Andrew Watson: I think there will be substantial change whatever we do. If we do nothing over the next 20 years it will be catastrophic. If we do nothing over the next 50 to 100 years it might even be terminal.
David Fisher: Andrew, Lovelock suggests that we are moving into a much warmer but stable situation for Gaia. Do you accept that idea?
Andrew Watson: I don't know.
David Fisher: And that it is something that, you know, hasn't existed for millions, perhaps 50 million years.
Andrew Watson: Well, that I think is certainly right. The Earth has been, broadly speaking, cooling over the last 50 million years and we are going to push it back into a very much warmer state. Is it going to be stable? That's a very good question. I don't know the answer to that. The fact is that the last time we had high levels of carbon dioxide in the atmosphere was 100 million years ago and the Sun was a little bit cooler at that time. __Now if we push it up...this is not something that most climatologists will talk about but I think that there is a small chance, maybe a 1% chance, that if we really hit the planet too hard we may push it into a runaway system in which the temperature simply goes up and up until the oceans boil into the atmosphere, and that would extinguish all life on Earth.__
Peter Cox: One of the things that is quite difficult to get across but is very important is the idea that we need to understand what might be called high impact low probability events. In a sense, in the last 20 years or so the climate modelling community has been kind of obsessed by working out what the most likely outcome is of us doing nothing. The issue now is that that's probably not the most important thing to know about. The most likely thing is not the thing that you should necessarily be most concerned with. What you should be concerned with is a bit like the insurance problem, is the highest risk, and the highest risk can be actually a very high impact, like a very large climate change that is unlikely but could still the highest risk of all to the system you are in and human society.
David Fisher: Andrew let's get out the crystal ball and just notch it forward to say 100 years time; what changes do you see?
Andrew Watson: If one takes the business as usual scenario in which we continue to emit a lot of carbon dioxide, then the planet will be probably four or five degrees warmer, the north polar cap will have been completely disappeared and much of the planet will be difficult to live on.
David Fisher: Why is that?
Andrew Watson: It will be just too damn hot. Many of the tropical regions are already actually quite hot to live in, but there will be large regions where people will not want to be because it is too hot. I would imagine therefore that there will be human conflicts on a grand scale. There are many, many people who live in those regions now. They will presumably be blaming the industrialised nations for their poor living conditions. I would also think that all of the natural ecosystems on the planet will be in crisis. There will be regions which would be further to the north presumably, such as in Southern Europe, where it would be possible to grow tropical forest but there won't be any because it won't have had time to grow. So I don't see a very happy situation. We will have to be using all of the land area that still can support crops to grow it. So that will mean there will be no space for the natural ecosystems that are important for the carbon cycle, for the other cycles of the planet.
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Listen to the Podcast @
http://www.abc.net.au/rn/scienceshow/stories/2007/1810013.htm#transcript
20 January 2007 Gaia and accelerating climate change The Science Show