Tuesday, 18 January 2011

Lies, damn lies, and Stephan Lewandosky

Stephan Lewandosky has written a piece for ABC Unleashed. He talks about the joys of cherry-picking and then includes this:
"....global warming is a hoax because it’s snowing in England."
(Sorry, that's a bit of cherry-picking of my own .)

The NO CARBON TAX Climate Sceptics party members -

David Stockwell and Anthony Cox
- have submitted their reply to ABC Unleashed. It may or may not be published by them.

Lewandowsky and the numbers of Global Warming.

Professor Lewandowsky says: “Statistics, when done properly, provide a robust and revealing tool to understand reality.”
He is right; statistics can help us understand the why and how of our physical world; good statistics can even help us prepare for our future. Have the statistics of anthropogenic global warming [AGW] helped us understand our physical world and helped us prepare for our future?

Lewandowsky warns us that “Single events carry little information” and to use single events to prove AGW is untrue is "cherry-picking." In Lewandowsky’s opinion one cold British winter [actually there have been 3] does not a summer make. Rather it is the long-term changes which prove AGW, the reduction in the Arctic ice-cap, the rising seas and the increasing temperature.

This is true. The Intergovernmental Panel for Climate Change [IPCC] says that a minimum of 30 years have to be taken into account before any conclusions about changes in the physical reality of climate can be made. On that basis the Arctic ice-cap was smaller in the 1930’s, and warmer, according to leading researcher Professor Petr Chylek. Sea levels have been rising for the last 10 thousand years, since the current interglacial or warm period began, at rates of increase much more rapid than the rates of today. And temperature has been increasing in the modern era since 1850 well before AGW is supposed to have begun.

This is the point about statistics; they are only as good as the information or data: the raw numbers. “Cherry picking” a section of data is not the only way of corrupting a statistical analysis; omitting or changing the data can do it as well. For instance Lewandowsky says “the Arctic icecap has shrunk by an area roughly equivalent to the size of W.A. since 1980”. It sounds bad doesn’t it? It must be AGW. But this is the statistical technique of omission. What the Professor has not mentioned is that the Antarctic has increased in size since 1980 by an area roughly equivalent to 2 W.A.’s. So, overall ice levels have increased.

Lewandowsky has used 2 graphs to prove that the full range of data will reveal the truth and allow people to so readily understand that they can predict the future. The 2 graphs show identical data but with different headings; one an imaginary share price and the other the official temperature record of the IPCC, NASA GISS.

Even if we accept the NASA GISS temperature record as accurate does it really represent reality? Reality from the AGW viewpoint is that the increases in CO2 have caused the temperature trend.
CO2 can’t have. CO2 has been increasing during the 20th Century at a constant rate but the temperature anomalies show many periods with cooling. Is it “cherry-picking” to focus on these cool periods?

No; for 2 reasons. Firstly, some of the cooler periods are longer than 30 years and so represent a climate period. It is legitimate to regard a cooler period as a contradiction to AGW and that some other factor is affecting the climate.

Secondly, Lewandowsky has not considered that there may be a better physical explanation for the temperature record; choosing an inferior explanation for temperature is called the technique of false correlation. In fact there is a better explanation than CO2.

The better explanation is the Sun. The measure of the Sun’s influence on the Earth’s climate is called the Total Solar Irradiance [TSI]. TSI is a measure of the absolute intensity of solar radiation, integrated over the entire solar irradiance spectrum which is incident to the Earth’s atmosphere. That is, the sunlight reaching the atmosphere. Measurements and estimates of TSI have been made as far back as 1600. Figure 6.5 of the last IPCC report, AR4, shows the variations in TSI over this period according to a number of studies.

So, how can we show whether TSI is a better explanation than AGW for the temperature trend shown by NASA GISS?

We can show this through statistics. Dr Geoffrey Glassman has compared the correlation between TSI and the temperature record over the 20th Century and found a 90% correlation. By comparison meteorologist Joseph D'Aleo calculates a statistical correlation between CO2 and temperature of only 42%.

