National Aeronautics and Space Administration

Orbiting Carbon Observatory

SCIENCE WRITERS’ GUIDE

December 2008
Orbiting Carbon Observatory SCIENCE WRITERS’ GUIDE

CONTACT INFORMATION AND MEDIA RESOURCES

Please call the individuals listed below from the Public Affairs Offices

at NASA or Orbital before contacting scientists or engineers at these 

organizations.

NASA Jet Propulsion Laboratory

Alan Buis, 818-354-0474, alan.buis@jpl.nasa.gov 

NASA Headquarters

Steve Cole, 202-358-0918, Stephen.e.cole@nasa.gov

NASA Kennedy Space Center

George Diller, 321-867-2468, george.h.diller@nasa.gov 

Orbital Sciences Corporation

Barron Beneski, 703-406-5528, beneski.barron@orbital.com

NASA Web sites

http://oco.jpl.nasa.gov

http://www.nasa.gov/oco

WRITERS

Alan Buis

Gretchen Cook-Anderson

Kathryn Hansen

Rosemary Sullivant

DESIGN

Deborah McLean
Orbiting Carbon Observatory SCIENCE WRITERS’ GUIDE

Science Overview............................................................................ 2

TABLE OF CONTENTS

Cover image credit: NASA

Instrument..................................................................................... 4

Feature Stories

The Human Factor: Understanding the Sources of

Rising Carbon Dioxide ......................................................

The Orbiting Carbon Observatory and the Mystery

of the Missing Sinks...........................................................

Toward a New Generation of Climate Models....................

NASA Mission Meets the Carbon Dioxide

Measurement Challenge.....................................................

 Orbiting Carbon Observatory Aims to Boost Carbon 

Management Options.........................................................

6

8

10

12

14

Orbiting Carbon Observatory Spokespersons................................. 16

Orbiting Carbon Observatory Science Team Members .................. 17

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Orbiting Carbon Observatory SCIENCE WRITERS’ GUIDE

SCIENCE OVERVIEW

The Orbiting Carbon Observatory is the latest mission in 

NASA’s ongoing study of the global carbon cycle. It is the first 

spacecraft dedicated to studying atmospheric carbon dioxide, 

the most significant human-produced greenhouse gas and the 

principal human-produced driver of climate change. 

This experimental NASA Earth System Science Pathfinder 

Program mission will measure atmospheric carbon dioxide 

from space, mapping the globe once every 16 days for at 

least two years. It will do so with the accuracy, resolution and 

coverage needed to provide the first complete picture of the 

regional-scale geographic distribution and seasonal variations 

of both human and natural sources of carbon dioxide emissions and their sinks—the reservoirs that pull carbon dioxide 

out of the atmosphere and store it. 

Mission data will be used by the atmospheric and carbon 

cycle science communities to improve global carbon cycle 

models, reduce uncertainties in forecasts of how much carbon 

dioxide is in the atmosphere, and make more accurate predictions of global climate change. 

The mission provides a key new measurement that can be 

combined with other ground and aircraft measurements 

and satellite data to answer important questions about the 

processes that regulate atmospheric carbon dioxide and its 

role in the carbon cycle and climate. This information could 

help policymakers and business leaders make better decisions 

to ensure climate stability and retain our quality of life. The 

mission will also serve as a pathfinder for future long-term 

satellite missions to monitor carbon dioxide. 

Scientists want to better understand the processes responsible 

for regulating the amount of carbon dioxide in the atmosphere, because the increasing concentrations of this efficient 

greenhouse gas are warming our planet and changing its climate. The concentration of carbon dioxide in our atmosphere 

is determined by the balance between its sources, which emit 

carbon dioxide into the atmosphere, and sinks, which remove 

this gas from the atmosphere. While natural sources roughly 

balance out natural sinks, human activities have thrown the 

natural carbon cycle out of balance.

