Dung you need to google "mann v steyn" and follow the links, and do some more googling on the bits you don't understand, especially the US legal system. After a years reading, you will be older, possibly more confused, and not necessarily wiser, and Mann v Steyn may not have reached court.

Mann is suing Steyn, for uncomplimentary written words. That is the easy bit. Then it gets complicated.

A cynic might argue that even if Mann wins, the display of dirty washing in public, might not be good for the AGW cause. Mann will also have to demonstrate that his reputation has been damaged. Mann continues to earn money, with the full confidence of the climate science community, however they did not form a long queue to provide support, in pre-trial court submissions, and Mann accidentally forgot to mention his Nobel Prize Status in a manner meeting the approval of the Nobel Prize Committee thingy.

Climate Science experts are so full of confidence in Mann's integrity, that they try to avoid the issue. They are also happy to carry on earning money for as long as possible, and none of them are actively urgjng him to hurry up and get himself exonerated.

When have Climate Science experts been wrong about anything?

Luckily St Trinians don't play Lacrosse. To get a Lacrosse Stick Graph, would have taken real cunning and ingenuity.

EM (Mar 19, 2016 at 12:14 PM),

The problem with each and every one of these studies is not the methods, though these are debatable, but the proxies themselves. For every single proxy there is no defined function between proxy response and temperature. It doesn't matter if it is tree rings, ring density, varved sediment thickness, isotopic composition of terrestrial carbonates etc. I could go on. I defy you to pick a single proxy used in these studies and show me how the response is related to temperature from an a priori constitutive point of view. Because of this inability we even see the preposterous use of 'teleconnections' to relate response to far field temperatures.

I find it interesting that most studies which use proxies to estimate 'global' climate are done by people without a detailed understanding of the systems they are studying. This applies to processes that result in a response to local temperature and to local environmental conditions

As a result one is simply averaging a mish mash of wiggles with varying degrees of weighting. The result is trendless such that when the modern record is appended looks like a hockey stick.

In my view the concept that one can take terrestrial proxies and produce a composite global temperature record over the past 1000, 2000 years or whatever time is philosophically deeply flawed. I have come to this view after more than 2o years developing and using isotopic proxies for terrestrial palaeoclimate studies.

That is not to say that useful information at the local scale cannot be determined but one must recognise the limitations.

Paul Dennis.

Not to mention the somewhat dubious links between poorly sited weather stations and true ambient temperatures, or methods employed to correct them and, in so doing, trash records from the better located sites; let alone the alterations imposed on older data to "improve" it. Is any past temperature data at all reliable?

Started this post with a humorous intent, but quickly became depressed at the whole seriousness of it all.

Dung

Some light reading.

Hockey sticks galore.

Dung

Iafydstta.

Light reading

Dung, proxies related to land (or in some cases shallow burial, as in cave deposits) parameters of interest (in this case temperatures). These then would include the proxies mentioned by Paul together with oxygen and other isotopic measurements made on ice cores. This is in contrast to estimates based on marine materials - corals, deep sea cores and the like.

I'm not exactly sure why Paul made this distinction. I would have thought that marine proxies of temperature suffer from the same problems.

Dung

Better summary, from the 70+ proxies ensemble by Marcott et Al (2013) and with the MBH98 graph superimposed.

I know already that your Morton's Demon will reject it, but it is worth a try.

Dung

I'll leave the clever stuff to Paul, but he has been trying to explain this.

In Paul's view all isotopic temperature proxies also vary as a result of other variables that confuse the parameter you are seeking to discover. We can use tree ring thickness as a more easily understandable example. We seek past temperatures and some people believe they can extract a temperature record from this data set. But, the thicknesses also reflect rainfall variations or changes in atmospheric CO2 levels - factors that influence the tree's growth. The proxy is thus not uniquely a temperature record. For any given measurement we don't know how much is a response to temperature, how much to moisture conditions or how much to changing CO2. Scarily the measurements might respond to factors we haven't even considered.

In the same way variations in the oxygen isotopic records in a cave stalagmite vary according to temperature, but also to the precipitating water's isotopic composition, and this, in turn, may reflect the geographic origin of weather systems above the cave over time. Thus once again the proxy (the isotopic composition of the stalagmite) does not uniquely record the parameter (temperature) we seek.

Dung, one accepts interpretations until they are proven false by better data or betterr explanation of that data. This should not blind us from realizing the complexities of the methods employed nor the pitfalls we might have to navigate.

One could argue that Paul's post is rather pessimistic, but I'll leave it to him to defend his position. I was merely trying to answer your questions. But like any good enquirer, the questions keep coming. Keep asking away and I'll try my best.

Dung, I would entirely agree, but I assume this was part of Mann's problem in that Geology was not going to produce the results he needed over the last 2000 years. Tree rings didn't either, so a bit of horticultural grafting was necessary, and some bits were composted, or fell down the back of the sofa or something technical.

Alan Kendall, noting the above, and your experience of Sedimentation, that is why I was curious about Cinque Ports! Can Sedimentation provide any useful information about temperature over the last few thousand years, or is your background in older and more solid sediments? I have done a bit of archaeology, and have been involved with some forensic type work.

I read here and elsewhere of Lake sediments etc being coredrilled and revealing/proving XYZ, based on sizes of winkles or something.

