Monday, September 20, 2010
Pick your proxy
What do we conclude when temperature proxies contradict both one another and real-world data?
We see here that a new proxy temperature measurement from South America shows the Medieval warm period and little ice age that Warmists like Michael Mann tried to "iron out" of their "hockey stick" graphs.
It also however shows a temperature upturn in the 20th century that exceeds the temperature observed in their proxy data for the Medieval warm period -- which contradicts what we certainly know about the Medieval warm period -- when the historical data that we have (Vikings farming in Greenland etc.) shows that period to be warmer than the present.
Additionally, we know that Briffa's Russian pine tree proxies showed a now famous DECLINE in 20th century temperatures -- a decline that Phil Jones & Co. famously used a "trick" to "hide". There is certainly no grounds from the thermometer readings to conclude that temperatures declined overall in the 20th century, though an argument could be made that there was no significant increase.
So where do we go from there? One could quite reasonably conclude that all temperatures are local and that we should not generalize from one place to another -- and that is a highly satisfactory conclusion for skeptics and a nasty one for the Greenies.
But my conclusion is even harsher than that. I don't see how we can trust ANY proxy unless we have ACTUAL temperatures to validate it against. And we just don't have such temperature data beyond about 150 years ago.
I am acutely aware of the validity issue because it lay at the heart of my own research into psychometrics. I was attempting in my work something just as daunting as what paleoclimatologists try to do. I was trying to put numbers to human attitudes and personalities.
One normally does that via a questionnaire. One uses questionnaires as proxies for what people are thinking. But how do you know that the answers to your questionnaire reflect anything real? You don't -- unless you seek some sort of validation for the measure you have constructed. You need some objective or independent data to compare your questionnaire answers with. And in my career I was a demon about insisting on such external validation.
Many of my colleagues were more insouciant however and took the questionnaire answers they had at face value. As a result I often was able to point out that they had got it wrong and that their research could not support the conclusions that the author concerned had drawn from it. I got a lot of papers published in the academic journals by pointing out such follies.
So if I had been in Briffa's shoes and found that the actual temperature record for the 20th century contradicted what my proxy data seemed to be showing, I would have concluded that the proxy was invalid and could not be used to support any conclusions. That is what any honest scientist would have done. Briffa, however, ignored the glaring invalidity of his proxy data and pretended to draw conclusions about temperatures for the last 1,000 years or so from it.
So from my perspective as a specialist in measurement, I can see no way of drawing sound conclusions about temperature from ANY proxy data so far available. The whole Warmist enterprise is an edifice built on sand.
Being a good scientist, however, I am going to specify what a valid temperature proxy would show. It would show the Roman warm period as warmest of all for the last 2500 years (when Hannibal took elephants over the Alps in WINTER and grapes grew in Northern England). It would show the Medieval Warm period as warmer than today (when Vikings farmed in Greenland). And it would show temperatures over the last 200 years as essentially flat (as even the Warmists claim a temperature rise of less than one degree Celsius over that period). I know of no such proxy in existence so far.
Given the inherently coarse resolution of proxies, it is in fact doubtful that any proxy COULD do what Warmists ask of it. Few people seem to realize that the graphs of leaping temperature that Warmists produce are calibrated in tenths of one degree. It may be possible to extract that degree of precision from thermometers but asking it of proxies is drawing a very long bow indeed.
I will stick with the well-established facts of history and conclude that present-day temperatures are in no way exceptionally warm. Publius Cornelius Scipio could well have made that sort of complaint but we cannot