In the 10,000 years before the Industrial Revolution in 1751, 

carbon dioxide levels rose less than one percent. Since then, 

they’ve risen 37 percent. Between 1751 and 2003, human 

activities added about 466 billion tons of carbon to the 

atmosphere as carbon dioxide. The burning of fossil fuels, and 

cement manufacturing, account for about two-thirds of these 

emissions, while land use changes (primarily forest clearing) 

make up the rest. Humans are currently adding almost 30 

billion tons of carbon dioxide to the atmosphere each year, 

and this rate of emission is increasing dramatically. In fact, 

carbon dioxide levels have risen by 30 parts per million in just 

the last 17 years, and are now increasing at about two parts 

per million by volume per year. The current globally averaged 

concentration is about 384 parts per million. 

Of all the carbon emitted by human activities between 

1751 and 2003, only about 40 percent has remained in the 

atmosphere. The remaining 60 percent has been apparently 

absorbed (at least temporarily) by the ocean and continents. 

Recent inventories of the ocean can account for about half of 

this missing carbon. The remainder must have been absorbed 

somewhere on land, but scientists don’t know where most 

of the land sinks are located or what controls their efficiency 

over time.

An improved understanding of carbon sinks is essential to 

predicting future carbon dioxide increases and making accurate predictions of carbon dioxide’s impact on Earth’s climate. 

If these natural carbon dioxide sinks become less efficient as 

the climate changes, the rate of buildup of carbon dioxide 

would increase—in fact, today’s carbon dioxide levels would 

be about 100 parts per million higher were it not for them. 

Scientists monitor carbon dioxide concentrations using a 

ground-based network consisting of about 100 sites all over 

the world. But the current network does not have the spatial 

coverage, resolution or sampling rates necessary to identify 

the natural sinks responsible for absorbing carbon dioxide, 

or the processes that control how the efficiency of those sinks 

changes from year to year. 

The Orbiting Carbon Observatory will dramatically improve 

measurements of carbon dioxide over space and time, uniformly sampling Earth’s land and ocean and collecting about 

8,000,000 measurements of atmospheric carbon dioxide 

Vegetation

As plants grow, they use 

CO2

 from the atmosphere 

to build and maintain their 

biomass, thus slowing atmospheric CO2

 increases.

The Orbiting Carbon Observatory is the latest mission 

in NASA’s ongoing study of 

the global carbon cycle—the 

cycling of carbon between 

its various storage reservoirs 

(the ocean, atmosphere, 

terrestrial biosphere and geologic fossil fuel reserves). The 

mission provides a key new 

measurement that can be 

combined with other ground 

and aircraft measurements 

and satellite data to answer 

important questions about 

the processes that regulate 

atmospheric carbon dioxide 

and its role in the carbon 

cycle and climate. Credit: 

Jennifer Mottar

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Orbiting Carbon Observatory SCIENCE WRITERS’ GUIDE

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Fossil Fuels

Burning coal, oil, or natural gas transfers carbon 

from fossil pools created hundreds of millions of 

years ago into Earth’s atmosphere, where it affects 

climate and ecosystems.

Soils

As leaves and plants die and decompose, some of the carbon in 

their biomass is incorporated into soil where it may be stored for 

long periods; the remainder returns to the atmosphere as CO2.

Fires

Fire due to human activities or 

natural causes also adds CO2

to the atmosphere. Following 

fire, recovering ecosystems 

accumulate carbon from the atmosphere, countering emissions 

by fires and fossil fuel use.

Ocean

CO2 mixes into surface waters and dissolves. 

Some of the carbon is incorporated into the 

biomass of marine organisms. Mixing and 

circulation carry carbon from surface waters 

into deeper waters where it can be stored out of 

contact with the atmosphere for long periods.

concentration over Earth’s entire sunlit hemisphere every

16 days. 