I fully accept dendrochronology has a method of dating wood, when compared against known samples, by comparing the pattern of good v bad growing seasons.

golf Charlie,

1) My experience is mostly with older sedimentary rocks

2) Most sediments do not themselves carry a temperature signal. However, geologically young terrestrial sediments commonly contain well preserved beetle wing cases and the assemblages of different beetle species commonly can be used to evaluate past temperatures.

3) Some lake sediments have yearly increments called varves but the lake must be deep and seasonally freeze over in order for them to form. Counting varves was used to date the gradual retreat of European and North American ice sheets.

Paul Dennis has alluded to the multitude of difficulties in making estimates of temperature from a wide range of proxies.

But as an example:-

The ratio of dO18/dO16 is obtained from measurements in ice cores and carbonates in calcareous sediments and fossil shells and tests, can be measured accurately and is widely available from long sequences of measurements .

In relation to the glacial/interglacial cycles the changes in the ratio dO16/dO18 are a result of changes in the average isotopic composition of O2 in seawater which result from H2O rich in O16 being preferentially evaporated and the resulting moisture being differentially accumulated in continental ice rather than returning to the ocean as precipitation run - off in which case the primordial ratio would be preserved.

Consequently the ocean water is enriched in O18 when there are large accumulations of continental ice and is depleted in O18 when there is less. There is not an assumption that the oxygen isotopes are thoroughly mixed in ocean water as the ratio varies significantly between measurements from ocean surface dwelling organisms ( such as in plankton) and deep water ( benthic) fauna .

However the similarity in the patterns of change in the ratio with time, on a global scale, has allowed the differentiation of a series of isotopic stages corresponding to changes in ice volume back 800,000 years and it is likely that the temperature roses and fell in proportion to the global continental ice volume.

But this is NOT a direct measure of temperature - although calibration exercises allow it to be used as a temperature proxy with some degree of confidence that the sequence of changes in the ratio correlate with temperature changes.

For more background try reading " The Two Mile Time Machine" ( R.B.Alley,2002) which gives a popular introduction to methods and results pertaining to ice cores.

Paul's comments - and corrections would be appreciated !

Martin A

EM - why do you waste our time by directing us to such irrelevant and offensive garbage?

Only you deniers regard it as "irrelevant and offensive garbage". The rest of us regard it as the best estimate to date of Holocene temperatures.

When you refer me to a peer reviewed paper with 293 citations which falsifies Marcott et Al (2013), then I will stop using it.

This discussion is moving on fast. Alan is absolutely right when he explains the issues associated with interpreting the oxygen isotopic composition of speleothems in caves. The same issues are attendant on any land based record based on carbonate deposits including tufas, lake carbonates, snails and other freshwater biota. There are two signal recorded by the oxygen isotope composition. One is the temperature at which the carbonate precipitated. The other is the oxygen isotope composition of the surface or groundwater. This is closely related to the local precipitation and depends on temperature, synoptic weather patterns etc. Disentangling the effects is not always possible, and certainly less so for ancient deposits and sediments. Most progress has been made in systems, caves for example, where there has been very detailed study of the isotopic composition of coeval drip waters and carbonates and how they vary over seasonal and longer cycles. A good example is the work of Bar-Matthews and colleagues on Soreq and Pequin caves in Israel. If you follow these studies you will find that the isotopic signal recorded in the cave deposits is dominated by a water amount effect and not by temperature.

Amongst the best isotopic records we have are those recorded by ice sheets and glaciers. Here our understanding of the system is better. Modelling the atmospheric water cycle as a distillation column allows us to make a priori predictions of how the oxygen isotope composition should vary as a function of temperature and see that this is very close to observations. That is if one takes a latitudinal gradient in temperature and the latitudinal gradient in precipitation isotopic composition. On the other hand if one samples at a single site through time, e.g. as in an ice core, the temperature-isotope composition relationship is different. This happens ona range of time scales from seasonal variations through decadal and millenial variations. The reasons are complex but relate to disequilibrium during evaporation from the source regions.

Palaeoclimate Buff is right when stating that the dominant isotope change in the oceans on the time scales of the ice ages is an ice volume effect. Water evaporated from the oceans is depleted in the heavy isotopes 2-H and 18-O. This is precipitataed as snow and locked up as continental ice on the waxing northern hemisphere ice sheets and not returned to the oceans. This drives the oceans towards an isotopically enriched composition. Again this is not a temperature signal. One might begin to look for temperature signals by comparing benthic to planktonic foraminifera species.

I hope I don't sound too pessimistic about the proxies. I think there is scope for some very excellent work on local scales. By this I mean detailed studies of single sites, caves etc. and even regions can provide some excellent data. Witness what I have said about Soreq and Pequin caves. The Greenland and Antarctic ice sheet record are another excellent example. Progress is also being made with understanding clumped isotope systematics. These are measures of the ordering of heavy isotopes in the carbonate anion. The degree of ordering is a function of temperature only and not dependent on the water isotope composition.

My pessimism and gloom is where I see such proxies abused as indicators of temperature and their amalgamation in multiproxy studies.

EM,

You are being very naive if you think number of citations is a mark of the calibre, or veracity of any kind of study.

What about this paper:

Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children. LANCET, FEB 28 1998
Wakefield AJ, Murch SH, Anthony A, Linnell J, Casson DM, Malik M, Berelowitz M, Dhillon AP, Thomson MA, Harvey P, Valentine A, Davies SE, Walker-Smith JA.

675 citations prior to retraction.