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Geoengineering becoming more necessary as emissions increase and temperatures continue to rise -

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Robyn Williams: Next stop, Cambridge, Trinity College, that most celebrated of ancient institutions where Newton and Bertie Russell resided. It also has had the odd Aussie such as Hugh Hunt, engineer, who has been on The Science Show before.

Just to catch up, obviously you are doing work on clocks, but are you doing any work on films these days as well, as you used to?

Hugh Hunt: Why do you say it's obvious I'm doing work on clocks?

Robyn Williams: We're surrounded by clocks!

Hugh Hunt: Well, I do like clocks. Films…I've done a few films recently, I'm doing one this year on the birth of television. Eighty years ago John Logie Baird invented a means of doing live television, and yes, this year is the 80th anniversary of that and we are doing a documentary for the BBC.

Robyn Williams: In which case you'd better do what I've suggested on this program before and that is recognise a certain person who worked in Ballarat in 1885 and invented television and carried the picture from Melbourne, the Melbourne Cup, to Ballarat in 1885, and Logie Baird picked up some of the ideas from him.

Hugh Hunt: Well, you've caught me with my pants down there! Who is this?

Robyn Williams: Henry Sutton. Henry Sutton, if you look him up, was working in his family emporium which used a lot of telephones and the transmission of signal. In fact Alexander Graham Bell came out to see him because his work was so well known way back there in the end of the 19th century, and Henry Sutton said to him, 'You know you've got that box on the wall with the speaker and you've got this thing you hold in your hand and stick on your ear, why not have something called the handset instead?' And all that happened. But Australians do not know, let alone anyone else, about Henry Sutton.

Hugh Hunt: That's crazy. Ballarat is on the map, it always has been, but it's even more on the map.

Robyn Williams: So you're working on a film concerning television and its invention.

Hugh Hunt: Yes, in the '20s John Logie Baird came up with this thing which he called the televisor which enabled a video signal, a movie to be transmitted over an ordinary wireless line. And it wasn't very high quality but then over the next 10 or 15 years it became the black-and-white television we knew in the '70s and '80s.

Robyn Williams: Going back to what we were talking about last time, that is geo-engineering, you were involved in an experiment that was trying to put water vapour up in the sky via a kind of dirigible or some great big space vehicle that squirted water out. It didn't quite happen, did it.

Hugh Hunt: Well, the idea of geo-engineering is to put something like sulphur dioxide or titanium dioxide up at 20 kilometres, which would reflect some sunlight, perhaps 1% or 2% of the Earth's incoming sunlight to cool the Earth.

Robyn Williams: Yes, but you were experimenting with water vapour first.

Hugh Hunt: Well, we wanted to get the ball rolling essentially by putting a little blimp, a helium balloon you might see at a fairground pumping water, just about a bathtub full of water, up to a kilometre. And this was to do nothing else but to illustrate the technologies and to get the process of doing experiments going. But we weren't allowed to do that experiment because it was considered to be a slippery slope onto something more sinister and something that might take our eye off the ball of reducing CO2 emissions.

Robyn Williams: And so what happened to the experiment? Did it get shelved?

Hugh Hunt: Yes, very summarily shot down, as it were. We were given the opportunity to reposition the experiment, but we only had three or four years of funding, and to try and do the experiment within that time scale became impossible.

Robyn Williams: But you're still keeping an eye on the general principle of geo-engineering.

Hugh Hunt: Indeed, and what we are about to do is have a meeting on what experiments are there worldwide…not experiments that will have any impact on the climate and not experiments that will do anything to modify the climate, but experiments that need to be done as a first step towards modifying the climate. In exactly the same way as Apollo 11, well, what about Apollo 1, Apollo 2, Apollo 3, and what about all the spacecraft before those? You don't start by sending a man to the Moon, you don't start by geo-engineering the climate, you have to start by doing much more benign and rather boring experiments.

Robyn Williams: Just to use one of your own phrases, can you re-freeze the Arctic?

Hugh Hunt: We don't know if we can re-freeze the Arctic, but we know that there's a high probability that the Arctic will be ice free in the next perhaps five or 10 years but almost certainly in the next 20 or 30 years. It may come a moment in the next five or 10 years that the question will be asked; can we re-freeze the Arctic? Or, more likely, we have to re-freeze the Arctic, because ice in the Arctic is so important for our climate. Can we re-freeze the Arctic? Well I jolly hope we can.

Robyn Williams: How would you start?

Hugh Hunt: Well, the Arctic is melting because it's getting warmer. It's getting warmer because of a blanket of carbon dioxide which is trapping the Sun's heat. It's also getting warmer because it's reducing in size. There is less reflectivity. And warm water which is coming up from mid-latitudes is melting it from underneath. Can we do something about reflectivity? We probably just need to make the Arctic bigger again. How can we do that? Well, we've got to stop some of the Sun's rays getting into the Arctic and making it colder. Putting sulphur dioxide up into the stratosphere is the most likely technique, but we will come up with others.

Robyn Williams: Would that be locally, above, say, the North Pole?

Hugh Hunt: Very interesting, putting sulphur dioxide into the atmosphere, into the stratosphere around mid-latitudes, somewhere just 20 degrees north of the equator or south of the equator has generally been explored as the way of cooling the whole planet most effectively. But perhaps if we don't want to cool the whole planet we have to research the possibilities of putting particles in the stratosphere in the Arctic itself. That research is still to be done and we don't know whether it will work.

Robyn Williams: Is anyone doing it?

Hugh Hunt: A lot of computer modelling is going on, and there's only so much computer modelling you can do before you wonder do you trust the computer models? And we do trust them but I don't think we trust them enough to commit what might be the future of humanity to decisions made based on those computer models. So the experiments we ought to be doing at the very least need to be done to validate the computer models, to see if the kinds of techniques that might be used to re-freeze the Arctic can be made to work.

Robyn Williams: One of the people who is working on this and has written a book is Oliver Morton, and he says the last thing you want to do is leave your remedy to the last moment, to when you are convinced you have a huge problem, but what you need to do is work towards a solution gradually but determinedly as you go.

Hugh Hunt: Absolutely agree with Oliver Morton. The question though is how do you know when the last moment is, and using a World War II analogy, I mean, the Normandy landings, they took place in 1944, and they were planned over a period of about three years…three years before, was that considered the last moment? Who was to know? But those Normandy landings were absolutely pivotal and risky, and if they had gone wrong it would have been seen as the biggest folly of the war. But the landings didn't go wrong. Oliver Morton is right, we mustn't leave things to the last minute. Now is the beginning of the last minute in my view, and it might take us 30 years to get these technologies working.

Robyn Williams: And Oliver Morton on geo-engineering next week. This is The Science Show on RN, and that was Hugh Hunt at Trinity College in Cambridge.