Scientific models have shown that we can reduce uncertainties 

in our understanding of the balance of carbon dioxide in our 

atmosphere by up to 80 percent through the use of precise, 

space-based measurements. Data from the existing groundbased monitoring network can be augmented with highresolution, global, space-based measurements of atmospheric 

carbon dioxide concentration accurate to 0.3 to 0.5 percent 

(about one to two parts per million out of the background 

level of about 385 parts per million) on regional to continental scales. This level of precision is necessary because atmospheric carbon dioxide concentrations rarely vary by more 

than two percent from one pole of Earth to the other. The 

Orbiting Carbon Observatory will have this level of precision. 

Scientists hope to use Orbiting Carbon Observatory data to 

address a number of questions about carbon dioxide and the 

carbon cycle. Among them:

•	 What natural processes absorb carbon dioxide from human emissions? 

•	 Will those processes continue to limit increases in 

atmospheric carbon dioxide in the future, as they do 

now? Or will they stop or even reverse and accelerate 

the atmospheric increases? 

•	 Is the missing carbon dioxide being absorbed primarily 

by land or the ocean and in what proportions? Which 

continents absorb more than others? 

•	 Why does the increase in atmospheric carbon dioxide 

vary from one year to the next while emission rates 

increase uniformly? 

•	 How will carbon dioxide sinks respond to changes in 

Earth’s climate or changes in land use? 

•	 What are the processes controlling the rate at which 

carbon dioxide is building up in Earth’s atmosphere? 

•	 Where are the sources of carbon dioxide? 

•	 What is the geographic distribution and quantity of 

carbon dioxide emitted through both fossil fuel combustion and less well understood sources, such as ocean 

outgassing, deforestation, fires and biomass burning? 

How does this distribution change over time?

Following launch from California’s Vandenberg Air Force 

Base aboard an Orbital Sciences Corporation Taurus XL 

rocket, the Orbiting Carbon Observatory will be placed in 

a near-polar Earth orbit at an altitude of 438 miles (705 

kilometers), orbiting once every 98.8 minutes and repeating 

its orbit track every 16 days. It will fly in a loose formation 

with the other Earth-observing satellites of NASA’s Afternoon 

Constellation, or “A-Train”: Aura, Glory, Parasol, Calipso, 

CloudSat and Aqua. Flying in the A-Train will complement 

the mission’s science return and facilitate observatory calibration and validation. 

The Orbiting Carbon Observatory is managed by NASA’s Jet 

Propulsion Laboratory, Pasadena, Calif., for NASA’s Science 

Mission Directorate, Washington. Orbital Sciences Corporation, Dulles, Va., built the spacecraft and launch vehicle and 

provides mission operations under JPL’s leadership. Hamilton 

Sundstrand, Pomona, Calif., designed and built the observatory’s science instrument. NASA’s Launch Services Program 

at NASA’s Kennedy Space Center in Florida is responsible for 

launch management.
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Orbiting Carbon Observatory SCIENCE WRITERS’ GUIDE

INSTRUMENT

The Orbiting Carbon Observatory’s single science instrument consists of three parallel, high-resolution spectrometers, 

integrated into a common structure and fed by a common 

telescope. The spectrometers will make simultaneous measurements of the carbon dioxide and molecular oxygen absorption 

of sunlight reflected off the same location on Earth’s surface 

when viewed in the near-infrared part of the electromagnetic 

spectrum, invisible to the human eye. 

As sunlight passes through Earth’s atmosphere and is reflected from Earth’s surface, molecules of atmospheric gases 

absorb very specific colors of light. If the light is divided into 

a rainbow of colors, called a “spectrum,” the specific colors absorbed by each gas appear as dark lines. Different gases absorb 

different colors, so the pattern of absorption lines provides a 

telltale spectral “fingerprint” for that molecule. The Orbiting 

Carbon Observatory’s spectrometers have been designed to 

detect these molecular fingerprints. 

