Mario Molina Interview (page: 2 / 8) Nobel Prize in Chemistry	Print Interview

Can you recall the moment when you first realized that the ozone layer was threatened? Did it feel anything like the joy a child feels, discovering the world of science for the first time?

Get the Flash Player to see this video. Mario Molina: It was indeed something that happened suddenly. Because we had realized that these compounds would actually reach the stratosphere, that they could decompose there, and in fact I even knew without too much trouble that these compounds could actually affect ozone to some extent. But I remember clearly one day -- actually doing calculations, finding out how much of these compounds reaches the stratosphere, and comparing that with some natural processes -- that I realized that the problem was really potentially very serious. So it seemed, in a sense, a moment of discovery. But it was different from the earlier ones I had as a child, because I was also very worried. It was not also, in this case, the scientific discovery, but also a discovery about something that could damage the environment. So it all seemed to be bad news at that time, and that's why it has been very rewarding much more recently, not just to have discovered that there was this potential danger, but also to have realized that society can actually do something about it. And so that's why I sense that, believe it's really a success story. Very different from that day in which I got very worried, because now essentially the international agreements recognize the problem and call for completely stopping the production of these chemicals that can harm the environment.

Was there a particular calculation you made that led to this conclusion?

Mario Molina: It was, indeed, just putting together all the information that we had, and putting it in context, and realizing that it's just the way one sets off a scientific hypothesis, a sequence of steps with these very serious consequences. So it's really just a moment when you put all this information together and realize that you have something important in front of you.

How did you determine that these particular compounds -- the chlorofluorocarbons -- were threatening the ozone layer?

Get the Flash Player to see this video. Mario Molina: It really started asking the question, "What happens to these compounds once released to the environment?" Our starting point was that these compounds have been measured to be throughout the atmosphere. Not just close to cities, but in the Northern Hemisphere, the Southern Hemisphere. That was just a starting point. These compounds are very stable. They are non-toxic, you can even breathe them. So the assumption was that there was no worry, because of the presence of these relatively small amounts -- parts per trillion amount -- of these compounds in the global environment. So that was just the starting point. The rest was just scientific research. We were asking the question, "What happens to these compounds?" We realized that they would eventually diffuse to the stratosphere, because nothing else would destroy them. In the stratosphere they would be destroyed, but that was not the end of the question. We had to pursue it several steps more. So what? And we had to follow what happens to the decomposition products from these compounds, and that's of course where the effects on ozone begin. So it's really taken a complete -- an overall -- picture of the problem that led us to our discoveries.

Was perseverance very important, sticking to this project to achieve the goal of this discovery?

Mario Molina: Perseverance is very important, because things don't always work at the beginning. First of all, you really have to define a goal, a goal that is attainable. But with perseverance, you keep working at this. If you realize the potential importance of what you're doing, that keeps you going. It's a drive that one needs to really achieve important research results, in most cases.

Your 1974 paper created enormous attention. We'd like to find out more about how you overcame the criticism you encountered, and the vindication you received when your findings were confirmed.

Mario Molina: What we did initially was communicate with other scientists, like it's normally done, to find out whether we were making some big mistake or not. Actually, our ideas were very well received in the small community that were experts in this field. It was more in terms of the implications of these findings that we had problems, and it was very clear that what we had to do is to continue learning more about this hypothesis that we initially had come up with. After all, we did not have much information in terms of actual measurements in the atmosphere to begin with. So what we saw as an important aspect of our role at that time was to make sure that the scientific community, as well as the government, take the problem seriously enough to put enough resources to find out more about the problem. And we succeeded with this effort -- again with the help of many other colleagues -- so that eventually many experiments could be carried out, to either verify or disprove this hypothesis that we were thinking of initially.

You were able to predict the existence of a hole in the ozone layer as early as 1974, but it wasn't until 11 years later that the hole was actually discovered. Were you at all nervous about that, before the hole was actually found? What was your reaction to that discovery?

Get the Flash Player to see this video. Mario Molina: Of course, we were not sure. We realized that the atmosphere is very complicated and that we didn't know -- certainly by far -- everything that there is to know about it. On the other hand, pieces of evidence began to come for measurements. Experiments were carried out, and we know that these gases were indeed reaching the stratosphere -- the CFCs. We know that the composition products were indeed there, but it was very difficult to measure these actual effects on ozone, because the ozone amounts in the stratosphere fluctuate. On the other hand, we actually did not predict that ozone would be depleted specifically over Antarctica. We just made a very general prediction that these -- the composition products -- could affect the ozone layer in general terms. So it actually came as a surprise that this large effect was happening in this coldest place on earth. On the other hand, with all the scientific research that had been carried out before the Antarctic ozone hole was found, it was just a matter of a few years for us and the rest of the scientific community to understand -- with experiments in the laboratory as well as in the atmosphere -- very clearly why is it that specifically Antarctica was the place where this hole appeared. And the reason, of course, is that it's very cold there, and clouds can actually form over Antarctica that do not form anywhere else in the stratosphere that are sufficiently cold to promote a new type of chemistry that we then investigated in the laboratory. So in other words, what happens is even though our predictions were not very specific, we lay down, together with our colleagues, a foundation and an infrastructure to really understand on a very rapid time scale the nature of all these effects once they became clear.

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