Speaker: The key question of course, is how can we distinguish between variations due to natural causes and those variations of the climate that are induced by human activity, and the key thing that convinced me ,and held me right, was a graph like this one that we marked out on the floor, that have been prepared from climate Scientists, like Professor Peter Cocks. Now explain to us the significance of this graph.
Peter Cocks: Okay, what we are going to do is to take a walk through the time, and the first thing to note, as we walk through it, is that the climate is not truly variable, it is a spiky based. Occasionally that is a damn word we are trying to associate with the volcano going off, that cools the system down, because of the dust it throws it up, but generally it just oscillates around. Then we get to a period around about 1910, where you can start seeing an outward trend, warming of the climate, a global warming if you like.
And the issue is, what caused that, was that humans or was that natural? So what we do to try and work that one out is, to take a climate model, and to put into various factors, and we can see with this green curve here, is a climate model that includes just these natural factors. Now this is when volcanoes go off, and the output from the sun, and you can see that the green curve can reproduce, reasonably well this midcentry warming.
So up to this point you can reasonably argue, climate variations can be explained by natural factors, but as we move on, we can see that is no longer true as you get to the later part of 20th century. From about 1970 onwards here, you can see the red curve, the observed temperatures, and the green curve really beginning to diverge. The question again is, what caused this recent warming?
So we are on the model again, and we include human factors, particularly we include the green house effect, mostly from carbon dioxide that comes from fossil fuel burning, and then we get this yellow curve. We can see, is what as we produced in the midcentry warming, we get this recent, rather rapid warming we produced, and that tells us two things, one is that the model looks realistic, it looks like the real world. The second thing the model tells us, that this recent warming is due to human beings.
Speaker: So there you heard, this seems little doubt that this recent rise is steep rise temperature, is due to human activity.
Speaker: If you look at the green line of natural variability, it's clear that without the action of human beings there would have been far less temperature change since the 1970s. We are all involved in this. Our whole way of life is structured around the burning of fossil fuels. I find it sobering to think that while I had been traveling the world, trying to record the complexity and beauty of our planet, then I too have been making my own contribution to global warming.
As I have recognized, when I presented life on earth all those years ago, we are a flexible and introverted species and we have the capacity to adapt and modify our behavior. Now we most certainly have to do so if we are to deal with climate change, it is the biggest challenge we have yet faced. This sea wall was built to keep out what we recognized was a force of nature, something beyond our control, but now we ourselves have become force of nature, we are changing the climate, and what happens next really is up to us.
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