Climate Change: Listeners' Questions Which continents emitted the most carbon dioxide over the past century? What's better for the environment, keeping your old car or buying a hybrid? What about compact fluorescent light bulbs? We get answers to these questions, and more, that were submitted by phone and e-mail.
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Climate Change: Listeners' Questions

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Climate Change: Listeners' Questions

Climate Change: Listeners' Questions

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From NPR News, this is ALL THINGS CONSIDERED. I'm Melissa Block.


And I'm Robert Siegel.


SIEGEL: But first, we're going to take time to answer some of your questions. And to help us answer them, we've invited NPR's science correspondent Richard Harris and from the World Resources Institute, Jennifer Layke. Thanks to both of you for coming today.


SIEGEL: And since we got so many variations of this question, let's start with a bit of a refresher here. What is the greenhouse effect and who coined the term, Richard?

HARRIS: Well, the greenhouse effect is a little bit of a misnomer because the idea is just the way the glass in a greenhouse traps heat in the greenhouse. There are molecules in our atmosphere that trap heat in the atmosphere. But they don't do it quite the same way as the glass does. But that aside, the idea is molecules, like carbon dioxide, will pick up some of the energy that's being reflected off the Earth and reradiate it as heat. And this gradually builds up as the carbon dioxide builds up in our atmosphere, which it has been doing and other gases as well, but carbon dioxide is the main one. So, absolutely, truly it is a real effect, and it is very closely measured.

SIEGEL: And when did people start talking about this greenhouse effect?

HARRIS: I think the term emerged, as best we can tell, in 1937 in a textbook written by Glenn Thomas Trewartha. So the term has been around for a long time.

SIEGEL: Okay. Well, the next question is from a caller in Gardiner, Montana.

BLOCK: Hi. My name is Abby Nielsen. And I'm wondering what the distribution of carbon dioxide emissions is throughout different continents. In other words, what percentage of the rise in carbon dioxide emissions over the last century or two is the U.S. responsible for? And what percentage other continents are responsible for as well?

SIEGEL: Jennifer Layke, do we know the answer to that question?

BLOCK: The accumulative emissions in the atmosphere are the result of several centuries of emissions and those in the last century - we look about the 20th century - about 30 percent of accumulative emissions have been the responsibility of the United States. Other continents and other countries are responsible for varying amounts and their rates of emissions are growing or changing rapidly. Asia, for example, is only responsible for 20 percent of the accumulative emissions, while sub-Saharan Africa is responsible for only 1.7 percent of the emissions.

SIEGEL: Well, the next question we have is a very basic and fundamental question about how we define climate change.

BLOCK: This is Sarah Purick in Chicago, Illinois. I'm wondering how do you differentiate between a cyclical climate change and a permanent change in the climate and therefore in the environment?

SIEGEL: The question how do we tell the difference between a cyclical climate change, which does exists. Yes, Richard.


SIEGEL: And some change is different from that and perhaps more long lasting or permanent.

HARRIS: Right. And that was debated for quite a while, and then scientists have finally put that to rest because there are temperatures ups and downs. And what they have done is they have looked at the temperature trends over the last century or so. And they said, could this be just part of one of those normal patterns? And they say, no, the differences are large enough that it really goes beyond what they could possibly expect just from the regular fluctuations. So there is a scientific consensus now that we're on a trend toward warming temperatures.

SIEGEL: Well the next caller is looking for some comparisons on emissions.

BLOCK: My name is Mark Scragen. I'm calling from Boise, Idaho. I'd like to hear some, sort of, cross comparison on sources of CO2 gases. For instance, how much CO2 is emitted a single jetliner taking off compared to how many cars what would equal, what would be greater - that sort of thing - to try to put a base on the various sources.

SIEGEL: Perhaps we can throw in how power plants contribute to it as well?

HARRIS: I'll start with this one, which is - we can say about 10 percent of the emissions come from cars and light trucks around the world. And about two percent, two or three percent come from airliners. When you look at the total emissions, they're down there. Not insignificant, but not invisible either at all. So in terms of power plants?

BLOCK: Well, if you look across, and let me just take the example of a single unit because it gives you a little bit of a comparison. An average car in the United States emits 4.5 tons of CO2 equivalent into the atmosphere per year. A power plant, by contrast is 8.3 million tons for a coal fired power plant. And you think about the the difference in the scale, you may be driving your car significantly but with kind of power that your choosing to purchase actually has a bigger impact over the lifetime of those emissions. The difference between the hybrid and a SUV, however, is quite significant.

HARRIS: And the power plants are about 40 percent of our greenhouse gas emissions.

SIEGEL: Well, that is still only accounting for about 60 percent of all the greenhouse emissions. So where is the rest coming from?

HARRIS: Industrial uses are a big part of it and a lot of heating, for example, buildings are a huge consumer of energy and...

BLOCK: Globally and another source of emission is actually land use change and that's that difference between where the United States is in it's development pattern. In other countries like Brazil or Indonesia that have a very serious conversion going on from forests to agriculture in order to help development cycles.

SIEGEL: Well, Jennifer, you mentioned SUVs and hybrids again, which brings us to an automobile question and one that has fueled a bit of debate for car owners.

BLOCK: My name is Celeste Budwinhunter. I'm from Houston, Texas. And my question is what is the advantage to trading in my car and buying a hybrid - since someone else will be driving my car - and since there's a lot of energy expended in building a hybrid, a lot of carbon dioxide emission so I would assume.

SIEGEL: Now, Jennifer, as you've told us that factory that's making the hybrid back in Japan is using up a lot of energy and is sending up a lot of emissions. So how does the equation work out?

BLOCK: Well, actually, from the perspective of the life cycle of emissions for an automobile, the majority of the emissions actually occur in the use phase. So it makes a big difference what you decide to drive. An average...

