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Friday, 17 November, 2000, 15:25 GMT
Climate change: Your questions answered

BBC News Online's environment correspondent Alex Kirby put your questions on climate change to scientists Dr Ralf Toumi and Joanna Syroka from Imperial College, London, in a live webcast.

Select the link below to watch:


Transcript of the forum:

Sam Huang, Taiwan: Is it true that if we don't eradicate emissions of carbon dioxide by reducing the use of fossil fuels by the year 2020, most parts of the Pacific continent will be underwater, and if so what kind of pragmatic measures can we take?

Dr Ralf Toumi: For a very long time the Pacific Islands have been recognised as being a high-risk area, so yes there is a severe risk. I am afraid for many of them, the only pragmatic option may well be to evacuate.

In terms of the border-lying countries, it really depends on where you are and the resources you have. Some countries are well off enough to support sea defences and defences of that kind. So the Pacific Islands really are more at risk.

Alex Kirby: So some of them could be underwater by 2020?

Dr Ralf Toumi: Yes.

Narinda Dhogra, USA: At the current rate of global warming, will glaciers become extinct in our lifetime?

Joanna Syroka: That is quite difficult question to answer. Some may, but definitely not all. The amount of warming that we have had over this past century has been about 0.75 degrees Celsius, I think. If that continues that may get rid of some glaciers but I don't think all of them will go in our lifetime.

Alex Kirby: 0.75 doesn't sound very much does it?

Joanna Syroka: No it doesn't but it only takes 3 degrees to create an Ice Age.

Alex Kirby: 3 degrees to create an Ice Age?.

Dr Ralf Toumi: In the global meaning, yes. The global average temperature of 3 degrees - 3 to 5 degrees.

David Rowe, England: Has the Earth ever been as hot as it is predicted to be in 100 years time and if so how did it sort itself out and how long did it take?

Dr Ralf Toumi: Yes it has been. We have been through several cycles which have been at least as warm. We have had very mild and balmy climates in the UK and there is fossil evidence for this.

How does it sort itself out? Well, the climate does go through cycles; the ocean circulation reverses and you end up with a different climate state. How long does it take to sort itself out? Well, that we don't know, because the resolution we have on those measurements is not very good. So it could be 50 years, it could be less than that. People are very worried about rapid climate change at the moment - it could slip quite quickly.

Alex Kirby: An awful lot of unknowns and things could change almost literally overnight.

Dr Ralf Toumi: Well we don't think overnight - but, yes, fast on a geological timescale, certainly.

Alex Kirby: And faster than the human lifetime?

Dr Ralf Toumi: Faster than a generation, certainly.

Marcello Vincento Gonzalvez, Brazil: What is the importance of the Amazon Forest in the carbon cycle and in the production of oxygen?

Dr Ralf Toumi: Well, the Amazon plays a great role as a carbon sink so carbon dioxide, although we emit here, because of its long lifetime, really circulates around the entire atmosphere, and the Amazon provides the great lung of the atmosphere. So it takes up a lot of the carbon dioxide and emits oxygen. So the climatic impact could be quite large but in fact more recently people have been more concerned about the forests that are in our part of the world and Siberia - there is actually a net sink for carbon dioxide. So all parts of the world are really important.

Alex Kirby: When you say sinks for carbon dioxide - do you mean they absorb the carbon dioxide and lock it up and keep it out of harm's way?

Dr Ralf Toumi: Yes, they keep it out of harm's way for the moment. It goes into the soil until eventually it perhaps gets burnt out and liberated back as carbon dioxide. So it is a cycle and it is a temporary reservoir.

Christopher Briggs, Norway: How can you be sure that man is the cause of climate change - because during the Industrial Revolution, emissions into the atmosphere were surely far, far worse than they are today?

Joanna Syroka: It sounds like a reasonable question but not if you actually look at the evidence of what the levels of carbon dioxide are in the atmosphere. In about the 1850s, at the time of the Industrial Revolution, it was probably around 200 parts per million of carbon dioxide in the atmosphere - today we have 350 parts per million. So actually it may seem worse, when we see pictures of smoky London and all these chimneys piping lots of pollution into atmosphere, but the CO2 levels are far, far greater today.

Alex Kirby: And of course there are far more of us and we want far higher living standards and we use much more energy.

Joanna Syroka: Exactly.

Dr Ralf Toumi: And globally.

Joanna Syroka: And globally, yes.

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