Well, it seems to me that the debate about climate change has been somewhat misplaced in the media here in the past few years. It has been disproportionately focused on what we don’t know about climate change or about infectanitism surrounding the signs of climate change.
The question is really not about what causes climate change. There is plenty of evidence that climate change is caused both by natural and human causes. And as a matter of fact, for most of the history of our planet, climate change has been caused only by natural causes. Let’s look at just some of them, such as milancovich cycles. These are cycles associated with the changes in the orbital parameters of our planet, the way how the earth is rotating and revolving around the sun. And this includes 3 different cycles—96,000 year cycle, which is sometimes known also as 100,000 year cycle; 40,000-43,000 year cycle; and 91,000-92,000, maybe 93,000 year cycles. They’re all overlapping in time and they are partly associated with the changes in the shape of the orbit of our planet. They are partly related to the changes in the tilt of the axis of the earth, and they are partly also related to the way how the earth is rotating on its axis while it’s moving around itself, around it’s axis and around the sun.
So all these changes, in turn, are leading to differences in the amount of solar radiation that the earth is receiving at different times. And this is inevitably leading to some climatic variations, and we see plenty of evidence of glaciations and interglacials that have been happening over the last of years. Change in climate of the earth as a whole, and also change in, in many ways, original characteristics of climate.
We also know both from the geological records and from the theoretical models that milancovich cycles are very likely to lead to multiple changes in the systems, in the natural systems of our planet, that can be amplified through a variety of positive feedbacks. They might be leading to changes in the thermal holansic relation, the changes in the salinity and temperature of the water changes and the distribution of the ocean currents.
We also know that the changes of the global temperature are very likely to lead to changes in the speed of formation of the glaciers or melting of the glaciers and this, in turn, is leading to very deep, very dramatic changes in the earth balance of our planet. So the question is really not about the cause, as the principle cause of climatic variability or climatic change. It’s very likely that there are many natural causes, and those are their names, certainly going to perhaps be the most prominent, that there are many others of them. Changes in the number of sun spots. Changes in the distribution of land mass and sea, due to platectonics. All this is contributing to the changes in our climate, and usually those changes are very, very slow.
Now, let’s look at climate change during the past 100 years, changes since the beginning of industrial period. Over the last century, we see that the concentrations of carbon dioxide have already almost doubled, and we have observed unprecedential temperature increase, which is very hard to compare to anything that we see in the geological records. We see climate changes, which is so much faster and so much more dramatic compared to very slow climatic variations over many thousands of years, compressed in this just very short period of time that there is certainly no doubt that the changes that we see over the past century, maybe century and a half, are by far faster, and probably also having much larger amplitude compared to changes, let’s say between the lotglacial maximum and the most recent climatic optimum that occurred about 5,000 to 6,000 years ago.
So we are really entering this new period in the evolution of our planet and the evolution of our climate that is very hard to compare to anything that we saw in the geological past. The same is true for the greenhouse effect that we very often see as the main, or one of the main causes of human induced climate change. Greenhouse effect is not just a human caused effect. It’s a natural phenomenon. As a matter of fact, it’s a very important natural phenomenon that maintains the temperature of our planet at a more or less permanent level. Without greenhouse effect, there would be no life on the earth. Without greenhouse effect, the earth would probably look very much like Mars.
So we need greenhouse effect. The problem is that we’re changing it. We’re building more and more carbon in the atmosphere, and by doing it, we’re enhancing greenhouse effect. We are building more and more energy that is trapped in the atmosphere and cannot leave the atmosphere for the outer space. And this is something that is leading to unprecedential increase of the temperature.
It seems to me that this is the way I wanted to focus on our attention, not on what precisely is causing climate change, or what precisely is causing the increase of concentrations of carbon dioxide, but what we can do about this very, very fast changes that… And that there is no doubt that these changes are caused by us. They’re caused by human society. They are incomparably faster than any natural variations. And so I think this is where we need to focus our attention.