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<div class="moz-cite-prefix">On 2013-11-13 03:50, spike wrote:<br>
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<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span>I
have been following hurricanes for years now after being told
they would get more frequent and more violent. This year has
been eerie quiet in the Atlantic. Do let us hope that doesn’t
point to global cooling. Warming would be OK, cooling, not.</p>
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<br>
Hurricane numbers are a bad indicator for climate: you get very few
data points even in a high hurricane year.<br>
<br>
Consider flipping a biased coin, trying to estimate how biased it
is. But you only get 2-10 flips each year. Worse, you are trying to
tell whether the bias is changing. <br>
<br>
[ The variance of the estimate from N trials with pN heads is
(1-p)/(N+1)^2 (it is a beta distribution). going from 2 to 10 flips
reduces the variance by a factor of 0.67, which is just a 19%
reduction of standard deviation. If you want to reliably detect a
change in p on the order of 10% you will need a lot more data - at
least more than 20 data points. ]<br>
<br>
I am always annoyed at how many people confuse weather - the
stochastic outcomes - with climate - the underlying parameters. <br>
<br>
<pre class="moz-signature" cols="72">--
Dr Anders Sandberg
Future of Humanity Institute
Oxford Martin School
Oxford University
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