Monthly Archives: July 2010

Ten indicators on global warming

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I thought this was rather good (= clear, coherent and substantiated). Links at the original article.

1. Humans are currently emitting around 30 billion tonnes of CO2 into the atmosphere (CDIAC). Of course, it could be coincidence that CO2 levels are rising so sharply at the same time so let’s look at more evidence that we’re responsible for the rise in CO2 levels.
2. When we measure the type of carbon accumulating in the atmosphere, we observe more of the type of carbon that comes from fossil fuels (Manning 2006).
3. This is corroborated by measurements of oxygen in the atmosphere. Oxygen levels are falling in line with the amount of carbon dioxide rising, just as you’d expect from fossil fuel burning which takes oxygen out of the air to create carbon dioxide (Manning 2006).
4. Further independent evidence that humans are raising CO2 levels comes from measurements of carbon found in coral records going back several centuries. These find a recent sharp rise in the type of carbon that comes from fossil fuels (Pelejero 2005).
5. So we know humans are raising CO2 levels. What’s the effect? Satellites measure less heat escaping out to space, at the particular wavelengths that CO2 absorbs heat, thus finding “direct experimental evidence for a significant increase in the Earth’s greenhouse effect”. (Harries 2001, Griggs 2004, Chen 2007).
6. If less heat is escaping to space, where is it going? Back to the Earth’s surface. Surface measurements confirm this, observing more downward infrared radiation (Philipona 2004, Wang 2009). A closer look at the downward radiation finds more heat returning at CO2 wavelengths, leading to the conclusion that “this experimental data should effectively end the argument by skeptics that no experimental evidence exists for the connection between greenhouse gas increases in the atmosphere and global warming.” (Evans 2006).
7. If an increased greenhouse effect is causing global warming, we should see certain patterns in the warming. For example, the planet should warm faster at night than during the day. This is indeed being observed (Braganza 2004, Alexander 2006).
8. Another distinctive pattern of greenhouse warming is cooling in the upper atmosphere, otherwise known as the stratosphere. This is exactly what’s happening (Jones 2003).
9. With the lower atmosphere (the troposphere) warming and the upper atmosphere (the stratophere) cooling, another consequence is the boundary between the troposphere and stratophere, otherwise known as the tropopause, should rise as a consequence of greenhouse warming. This has been observed (Santer 2003).
10. An even higher layer of the atmosphere, the ionosphere, is expected to cool and contract in response to greenhouse warming. This has been observed by satellites (Laštovi?ka 2006).

(My position is still basically as set out here though.)

Posted in agw

Whiteout

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This film would have worked much better with an old soak playing the character of the Marshall. Instead we had Kate Beckinsale, a good actress, being used as eye candy. Frustrating. 3/5

Home at last :)

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Home after a week, with a great deal of thanks to some wonderful NHS staff and the one above. The other kids were most excited to see her, but were even more interested in the birthday cake 🙂

This’ll be the last update on the baby; thanks for all prayers and messages, they do make a difference.

Seven Links

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Phil tagged me with this.

1. Your first post: Working out how to use this thing

2. A post you enjoyed writing the most. ‘The most’ is much too restrictive, as I’ve enjoyed writing on the blog a lot. If I can take enjoyment to mean cathartic, probably this one.

3. A post which had a great discussion. To my very great regret several years worth of commenting on this blog is now in cold storage, awaiting the day when Haloscan comments can be imported into blogger – so you can’t see the answer to this one.

4. A post on someone else’s blog that you wish you’d written. Ooh, how to choose this? So many contenders. It would probably be something by John Michael Greer. I’m trying to do from a Christian point of view what he has done from a Druid point of view, but there is a lot of overlap.

5. A post with a title that you are proud of. The colour of my shirt.

6. A post that you wish more people had read. This one on the authority of Scripture (and my Anglican triangle)

7. Your most visited post ever. Don’t know. Might be this one, which tells you all you need to know about blog stats.

I tag Banksy and Doug.

Happiness is a team sport

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Courier article – posted here two weeks after publication.
I wonder how many people on Mersea were closely following the fortunes of the England team in the World Cup. By the time this gets published we’ll know who has won it this year. Personally I’d like it if a country that has never won it before wins the prize – so Holland or Spain – but the form of the German team (playing their semi-final tonight as I write this) is ominous.

