Bishop Hill Revkin does low climate sensitivity
Feb 4, 2013 Andy Revkin has taken a long hard look at the trend towards low climate sensitivity estimates and seems to conclude that things are just as the sceptics have said.
I can understand why some climate campaigners, writers and scientists don’t want to focus on any science hinting that there might be a bit more time to make this profound energy transition. (There’s also reluctance, I’m sure, because the recent work is trending toward the published low sensitivity findings from a decade ago from climate scientists best known for their relationships with libertarian groups.)
Nonetheless, the science is what the science is.
It's a must-read.
Bishop Hill
Anthony has further insights, gleaned from an email exchange Revkin had with Gavin Schmidt of NASA. Schmidt's view is this:
Andy, I think you may be slightly misrepresenting where the ‘consensus’ on this issue has been. While there have been occasional papers that have shown a large tail, and some arguments that this is stubborn – particular from constraints based on the modern tranisent changes – there has always been substantial evidence to rule these out. Even going back to the 2-11deg C range found in the initial cpdn results in 2005, many people said immediately that the high end was untenable (for instance).
Indeed, the consensus statements in the IPCC reports have remained within the 1.5 – 4.5 range first set by Charney in 1979. James’ work has helped improve the quantifications of the paleo constraints (particular for the LGM), but these have been supported by work from Lorius et al (1991), Kohler et al (2010), etc. and therefore are not particularly radical.
By not reflecting that, you are implying that the wishful thinking of people like Ridley and Lindzen for a climate sensitivity of around 1 deg C is tenable. It is not, and James’ statement was simply alluding to that. For reference, James stated that his favored number was around 2.5 deg C, Jim Hansen in a recent letter to the WSJ quote 2.5-3.5 (based on the recent Palaeosens paper), and for what it’s worth the CMIP5 GISS models have sensitivities of 2.4 to 2.7 deg C. None of this is out of the mainstream.
Lindzen has of course argued for sensitivity around 1deg;C, but Ridley was arguing for 1.6 in his WSJ essay. The idea that figures like this are "untenable" seems to me to be extraordinary given that our only fully empirical estimate and a series of other studies give precisely this figure.
To Schmidt's comment, Revkin adds this:
In policy circles, including popular calculations of emissions trajectories necessary to avoid a high chance of exceeding 2 degrees C. of warming, the hot tail has not been trimmed (unless I’m missing something?).
To me, that says the climate science community — including the Intergovernmental Panel on Climate Change science working group — has not adequately conveyed the reality you state here.
And Richard Betts agrees:
You’re right – see, for example, the Stern Review, Table 1.1 right-hand column, citing Meinshausen (2006) to give a wide range of warming for different stabilisation levels, and compare that with the other 2 columns (TAR range and Hadley Centre model range) – the Meinshausen range was then used later in the review to inform the economic impacts modelling (Box 8.1, page 220)
So Stern used a fat-tail distribution not the TAR distribution.
Bishop Hill
I'm struggling to reconcile Richard Betts' observations with the remarks on climate sensitivity by Chris Hope on the PAGE2002 model (the basis of the Stern Review) as reported in my post on Climate Sensitivity and the Stern Report.
The mean value is unchanged from the default PAGE2002 mean value of 3°C, but the range at the upper end is greater. In PAGE2002, the climate sensitivity was input as a triangular probability distribution, with a minimum value of 1.5°C and a maximum of 5°C.
I'm going to ask Richard and Chris to clarify. Please don't jump to conclusions in the meantime.
Bishop Hill
Gavin tweets:
@Revkin somewhat overstates impacts of changes in CS. It is not too small to be negligible, nor so large to be a nightmare
Reader Comments (147)
Bengt,
That confirm my suspicion and reinforces my hypothesis that all of this is a theological dicussion.
You can write the Summa Theologicae and spend eight centuries in very learned, sophisticated and academic discussions, but rather pointless if you happen to question the premises.
