This week I've come to the east Bohemian town of Hradec Kralove, to the Czech Republic's only solar and ozone observatory, which was established over half a century ago, in 1951. My guide is a physicist named Karel Vanicek, who has been working here since the mid 1970s. Of course ozone depletion is now a well-known problem and I asked Mr Vanicek when he and his colleagues in Hradec first began to notice that the ozone layer was starting to disappear.
"In the beginning of the 80s we identified the start of a decrease in the total amount of ozone in the atmosphere, coming from our observations. But at that time we were not in touch with our colleagues outside the Eastern Bloc and therefore a lot of pieces of information were available to us only from scientific papers, books etceteras. But after 1989 we very rapidly penetrated outside and nowadays I have to say that we've been running a very wide programme that covers much more aspects or tasks outside the country. We have been co-operating with the web meteorological organisation in maintenance of the global network. Every year we have two or three operators here from Africa, Asia or South America here to give them training in how to operate and process the data that could describe the behaviour of the ozone layer in their home countries."
Karel Vanicek told me that as the equipment used at the Hradec Kralove observatory became more modern there was less to see, and they began to get fewer visitors. Nevertheless, there are many curious contraptions to be seen there and I asked him what one device on the wall was for.
"This is a barometer. It is a very old instrument, but attractive. Now we measure atmospheric pressure with a small cell that is located outside the building in the meteorological garden that is not attractive like this manually manufactured instrument."
What about these old pieces in the cabinet?
"Yes, we have here a small museum where the historical solar radiometers are exposed. The instruments that are now used for solar radiation measurements are located on the roof."
I see here in the cabinet two or three glass crystal balls - what are they for?
"This crystal sphere works as a lens. As the solar beams go through it focuses them in one point on a paper strip where the trace is burned by the focused solar radiation, and therefore it allows us to register how long the solar disc was not affected by clouds, therefore how long we had direct sun radiation."
I should add that this looks like a classic crystal ball for seeing the future.
"Yes. In the past it happened frequently that visitors liked to take these balls from our roof and therefore several balls have been stolen."
Before we left for a tour of the observatory's roof, Mr Vanicek showed me a ferociously complicated looking, constantly updating graph on a computer in his office. He pointed out that the standard height for thermometers was two metres from the ground, and explained why.
"At two metres the air is not affected by the overheated surface. Because normally, if you have a look, the temperature at two metres is now about 26 centigrade, but the temperature at five centimetres is 35. During the hot sunny days in the summer months there could be a difference of 20, 30 centigrade. That's a big gradient so if we measure the temperature too close to the earth's surface the temperature would be affected too much by the earth's surface, and wouldn't represent the free air temperature."
Now we're here on the roof at the solar observatory.
"This is the Dobson ozone spectrophotometer which has been used here since 1961. It is a well-calibrated and robust, but manually operated instrument. And we still use it as a reference instrument which represents our long term data series. On the other side there is an automated Brewer ozone spectrometer, which we've been using since 1994. And this one is fully-automated and controlled by PC."
This to me just looks like two white boxes on top of each other.
"Yes, but full of very precise electronics and optical pieces."
On top of this machine there's a little glass dome. Is that where the information goes in, so to speak?
"Through this dome solar radiation comes from the zenith. The radiation is used for analyses of the UV part of the solar spectrum. There is another window and this window is the inlet to the optical system that measures ozone in the atmosphere."
This dome is quite small, it's about half the size of the palm of my hand, roughly.
"Yes, it is, but it is made from precise quartz, and therefore it is also an expensive part of the instrument. Because it is made from a monolithic quartz crystal. Maybe you don't know this but normal glass observes UV, but if we want to measure UV radiation, and you want to protect the inlet windows by glass it must be quartz glass, it must be pure quartz."
This expensive machinery is on the roof here, we're quite high up - does it get affected by the weather, is it damaged by the weather?
"This one is waterproof; it has been permanently exposed here since 1994. It is so well constructed that it is completely waterproof, inside heated during the winter time. The instrument moves itself, it calibrates itself, as I told you it is something like an automated robot."
Here's a very strange looking contraption, it's got something that looks like a car steering wheel over it. What is this?
"It's not a car steering wheel (laughs) but a special ring that shades the solar disc. Therefore the radiometer whose sensor is shaded by this ring measures only radiation that comes from the zenith. And therefore this gives us information as to how much solar radiation is scattered by atmospheric gases."
I'm surprised how small these meters are - they're all tiny things.
"Yes, they are because if the instrument were too big it would be difficult to maintain their inner thermodynamics so stable, and this would affect the measurements and cause unacceptable errors."
For two decades now we have been hearing how the ozone layer has been depleted, we don't dare sunbathe without protective cream and we have been doing away with the chemicals which caused so much of the damage. Before I left the Hradec Kralove solar and ozone observatory I just had to ask Karel Vanicek how he saw the future of the ozone layer. He told me he was an optimist.
"All evidences show that the implementation of the rules defined by the Montreal Protocol for the Protection of the Ozone Layer and it's amendments - strong amendments, coming from last year - we see that the total amount of ozone depleting substances in the atmosphere is decreasing. And now we expect that in the next five or ten years, if things go well, we'd be able to identify the beginning of the recovery of the ozone layer. But everything depends on one key issue: the Montreal Protocol and its amendments must be respected and fulfilled in developing countries. Because some big developing countries like China, Brazil, Nigeria and so on, if they don't have suitable and safe technologies they would use strong CFCs and in that case this positive development could be broken, and we could return back to the condition that was typical for the end of the 80s."
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