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Global warming a severe problem and the dilem -

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Robyn Williams: Kevin Trenberth is head of climate analysis at the US National Centre for Atmospheric Research. And at the University of New South Wales he summed up our present situation like this:

Kevin Trenberth: You know, I think the scientific evidence is clear and that's certainly the case in the science community. The science community, the surveys that have been done suggest that some 97%, 98% of the science community believes that global warming is a severe problem and that we need to do something about it. There are very few who are deniers of some sort.

And so the thing that makes most sense to me that we should advocate is that there has to be some kind of a price on carbon, and the reason for that is because of the costs of all the things that are going on. There are hundreds of millions of dollars that are occurring right now because of the climate change that has already gone on, and so there is a real cost to not doing anything at the moment, and yet in the US we actually still subsidise fossil fuels, and so the marketplace cannot even function properly as it stands right now.

Putting the right kind of price on carbon, whether through a carbon tax or some other mechanism, is the right thing to do in terms of helping the marketplace and the private sector begin to respond. And I think if that were done appropriately then indeed we would see some amazing things happen.

Robyn Williams: And Dr Kevin Trenberth on carbon dioxide:

Kevin Trenberth: The problem with carbon dioxide is that it has a long lifetime. That is of course why the carbon dioxide keeps going up, so it accumulates in the atmosphere. It has a lifetime of over 100 years, some of it lasts actually a very long time. If we take actions now to limit the amount of carbon dioxide we put into the atmosphere it begins to have real benefits 30, 40, 50 years out, 100 years out. So it really has major benefits for our grandchildren, you know, two generations further down the road. But it doesn't have immediate benefits.

And some people have said, well, maybe we shouldn't do anything as a result of that. So this relates very much to your value system as to what kind of a planet you think you are leaving the future generations. And as to what you do about this, Australia has started a carbon tax and is moving in the right direction to get their own house in order I think. But Australia is a country which is probably more vulnerable to these kinds of changes than just about everywhere else, and so I think Australia needs to make demands on the United States in particular and China to limit the amount of greenhouse gases that are going into the atmosphere. And as long as you've got your own house in order you can stand up and make those kinds of demands.

Robyn Williams: And finally, Kevin Trenberth on fire:

Kevin Trenberth: There's always a component of global warming in everything that we do nowadays, and the reason is that the environment in which all of the weather is occurring now is different than it used to be, and the main memory of that is through the oceans. I did a little sum, this was kind of a fun thing, with regard to the drought that occurred in the US that led to these wildfires in Colorado. In Denver there were five days in a row where it was close to 40°C. No wonder there were wildfires. But the snowpack at 1st May was the lowest on record. It had been quite dry. Actually I went up to Aspen in June and there was no snow anywhere. So not only is there no snow but there's no moisture anywhere. So all of the heat was just going into further drying out the vegetation, creating conditions that are favourable for a wildfire.

But if you add up the extra amount of energy that is available, it's in the order of one watt per square metre, a really tiny amount, if you add it up for six months, what it comes down to is it's the equivalent of running a microwave oven at full power for 36 minutes. That's the amount of extra energy that gets accumulated. And these microwave ovens would be in every square foot, in other words ten per square metre, and that's the extra energy that you've accumulated, and so no wonder things caught on fire. And so this is where in a drought there is a memory that builds up of the global warming component.

Robyn Williams: Dr Kevin Trenberth is head of climate analysis at the National Centre for Atmospheric Research in Boulder, Colorado.