All entries for June 2005

June 13, 2005

Probability Puzzle Time!

Writing about web page http://www.gchq.gov.uk/recruitment/careers/math_apply.html

This puzzle from the GCHQ recruitment website has completely flummouxed me. I suspect there is some sort of general method to dealing with stuff like this, but I have no idea what it is.

2. Alice and Bob play coin toss: Alice pays Bob £1 for each head and Bob pays Alice £1 for each tail they throw. They continue playing until one player loses (runs out of money). Initially Alice has £6 and Bob has £14.

a. Determine, with proof, the probability that Alice loses.
b. Determine the probability that Alice loses but also has at some time previously been within £1 of winning.


June 11, 2005

How Much Effect Is There From the Sea?

Follow-up to Humanity's Greenhouse Footprint from The Militant Wing of Pacifism

CS responded to one of the previous posts with:

A little known fact is that much of the world's CO2 is stored in sea-water, and a rise in temperature reduces the water's capability to retain CO2, so the oceans give off CO2 as they warm. While I don't have exact figures to hand, I think the contribution of natural warming to CO2 levels in this manner is significant.

I pretty much ignored it, previously, because it wasn't really significant to my point – even if human global warming is triggering other carbon sources, this still counts as human caused climate change, in that it wouldn't be happening if we weren't releasing. It just adds a degree of superfluous indirectness to the preceeding. It didn't occur to me to investigate this particular 'fact'.

So, from RealClimate :

This question keeps coming back, although we know the answer very well: all of the recent CO2 increase in the atmosphere is due to human activities, in spite of the fact that both the oceans and the land biosphere respond to global warming.

Why? Because we've actually measured the Carbon content of the seas. The following is pasted pretty much directly from that entry. (Because I can't get blockquotes working right…) They've given references, so you can check up their assessments if you desire:

Pasted section begins

On time-scales of ~100 years, there are only two reservoirs that can naturally exchange large quantities of CO2 with the atmosphere: the oceans and the land biosphere (forests and soils). The mass of carbon (carbon is the "C" in CO2) must be conserved. If the atmospheric CO2 increase was caused, even in part, by carbon emitted from the oceans or the land, we would measure a carbon decrease in these two reservoirs.

Number of observations of carbon decreasing in the global oceans: zero.

Number of observations of carbon increasing in the global oceans: more than 20 published studies using 6 independent methods.
The methods are:
(1) direct observations of the partial pressure of CO2 at the ocean surface (Takahashi et al. 2002),
(2) observations of the spatial distribution of atmospheric CO2 which show how much carbon goes in and out of the different oceanic regions (Bousquet et al. 2000),
(3) observations of carbon, oxygen, nutrients and CFCs combined to remove the mean imprint of biological processes (Sabine et al. 2004),
(4) observations of carbon and alkalinity for two time-periods combined with an estimate of water age based on CFCs (McNeil et al. 2002), and the simultaneous observations of atmospheric CO2 increase and the decrease in (5) oxygen (Keeling et al. 1996), and (6) carbon 13 (Ciais et al. 1995) in the atmosphere.

The principle of the last two methods is that both fossil fuel burning and biospheric respiration consume oxygen and reduce carbon 13 as they produce CO2, but the exchange of CO2 with the oceans has only a small impact on atmospheric oxygen and carbon 13. The measure of atmospheric CO2 increase together with oxygen or carbon 13 decrease gives the distribution between the different reservoirs.

All the estimates show that the carbon content of the oceans is increasing by 2±1 PgC every year (current burning of fossil fuel is 7 PgC per year). One method is able to go back in time and shows that the carbon content of the oceans has increased by 118±19 PgC in the last 200 years. There is some uncertainty about the exact amount that the oceans have taken up, but not about the direction of the change. The oceans cannot be a source of carbon to the atmosphere, because we observe them to be a sink of carbon from the atmosphere.

Why are the ocean and land taking up carbon, when we know that warming of the oceans reduces the solubility of CO2 and warming of the land accelerates bacterial degradation of the soils? The answer is that warming is not the only process that influences the oceans and land biosphere. The dominant process in the oceans is the response to increasing atmospheric CO2 itself.


June 09, 2005

Bellamy KO'ed by Scientific Fact

Follow-up to Lies, Damned Lies, and Global Warming Deniers from The Militant Wing of Pacifism

Well, it seems that Monbiot has won his little spat with David Bellamy. That would be the Bellamy I blogged about previously for making crap up about Global Warming. He's just been kicked out from the Centre for Alternative Technology for:

Some of Prof Bellamy’s recent published statements seem to be flying in the face of the considered opinion of the majority of the scientific community. Such statements are clearly inconsistent with the standpoint of CAT.

Of course, it would be unseemly for me to gloat too excessively at his personal misfortune, but really, if you want to pick a fight, then you really need to make sure the facts are at least partially on your side. On subjective issues of judgement, there is always plenty of wriggle room in any argument, but if your statements are based on complete and utter lies, then you are just looking like an idiot.

This has been blogged about somewhat, here and here.


June 06, 2005

Silly, silly poll on religion

Writing about web page http://wid.ap.org/polls/050606religion.html

So, some people are raving and ranting about the results of a new poll by AP.

Most of this is stating the complete bleeding obvious. Of course the US is more religious than Canada and the UK and stuff. But some of the claims being made by the poll are pretty silly. And if you look carefully, you will find that the poll was in fact badly done.

The specifically dubious claim is that:

Nearly all U.S. respondents said faith is important to them, and only 2 per cent said they do not believe in God.

Now, let's dig up the actual results:

Now, they've all focused on that first single entry:

  • I don't believe in God.

But check out some of the other entries:

  • I don't know whether there is a God, and I don't believe there is a way to find out.

  • I don't believe in a personal God, but I believe there is a higher power of some sort.

  • Not sure.

By the definition of belief, all of the above in fact qualify as not believing in God. If you don't know whether X exists, obviously you don't believe in its existence. You just don't believe in it's non-existence either. And an impersonal God is indistinguishible from a natural law – many scientists, such as Einstein, believed for example in the universality of a natural order, and they don't believe in God. And if you are not sure what you believe in, how can you make the positive statement that you believe in God?

Here's the thing. Implicit in the question was the definition of 'not believing in God' as 'believing in the absence of God'. Now, this is an incredibly strong and irrational statement to make, and the vast majority of self-declared atheists would not agree with it. No scientist worth his/her salt would dare make such a statement.

That's why it is hugely misleading for the above ranters to treat this latest poll as proof of the end of secularism in the US, or whatever. Rest assured, fellow comrades, there is still some sanity in the old US of A.


Final exam!

Final exam in 75 minutes!

Then I'll sleep for a few years or so.


June 01, 2005

The Cornstarch Sounds Yum, Though

Writing about web page http://www.maths.bris.ac.uk/~mardd/Pages/Research/shear_thickening/images/cornstarch.wmv

Exam number 4 (out of 8) finished. God I'm tired.

Something pretty neat.

Well, neat if you are a geek like me, I suppose.


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