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Public Radio's Environmental News Magazine (follow us on Google News)

Greenhouse Gamble

Air Date: Week of

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Host Steve Curwood spins the greenhouse gamble wheel with MIT professor Ronald Prinn to see how much the earth may warm.


CURWOOD: It's Living on Earth, I'm Steve Curwood in Bonn, Germany for the climate change negotiations. And when it comes to global warming, the amount of information out there can seem overwhelming. There are studies upon studies predicting how much carbon could be released into the atmosphere in the coming years and how the planet might respond over the next 100 years. Many of the studies have come up with similar results, but there are some important differences as well. A group of scientists and economists has come up with a way that tries to make sense of that range of possible outcomes. They reviewed a hundred different global warming scenarios generated by computer models. They crunched the results and gave them odds. Then they used the numbers to make pie-shaped wedges and pasted them onto a giant gambling wheel, like the kind you might find at a casino or TV game show. Just before I left for Bonn, I went to visit Ronald Prinn. He's the co-director of this project. I found him and his global warming version of the wheel of fortune in his office at the Massachusetts Institute of Technology.

[spinning sound]

PRINN: We call it the greenhouse gamble, somewhat tongue in cheek in saying that. The special aspect of the wheel, of course, is that in this illustration of the odds of various amounts of warming, if we don't enact any policies, you only get one spin. And whatever it lands on you live with. So if it lands on the 'greater than eight degrees Fahrenheit' and you see this, the odds are not zero. You could land on the 'greater than eight degrees Fahrenheit' and then obviously we will be in deep trouble.

CURWOOD: Well it's time to give the wheel a spin. Go ahead Professor Prinn. Let's find out what's going to happen to the planet.

[spinning sound]

CURWOOD: Bingo! 'Three to four degrees Fahrenheit rise.'

PRINN: That's right in the middle of the range. And maybe no surprise, it's one of the biggest slices of the pie. We had very high probability that we were either going to land on 'three to four' or 'four to five degrees Fahrenheit.'

CURWOOD: It's just on the line between 'three and four' and 'four and five.'

PRINN: Exactly.

CURWOOD: What would that mean for this planet?

PRINN: That amount of warming globally is not the amount of warming you would get in the tropics or the poles because the warming is uneven. There'll be a lot more warming in the polar regions than in the tropics. So four degrees F global average increase in temperature would correspond in the Arctic and Antarctic regions to perhaps six or seven degrees F temperature there. So one would begin to really worry at that point about the stability of the ice sheet, the stability of the boreal forest regions, the stability of the tundra regions.

CURWOOD: What are the implications of that?

PRINN: Well the ice sheets in the high latitudes are important in a number of ways. First they do contain a lot of water. And if they melt then they contribute to sea level rising. The sea level will rise with global warming anyway and that is because when you heat up water, the ocean water, it expands. Most of us are familiar with the fact that when you heat things up they tend to expand. Well ocean water certainly behaves like that. So along with this global warming we're talking about here, we would project perhaps up to maybe a half a meter of sea level that could accompany this amount of warming.

CURWOOD: OK, here we are at MIT in Cambridge Massachusetts. We're on a river, the Charles River. It's beautiful out there today. If there were a rise in the ocean, it's just down there at a dam, what would things be like here at MIT?

PRINN: Well, we would have a couple of hundred years to adjust to it. One presumes that if we wanted to keep MIT where it is now and not move further inland, with the help of the rest of the city of Boston that we would increase the size and the height of the dam and construct similar systems, dike systems, around the city of Boston to protect the low-lying areas. Perhaps the rich countries could preserve to build dikes, to preserve New Orleans, for example, which would be one city that would be certainly susceptible to sea level rise. But what about the folk in Bangladesh where routinely already significant fractions of their coastal land area get inundated when they have large typhoons. Even a half a meter sea level rise for Bangladesh would be a very very serious issue for them.

CURWOOD: Now what about the odds of not having much of anything at all happen with temperature change and the planet?

PRINN: Yeah. Next to the 'greater than eight degrees F' there's one that says 'less than two degrees F.' And that's a very small amount, it's about equivalent to what we've seen over the past 120 years in warming and we've survived. So if we landed on the 'less than two degrees Fahrenheit' small slice there, when we spin the wheel, then we can count our lucky stars, right? That the global warming is not going to be anything that we should be deeply worried about.

CURWOOD: So alright, I'll give it a spin here.

[spinning sound]

PRINN: 'Seven to eight degrees Fahrenheit' this time.

CURWOOD: Oh my. So what does that mean?

PRINN: Well, this is the outcome that nobody would want. We would be looking at something like maybe 12 degrees Fahrenheit or more temperature rise in the polar regions. This amount of global warming in the middle of the continent could mean significant drying out. This amount of global warming would certainly be accompanied by more rainfall in many areas of the world because higher ocean temperatures mean more evaporation, more total rainfall. The difficulty at the end is we don't where we're going to land on the wheel. And the challenge for policymaking is to replace the wheel that we have here by one that has much smaller slices where you're getting the high amounts of temperature rise and much bigger slices where we're getting relatively small amounts of temperature rise. So that's the aim, that would be the aim of a policy, to change the sizes of the slices on this wheel.

CURWOOD: Ronald Prinn is professor of atmospheric chemistry here at the Massachusetts Institute of Technology. He also directs the Center for Global Change Science. Thank you sir!

PRINN: You're welcome.




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