Each of the three spectrometers is tuned to measure the 

absorption in a specific range of colors. Each of these ranges 

includes dozens of dark absorption lines produced by either 

carbon dioxide or molecular oxygen. The amount of light 

absorbed in each spectral line increases with the number 

of molecules along the optical path. The Orbiting Carbon 

Observatory spectrometers measure the fraction of the light 

absorbed in each of these lines with very high precision. This 

information is then analyzed to determine the number of 

molecules along the path between the top of the atmosphere 

and the surface. 

If the amount of carbon dioxide varies from place to place, 

the amount of absorption will also vary. To resolve these variations, the Orbiting Carbon Observatory’s instrument records 

an image of the spectrum produced by each spectrometer 

three times every second as the satellite flies over the surface 

at more than four miles per second. This information is then 

transmitted to the ground, where carbon dioxide concentrations are retrieved in four separate footprints for each image 

collected. These spatially varying carbon dioxide concentration estimates are then analyzed using global transport 

models, like those used for weather prediction, to infer the 

locations of carbon dioxide sources and sinks. 

The instrument views Earth through a telescope mounted in 

the side of the spacecraft. Reflected sunlight is first focused at 

a field stop (a rectangular aperture at the focus of the telescope that limits the field of view) and then realigned before 

entering a transfer optics assembly that ensures all three 

spectrometer channels view the same scene. A beam splitter 

selects specific ranges of colors of light to be analyzed by each 

spectrometer, which is then refocused on a narrow slit that 

forms the entrance to each spectrometer. 

Once light passes through the spectrometer slits, it is aligned, 

and then divided into its component colors by a diffraction 

grating. This is similar to the way light shined through a 

prism creates a rainbow. 

The light is then refocused by a camera lens onto each spectrometer’s focal plane array—image sensing devices designed 

to detect very fine differences in the intensity of the light 

within its spectrometer’s spectral range. There, it forms a twodimensional image of a spectrum and is recorded. 

The Orbiting Carbon Observatory’s science instrument consists of three high-resolution spectrometers integrated into 

a common structure and fed by a common telescope. The 

spectrometers measure how carbon dioxide and molecular 

oxygen absorb sunlight reflected off the Earth’s surface, 

as viewed in the near-infrared part of the electromagnetic 

spectrum. Each spectrometer focuses on a different, narrow range of colors to detect the “fingerprints” of carbon 

dioxide and molecular oxygen. Credit: OCO Team.
Orbiting Carbon Observatory SCIENCE WRITERS’ GUIDE

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The instrument measures the absorption of reflected sunlight 

by carbon dioxide in two color ranges. The first absorbs carbon dioxide relatively weakly, but is most sensitive to the concentration of carbon dioxide near Earth’s surface. The second 

absorbs carbon dioxide more strongly, and provides a totally 

independent measure of carbon dioxide in the atmosphere. 

That color range provides critical information about the pathway the light has taken and can detect clouds, aerosols and 

variations in atmospheric pressure and humidity, all of which 

can interfere with accurate measurements of carbon dioxide.

The third range of colors, within the molecular oxygen 

A-band, is used to measure how much molecular oxygen 

is present in the light’s pathway. To accurately derive the 

atmospheric concentration of carbon dioxide using instrument data, scientists first need to compare them to measurements of a second atmospheric gas. Because the concentration 

of molecular oxygen is constant, well-known and uniformly 

distributed throughout the atmosphere, it provides an excellent reference measurement. The molecular oxygen A-band 

spectra can also assess the effects of clouds, aerosols and the 

atmospheric pressure at Earth’s surface.

The observatory will continuously collect 12 soundings per 

second while over Earth’s sunlit hemisphere. At this rate, the 

instrument will gather between 33,500 and 35,500 individual 

measurements over a narrow ground track each orbit. The 

surface footprint of each measurement is about 1 square mile 

(just under 3 square kilometers). Over the course of each 

16-day ground repeat cycle, it will collect about 8,000,000 

measurements, with orbit tracks separated by less than 1.5 

degrees longitude (100 miles or 170 kilometers) at the equator. With measurement footprints of this size and density, the 

instrument can make an adequate number of high-quality 

soundings, even in regions with clouds, aerosols and variations in topography.

