From: Telmo Menezes <[email protected]>
To: "[email protected]" <[email protected]>
Sent: Tuesday, May 12, 2015 12:22 PM
Subject: Re: Michael Shermer becomes sceptical about scepticism!
With climate change and cures for cancer you need statistics, because there
are no such laws in these fields. There is no equation where you can plug-in a
CO2 concentration and get a correct prediction on global temperature change.
There's a law where you can plug in atmospheric composition and solar radiance
and get a correct prediction of the equilibrium temperature. That's what
Arrhenius did in 1890. It's precisely because we do have equations for the
energy balance of the Earth and how CO2 affects it, that anthropic global
warming is as solid a fact as evolution and nuclear fission. If it were *just*
observations there might be room for doubt as to why temperature has gone up.
But the mechanism is well known and has been for a century.
>>How can we know that the greenhouse effect is the only thing to consider when
>>dealing with something as complex as the earth and its biosphere? Ok, CO2 in
>>the atmosphere reflects back some percentage of the infrared radiation which
>>leads to more solar energy being trapped in the system.
One key thing to understand about the physical properties of CO2 dipolar gas
molecule is that it absorbs/re-emits IR frequencies(i.e. is opaque) in an IR
frequency range that water vapor (e.g. H2O) -- which is the most significant
global warming gas there is overall is transparent in. This is critically
important in understanding why CO2 gas has such an impact on climate. It is
because it closes (partially closes of course) a critical window of
transparency, that exists in the H2O infrared frequency absorption profile
through which infrared energy -- of that frequency range -- could otherwise
escape out from the atmosphere to be re-radiated out into outer space.CO2 does
not act alone, its effects are very much a result of its partially closing off
this infrared frequency transparency hole or window through which large amounts
of infrared energy would have been able to be directly radiated out into the
cold sink of outer space.-Chris
But what about the clouds? And the vegetation? Don't these things have a role
in infraread blocking and sun light refraction/absorption? And many other
things we might not be thinking about... My point is: who's to say that there
isn't some negative feedback loop that keeps the temperature stable? It's not
such a silly hypothesis if you think in terms of self-sampling. The Earth must
be stable enough to maintain the conditions for uninterrupted biological
evolution for almost 4 billion years.
But if you'd like to actually formulate the alternative hypothesis I might
do the analysis.
Ok. My alternative hypothesis is that there is no trend of global temperature
increase in the period from 1998 to 2010 (as per Liz's chart's timeframe),
when compared to temperature fluctuations in the 20th century (as defined by
the metric in the chart).
OK. Here's one way to do it. The ten warmest years in the century from 1910
to 2010 all occurred in the interval 1998 to 2010, the last 13yrs of the
century. Under the null hypothesis, where the hottest year falls is uniform
random, so the hottest year had probability 13/100 of falling in that interval.
The next hottest year then had probability 12/99 of falling in the remaining
12yr of that interval, given the hottest had already fallen it. The third
hottest year had probability 11/98 of falling in that interval, given the first
two had fallen in it, and so on. So the probability of the 10 hottest years
falling in that 13yr period is
P = (13*12*...5*4)/(100*99*...*92*91) = 1.65e-11
To this we must add the probability of the more extreme events, e.g. the
probability that the ten hottest years were in the last 12
P = (12*11*...*5*4*3)/(100*99*...*92*91) = 3.81e-12
and that they were in the last 11
P = (11*10*...*5*4*3*2)/(100*99*...*92*91) = 6.35e-13
and that they were in the last 10
P = (11*10*...*5*4*3*2)/(100*99*...*92*91) = 5.77e-14
Summing we get P = 2.10e-11
A p-value good enough for CERN. But this isn't a very good analysis for two
reasons. First, it's not directly measuring trend, it's the same probability
you'd get for any 10 of the observed temperatures falling on any defined 13
years. So you have infer that it means a trend from the fact that these are
the hottest years and they occur in the 13 at the end. Second, it implicitly
assumes that yearly temperatures are independent, which they aren't. If
temperatures always occurred in blocks of ten for example the observed p-value
would be more like 0.1. But this shows why you need to consider well defined,
realistic alternatives. Your alternative was "no trend", but no trend can mean
a lot of things, including random independent yearly temperatures.
A better analysis is to select two different years at random and count how
many instances there are in which the later year is hotter. Under the null
hypothesis only half should count. This directly counts trends. And this is
independent of whether successive years are correlated. There are 10000
possible pairs in a century which is large enough we can just sample it. I got
the NOAA data from 1880 thru 2013, so I used a little more than a century.
For example taking a sample of 100 pairs gives 86 in which the later year was
warmer (I counted ties as 0.5). The null hypothesis says this is like getting
86 heads in 100 tosses, which obeys a binomial distribution. The probability
of getting 86 or more heads in a 100 tosses is 4.14e-14.
Brent, I tip my hat to you. I was preparing to write some objections after
reading your first analysis, but your pair sampling analysis already addresses
them. You convinced me that there is, in fact, a global temperature increase
trend in the last century.
So are you also convinced that increased CO2 is causing it?
I am still worried about the reliability of the temperature values themselves.
I would be less worried if the raw data was made public.
Normally I trust scientists. In this case, the thing got so mixed up with
politics that it makes me uneasy. Mainly because I observe politicians to be
caught lying too often about very big things. I know, you are going to say that
this is absurd because the Koch Bros have much deeper pockets. Maybe so. You
are probably right, but if I am being too paranoid, perhaps you can at least
understand why I would think like that, given recent history.
Assuming the temperature values are correct, I would say that it seems very
plausible that increased CO2 is causing the warming.
Telmo.
Brent
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