Before watching the England-Germany game – for which I didn’t entertain much hope, although I thought we’d limit it to a 3-1 defeat – I was watching the BBC build-up, and there was an interview with Boris Becker, where he said (rather smugly, it must be admitted) “football is a team sport, and Germany has the better team”. It was annoying to admit it, but he was right. Doubtless there are all sorts of long-term reasons why England doesn’t do well at international tournaments but the sight of our players doing their best to impersonate cranially-challenged poultry was unnerving. I’m sure that Capello’s slavish adherence to 4-4-2 had something to do with it, but….

There was another bit of feedback from the victorious Germans after the match. Thomas Muller – who scored twice against us – said “”It is difficult to have so many ‘alpha males’ and have them row in the same direction. You don’t only need chiefs, you also need a few Indians. You need people who are willing to do the hard work. It may be a problem with England that players are simply not mentally prepared to go that extra mile for their team-mates.” It was annoying to admit it, but he was right.

Football is a team sport. It doesn’t matter how many ‘new Maradonas’ or ‘new Zidanes’ a team might have – if they don’t work together, if they don’t have a common purpose, if they are not prepared to make personal sacrifices in pursuit of a larger goal – then they will fail. The failures will be both individual and corporate. The team of brilliant individuals will always lose out to the team of lesser talents prepared to work together.

The great French philosopher Albert Camus once wrote “After many years during which I saw many things, what I know most surely about morality and the duty of man I owe to sport and learned it in the RUA” – the RUA being his football team, for whom he kept goal. It is, in truth, not a complicated lesson to learn. If we look after each other, and work for the common good, then everyone benefits.

This doesn’t just apply to leisure pursuits like football. It applies to every sphere of our lives, and in our context of increasing economic misery, it will apply most of all to the fundamental matters of life – having enough to eat, having a roof over our head, having clothes for our children to wear. If we look after each other, and work for the common good, then everyone benefits.

When exploring the context of our contemporary crises – of economic collapse, resource exhaustion, wars and the rumours of wars – I am very struck by the way in which the best-informed commentators continually return to one basic truth. There are so many things that can be done to help prepare people for what is coming – getting out of debt, learning to grow our own food, investing in alternative energy – but the single most important thing is to build up a community. This is because a community working together can withstand a very great deal more than a loose collection of individuals all looking out for their own interests.

Which is one of the blessings that Mersea enjoys. Partly – but not just – because of the geographical accident of being an island, Mersea does have a community identity, and we need to do as much as we can to support and foster it. There are many ways in which that can be done – and I’ll return to what they are in later columns – but one way is to be involved with, and supportive of, the West Mersea Mayor and Council, and the work that they do. In an ideal world the local council would have much more authority within Mersea than they presently enjoy – and Colchester Borough, and Essex County, and, indeed, Whitehall and Westminster would all have much less – but it will take some time for rationality to break through the entrenched bureaucracy. In the meantime we need to work with what we’ve got and work as constructively and co-operatively as we can. If we don’t hang together, we will most assuredly hang separately.

Our common future will only be reached collaboratively. That is, our happiness is a team sport, and if we look after each other, and work for the common good, then everyone benefits.

The Hockey Stick Illusion – a brief criticism of a criticism

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Real Climate has published something of a review of Montford’s book. When I read it (yes, I do read Real Climate, as much as I can – that is, I tend to have enough time, I just find it difficult to digest nonsense 😉 it occurred to me that it was a perfect example of bad criticism, and thus – as I’ve mentioned before – something which I do think falls into an area where I have a little expertise.

I’m only going to explore one item in Tamino’s review; for more substantial responses go here and here; in brief, Tamino doesn’t engage with the substantive argument. No change there then.

First, it will be worth summarising one of the arguments that Montford makes. Rather helpfully for the statistically challenged, like myself, Montford takes time to explain what Principal Components analysis (PC analysis) actually does: it sifts raw statistical data in order to extract significant information (notable patterns). Crucially, each ‘sifting’ extracts less useful information than the last, so PC1 is very useful but each successive PC is less so. Montford: “while the PC1 might explain 60% of the total variance, by the time you get to PC4, you might be talking about only 6 or 7%. In other words, the PC4 is not telling you much of any significance at all”. Montford uses this very helpful analogy:

