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

Tipping Point?

Air Date: Week of

Earth Day at Golden Gate Park. (Courtesy of 350.org)

NASA scientist James Hansen and other leading scientists say 350 parts per million of carbon dioxide in the air should be our target goal to reduce greenhouse gas emissions. Professor Richard Alley of Pennsylvania State University explains to host Bruce Gellerman where that number comes from and how we can get there.


GELLERMAN: Today, the amount of CO2 in the atmosphere is 385 parts per million and organizers of a new environmental group called “350 dot org” say that’s got to come down. 350 parts per million maybe the new atmospheric gold standard for some, but Richard Alley, professor of Geosciences at Penn State University says it’s not gospel:

ALLEY: It is certainly not a sacred or a magic number. People have tried asking experts, “How high before you get scared?” “How high before YOU get scared?” And the experts came back and said, “Scared about what?”

Dr. Richard Alley is the Evan Pugh professor of geosciences at Pennsylvania State University. (Courtesy of Pennsylvania State University)

If we’re worried about rare and endangered species, even a little bit that starts forcing them to migrate out of their little island of ecosystem and there’s nowhere to go ‘cause there’s a corn field in the way, makes you really nervous. If you’re worried about the global economy, you might be able to bump it up a little bit higher. And so this 350 is some experts, some thinkers looking at the whole weight of things and saying, “That’s where I get nervous.”

GELLERMAN: Well right now we’ve got 385 parts per million. We’re looking at a ten percent reduction if they want to go back to 350. So how do we reduce our parts per million from 385 to 350?

ALLEY: There’s this huge recipe of possibilities that you can do. You can take the CO2 out of the air and put it back in the ground. You can take it from the power plant or take it from the air and people are trying to figure out how to do that. You get more economy out of the fossil fuel that you use. You replace the fossil fuel with something else that doesn’t raise CO2.

Earth Day at Golden Gate Park. (Courtesy of 350.org)

GELLERMAN: There are countries that are working; you know, very aggressively to reduce their carbon levels. But even if the Untied States decided to go on board with them, would it matter if China and India didn’t?

ALLEY: We can’t solve the problem by ourselves but I don’t think that the world can solve the problem without us.

GELLERMAN: Well Professor Richard Alley, thank you very much.

ALLEY: A real pleasure, thank you.

GELLERMAN: Richard Alley is a professor of Geosciences at Penn State University.



Dr. Richard Alley’s Homepage


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