Climate Change: Listeners' Questions

Host Robert Siegel asks NPR's Richard Harris and Jennifer Layke of the World Resources Institute to answer some of our listeners' questions about climate change.

Among them: 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? And how should one best dispose of a banana peel?

We get answers to these questions, and more, that were submitted by phone and e-mail.

Greenhouse-gas emissions are constantly brought up as the root of temperature trends. Do we clearly understand this effect?

— Ronald Rossi of Jericho, Vt. --

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 is 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's 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.

Robert 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.

I am 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?

— Abby Nelson of Gardner, Mont. --

Jennifer Layke: We know a fair amount about how different continents have contributed to the problem. The cumulative emissions in the atmosphere are the result of several centuries of emissions, and those in the last century — if you look at the 20th century — about 30 percent of the cumulative 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 cumulative emissions, while sub-Saharan Africa is responsible for only 1.7 percent of the emissions.

I'm wondering how you differentiate between cyclical climate change and a permanent change in the climate and therefore the environment?

-- Sarah Pearick in Chicago —

Siegel: The question – how do we tell the difference between cyclical climate change – which does exist, yes, Richard – and some change that is differing from that and perhaps more long-lasting, permanent?

Harris: Right, and that was debated for quite a while, and scientists have finally put that to rest, because there are temperature 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 in ups and downs. So there is a scientific consensus now that we're on a trend toward warming temperatures.

The other part of it is the physics of what we were talking about earlier, the greenhouse effect. Physicists will tell you these molecules trap heat in the atmosphere, so it makes sense that there would be a temperature trend.

I'd like to hear some sort of a cross-comparison on sources of CO2 gases. For instances, 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?

-- Mark Scriabin of Boise, Idaho --

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

Harris: Yeah, I'll start with this one, which is we can say about 10 percent of emissions come from cars and light trucks around the world, and about 2 percent – 2 to 3 percent – come from airliners. So when you look at the total emissions, they're down there – not insignificant, but not invisible either at all. In terms of power plants?

Layke: 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 about 4.5 tons of CO2 equivalence 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 difference in the scale – you may be driving your car significantly, but the kind of power that you're choosing to purchase actually has a bigger impact over the lifetime of those emissions. A difference between a hybrid and an SUV, however, is quite significant.

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

Siegel: Well, then that's still only accounting for about 60 percent of all the greenhouse emissions. 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.

Layke: Globally, another source of emissions is actually land use change. And that is the difference between where the United States is in its development pattern and other countries like Brazil or Indonesia that have very serious conversion going on from forests to agriculture in order to help development cycles.

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 is a lot of energy expended in building a hybrid – a lot of carbon dioxide emissions, I would assume.

-- Celeste Budwitt-Hunter of Houston --

Siegel: Now, Jennifer, as you've told us, that factory that is 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?

Layke: Well, actually, from the perspective of a 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.

So an average car in the United States, if you look at an average car for a sports utility vehicle, for example, you emit a ton of CO2 when you drive about 1,300 miles – that's 1,300 miles; we 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.

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

-- Jen McCooch of Atlanta --

Layke: This is a really good question. It's a real dilemma that we're going to face over the next 20 years. How do we begin to think about where we're going to get our energy sources? If you think about the nuclear question, a couple of things you have to bear in mind – what are the costs associated with the technology and what alternatives do we have? The costs associated with the technology in this case is a significant cost that is not cost-competitive without subsidies. On the other hand, the cost of climate change could be astronomical compared to the cost of building a nuclear reactor.

The most important point from 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 and energy efficiency, changing the temperature in your household air conditioner or your heater.

Siegel: But Jen used 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?

Layke: Well, we certainly haven't solved the fuel challenge associated with nuclear energy or the long-term storage questions.

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

-- Patty Cupfleisch of Columbus, Ohio --

Harris: The Great Lakes. Well, I think nothing very 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.

Do carbonated beverages add to CO2 production which affects global warming?

-- Drew Mehlman of Winwood, Penn. --

Layke: Well, what's interesting about the carbonation in our beverages is that we actually are mining for that CO2. We're 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 is emitted into the atmosphere.

Siegel: What do you mean by we're mining for that CO2?

Layke: We actually go underground to tap reservoirs of CO2 from underground storage. Many companies actually could bottle and share or distribute their CO2 but the market price and the distribution systems haven't been in place.

Since we've seen a huge boom in population in the 20th century, how much of an impact has that had – just the sheer amount of people that have been seen on the globe?

-- Joel Kearns from Kent, Wash. --

Harris: That's been a very major factor. I mean, 60 years ago, there were what, 2.5 billion people on the planet? There are 6.5 billion now? And in 20 more years, there could be 8 or 9 billion people on the planet. And as we grow in our population, our demand for energy increases dramatically. So yeah, it's not that people are emitting carbon dioxide themselves, but everything else we do actually does.

The new fluorescents have plusses and minuses. They consume less power, but they contain mercury. How to decide whether to use them?

-- Jim France of Greensboro, N.C.

Layke: 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 was that really necessary? Because another listener said, do we really need this packaging? And the answer is yes, because apparently they do it in order to prevent the bulbs from breaking during shipping, because again, you don't want to get that mercury out into the environment.

What should I do with my banana peel, if I'm concerned about global warming? Should I send it down my food waste disposer to a wastewater treatment plant and let it be turned into fertilizer? Should I put it in a garbage truck and send it to a landfill or incinerator? Should I compost it in my backyard?

-- Kendall Christiansen of Brooklyn, N.Y.

Harris: Well, that's an interesting question. 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 a 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 a banana. So even if you burned it or tossed it in the landfill, as long as you don't produce methane gas in the process in burying it in the landfill, you can't really go too far wrong with your banana peel disposal.