To enhance the quality and verify the validity of mission data, 

the observatory will collect science observations in three standard observational modes: nadir, glint and target.

In nadir mode, the satellite points the instrument straight 

down to the ground. This mode provides the highest spatial 

resolution on the surface and is expected to return more 

usable soundings in regions that are partially cloudy or have 

significant surface topography. Nadir observations may not be 

suitable over dark ocean surfaces or in areas covered by snow.

In glint mode, the spacecraft points the instrument at the spot 

on Earth’s surface where the sun’s reflection is most intense. 

Glint mode provides up to 100 times more signal than nadir 

mode, improving observations over dark ocean surfaces. 

Target-tracking mode is used primarily for validating the 

observatory data against ground calibration sites. The observatory locks its view onto a single specific surface location while 

it flies overhead. 

The mission plans to alternate between nadir and glint modes 

over each sequential 16-day global ground track repeat cycle, 

so the entire Earth is mapped in each mode on roughly 

monthly time scales. Up to one target observation can be 

taken each day to validate the data.
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Orbiting Carbon Observatory SCIENCE WRITERS’ GUIDE

FEATURE STORIES

THE HUMAN FACTOR: UNDERSTANDING THE 

SOURCES OF RISING CARBON DIOXIDE

Every time we get into our car, turn the key and drive somewhere, we burn gasoline, a fossil fuel derived from crude oil. 

The burning of the organic materials in fossil fuels produces 

energy and releases carbon dioxide and other compounds into 

Earth’s atmosphere. Greenhouse gases such as carbon dioxide trap heat in our atmosphere, warming it and disturbing 

Earth’s climate. 

Scientists agree that human activities have been the primary 

source for the rise in atmospheric carbon dioxide observed 

since the beginning of the fossil fuel era in the 1860s. Eightyfive percent of all human-produced carbon dioxide emissions 

come from the 

burning of fossil 

fuels like coal, 

natural gas and oil, 

including gasoline. 

The remainder 

results from the 

clearing of forests 

and other land use, 

as well as some 

industrial processes 

such as cement 

manufacturing. The 

use of fossil fuels 

has grown rapidly, 

especially since the 

end of World War 

II and continues 

to increase exponentially. In fact, 

more than half of 

all fossil fuels ever 

used by humans 

have been consumed in just the last 20 years. 

Combined, these human activities add a worldwide average 

of almost 1.4 metric tons of carbon per person per year to the 

atmosphere. Before industrialization, the concentration of 

carbon dioxide in the atmosphere was about 280 parts per million. By 1958, it had increased to around 315 parts per million, and by 2007, it had risen to about 383 parts per million. 

These increases were due almost entirely to human activity. 

Yet while we are able to accurately measure the amount of 

carbon dioxide in the atmosphere, much about the processes 

that govern its atmospheric concentration remains a mystery. 

Scientists still do not know precisely where all the carbon dioxide in our atmosphere comes from and where it goes. They 

want to learn more about the magnitudes and distributions of 

carbon dioxide’s sources and the places it is absorbed (sinks). 

This will help improve critical forecasts of atmospheric carbon 

dioxide increases as fossil fuel use and other human activities 

continue. Such information is crucial to understanding the 

impact of human activities on climate and for evaluating options for mitigating or adapting to climate change.

But scientists soon expect to get some answers to these and 

other compelling carbon questions, thanks to the Orbiting 

Carbon Observatory, a new Earth-orbiting NASA satellite set 

to launch in early 2009. The new mission will allow scientists 

to record, for the first time, detailed daily measurements of 

carbon dioxide, 

making more 

than 100,000 

measurements 

around the world 

each day. The new 

data will provide 

valuable new insights into where 

this important 

greenhouse gas is 

coming from and 

where it is being 

stored.

