Climate change and photos of trees

[Relative amateur]

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.

[agg221]

Peter, as we discussed an interesting piece of work.

 

I'm not sure that it is valid to draw fit lines on the plots in this fashion - if you think about the data, it is measured on a scale where 5 = full leaf, so the y scale cannot exceed this value. As such, once full leaf is consistently achieved before the date of the photograph you will hit a line of consistent 5 from then on. Allowing for differences in perception, you may actually hit a peak line slightly below this and the London data looks like this could have already occurred. Thinking about the counterpart plot which would show a consistent level of leaf development against date, this could show a linear trend. As such, your plot should ultimately consist of two lines with a knee. If software fitting was used it will try to create a single line of best fit, meaning that if you have already reached the knee, as could be the case for London, the trend line will be incorrect.

 

This doesn't detract from the value of the work though, which is still very interesting.

 

I don't have any equivalent series of photographs to add, but I believe The Essex Field Club recorded leafing out dates for elms for a very extended period. I'm not sure if they are still doing so (and if not, when they stopped - elm has not died out in this area) but Mark Hanson should know. Butterfly Conservation may also have continued the trend data as they track it with regard to the White Letter Hairstreak. This would at least corroborate the findings.

 

Alec

[Vespasian]

I have an interesting opinion on climate change...

 

which is to say, whether its man made natural or a bit of both such is the scale of the problem (if it even is a problem) nothing much can be done about it...

 

But governments can use the issue for their own reasons.... tax on fuel and subsidizing alternative energy..

 

So the underlining questions should be, why are governments around the world spending billions on alternative energy... once you figure that out, you'll see why climate change is always in the headlines..

[matelot]

In medieval London the Thames used to freeze over each winter and they would have special "winter fairs" on it. I believe in man made global warming, but perhaps "natural" global warming is a larger effect....

[Lucan]

From experience those graphs don't look like there are any statistical proven correlations, data looks to random. What are the r-squared value of the lines?

[Peasgood]

Two pictures of trees coming into leaf in spring mean pretty much nothing as far as warming is concerned. It could just as easily be showing how smog has been reduced due to much cleaner air these days.

[Vespasian]

Two pictures of trees coming into leaf in spring mean pretty much nothing as far as warming is concerned. It could just as easily be showing how smog has been reduced due to much cleaner air these days.

 

 

If you factor in Ocean currents, El Nino's volcanic eruptions sun spot activity and other not so obvious variables it might then be useful take a look at tree growth cycles...

 

but, only if you can compare todays cycles to photographic evidence from, Oh, lets say from ten thousand years back...

 

which is to say I don't think anything useful can be deduced from photos of leaves on tree's..

Though I dare say its a bit of speculative fun if nothing else..

 

Oh, I wouldn't like anyone to use pics of tree's as evidence to jack up the price of diesel though, though I dare say some political numpties would do it...

any excuse an all that!!!.

[mdvaden]

I would be worried if we did not get climate change. Climate change has been going on virtually forever.

 

I'm sure 100% of scientists should believe that.

 

If there is a problem it's not that climate changes, but that certain people want to try and keep the climate and conditions the same.

 

When people realize that climate can and will change some, and allow for it, it will be easier to adapt and make changes.

[Billhook]

There are so many variables that I cannot see how you can reach a conclusion.

 

It all started with "The Greenhouse Effect" and man made global warming.

 

This had only one conclusion, that man was the cause of heating up the atmosphere by burning things, from forests to fuels.

 

Suddenly it transferred from Global Warming to Climate Change. This opens up a whole new range of possibilities and could account for the planet cooling as well as heating up.

 

Somehow you have to balance the emotive picture of a polar bear balancing on what looks like the last iceberg in the North Pole, with the fact that the coldest temperatures ever recorded have been found recently at the South Pole.

 

Many are distrustful of the scientists because of the smell of money.

If you were an underfunded weather scientist working on a boring job and suddenly some politician asks you to go to a smart conference in Copenhagen, staying in a plush hotel, that may be attractive.

When you make a case for global warming and you are asked to more conferences you soon realise that the stronger you make your case, the more money is thrown at you perhaps to such an extent that you start to manipulate graphs and figures to suit.

 

I think that most people will agree that we want to breathe clean air, and that we need to conserve energy by not wasting our reserves and going for renewables where they make sense.

 

If we go down this road surely this will also achieve the objectives of the global warming brigade by cutting down on greenhouse gases, and everyone will be happy (apart from the oil companies!).

 

We all have to believe in Climate Change, just look at the difference between the weather today and a week ago!

[peatff]

The earth is not at the same distance from the sun all the time as it is on an elliptical orbit so when we are further away it will be cooler. I tested this hypothesis by sitting further away from the fire and it works.