LA,
How many Hurricanes can twist on a plus-minus zero?
Feb 4, 2013 at 6:07 PM | Paul Matthews
And speaking of "goalpost-moving", there's an example in the comments ... Straight from the Lemon(s)ade stand, so to speak:
YMMV, but I'm not sure how a 1975 "Ph.D in zoology and physiology" qualifies Lemons to claim "expertise" in:
Oh, well, perhaps not unlike fruit-fly expert, David Suzuki - or water expert, Peter Gleick - Emeritus prof. John Lemons is a self-proclaimed guru on the "ethical" green-front.
Thanks Hilary - I wasn't expecting my prediction to come true that quickly!
Another climate expert, Christopher Green (economics) has followed a similar path:
followed by more paragraphs of meaningless self-righteous waffle.
I predicted the end of global warming in America a few months ago. The NYT shut its environment desk, now Revkin is doing his part by questioning the science. Turkey voting for Christmas.
The only reason we are aware of AGW is that Hansen was given $720,000 by a Soros front to fight his own employers, NASA who were trying to stop him embarrassing them with his hysteria. What did Hansen spend this money on ? Soros has one of the biggest hedge funds in the world. Even bigger than Lord Stern's employer Jeremy Grantham.
Richard Tol (Feb 4, 2013 at 8:15 PM)
"The impact of a lower climate sensitivity on emission reduction policy is one of three..."
You omitted a fourth, namely:
If the aim is to replace fossil-fuel energy with a not-hugely-more expensive form of energy, a lower sensitivity allows additional time for technology to evolve.
.
We're constantly told that solar prices are reducing...if that's a reasonable technology to switch to [I have my doubts], waiting longer is a good. Or perhaps the next generation of nuclear energy. Or something as-yet unproven at scale, such as molten-salt reactors.
Feb 4, 2013 at 6:37 PM | MarkB
Right on the nose! Bertolt Brecht would salute you, affectionately.
There's a nice record of ocean chemistry changes here: (NOT)
http://stevengoddard.wordpress.com/2011/02/17/monterey-bay-aquarium-shows-no-change-in-ocean-ph/
Feb 4, 2013 at 5:15 PM | steveta
Monterey Bay, an interesting choice to demonstrate that there is no change. The bay receives upwelling deep ocean water. This will be relatively low in CO2 and has a higher pH, insulating the bay from possible changes in pH due to extra dissolved atmosphericCO2. Even so a trend of decreasing pH is apparant in the data.
http://www.cencoos.org/sections/conditions/changing_ocean.shtml
http://www.cencoos.org/visual_media/news/Climate_Change/California_Upwelling_Narayan.JPG
ttp://www.cencoos.org/visual_media/news/Climate_Change/MBARI_pH_pCO2_1993_2008_C1_M2_transect_means.JPG
Latimer Alder Feb 4, 2013 at 5:06 PM
I saw your comment at dot earth and was tempted to answer it over there, but alas, I fear that audience is not generally open to technical details.
I don't know about a global GISS-like compilation of ocean pH, but this one is kind of interesting.
http://hahana.soest.hawaii.edu/hot/trends/trends.html
(Select "pH Comparison" on the drop down menu.)
It even has a history of GISS-like adjustments, which is documented on this discussion at Niche Modeling
http://landshape.org/enm/errors-adding-up/
The discussion is best read with "oldest comments first" selected. Unfortunately, you'll have to live with the nesting and frequent hitting of the "list more comments" button.
The discussion got somewhat animated at times, but within my comments there are several other links that point to the state-of-the-art with regard to ocean pH measurements.
In short, my opinion of ocean pH measurements is that there is some good science being attempted, but certainty of trends is overstated (usually by omitting error bars), complexity of the method is not appreciated, and there is still a whole lot not known about the ocean's buffering capacity.
That, of course, doesn't stop ocean acidification from being "Plan D" on the CAGW drawing board (with Global Warming, Climate Change, and Climate Extremes having been A, B, and C).
models dont constrain the estimates for sensitivity. un fool yourselves guys.