In the absence of 

significant carbon 

dioxide emissions 

by human activities, atmospheric 

uptake and loss 

approximately 

balance. “Carbon 

dioxide in the atmosphere remained pretty stable during the 

pre-industrial period,” said Gregg Marland of Oak Ridge 

National Laboratory in Oak Ridge, Tenn. “Carbon dioxide 

generated by human activities amounts to only about four 

percent of yearly atmospheric uptake or loss of carbon dioxide, but the result is that the concentration of carbon dioxide 

in the atmosphere has been growing, on average, by fourtenths of one percent each year for the last 40 years. Though 

this may not seem like much of an influence, humans have 

essentially tipped the balance of the global cycling of carbon. Our emissions add significant weight to one side of the 

balance between carbon being added to the atmosphere and 

carbon being removed from the atmosphere. 

The Vulcan Project maps American carbon dioxide emissions. The map 

shows annual emissions in 2002 (in kilotons of carbon, with 1 kiloton 

equivalent to about two million pounds) from urban centers (larger red 

patches), widely scattered point sources like remote power stations or 

smelters (small red dots), and highways. Credit: Jesse Allen, NASA/Earth 

Observatory, based on data from the Vulcan Project
Orbiting Carbon Observatory SCIENCE WRITERS’ GUIDE

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“Plant life and geochemical processes on land and in the 

ocean ‘inhale’ large amounts of carbon dioxide through photosynthesis and then ‘exhale’ most of it back into the atmosphere,” Marland continued. “Humans, however, have altered 

the carbon cycle over the last couple of centuries, through the 

burning of fossil fuels that enable us to live more productively. 

Now that humans are acknowledging the environmental 

effects of our dependence on fossil fuels and other carbon 

dioxide-emitting activities, our goal is to analyze the sources 

and sinks of this carbon dioxide and to find better ways to 

manage it.”

Marland said the Orbiting Carbon Observatory will help us 

pin down where the carbon dioxide that’s tipping the balance 

is coming from, such as from the burning of fossil fuels, mineral production facilities and forest burning.

The mission’s highly sensitive instrument will measure the 

distribution of carbon dioxide, sampling information around 

the globe from its space-based orbit. Though the instrument 

will not directly measure the carbon dioxide emissions from 

every individual smokestack, tailpipe or forest fire, scientists 

will incorporate the observatory’s global measurements of 

varying carbon dioxide concentrations into computer-based 

models. The models will infer where and when the sources 

are emitting carbon dioxide into the atmosphere. Current 

estimates of human-produced carbon dioxide emissions into 

the atmosphere are based on inventories and estimates of 

where fossil fuels are burned and where other carbon dioxideproducing human activities are occurring. However, the 

availability and precision of this information is not uniform 

around the world, not even from within developed countries 

like the United States.

“The Orbiting Carbon Observatory data differ from that 

of other missions like the Atmospheric Infrared Sounder 

instrument on NASA’s Aqua satellite by having a relatively 

small measurement ‘footprint,’” said Kevin Gurney, associate 

director of the Climate Change Research Center at Purdue 

University in West Lafayette, Ind. “Rather than getting an average amount of carbon dioxide over a large physical area like 

a state or country, the mission will capture measurements over 

scales as small as a medium-sized city. This allows it to more 

accurately distinguish movements of carbon dioxide from 

natural sources versus from fossil fuel-based activities.”

“Essentially, if you visualize a column of air that stretches 

from Earth’s surface to the top of the atmosphere, the Orbiting Carbon Observatory will identify how much of that 

vertical column is carbon dioxide, with an understanding that 

most is emitted at the surface,” said Marland. “Simply, it will 

act like a plane observing the smoke from forest fires down 

below, with the task of assessing where the fires are and how 

big they are. Compare that aerial capability with sending a 

lot of people into the forest looking for fires. In this vein, the 

observatory will use its vantage point from space to peer down 

and capture a picture of where the sources and sinks of carbon 

dioxide are, rather than our cobbling data together from multiple sources with less frequency, reliability and detail.”

