Copyright ©2008 NPR. For personal, noncommercial use only. See Terms of Use. For other uses, prior permission required.

JOE PALCA, host:

And now, we're going to turn to a new, another source of information, more data about the Earth's global climate. And that's going to come from a new satellite that NASA is launching. It would be really useful if there was a better measurement of exactly where the CO2 on Earth was going, coming from and going to.

And this week, NASA previewed a new mission that aims to do just that. It's called the Orbiting Climate Observatory. It's set to launch later this year and the data it gathers will help scientists make better CO2 maps of the Earth.

And joining us now with a preview of that mission is David Crisp. He is principal investigator for the Orbiting Carbon Observatory Mission. He's also a senior research scientist at NASA's Jet Propulsion Laboratory in Pasadena and he joins me from his office at JPL today. Thanks very much for being on the program, Dr. Crisp.

Doctor DAVID CRISP (Senior Research Scientist, NASA Jet Propulsion Laboratory, Pasadena): Good to be here, Joe.

PALCA: So tell me a little bit more about this space, this orbiting satellite. What exactly is it going to measure? Is it CO2 or is it any kind of carbon?

Dr. CRISP: Well, the quantity that we actually measure is atmospheric carbon dioxide. It's the gas that we release every time we light a fire or start your car or even exhale. And what we're trying to do is understand the processes on the Earth that are controlling the amount of carbon dioxide that stays in our atmosphere over time through these releases.

And so we'll be making global maps of the Earth about once every 16 days or about twice a month for a two-year period starting about one year from now.

PALCA: Uh-huh. And what, I mean, what is the value, can you really tell where the CO2 is coming from or can you see i. I mean, is the important bit that you're doing it over a two-year period or is it that you're doing it in any one snapshot?

Dr. CRISP: Well, the most important thing is that we'll be able to record the amounts of CO2 in the atmosphere very precisely over the entire globe on a fairly short time scale.

The important thing there is right now, we make measurements of carbon dioxide entering our atmosphere from about a 120 sites globally. These are individual little observatories that make measurements typically on order of once a week. They send their measurements to the NOAA, ESRL Laboratory in Boulder for analysis, and from that data, we have currently a pretty good picture of what the global amount of CO2 in our atmosphere is and how fast it's been building up overtime.

Now, a very interesting thing that those data have shown us though is that since about 1970, almost half the carbon dioxide we have been putting into our atmosphere by burning fossil fuels like oil and coal, and also biomass burning, either clearing forest or burning our crops quite frankly. Those processes have been putting almost twice as much CO2 in the atmosphere as it stayed there over time.

The rest of that CO2 has been being absorbed by the oceans and the atmosphere, but almost half of the CO2 that's being absorbed by the oceans and - I'm sorry, the oceans and the land biomass, trees and plants and stuff on land. But almost half of the CO2 that's been absorbed by those processes can't be accounted for right now. We don't know where it's happening.

PALCA: Hmm.

Dr. CRISP: And even though we've got this great global network that makes very precise measurements over at a number of points around the Earth, that network isn't dense enough to tell us where the CO2 is coming from and where it's going to. With the precision that we need to identify and what we called the CO2 sources and CO2 sinks, a sink is, of course, where the CO2 gets absorbed.

PALCA: Mm-hmm.

Dr. CRISP: So what the OCO mission, the Orbiting Carbon Observatory, is designed to do is to make global maps of carbon dioxide with a precision and with a spatial and temporal resolution - time resolution, so that we can actually see where the CO2 is coming from and where it's going to on scales that are small compared to, say, the size of New York state. From that information, we'll begin to see more clearly what processes are controlling the CO2 on our atmosphere over time, then we can study those processes more comprehensively that we've been able to, to date.

PALCA: Okay. Let's take your calls now. Our number is 800-989-8255.

And let's go to Greg(ph) in Tulsa, Oklahoma. Greg, welcome to SCIENCE FRIDAY.

GREG (Caller): Oh, thank you very much for having me on.

PALCA: Sure.

GREG: I was just going to ask exactly how do they - how this orbiting satellite then measures carbon dioxide in the Earth's atmosphere? Is it through spectroscopy or - and then how - also, how accurate it is and are there any other chemicals in the atmosphere that would be confused with carbon dioxide?

PALCA: Okay.

GREG: I will take my answer off the air. Thank you very much.

PALCA: Oh, okay. Thanks, Greg.

Dr. CRISP: That is an excellent question, Greg. In fact, we do use spectroscopy. We have three very, very high-resolution spectrometers onboard that measure the absorption of sunlight by the atmosphere. And as you probably know, gases like carbon dioxide and oxygen and other gases in our atmosphere, water vapor, in particular, have very, very distinctive absorption features in the atmosphere. They absorb in some colors, but not in others.

So what we've done is designed some very, very sensitive spectrometers that are specially tuned to measure just carbon dioxide in two different spectral regions that are in the near infrared, just beyond where your eye is sensitive - out at about twice the wavelength your eye is sensitive, actually, at about 1.61 microns and 2.06 microns

Those measurements, we actually divide the spectrum into about over a thousand pieces over very narrow spectral range. Our resolving power, if you understand what that means, is about 20,000 in these spectrometers. So there's…

PALCA: I don't think I understand that. But let's just skate past that.

Dr. CRISP: Okay. Don't worry about it.

PALCA: Okay. Good.

Dr. CRISP: We just resolved the colors very, very finely.

PALCA: All right.