Sensitivity suddenly pops up in four blogs on the same day – this one, Climate etc, WUWT and Dot Earth. It seems to be a big thing that it has turned out to be quite a bit lower than IPCC says. This seems to please lukewarmers but I am not one of them – I am a complete denier, and the importance of sensitivity to me is something of the order of discussing how many angels can fit through the eye of the needle. Nevertheless, most climate people follow it so let’s have a go at it. There is no warming now and there has not been any for the last 16 years while carbon dioxide kept increasing. No amount of talk about sensitivity can explain this. The theory of greenhouse warming demands that increasing carbon dioxide must cause warming. For a scientist, sixteen years with no warming ought to be enough to tell him that the experiment has failed, that the attempt to cause warming by putting carbon dioxide in the air just does not work. When greenhouse warming comes up the climate scientists always cite the work or Arrhenius. You may not be aware of this but if you follow Arrhenius and calculate sensitivity you will get 1.1 degrees for doubling of CO2, not 3 degrees as IPCC tells us. The IPCC realized from the start that 1.1 degrees will not scare anyone so they decided to use the help of water vapor to jack up the Arrhenius heat. It goes like this. First, carbon dioxide warms the air. That warm air can now hold more water vapor. The greenhouse effect from that extra water vapor will then cause additional warming that gets added to the original warming from carbon dioxide. Their computers tell us that this can triple or raise even more the original warming from carbon dioxide. This is called positive water vapor feedback. And that is where all those dangerous predictions of warming come from. But this is all wrong as Miskolczi’s analysis of radiosonde measurements proves. He showed that atmospheric absorption of long-wave radiation was constant for 61 years while at the same time carbon dioxide increased by 21.6 percent. This substantial amount of carbon dioxide did not increase IR absorption by the atmosphere by one whit. And it is this absorption of radiant energy that is needed by the greenhouse gases to create their eponymous warming. No absorption means no greenhouse effect, case closed. And this settles the sensitivity issue: true sensitivity for doubling of carbon dioxide is exactly zero. Miskolczi theory also tells us that water vapor feedback is negative, not positive, as IPCC claims. Negative feedback works like this. Both carbon dioxide and water vapor are greenhouse gases and as carbon dioxide increases water vapor decreases. Their absorption effects cancel out mutually and as a result radiosondes will see no change in absorption as Miskolczi observed. Because of this all model predictions of dangerous warming ahead are false. And since many of them have been used to justify global warming laws and and regulations these laws and regulations have been passed under false premises. They have to be voided.
Richard Tol Feb 4, 2013 at 8:15 PM
One other possibility would be:
If the aim was to have a "negligible" effect on temperature, and climate sensitivity was deemed to be "negligible" then the need for emission policy reduction would be negated.
Naturally, this would lead to the question of what a "negligible" effect on temperature would be. Richard, as an exercise in thought, may I ask what you would think would be the minimum climate sensitivity needed to justify an emission reduction policy?
I would also like to say that I greatly enjoy your contributions to the both the Bishops blog and the Irisheconomy. Keep up the good work.
@Arno Arrak
Many thanks.
Arno Arrak writes:
"You may not be aware of this but if you follow Arrhenius and calculate sensitivity you will get 1.1 degrees for doubling of CO2, not 3 degrees as IPCC tells us. The IPCC realized from the start that 1.1 degrees will not scare anyone so they decided to use the help of water vapor to jack up the Arrhenius heat. It goes like this. First, carbon dioxide warms the air. That warm air can now hold more water vapor. The greenhouse effect from that extra water vapor will then cause additional warming that gets added to the original warming from carbon dioxide. Their computers tell us that this can triple or raise even more the original warming from carbon dioxide. This is called positive water vapor feedback. And that is where all those dangerous predictions of warming come from."