Gurney believes the Orbiting Carbon Observatory will also 

complement a NASA/U.S. Department of Energy jointlyfunded project he is currently leading called Vulcan. 

“Vulcan estimates the movement of carbon dioxide through 

the combustion of fossil fuels at very small scales. Vulcan 

and the Orbiting Carbon Observatory together will act like 

partners in closing the carbon budget, with Vulcan estimating movements in the atmosphere from the bottom-up and 

the Orbiting Carbon Observatory estimating sources from 

the top-down,” he said. “By tackling the problem from both 

perspectives, we’ll stand to achieve an independent, mutuallycompatible view of the carbon cycle. And the insight gained 

by combining these top-down and bottom-up approaches 

might take on special significance in the near future as our 

policymakers consider options for regulating carbon dioxide 

across the entire globe.”

For more information on this topic, contact:

Kevin Gurney

Purdue Climate Change Research Center

Purdue University, West Lafayette, Ind.

Phone: 765-494-5982

Email: kgurney@purdue.edu

Gregg Marland

Oak Ridge National Laboratory

U.S. Department of Energy, Oak Ridge, Tenn.

Phone: 865-241-4850

Email: marlandgh@ornl.gov

Related Links:

NASA’s OCO Mission Web sites:

http://oco.jpl.nasa.gov

http://www.nasa.gov/oco
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Orbiting Carbon Observatory SCIENCE WRITERS’ GUIDE

FEATURE STORIES

THE ORBITING CARBON OBSERVATORY AND 

THE MYSTERY OF THE MISSING SINKS

Picture a tree in the forest. The tree “inhales” carbon dioxide from the atmosphere, transforming that greenhouse gas 

into the building materials and energy it needs to grow its 

branches and leaves. 

By removing carbon dioxide from the atmosphere, the tree 

serves as an indispensable “sink,” or warehouse, for carbon 

that, in tandem with Earth’s other trees, plants and the ocean, 

helps reduce rising levels of carbon dioxide in the air that 

contribute to global warming. 

Each year, humans release more than 30 billion tons of 

carbon dioxide into the atmosphere through the burning of 

fossil fuels for powering vehicles, generating electricity and 

manufacturing products. Up to five-and-a-half additional tons 

of carbon dioxide are released each year by biomass burning, 

forest fires and land-use practices such as slash-and-burn agriculture. Between 40 and 50 percent of that amount remains 

in the atmosphere, according to measurements by about 100 

ground-based carbon dioxide monitoring stations scattered 

across the globe. Another estimated 30 percent is dissolved 

into the ocean, the world’s largest sink. 

But what about the rest? The math doesn’t add up. For years, 

scientists have sought to find the answer to this mystery. 

Though scientists agree the remaining carbon dioxide is 

also “inhaled” by Earth, they have been unable to precisely 

determine where it is going, what processes are involved, and 

whether Earth will continue to absorb it in the future. A new 

NASA satellite scheduled to launch in early 2009 is poised to 

shed a very bright light on these “missing” sinks: the Orbiting 

Carbon Observatory. 

“It’s important to make clear that the ‘missing’ sinks aren’t 

really missing, they are just poorly understood,” said Scott 

Denning, a professor of atmospheric sciences at Colorado 

State University in Fort Collins, Colo. “We know the ‘missing’ sinks are terrestrial, land areas where forests, grasslands, 

crops and soil are absorbing carbon dioxide. But finding these 

sinks is like finding a needle in a haystack. It would be great 

if we could measure how much carbon every tree, shrub, peat 

bog or blade of grass takes in, but the world is too big and 

too diverse and is constantly changing, making such measurements virtually impossible. The solution is not in measuring 

carbon in trees. The solution is measuring carbon in the air.”