Both the science of TSI and AGW are supposedly well established yet the amount of money being invested in AGW is vastly greater than that being spent on TSI with less than half the statistical justification. This may be good business but it is not good science. Lewandowsky says that for statistics to be effective one should use “All the data, for the entire globe, and for all available years.”

But Lewandowsky has not met his own criteria of “All the data”. The NASA GISS record is NOT the complete temperature record of AGW. The complete record is Michael Mann’s hockey-stick.
The hockey-stick is a 2000 year temperature record based on dendro-climatic or tree-ring data. The hockey-stick purports to show an even temperature until the 20th Century when temperature increases at the same time as CO2.

We have already seen that TSI is a better statistical explanation for 20th Century temperature but what is the best explanation for the rest of the 2000 years?

The best explanation is not CO2. A new paper which was published with the honour of occupying the entire edition of a major research journal, The Annals of Applied Statistics, shows this. The paper is by 2 expert statisticians, Blakeley McShane and Abraham Wyner, who show that current temperature is not exceptional and that prior temperatures during what is known as the Medieval Warm Period [MWP] were as warm and probably warmer than today.

In the spirit of Lewandowsky’s study we showed his graphs to David Stockwell’s school-age daughters who also thought the trend would be up. However, when the girls were shown a graph of the MWP consistent with McShane and Wyner’s analysis, they extended the graph downwards. The conclusion, perception of trend direction depends on the duration examined.
More importantly, when asked if this was a good way to predict the future global temperature of the planet they said “Of course not!” Smart girls.

McShane and Wyner’s study is a major contradiction to AGW. Real data, the same used by AGW, a variety of statistical methods, including those relied on by AGW, fail to show anything unusual about the present temperature; and that includes Lewandowsky’s record extremes which the IPCC has shown to have occurred 9 times over the last 1000 years.

With the past and the present statistically defeated for AGW what can AGW do? As Lewandowsky shows, like any fortune teller, it looks to the future where, statistically, anything is possible.
Predictions are the stock in trade of AGW; all the AGW experts have used statistics to tell us what the future climate will be. The results have been statistically improbable in that they have all been wrong at both the short term and the long term. For instance, in the short term the MET, England’s national weather service, has predicted mild winters from 2008; the winters have been some of the coldest in the last century. In 2005 the MET predicted a cold winter; it was mild.

In Australia the Bureau of Meteorology [BoM] and CSIRO have predicted on the basis of climate model projection that the severity and intensity of droughts will double by 2050. David Stockwell has published a peer-reviewed comparison of their models with the observations, which shows droughts DECREASING over the last century, broadly in line with INCREASING rainfall over the period. The claim of increasing droughts in Australia was based only on model simulations and was premature. This is a classic case of the statistical method of garbage in, garbage out.

In 2007, CSIRO and BoM scientists Power and Smith published a paper claiming that the Southern Oscillation Index [SOI] has shifted to a permanently lower level. This echoed a claim by leading AGW NASA scientist Jim Hansen that one of the consequences of AGW might be permanent El Nino ('small boy') conditions, leading to persistent droughts in Australia. In a peer-reviewed statistical analysis David Stockwell showed that the change in the SOI was not statistically significant and the apparent decrease largely due to a run of El Nino events during the late part of the 20th Century.

The recent floods in Australia and around the world have shown Stockwell’s analysis to be correct. Despite comments by prominent AGW scientists like David Karoly, Ian Lowe and Tim Flannery, the same experts who were predicting worse droughts, these are entirely natural conditions; the flood records for Queensland show that in the past, before AGW began, there were bigger and regular floods.

As Professor Stewart Franks notes natural variability is creating the weather not AGW.
Lewandowsky in his study has gone to the public for vindication. One can only hope his study instructions were not as forthright as the condemnation in his article of the “damn liars” who “deny climate science”.
The general public is the ultimate arbiter and that is as it should be in a democracy. Science and statistics are the handmaidens of public decision making and they should be transparent and honest, “crystal clear” as Lewandowsky says. If they aren’t then the numbers will not stack up.

The numbers of AGW don’t stack up and Lewandowsky’s test subjects will be left to decide whether “lies, damned lies, [or] statistics” best describes AGW.