SIEGEL: You mean, driving the car is more - that's creating more emissions than making the car?

BLOCK: That's right. So an average car in the United States - if you look at an average car for a sport utility vehicle, for example, you've emitted ton of CO2 when you drive about 1,300 miles. We've drive about 12,000, 14,000 miles a year. An average hybrid will emit one ton if you drive 6,000 miles. So it's quite a significant difference in terms of your annual driving.

SIEGEL: And that's all a part of that 10 percent of emissions that we're attributing to cars and trucks. Jen Macuch(ph) of Atlanta, Georgia, called with a question about alternative energy, specifically nuclear energy.

BLOCK: What are the dangers of using nuclear power as a solution to energy consumption and production of energy in the era of climate change? Thank you.

SIEGEL: Who's going to take that one? Jennifer?

BLOCK: On the other hand, the cause of climate change could be astronomical compared to the cost of building a nuclear reactor. But most important point for my perspective is actually how do we begin to think about this from what alternatives we have? And clearly we have a lot of alternatives today that are available, like, pursuing conservation energy efficiency, changing the temperatures in your household - air conditioner or your heater.

SIEGEL: But, Jen, it was also used - she had the word danger in her question and I think she may be expressing an apprehension that many listeners have, which is - is nuclear energy a more dangerous alternative to the other sources of energy we have because of radiation or because of what we do with the fuel?

BLOCK: We certainly haven't solved the fuel challenge associated with nuclear energy or the long-term storage questions.

SIEGEL: Well, the Great Lakes were a big topic of concern for our listeners. As in this call from Petty Caflisch(ph) of Columbus, Ohio.

BLOCK: Certainly, we've heard about the oceans and icebergs and melting, but what will become of the fresh water supply that is made up of the Great Lakes?

SIEGEL: The Great Lakes, Richard.

HARRIS: The Great Lakes, well, I think, nothing pretty much in the short run the lakes themselves. But you do have to be concerned about changes in weather patterns and things like more air-conditioning needs in Chicago, and things like that. I mean, people around the Great Lakes will feel a lot of the effects, but the lakes themselves are not going to wither away.

SIEGEL: It'd still be very good lakes, at least. Here's an interesting question. It's about what we drink.

BLOCK: Hi. My name is Drew Melman. I'm from Wynnewood, Pennsylvania. And my question is do carbonated beverages add to CO2 production, which affects global warming?

SIEGEL: Jennifer?

BLOCK: Well, what's interesting about the carbonation in our beverages is that we actually are mining for that CO2. We are emitting it all over the place but we're mining for the CO2 in our beverages. And, in fact, this is a very small portion of the overall CO2 that's emitted into the atmosphere.

SIEGEL: Well, what do you mean by we're mining for that CO2?

BLOCK: We actually, go underground to tap reservoirs of CO2 from underground sources. Many companies actually could bottle and share or distribute their CO2. But the market price hasn't been - and the distribution systems haven't been in place.

SIEGEL: Okay. Well we move on to a question we received from Washington State.

BLOCK: This is Joel Kerns from Kent, Washington. Since there's been a huge boom in population for the 20th century, how much of an impact has that had, just the sheer amount of people that have been seen on the globe?

SIEGEL: What do you make of that, Richard, the population boom accounts for global warming?

HARRIS: That's been a very major factor. I mean, 60 years ago, there were, what, two and half billion people on the planet. There are six and a half billion now and in 20 more years there could be eight or nine billion people on the planet. And as we grow in our population, our demand for energy increases dramatically.

SIEGEL: What's the answer, Jennifer?

BLOCK: Compact fluorescents are actually a really interesting technology and they are an important part of what we can do individually to change out our own footprint. The mercury issue is real, however. We hope that over the next couple of years, we're going to have a lot more recycling centers. EPA is initiating recycling centers around the country, and many communities are getting active with recycling as well because the mercury is a hazard.

SIEGEL: And I gather, Richard, that the mercury accounts for the packaging of the compact fluorescent light bulbs.

HARRIS: That's right. You get it in this really hard-shell packaging, which is really annoying to get out. And I was trying to figure out, you know, was that really necessary. And the answer is yes because, apparently, they do it in order to prevent the bulbs from breaking during shipping, and you'd - because - again, you don't want to get that mercury out into the environment.

SIEGEL: Well, finally, we have a question about garbage.

BLOCK: My name is Kendall Christensen and I'm from Brooklyn, New York. My question is what should I do with my banana peel, if I'm concerned about global warming? Should I send it down my food waste disposal to a waste water treatment plant or let it be turned into a fertilizer? Should I put it in a garbage truck and send it to a landfill or incinerator? Should I compost it in my backyard? Thanks.

HARRIS: Well, I think that - probably composting it in your backyard would be the best option because you might be able to turn it into a little soil carbon and the carbon might stay in the soil. But the other options aren't too bad either. There's not much carbon in the banana peel to begin with. And let's not forget the carbon in the banana started in the atmosphere, the banana plant grabbed it out of the atmosphere and put it in the banana. So even if you burn it or toss it in the landfill, you know, you can't really go too far wrong with your banana peel disposal.

SIEGEL: Well, Richard Harris of NPR and Jennifer Layke of the World Resources Institute, thank you both very much for talking with us today.

BLOCK: Thank you.


SIEGEL: And thanks to all of you for submitting your questions.


BLOCK: If you want to measure your family's CO2 output, we've got a calculator at our Web site,, to help with that. You'll also find information about how you can participate in what we call our Carbon Counting Challenge. We're looking for families that are game for a little competition to see who can reduce their carbon footprint the most. Just ahead, we'll meet a family that's already taking the challenge on ALL THINGS CONSIDERED.

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