“The PCs are often described as being like the shadow cast by a three-dimensional object. Imagine you are holding an object, say a comb, up to the sunlight, and it is casting a shadow on the table in front of you. There are lots of ways you could hold the comb, each of which would cast a different shadow onto the table, but the one which tells you the most about the object is when you expose the face of the comb to the light. When you do this, the sun passes between the teeth and you can see all the individual points. You can tell from the shadow that what is being held up is a comb. This shadow is analagous to the first PC. Now rotate the comb through a right angle, so that you are pointing the long edge of the comb to the sun. If you do this, the shadow cast is just a long thin line. You can see from the sahdow that you are holidng a long thin object, but it could be just about anything. This would be the second PC. It tells us something about the object, but not as much as the first PC. You can rotate through a right angle again and let the sunlight fall on the short edge of the comb. Here the shadow is almost meaningless. You can tell that something is being held up, but it’s impossible to draw any meaningful conclusions from it. This then, is the third PC.”

This is how Tamino ‘responds’:

Principal Components

For instance: one of the proxy series used as far back as the year 1400 was NOAMERPC1, the 1st “principal component” (PC1) used to represent patterns in a series of 70 tree-ring data sets from North America; this proxy series strongly resembles a hockey stick. McIntyre & McKitrick (hereafter called “MM”) claimed that the PCA used by MBH98 wasn’t valid because they had used a different “centering” convention than is customary. It’s customary to subtract the average value from each data series as the first step of computing PCA, but MBH98 had subtracted the average value during the 20th century. When MM applied PCA to the North American tree-ring series but centered the data in the usual way, then retained 2 PC series just as MBH98 had, lo and behold — the hockey-stick-shaped PC wasn’t among them! One hockey stick gone.

Or so they claimed. In fact the hockey-stick shaped PC was still there, but it was no longer the strongest PC (PC1), it was now only 4th-strongest (PC4). This raises the question, how many PCs should be included from such an analysis? MBH98 had originally included two PC series from this analysis because that’s the number indicated by a standard “selection rule” for PC analysis (read about it here).

MM used the standard centering convention, but applied no selection rule — they just imitated MBH98 by including 2 PC series, and since the hockey stick wasn’t one of those 2, that was good enough for them. But applying the standard selection rules to the PCA analysis of MM indicates that you should include five PC series, and the hockey-stick shaped PC is among them (at #4). Whether you use the MBH98 non-standard centering, or standard centering, the hockey-stick shaped PC must still be included in the analysis.

[…snip…]

The truth is that whichever version of PCA you use, the hockey-stick shaped PC is one of the statistically significant patterns. There’s a reason for that: the hockey-stick shaped pattern is in the data, and it’s not just noise it’s signal. Montford’s book makes it obvious that MM actually do have a selection rule of their own devising: if it looks like a hockey stick, get rid of it.

So – Tamino’s argument is that because the hockey-stick shape emerges with the fourth ‘cut’ it still counts as statistically significant. Although he accepts that the standard convention is to use just two passes (= PC1 and PC2) he goes on to say “applying the standard selection rules to the PCA analysis of MM indicates that you should include five PC series, and the hockey-stick shaped PC is among them (at #4)”. (Please shout if I’ve misunderstood the substantive point that Tamino is making here.)

Can people see why I find this an inadequate response to Montford? Montford explains PC analysis at length, and a significant element of the argument is that the #4 cut doesn’t give useful data. Tamino at first accepts this (with a link expanding the acceptance) but then seems to go back on himself by simply asserting that five series should be included, and that the hockey-stick shape (#4) is significant. Why? Where is the argument for this?

There are ways in which Montford could be shot down here – and I would imagine that a competent statistician, familiar with these issues, could do it quite swiftly _if_ Montford is wrong. My point is a broader one – purely as a matter of rhetoric, Montford has the more compelling argument. He makes a point and explains it in detail – I understand the argument that Montford is making and it seems coherent. Tamino’s response is very different, in effect it is merely an assertion, which we are to take ‘on authority’. As the authority of the realclimate site is – for me – completely shot, the argument falls.

If there is another place where realclimate defends the statistical usefulness of a PC4 analysis, I’d be interested to read it.

Big sister and little sister

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Doctors are all now saying lots of positive things, thanks be to God. She is feeding well (from mum as well as from tubes!) and making steady progress. Do please keep praying though! I’ll probably put something up first thing each day while she’s in hospital; I can read all the comments/ replies through the day – and I/we do appreciate them.