just seems like there are wide variables in terms of the future output CO2 and thus impossible to calculate to a high degree of certainty.”
Not at all. There’s a very strong correlation between economic growth and CO2.
Is economic growth uncertain? Of course. Which is why we have such a wide range of scenarios.
You’ll note that ALL scenarios go above 2 degrees. And that since the SRES the scenario that reality has most closely followed is A1.
Of course, a plague could wipe out 90% of humans. In which case, emissions becomes less of an issue. Can you estimate the probability of that occuring?
“If you look at the peer reviewed scientific literature, the debate is over.” Al Gore
Is that correct, Al ?
Chris Robertson (541) — Please read “The Discovery of Global Warming” by Spencer Weart, first link in “Science Links” section of the sidebar.
> Chris Robertson
What that means depends on the context, of course.
Do you know the context?
What were they talking about exactly?
Certainly he doesn’t mean all science is done.
He must be referring to some particular question.
You might want to look into the details a bit more.
Formally posting as “Eric” in [527]
I read the SRES. Thanks for the reply.
Seems like a pretty broad assumption to make that economic growth and or population growth automatically means more CO2 output; regardless of the the variant level these scenarios assume. If the reason why it’s assumed to be that way is cause it’s always been that way that’s a pretty specious justification.
There are very serious endeavors underway to deal with this issue. Frankly, it’s insulting that these models seem to place SO little value in their efforts that they are not accounted for with the models.
And I don’t agree with your assumption that without “significant policy intervention” this solution is solvable.
Carbon price setting will serve just to make the resource more scarce, and good luck trying to get the Chinese government to go along with a price setting for carbon. It’s never going to happen. This solution requires a technological solution, not a governmental one.
Yes, Chris, that’s right.
Of course your quote is out of context (are there ANY posters here who are surprised at that???).
“Is AGW real and a genuine problem we need urgent action on?”
Yes. The peer reviewed scientific literature says that that debate is over.
539, no you DO assume they are wrong.
You want to wait, therefore acting as if they are wrong and there’s nothing to worry about that is the result of them very specifically being wrong in a “there’s no problem” kind of way, which your arguments about how MWP was warmer, so therefore there’s no problem, right?
If the MWP is wrong in a way where it was LESS then we’re in a worse situation than we figured because the effect of CO2 could be at the upper end (since the MWP puts a constraint on the upper levels of sensitivity of temperature to CO2).
Of course you never SAY anything, just “ask questions”. In a very Glen Beck style of way.
In just such a way as “Are you preferring to smoke up now and leave someone else’s kids to clean up your mess after you die rich, fat and happy? I’m just asking”
So are you misanthropic?
Phil c,
The global or regional nature of the Little Ice Age is not completely settled, one of the main problems being that the events in different regions are not synchronous. Today’s warming is global, with direct measurements that allow modeling and attribution of the forcings. In the Little Ice Age, it is not likely there was any significant change in forcing from CO2, but from volcanoes and possibly solar intensity. The Realclimate glossary has a bit of things to say about it.
533
Silk “Are you saying that, because the earth is a very complex system, we can’t model it and therefore we should give up? Because if you /are/ saying that, this discussion is utterly pointless and we can all go home now.”
The main concern about the models is not that they are pointless but that they are presented to the public as if they are a true measure of what will happen.
Do the models take into account cosmic rays in the formation of clouds – they cant do this properly because no one really knows if really do effect clouds and if so to what extent.
Should if the experiments at CERN provide information that cosmic rays do seriously effect clouds that would show that the models must have been missing an important driving mechanism.
546
Thanks for sharing
phil c (548) — The CLOUD experiment at CERN is most unlikely to be definitive due to wall effects. In any case, cosmic rays have been the subject of more than one threaed here on RealClimate. In those, it is pointed out that cosmic ray flux has not changed in the 50+ years of measurements while the climate certainly has.
Here is my amatuer understanding: in almost all parts of the globe there is a superabundance of CCNs; cosmic rays don’t have much chance of causing any more condensation as the necessary CCNs are there anyway.