Blog

A new paper has been published in the journal Nature entitled: ‘Subtropical to boreal convergence of tree-leaf temperatures’ by Brent R. Helliker & Suzanna L. Richter, which has implications for climate reconstructions using tree ring data.

The Abstract states:

The oxygen isotope ratio (18O) of cellulose is thought to provide a record of ambient temperature and relative humidity during periods of carbon assimilation. Here we introduce a method to resolve tree-canopy leaf temperature with the use of 18O of cellulose in 39 tree species. We show a remarkably constant leaf temperature of 21.4 2.2 °C across 50° of latitude, from subtropical to boreal biomes. This means that when carbon assimilation is maximal, the physiological and morphological properties of tree branches serve to raise leaf temperature above air temperature to a much greater extent in more northern latitudes. A main assumption underlying the use of 18O to reconstruct climate history is that the temperature and relative humidity of an actively photosynthesizing leaf are the same as those of the surrounding air. Our data are contrary to that assumption and show that plant physiological ecology must be considered when reconstructing climate through isotope analysis. Furthermore, our results may explain why climate has only a modest effect on leaf economic traits in general.

There is a summary of the paper in Nature News here.

The authors state in the text of the article:

“Our analysis shows that reconstructing ambient humidity by using tree-ring d18O becomes increasingly dubious as MAT [mean annual temperature] decreases. Caution is therefore advised when interpreting treering d18O data from high latitudes for both contemporary samples and samples of relictual wood from high-latitude forests of the past.”

and:

“The discovery of relatively invariant leaf temperatures has two important ramifications that transcend stable-isotope studies. First, elevated canopy temperature and depressed leaf relative humidity should have a large effect on real and modelled water loss from boreal ecosystems. Second, if the architectural controls of branches on leaf temperature are as widespread as our data suggest, then direct climatic selection on the evolution of leaf traits would be relaxed, whereas the selective force of climate on other plant organs (for example stems and roots) would remain. Our results therefore offer a possible explanation for the unexpected finding that climate is a minor correlate with global leaf economic traits.”

Roger Pileke Sr’s take on this is:

This study has major implications with respect to the use of tree ring data to reconstruct long term air temperature trends, as the authors indicate in their text.

This study also illustrates the dynamic response of vegetation to their environment so as to maximize the ability to grow and compete within their ecological environment. This biological effect must be incorporated within climate models that seek to accurately simulate the response of the climate to human and natural effects, including the increase of the atmospheric concentration of CO2.

The first United Nation’s Intergovernmental Panel on Climate Change (IPCC) Report had a Chapter headed “Validation of Climate Models”. A similar Chapter occurred in the first draft of the Second Report. I commented that since no climate model has ever been validated, the word was inappropriate. The next draft had changed the Title, and the words “Validated” or “Validation” to “Evaluated” or “Evaluation” fifty times. Since then the word “validation” is never used, only “evaluate”.

No IPCC document has even discussed what measures might be required before a computer model of the climate might be “validated”

“Validation” is a term used by computer engineers to describe the process of testing of a computer model before it can be made use of. It has to include a capacity to forecast future behaviour to satisfactory level of accuracy. Since no such procedure has ever been carried out for any climate model they are not only completely unsuitable for future forecasts, but the level of accuracy of any such forecast is unknown. As a result they are unable to place levels of reliability on any of the models, or on any “projection’ resulting from them..

The Glossary to the IPCC 4th Report does not contain a mention of either “validation” or “evaluation’, but it is plain in the text that “evaluation” includes “attribution” which derives a cause/effect relationship from a “correlation” contrary to the demands of basic logic.

From the Glossary on “Detection and Attribution”:

“Detection and attribution Climate varies continually on all time scales. Detection of climate change is the process of demonstrating that climate has changed in some defined statistical sense, without providing a reason for that change. Attribution of causes of climate change is the process of establishing the most likely causes for the detected change with some defined level of confidence.”

