Last week, I was giving a seminar to a group of engineering students. Everything was fine, but when I started discussing climate change, a discussion ensued which I think is worth reporting here.
The question. Professor, it is all right that you tell us these things about climate change, but I have to tell you that, a few weeks ago, we had here another professor who told us more or less the opposite; that is he told us that carbon dioxide is plant food, that models are uncertain, that there is much exaggeration and alarmism about climate change. Now, he is a scientist, just like you. So, what should we think?
My Answer. I understand your question and I even know rather well the person you are mentioning: a colleague of mine; a chemist by training, just like me. Of course I could dispute his statements about climate one by one but, from your point of view, it would only create confusion. Your question is not about the details of climate science but, rather, why there is this strong disagreement among two scientists.
Let me try try a personal interpretation. The point is, I think, is that with climate we are discussing about science and not about engineering. These are two different things, engineering is about building things that work using knowledge we believe is well established. Science, instead, often deals with matters which are uncertain and where the data are insufficient. As a scientists, you have to work with what you have and you are supposed to be creative. You have to question the data, the theories and everything if you want to understand what you are studying. And if you do that, then you have to take the risk of following the wrong road. This is the way science progresses. Then, if it turns out that new data contradict your interpretation, well, there is no blame in changing your mind. Of course, you understand that this kind of attitude would be no good for an engineer who is supposed to design such things as bridges or planes.
So, when we deal with climate change, it is perfectly legitimate for scientists to have different opinions. For instance, I am in contact with a colleague who believes that global warming is not a serious problem if we take into account the depletion of fossil fuels. According to his interpretation, soon depletion will force us to strongly reduce our emissions of carbon dioxide and the earth's climate will stabilize without creating big problems. I don't agree, but I recognize that it is a legitimate position: the data and the models we have are uncertain enough that my colleague's interpretation is a possible future.
Still, even engineers sometimes have to deal with uncertain situations and insufficient data. In this case, you know that you don't have to be creative. You have to be extremely conservative - it is exactly the opposite attitude to that of scientists. That is, you don't need perfect models of the deformation of tubular structures in steel to understand that if the Titanic hits an iceberg, then the results will not be good. If you like, it is a moral issue: you just can't afford to put people's lives at risk and that holds for both engineers and scientists. But, occasionally, scientists don't have this point so clear.
Let me go back to my colleague; the one who spoke to you last time. This colleague of mine has stretched a lot the uncertainties related to climate science - I think well over legitimacy - but it is also true that these uncertainties exist and, within some limits, it is legitimate to emphasize them, especially for a scientist who is trained to push science forward by questioning the established positions. What is not legitimate at the present stage is to neglect the risks of climate change. That is, I think my colleague sees the climate question as a gigantic scientific experiment in progress and, as a scientist, he thinks it is legitimate for him to question the data, to question the interpretation, in short to play the role of the contrarian. As an additional note, I know that my colleague has built his long and distinguished career on petroleum chemistry and we may imagine that he resists the idea that acting against climate change could force us to stop using petroleum. But the important point is that he doesn't realize, unfortunately, that he is playing with the life of people, and especially with the life of young people as you are.
It is, in the end, a moral issue, as I said. In this case, there is the additional point that you have much more future - many more years to go - than your teachers. So, the climate related risk for you is much larger than for them. If your teachers don't understand this point, I think they are failing you and I am sure you are smart enough to understand what I mean.
Now, if you like, I could tell you more details about climate science but perhaps it is not needed. If you reason like good engineers, as you are being trained to become, you can look at the data and make up your mind by yourselves.