Dr. CRISP: And can measure the actual amount of absorption by CO2 very, very precisely in each one of those colors. And the objective here is to make measurements of reflected sunlight over the entire sunlit hemisphere of the Earth, with a precision needed to measure CO2 concentrations to about one part in 380. And let me explain why that is.

There are currently - currently, the mixing ratio, the concentration of CO2 in our atmosphere is about 380 parts per million, by volume. And we have been - we would like to measure variations as small as about one part per million, by volume.

PALCA: Mm-hmm.

Dr. CRISP: We need to make measurements that precise because CO2 is a long-lived gas. It tends to stay around for a long time, so it gets very well mixed into the atmosphere. And the largest spatial gradients that we know of in our atmosphere from pole to pole and from season to season are only about eight to 10 parts per million out of 380 parts per million. So we need to make very precise measurements with the OCO mission in order to resolve those fairly small variations in CO2 around the Earth.

PALCA: We're talking with David Crisp from JPL about the OCO, the orbiting - I'm sorry, the Orbiting Carbon Observatory mission.

I'm Joe Palca. And this TALK OF THE NATION from NPR News.

I'm sorry. I might have interrupted you there, Dr. Crisp, was there a final point to be made about that?

Dr. CRISP: Well, only that what our objective is, is to make measurements that are accurate to about three-tenths of 1 percent or one part in 380 over the entire globe on - basically, monthly intervals. And then what we'll do, of course, is we'll - with that - with the spectroscopic technique, we'll be able to tell you how CO2 is varying on these regional scales from month to month.

And, you know, as you know, the entire - the carbon - or I should say, land plants absorb more carbon dioxide in the spring and summer months when they're green than they do during the winter months. We have to resolve that process, too. So we have to make measurements on pretty much monthly intervals in order to resolve those processes over the year.

PALCA: That's really going to be a remarkable thing to see - sort of - almost as if just watch the planet breathing.

Dr. CRISP: That's exactly what we're doing. And we actually - that's our mission theme, it's watching the Earth breath.

PALCA: And I thought it up all by myself. You should hire me. Never mind.

Dr. CRISP: Oh, absolutely. We need you as a slogan.

PALCA: I'm sure. I'm sure. Let's see - let's take another call now and go to Harmon(ph) in Windsor, Ohio. Harmon, welcome to SCIENCE FRIDAY.

HARMON (Caller): Thank you very much. Is it possible and is it important to measure a vertical gradient, in other words, will you have a three-dimensional or just a two-dimensional map of carbon dioxide?

PALCA: You mean at different levels above the earth, above the ground is what you're saying?

HARMON: Yes.

PALCA: Interesting question.

Dr. CRISP: Actually, as a scientist, I would love to be able to make measurements that are truly four-dimensional, and that means all of the three-dimensions you're thinking of and as well as in time.

For the OCO mission, I want everybody to understand, this is an exploratory science mission. We're just learning how to do this. And for that mission, our requirement is actually just to make the two-dimensional maps and then met(ph) over time, is the third dimension.

As time goes on, the next mission that follows this one up may be able to make measurements that have some vertical profiling information as well. And that will be a value for a variety of things, both for understanding how the Earth's carbon cycle works a little bit better, but also for helping us to train our models, our numerical models a little bit better for understanding how they're transporting CO2 around the globe. So there would be some value on that. And so once again, I'll leave that for the next investigator.

PALCA: Harmon, thanks very much for that call.

HARMON: Thank you very much.

PALCA: Interesting point. So, I guess, the other problem, of course, is to figure out - I mean, you will be seeing these things. This mission doesn't really give you much of a chance to do anything about it. It would be great if there were some sort of experimental - I mean, I've heard about this, you know, putting iron into the ocean. It would be interesting to see whether that was actually having an effect in real time.

Dr. CRISP: Yes. I'm like the meteorologist who only can measure the weather and can't do anything about it, right?

PALCA: Yeah.

Dr. CRISP: No. In fact, one of the things that you have to understand is that until - that everybody has to understand is that until we actually understand the processes both natural and manmade that are controlling carbon dioxide in our atmosphere today, it would be foolhardy, is about the nicest word I can say, to start experimenting with our planets and doing the deliberate sequestration efforts that aren't well monitored and not - aren't well understood.

PALCA: Okay.

Dr. CRISP: And so…

PALCA: I'm afraid, Dr. Crisp, we're going to have to leave it there. And I'm sorry to interrupt. But we ran out of time for this segment. Thanks very much for joining us.

(Soundbite of music)

Dr. CRISP: Thank you very much.

PALCA: David Crisp is a senior research scientist and principal investigator for the Orbiting Carbon Observatory.

We have to take a short break. But we'll be back to talk about the humor of - of climate change. Stay with us.

I'm Joe Palca, and this TALK OF THE NATION from NPR.

Copyright © 2008 NPR. All rights reserved. No quotes from the materials contained herein may be used in any media without attribution to NPR. This transcript is provided for personal, noncommercial use only, pursuant to our Terms of Use. Any other use requires NPR's prior permission. Visit our permissions page for further information.

NPR transcripts are created on a rush deadline by a contractor for NPR, and accuracy and availability may vary. This text may not be in its final form and may be updated or revised in the future. Please be aware that the authoritative record of NPR's programming is the audio.

Comments

 

Please keep your community civil. All comments must follow the NPR.org Community rules and terms of use, and will be moderated prior to posting. NPR reserves the right to use the comments we receive, in whole or in part, and to use the commenter's name and location, in any medium. See also the Terms of Use, Privacy Policy and Community FAQ.