Good of you to remind us that you cannot separate the discussion of sensitivity from discussion of forcings. Because there is, even at this very late date, not one well confirmed physical hypothesis about any forcing then we are forced to conclude that all their talk of sensitivity will not bring them to empirical science any more than their talk of forcings did. Talk of sensitivity will always be locked into talk of computer models. No matter what the climate does, they can set a range for sensitivity that is frightening.
models dont constrain the estimates for sensitivity. un fool yourselves guys.
It wasn't "us" who brought the use of models into the whole business. Most of "us" wouldn't believe a model estimate for anything climatic.
When Mann, Hansen, Schmidt et al stop quoting values from models, then I imagine so will all the sceptics.
I personally have issues with sensitivity having any bounds at all. If it is a real thing, then it is an exact value. It needs to be put into a model, in order for it to be a good model, not extracted from it.
It's as if the income tax rate was determined by the Treasury investigating its economic models, rather than its economic models being build using the known values.
This is entertaining beyond description.
The folly of humanity is pitiful indeed.
The hubris of these cynical, lying, arrogant, self-absorbed, deceptive con-artists and their solemn lucrative calls for doom and fear is amazing and disgusting.
Entropic man, one might expect that freshwater chemistry would be more sensitive to pH changes than a buffered ocean (which may likely be the source of CO2, depending on conditions).
You don't have to look too long to find literature claiming "No evidence of widespread recent "industrial acidification" is apparent from extensive paleolimnological assessments in Arctic Europe"
http://www.eoearth.org/article/Historical_changes_in_freshwater_ecosystems_in_the_Arctic#endnote_47
Seek, and ye shall find whatever you want.
The oceans have never boiled dry in the billion years (or whatever it is) since they first existed so a minuscule change in the amount of a trace atmospheric gas probably isn't going to do it in our lifetimes (or in our children's children's lifetimes0 either. I'm not losing any sleep over it anyway.
'that there might be a bit more time to make this profound energy transition'
The profound energy transition is the absorption of massive new oil fields in the former Soviet Union, Venezuala and the rest of the world without crashing the price of oil.
@entropic man
You really are struggling with the concept of 'science' aren't you? Especially the observations, experiments and measurements bit.
If you want to demonstrate that 'ocean acidification' is occurring you have to go and take measurements all over the ocean, not just in the bits that you think will show the greatest effect.
And its no good to dismiss one site because you fell that there are other ocean effects there that cancel out the 'acidification' or otherwise make it less favourable. That is precisely the point that s trying to be established....in the lab there seems to be a small effect...but can we detect that effect in the big wide world also? And in that endeavour data showing no effect is just as valid as that which does show an effect.
Byrne et all (which you kindly referenced for me) - in their cruise around the North Pacific also reported large areas with no apparent pH effect.
So if your hypothesis comes down to
'ocean pH is decreasing apart from in all the places where it doesn't seem to be - like Monterey Bay, large swathes of the North Pacific and maybe all those myriad places where we haven't even bothered to look - like the Southern Ocean, Asia and Australasia, anywhere with cold water near the Arctic or Antarctic, North Atlantic above 25N, Europe, the Mediterranean, Baltic, Southern Atlantic etc'
then it is pretty weak stuff.
models dont constrain the estimates for sensitivity. un fool yourselves guys.
As noted by mooloo they do if you live in a model universe, and I'd add they also do so even if you've finally ventured out, but had a model prior life, as it were.
@john m
Thank you for your contribution. I read your link to the landshape discussion with interest. But - as a recent participant in a 'Kill the Denier' discusion at Deltoid's blog, I foumd it more like a sedate vicar's tea party than a heated discussion!
And thanks for the link to the Hawaiian data.
