Relative amateur

Some replies: Alec - interesting idea. You are probably right that linear regression isn't precisely right for analysing this, perhaps some sort of logarithmic regression. But I challenge anyone to look at the graph (itself the result of a very democratic process) and not agree that in the latter period the trees are in fuller leaf on Nov 11 than in the earlier. Interesting about the Elm data; how to get in touch with Mark Hanson? Though having said that, my colleague Tim Sparks is very involved in that sort of territory - it is the photos that particularly interest us now. Vespasian: I really don't agree! The current extreme emerging climate change (if you look at the data from e.g. ice cores) is due to human intervention starting with the industrial revolution. If we don't want our grandchildren, possibly our children, to have a grim time we should do something. Do you really think our current government likes subsidising renewables or putting taxes on fuels??! Matelot: The 'Little Ice Age' that caused the Thames to freeze was quite tough, certainly, but is thought to be a local phenomenon, at most a slight cooling of the Northern Hemisphere. Again, it pales into insignificance in comparison to the global warming now going on. To get a clear picture you have to look globally - local variation confuses more than shed light. Lucan: I don't have the r squared data for them (will try and get it), but I don't agree, visually it srikes me as thoroughly significant. Peasgood: one of the reasons we haven't published the data is that we need to rule out all the other possibilities, and smog could possibly be one (I'm not well informed on the bio-chemistry of what makes leaves fall). That is why we are trying to find photos from a different places, ideally in the country. Vespasian #2: not sure I understand you. Anthropogenic climate change is all about the last couple of centuries, and the additional impact of C02 on top of all the other things you mention. The people who think about this all day and every day (not me) haven't forgotten them. mdvaden: the two worries about the sort of climate change we are currently at the beginning of are (i) it looks as if it will cause change that is quite a lot quicker than humans and other species can respond to, and (ii) there is a risk of what has been called 'dangerous climate change'; rapid, runaway effects which might take place over a period of a decade or two - this has happened in the distant past. It is about risk; do we really want to take the chance? Billhook: The climate scientists I know have a lot of integrity. I think the money argument holds absolutely no water. phedders: the 97% applies to climate researchers publishing peer-reviewed papers, which I think is a pretty tough test. The data is here. I repeat, the people I know who do this for a living have a great deal of integrity, and as far as I can tell would dearly love to be researching a subject that didn't have such depressing implications. matelot again: yes, the climate always has changed. This time looks as though it will be different. Paul Barton and Kveldssanger: good points, which I can't answer - though why would you get such a variation if they do it by day length? I'll have to invite Prof Sparks to address that.

Here is a project that I hope some will find interesting. I am assuming, incidentally, that most on this forum are not skeptical about the reality of climate change (in common with 97% of scientific researchers!). Have a look at the first picture below, which was provided by Professor Tim Sparks, with whom I have worked on this. It shows two views of the same scene, importantly taken on the same date. And the key point is that it shows different levels of foliage. The progress of the seasons was obviously different in the two years. This led us to look for other photos taken on the same day in different years. For the comparison to be really useful they have to be either in the autumn or spring so you can see fairly easily how much foliage there is - there is not much variation in the summer! And this turns out to be quite tricky - all those photos in the album you inherited from your mum don't tend to be of the same view, and very rarely have accurate dates on them - 'Easter 1934' if you are lucky! Tim and I cast about, and we came up with Armistice Day (Nov 11) in Whitehall, May Day in Moscow (though some suspicion as to whether the trees had been trucked in to look impressive!) and, bizarrely enough, Queen Beatrice' birthday in Holland, officially on April 30. But Armistice Day was the winner, with quite a lot of newspaper and archive photos and videos. See the next pic for some examples; we managed to find a good 60 or so from different years. Tim did some work with classes full of students, inviting them to judge, on a 5 point scale, whether the trees were in full leaf or leafless. There were surprising levels of disagreement, and also some inconsistencies in the same year. See the third image, a graph, in which the vertical lines connect photos of the same year with trees in different states of leaf. Obviously there are very big variations from year to year, as would be expected, so one has to concentrate on the long term trends. The overall message is pretty clear, though, from the line on the graph. London Plane trees, Platanus × acerifolia, have clearly tended to lose their leaves later on as the twentieth century passed. Very similar things happened in Paris, and this correlates very well with the temperature record for the period - next graph. This provides a rather different perspective on the overall subject of climate change, though we haven't yet published it - you heard it here first! One of the complications is the 'urban heat island effect' - cities are warmer than the country, and that may have influenced the result; also, the causes of leaf fall are more complex than just temperature. But to find that trees - when their foliage is captured in a photo - are telling the story of climate change, is I think moving, powerful and somewhat poetic. We'd love to get more data on this. Does anyone have any other photos to contribute, ideally a lot of them? The criteria are hard to meet: - photographic views of the same foliage - with trustworthy, identical dates in different years - during the period when foliage either develops or leaves fall.

I've taken the advice on board, and am working with Alec (AGG221) shortly to see if I can absorb some of his wisdom.

Thanks for the advice, all.

There's one on Ebay right now at £6.5k - Woodmizer LT15 / mobile sawmill | eBay

Hmmmm,a large part of the reason for this is that I haven't managed to find anyone with a mobile mill of any sort in the relevant part of France )Tarn et Garonne) - if anyone knows anyone? And £18k (+ VAT!) also seems rather a lot, I'm pretty sure I need a fairly basic machine costing a lot less than that.

Greetings all, I'm writing as a complete newcomer to Arbtalk; nice place. I'm a woodworker, who has recently benefited from sizeable oaks coming down in London (involuntary, in that case), where I live, and in southern France, where my father-in-law lives. I intend to turn them into 30 - 50mm thick boards, plus a few a bit thicker, and when seasoned I'll certainly have enough wood to see me out, with plenty left over to mend the barn of the farmhouse in France. I've spent a long time thinking about what sort of mill to use, and come to the conclusion that a swing mill is the answer; because (1) one never really uses wide boards in my sort of work (can't be doing with that rustic look), (2) chainsaw mills look like hard work to me, and (3) the French log (should I be calling it a stick?) in particular weighs about 3 tonnes, is in a thoroughly inconvenient place, and the chap who runs the local sawmill seems to be better at Gallic shrugs than what we might call can-do. What I'd really love to do is hire a Lucas or Peterson mill for a week or so and do my own thing - first in London (Greenwich), then take it to France in a van and bring it back. Would anyone be up for that? Second best would I suppose be to spend a day here with its owner making sure I wasn't likely to do anything daft with it. I've seen the thread somewhere on Arbtalk where the merits of hiring mills on a 'machine only' basis were discussed, and for the life of me I can't see that they are more damageable or dangerous than plenty of other bits of kit regularly for hire.