oops cut and pasted wrong quote.....Good morning Keith....
I don't want to insult you...I am not sure what you know about statistics. Keep in mind that I have not seen these statistics and do not know what methodology they used to measure the data. I also don't necessarily buy the whole global warming issue so I am not going to offer an opinion. the gold standard in statistcal methodology is to say that something does not happen by chance is that the data has to prove that the hypothesis (global warming, medicall illnesses in certain populations, accidents in youth drivers etc) is happening not due to chance. When one does research, you collect the data points and analyze them. In order to even begin to have the correct numbers to make an analysis, you must have 11 (I am almost certain) objects/subjects, data points so that you have the minimum of 10 degress of freedom-which translates into the power. This means that there are enough numbers to make a statistical measurement. Below this, statiscal analysis can be fraught with error. So the larger the data set, the more power, and certainty and confidence you can have when one has something that is statistically significant p value <0.05-95% certainty that the hypothesis is not due to chance. In the argument below, they are saying that they now have a large enough set to accept the hypothesis that this does exist. I just assume that whatever it is that they are measuring, this last set of data that was added to the earlier goups, through their methodology, now accepts the hypothosis that it does exist. I do not know what they are measuring, how they are controling for variables or anything like that. And I do not know what tests they are using and whether these tests are good ones to measure this.
I suppose the take home message is, the more data, the stronger the numbers are to measure to either accept or not the hypothesis. When I read medical journals and these big institutions start throwing statistically significant this or that-I first ask-how many were in the study, what was the hypothesis, did they do some off the wall statistical test and if they did-it usually means that they had to search for a statistical test that would make their data significant when another one should have been used.
"Basically what's changed is one more year [of data]. That period
1995-2009 was just 15 years - and because of the uncertainty in
estimating trends over short periods, an extra year has made that trend
significant at the 95% level which is the traditional threshold that
statisticians have used for many years.
This statement is misleading.....a trend at 90% is just a trend. it is not a significant one. When it crossed to 95%. Then one can use significant-otherwise-baloney. I would like to see the raw data and what test they use....but i really don't have the time or inclination...we all know the world is going to hell in a hand basket and I am just along for the ride and occassional doomsday party.
SOn Sun, Jun 12, 2011 at 3:27 AM, Keith In Köln <keithintampa@gmail.com> wrote:
Uhm.....Call me a little slow, but I haven't a friggin clue what that meant.
On Sat, Jun 11, 2011 at 11:07 PM, Bruce Majors <majors.bruce@gmail.com> wrote:
--
10 June 2011 Last updated at 13:59
Global warming since 1995 'now significant'
Richard Black By Richard Black Environment correspondent, BBC News
Climate warming since 1995 is now statistically significant, according
to Phil Jones, the UK scientist targeted in the "ClimateGate" affair.
Last year, he told BBC News that post-1995 warming was not significant -
a statement still seen on blogs critical of the idea of man-made climate
change.
But another year of data has pushed the trend past the threshold usually
used to assess whether trends are "real".
Dr Jones says this shows the importance of using longer records for
analysis.
By widespread convention, scientists use a minimum threshold of 95% to
assess whether a trend is likely to be down to an underlying cause,
rather than emerging by chance.
If a trend meets the 95% threshold, it basically means that the odds of
it being down to chance are less than one in 20.
Last year's analysis, which went to 2009, did not reach this threshold;
but adding data for 2010 takes it over the line.
"The trend over the period 1995-2009 was significant at the 90% level,
but wasn't significant at the standard 95% level that people use,"
Professor Jones told BBC News.
"Basically what's changed is one more year [of data]. That period
1995-2009 was just 15 years - and because of the uncertainty in
estimating trends over short periods, an extra year has made that trend
significant at the 95% level which is the traditional threshold that
statisticians have used for many years.
"It just shows the difficulty of achieving significance with a short
time series, and that's why longer series - 20 or 30 years - would be a
much better way of estimating trends and getting significance on a
consistent basis."
Professor Jones' previous comment, from a BBC interview in Febuary 2010,
is routinely quoted - erroneously - as demonstration that the Earth's
surface temperature is not rising.
Globally consistent
The dataset that Professor Jones helps to compile - HadCRUT3 - is a
joint project between the Climatic Research Unit (CRU) at the University
of East Anglia (UEA), where he is based, and the UK Met Office.
It is one of the main global temperature records used by bodies such as
the Intergovernmental Panel on Climate Change (IPCC).
HadCRUT shows a warming 1995-2010 of 0.19C - consistent with the other
major records, which all use slightly different ways of analysing the
data in order to compensate for issues such as the dearth of measuring
stations in polar regions.
Shortly before the UN climate summit in Copenhagen, Phil Jones found
himself at the centre of the affair that came to be known as
"ClimateGate", which saw the release of more than 1,000 emails taken
from a CRU server.
Critics alleged the emails showed CRU scientists and others attempting
to subvert the usual processes of science, and of manipulating data in
order to paint an unfounded picture of globally rising temperatures.
Subsequent enquiries found the scientists and their institutions did
fall short of best practice in areas such as routine use of professional
statisticians and response to Freedom of Information requests, but found
no case to answer on the charges of manipulation.
Since then, nothing has emerged through mainstream science to challenge
the IPCC's basic picture of a world warming through greenhouse gas
emissions.
And a new initiative to construct a global temperature record, based at
Stanford University in California whose funders include "climate
sceptical" organisations, has reached early conclusions that match
established records closely.
http://www.bbc.co.uk/news/science-environment-13719510
--
Mario Huet
Libertarian Alliance Forum
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