It was the ubiquity of this dataset in the literature that first got me interested in the topic of real oceanic pH measurements a couple of years ago. Because wherever I looked for information, the same graph kept cropping up from the same site. Like the 'most influential tree in history at Yamal', the Hawaii dataset is everywhere. In IPCC reports, in review articles, quoted in seemingly every paper that mentions 'ocean acidification'
And being a nasty suspicious cove where anything to do with 'climatology' is concerned, I started to wonder if these 126 measurements are all there is to empirically support the idea of 'ocean acidification'.
So I looked around a bit, asked the relevant guys for all the other data (even got the True Believers at Deltoid to do their best to find some more :-) ) and I think I have tracked down a further four datasets similar to Hawaai. But that is all there is. Just five places around the world that have done any even remotely consistent pH measurements over the last decade or more. And they are predominantly in warm waters (Hawaii, Bermuda, Canaries). Nowhere near a comprehensive global survey like was doen to demonstrate global warming.
To do some comparisons between the two. To show that global warming was occurring I estimate that 3000 worldwide sites provided regular daily max/min data over at least 30 years. Simple arithmetic shows that this totals around 50,000,000 observations to analyse.
For 'ocean acidification' we have (at most) 10,000 observations taken from just 5 sites predominantly in warm waters. One fivethousandth as many.
Seems to me that the paucity of data means that a great deal of recent oceanography - all of which presumes that 'OA' is a major effect and is actually occurring worldwide right now - may be built on empirical sand.
There simply is not enough collected data to be sure that anything at all is happening worldwide, let alone its magnitude.
Here's some places for which I have not been able to find any published pH data. Europe. Australia, Asia, The Southern Ocean. The Indian Ocean. The Arctic Sea, The Baltic, The Mediterranean, The Pacific South of Hawaii, The South Atlantic, The North Atlantic above 25N. Lots and lots and lots of oceans (70% of the earth's surface) with no data at all.
Maybe one day a proper collection regime will shows us whether this effect is actually occurring or not. But right now, we just don't know.
I'm with Arno Arrak. The atmospheric greenhouse effect is a work of fiction. Thus all talk of CO2 sensitivity is also pure fiction.
Could someone (ideally Andrew), expand on this teaser:
I would like to know what isthat empirical estimate and from where does it originate, and
what is the basis for believing that is the only empirical estimate.
Much obliged.
On "Unthreaded" recently I quoted this:
Judith Curry's conclusion re sensitivity illustrates it perfectly:
@ Latimer Alder
It is a truth universally acknowledged, that a carbonate sedimentologist in possession of a good fortune must be in want of a comfortable field area, warm water and tropical beaches.
"And they are predominantly in warm waters (Hawaii, Bermuda, Canaries)."
It seems the universal truth applies to chemists too. Florida would be a good place to look for more data.
@Steve Mosher:
Well, quite, but that strikes me as a trivial point.
Put it another way:
How is the entire body of climate models used by the IPCC unable to produce estimates (central tendency of simulation outcomes) of climate sensitivity of less than 2 degrees?
Why can they not do it, or in other words why do they refute it?
I don't think such a question requires "un fooling".
@Robin Guenier
I think Judith Curry is the brightest climate scientist about.
There's a pattern here. For years the IPCC has set climate sensitivity at 3.3-3.5 and none of the team said anything. Now Annan, and others, are saying the climate sensitivity is nearer to 2 than three Gavin pops up and says, "Yeah we knew that." So the consensus community knew the IPPC estimates were ove 50% of what they suspected but they said nothing? What sort of people are these alarmists?
And they are predominantly in warm waters (Hawaii, Bermuda, Canaries). Nowhere near a comprehensive global survey like was doen to demonstrate global warming.
Latimer, if you were being handed a grant of a few 100K to investigate ocean PH, isn't this exactly where you'd go to too?
@steveta, @ hector pascal
I hadn't made that connection before...but you might have a point. I haven't read about any oceanographers publishing any pH data taken in winter off Cape Horn or in the Bering Straits. Hawaii, Bermuda and the Canaries are surely far better places to study 'the oceans'.
But it reminds me that in the US the Sea Level Research Group is based in Boulder, Colorado.