The use of the term “attribution” evades the firm logical principle that a correlation, however convincing, does not prove cause and effect, not even to any level of “likelihood” or spurious “probability. Their “attribution” process consists in downgrading, distorting and even ignoring alternative reasons for a correlation in order to claim that their explanation had been proved.

The IPCC admit that none of there models have been properly validated, because they refuse to use the word “forecast”, only “projection”. A “projection” is merely the consequence of the initial assumptions and it has no value as a forecast unless it has been tested against future climate behaviour.

This is what the Glossary says:

“Climate prediction A climate prediction or climate forecast is the result of an attempt to produce an estimate of the actual evolution of the climate in the future, for example, at seasonal, interannual or long-term time scales. Since the future evolution of the climate system may be highly sensitive to initial conditions, such predictions are usually probabilistic in nature. See also Climate projection; Climate scenario; Predictability.

Climate projection A projection of the response of the climate system to emission or concentration scenarios of greenhouse gases and aerosols, or radiative forcing scenarios, often based upon simulations by climate models. Climate projections are distinguished from climate predictions in order to emphasize that climate projections depend upon the emission/concentration/radiative forcing scenario used, which are based on assumptions concerning, for example, future socioeconomic and technological developments that may or may not be realised and are therefore subject to substantial uncertainty.

Predictability The extent to which future states of a system may be predicted based on knowledge of current and past states of the system. Since knowledge of the climate system’s past and current states is generally imperfect, as are the models that utilise this knowledge to produce a climate prediction, and since the climate system is inherently nonlinear and chaotic, predictability of the climate system is inherently limited. Even with arbitrarily accurate models and observations, there may still be limits to the predictability of such a nonlinear system (AMS, 2000)”

These definitions confuse the separate role played by the models and the scenarios. The models merely “project” the rate at which “radiative forcing” increases with increase in greenhouse gases. They cannot be used to “project” what might happen in the future without “scenarios” which are guesses of the future economic development of the world, from which future emissions of greenhouse gases may be deduced. Then, they have to use anothert set of unvalidated models to calculate how much of these emissions might end up in the atmosphere, so the climate models can calculate the radiative forcing, and from that the temperature increase.

The resulting “range” of temperature and other properties for the year 2100 is therefore completely arbitrary; so the actual levels are decided by the demands of the politicians. The “Low” figure could easily be negative, but oh no! it has to be just a bit high. The “HIgh” figure is what the market will bear currently and it has therefore changed over the years. There have been several occasions in my experience of the IPCC when it had to be suddenly raised, doubtless after a call from the politicians. They used such devices as inventing an extra severe scenario (A1F1) or an extra severe model to do this.

The “High figure is the most important as it is the one used by the Al Gores and Nicholas Sterns of this world to scare us into escalating economic disaster

Since none of the curves have a known or calculable level of accuracy the range could be indefinitely extended in both the upwards and downwards directions. The IPCC actually say this; but, of course, only for the upward direction

Here is what the Glossary says about the Scenarios:

“Climate scenario A plausible and often simplified representation of the future climate, based on an internally consistent set of climatological relationships that has been constructed for explicit use in investigating the potential consequences of anthropogenic climate change, often serving as input to impact models. Climate projections often serve as the raw material for constructing climate scenarios, but climate scenarios usually require additional information such as about the observed current climate. A climate change scenario is the difference between a climate scenario and the current climate.”

These scenarios have not been developed by scientists, but by environmental activist economists attached to the IPCC WGIII (Impacts) Committee, and they are generally grossly exaggerated. Even the figures chosen for the beginning (2000) are all wrong; so they are even unable to predict the past.

The scenarios have been roundly criticised by expert economists. without response. They include such outrageous assumptions as:

1. a 12-fold increase in coal consumption,
2. increases in atmospheric carbon dioxide of 1% a year, instead of the current 0.4%,
3. increases in atmospheric methane, instead of the current fall,
4. absurd increases in Gross National Product, and population,

They were foisted on the scientists of the IPCC Committee WGI (Science) without consultation, so that the future can be confidently exaggerated by them.

Cheers
Vincent Gray
Wellington, New Zealand