This episode is presented by eBay.

Rob, everyone loves a deal and a bargain from time to time, don't they? Absolutely, mate. And you know where you can grab a great deal? Talk to me. Where? The eBay app. Yes, you are correct. You didn't need to talk to me. I already knew it. I love eBay. When you're buying, you can discover loads of hidden gems. there's so many items where you think I would have never found that anywhere else.

Then when you're buying, you can discover loads of hidden gems. There's so many items where you think I would have never found that anywhere else. Then when you're selling, it's so simple and most

importantly, free. It's free, Rob. When it's this easy to sell for free and there's great deals

on things you love. You can't help but say when it's eBay. It excludes vehicles and business

sellers.

Welcome to Science Talk, the weekly podcast of Scientific American for the week of January 28th, 2009.

I'm Steve Merski. This week on the podcast, we'll talk with scientist and writer Tyler Volk about his new book, CO2 Rising, the world's greatest environmental challenge.

Plus, we'll test your knowledge about some recent science in the news.

Tyler Voque is Science Director of Environmental Studies and Associate Professor of Biology at New York University.

CO2 Rising explains the global carbon cycle, what happens to all the individual carbon atoms that are

constantly cycling into out of and through the biosphere that might sound very dry but

Volk brings it alive we spoke in his office at NYU one of the mind-boggling facts, this is no local pollutant.

Every burst of CO2 that goes into the air from some power plant in Illinois

is going to spread equally all around the world.

And the same goes for CO2 emissions from China.

They spread all around the world.

And so it's unlike any other environmental substance we've ever looked at, perhaps.

Right.

I mean, Chernobyl is a terrible thing, but that is not a worldwide spread of what got spewed out there.

Yeah, the winds did spread it into northern Europe, and so that was very bad,

but it wasn't a pure worldwide equal spread. So what is there, how do you know that you are getting

...