I've been to Boulder. You fly into Denver, where the airport proudly boasts that it is a mile high.
http://www.flydenver.com/fooddetails?URI=tcm:8-603
and then you drive some. And a quick look at a map shows you that the nearest ocean (Pacific, San Francisco, other side of the Rockies) is about 1000 miles away. With the exception of Kansas City is difficult to come up with a city in the USA further away - both vertically and horizontally from sea level.
Normally one expects researchers to get some intuitive feel for the subject they are studying...this helps them to think more deeply about their topic and devise better experiments/observational regimes. Seems that the chances of the Sea Level Research Group doing this are about zero. They are simply too far away from their field.
Geronimo asks "What sort of people are these alarmists?"
James Annan already told us:
Revkin says: " There’s also reluctance, I’m sure, because the recent work is trending toward the published low sensitivity findings from a decade ago from climate scientists best known for their relationships with libertarian groups".
THis is Revkin speak for: "Shit, the skeptics were right all along, and I've been denigrating them for 10 years".
Revkin says: "To me, that says the climate science community — including the Intergovernmental Panel on Climate Change science working group — has not adequately conveyed the reality you state here".
This is Revkin speak for: "Climate scientists and the IPCC have been lying when they tried to alarm us into action by grossly overstating the situation"
.
Foxgoose, at which planet did you live Feb 4, 2013 at 8:28 PM?
Feb 5, 2013 at 9:17 AM steveta_uk wrote
quote
Latimer, if you were being handed a grant of a few 100K to investigate ocean PH, isn't this exactly where you'd go to too?
unquote
This gives me hope for my swivelly-eyed Kriegsmarine Hypothesis: it can best be field tested off Fiji, with the marine biologists, oceanographers, physicist etc on a big old oil tanker full of light oil/surfactant and a ground party ashore managing the shore comms, press visits etc. I have volunteered to carry the bags.
JF
(Actually, if the bureaucrats realised that, it might give the idea some traction.)
I think the most impressive think about all of this is the right at the front, Revkin dismisses SkS first response to the news totally out of hand.
And they are predominantly in warm waters (Hawaii, Bermuda, Canaries). Nowhere near a comprehensive global survey like was doen to demonstrate global warming.
-------------------
Latimer, if you were being handed a grant of a few 100K to investigate ocean PH, isn't this exactly where you'd go to too?
------------------
Steveta, I've seen no end of excellent chemistry performed on medicinally interesting compounds isolated from marine organisms growing in tropical lagoons and coral reefs.... :)
Clearly the warmers are facing up to the facts and sounding a retreat....but one thing really gets me. If the footprint of AGW is a warming of the Troposphere and nothing has ever been found then game over...a long time ago.
james griffin,
the game has been up for a while. The game has changed to 'how to backtrack and reposition without saving face or losing grant money" - whuch is why we're getting the really odd juxtaposition of "I've always said climate sensitivity was low (historical justification), but it's still dangerous so we still need the money (present day pragmatics)"
It's actually amusing to watch.
Feb 5, 2013 at 1:43 AM | steven mosher
... after you.
What is the evidence that 'climate sensitivity' is a constant?
Michael Hart, I guess you are thinking of Djerassi's astonishing series on "minor and trace sterols in marine invertebrates"?
@jonathan jones, @michael hart
And along with those stunning pieces of chemistry, I am led to believe that those self-same islands are also home to many real-time experiments in the physiology of human ethanol metabolism and of DNA exchange between individuals............
Seek, and ye shall find whatever you want.
Feb 5, 2013 at 4:27 AM | michael hart
A good king surrounds himself with advisers who tell him what he needs to know.
A bad king surrounds himself with advisers who tell him what he wants to hear.
On today's internet we can all be kings, choosing our own virtual advisers.
Related to a number of posts above, pondering Climate Scientists' career prospects whern it is clear that they have been peddling bilge, I give you email 4195 from the Climategate emails
Email 4195
<B>"Tim, Chris, I hope you’re not right about the lack of warming lasting till about 2020.".</B>
I.E. Phil Jones would rather we had a climate catastrophe rather than not.
How's that one working out for you, Phil?
Those of you advising each other that oceanography is only done in warm waters with a beach bar nearby might like to browse these databases.
http://cdiac.ornl.gov/oceans/CDIACmap.html
http://cdiac.ornl.gov/oceans/glodap/
I also include an informal map of historical pH changes.
http://en.wikipedia.org/wiki/File:WOA05_GLODAP_del_pH_AYool.png
Citizen scientists doubtful that small pH changes matter should remember that pH is the inverse decimal logarithm of the hydrogen ion concentration. A one unit drop in pH increases hydrogen ion concentration tenfold.
@entropic man
You say
'Seek, and ye shall find whatever you want'
Apart, it appears, from very much empirical evidence that 'ocean acidification' is actually occurring. And the reason we can't find it is that the work to show whether it is or isn't ain't been done.
Those 'scientists' who so confidently assert that 'OA' is a done deal, a 'scientific fact', or an unquestionable consequence of CO2 emissions ..or whatever are simply being 'economical with the actualite (*)'
Which is not a good place for them to be.
* posh way of saying that their relationship with the truth is more distant than is desirable.
Just wondering...
If the concept of climate sensitivity is correct, that means that global temperature is a simple function of radiative forcing:
DT = L DF where D is Delta and L is lambda.
If that is the case, is there any response to the cyclical yearly variation in solar radiative forcing (globally)?
That is an oscillation of about 6.82 W/m^2 every year, much larger than the CO2 forcing. Due to the eccentricity of the orbit TOA insolation varies from about 1382 in December to 1343 W/m^2 in July, or a net variation of 6.82 W/m^2 (1/4 (1382-1343)x(1-albedo)).
Has this any effect?
I cannot find any signal of this oscillation in the detrended monthly temperature record.
Or is it the wrong kind of radiative forcing?
But its all just OPINION...!
"the wishful thinking of people like Ridley and Lindzen" (Schmidt)
It doesn't occur to him that he might be the wishful thinker and that Lindzen (in particular) is just telling it like it is, and always has done?
Interesting to consider what Schmidt might be wishing for though - I suspect his career might come into it...
Imagine you have a cake recipe that needs ingredients to be measured in portions of 50 grams. Imagine you have a kitchen scale that gives you the weight in steps of 1 kg.
How do you make that delicious cake?
Simple: take many scales (about 11), weight the ingredients many times, find the mean (ensemble) et voila... You are ready to compete with Nigella Lawson.
I believe we are doing the same with the estimation of climate sensitivity from model simulations. No matter how you disguise it in very complicated statistics.
We want to measure (or simulate) the effect of about 3W/m2 change in radiative forcing with models that have a discrepancy among them of more that 35W/m2 for clear skies solar radiation, even higher for all sky conditions; that change in steps of 20W due to improvements in emissivity or albedo computations; that have regional bias (regions as large as the whole Europe) between 40 and 200W/m2; massive discrepancies in evaporation (very energetic process), and huge mismatches in water vapour content and precipitation.
How do you estimate the impact of a tiny 3W/m2 forcing, then?
Simple: take many models, run them for many years, take the mean(ensemble), and voila... delicious cake.
@entropic man
You say
'Seek, and ye shall find whatever you want'
Feb 5, 2013 at 1:36 PM | Latimer Alder
Actually, Mr. Adler, michael hart was the one who said that; Feb 5, 2013 at 4:27 AM
"Apart, it appears, from very much empirical evidence that 'ocean acidification' is actually occurring. And the reason we can't find it is that the work to show whether it is or isn't ain't been done."
Curious you should say that the work has not been done, when I have just given you links to large database of collected observations. Perhaps, bad king Adler, you are unwilling to seek in places where you might find unwelcome information.