The Orbiting Carbon Observatory will do just that: measure carbon in the air, from Earth’s surface to the top of 

the atmosphere.

“NASA’s Orbiting Carbon Observatory satellite will work as a 

detective from space, measuring the distribution of carbon dioxide thousands of times daily as it orbits the planet, providing the data to create very precise carbon dioxide maps that 

will help us confirm the whereabouts, nature and efficiency 

of the sinks absorbing the 30 percent of carbon dioxide that 

disappears each year from the atmosphere,” said Steve Wofsy, 

a professor of atmospheric and environmental chemistry at 

Harvard University in Cambridge, Mass., and a co-investigator for the mission.

Carbon, a chemical element that is the basis of all known life 

and part of the chemical compound carbon dioxide, is the 

basic “currency” of the carbon cycle. It is “inhaled” by sinks 

to fuel photosynthesis in plant life. It is “exhaled” by natural 

sources when plant life dies or burns, and through human 

activities like the burning of fossil fuels, crops and forests. 

If we think of Earth as “breathing,” the balance between photosynthesis, or “inhaling,” and respiration, or “exhaling,” was 

about equal until humans began mining and burning large 

amounts of fossilized organic matter like coal, oil and natural 

gas a couple of hundred years ago. 

Global measurements of the carbon 

stored by plants (net primary productivity) during photosynthesis are an 

important piece of the climate change 

puzzle. Scientists need to know how 

much of the carbon dioxide released 

by burning fossil fuels can be absorbed by the biosphere and how 

much will linger in the atmosphere, a 

dilemma the Orbiting Carbon Observatory is expected to help resolve. Credit: 

NASA map by Robert Simmon and 

Reto Stöckli, based on MODIS data
Orbiting Carbon Observatory SCIENCE WRITERS’ GUIDE

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Until about 1990, most scientists believed land was primarily 

a source of carbon dioxide to the atmosphere because forests 

are continuously being destroyed by human activities like deforestation in tropical areas, urban and suburban development 

and land clearing for farming. 

“The amazing truth is that on a global scale, photosynthesis 

is greater than decomposition and has been for decades,” said 

Denning. “Believe it or not, plant life is growing faster than 

it’s dying. This means land is a net sink for carbon dioxide, 

rather than a net source.”

Denning outlined the six different ways carbon dioxide sinks 

can develop on land: 

•	 Carbon dioxide fertilization, a process often prominent 

in land areas, happens when more carbon dioxide in the 

air stimulates photosynthesis to produce a temporary 

“bump” in the growth rates of plant life. 

•	 Agricultural abandonment occurs where once-deforested 

land formerly used as family farms is abandoned, allowing 

forests to re-grow into terrestrial carbon dioxide sinks. 

•	 Forest fire suppression, the aggressive extinguishing of 

forest fires that has led to preservation of more wooded 

areas than existed 100 years ago, saves trees that pull 

carbon dioxide from the air for growth. 

•	 Woody encroachment occurs when cattle graze on grass 

but leave behind carbon dioxide-absorbing woody shrubs 

that accumulate over land ranges throughout the western 

U.S. and elsewhere. 

•	 Boreal, or northern, warming takes place in northern 

latitude forests that are experiencing longer frost-free 

growing seasons due to global warming, allowing more 

woody growth and more absorption of carbon dioxide. 

•	 Lastly, carbon dioxide sinks are created when nitrogen in 

agricultural fertilizer or nitrogen oxide from car emissions 

dissolves into clouds, spreads for hundreds of miles on 

vegetation with rainfall, and acts in tandem with carbon 

dioxide fertilization to accelerate plant growth.

The Orbiting Carbon Observatory will help scientists locate 

and characterize areas experiencing these biological processes.

“The future behavior of carbon dioxide sinks is one of the 

most uncertain things in predicting climate in the 21st 

century,” said Denning. “Mapping today’s sinks will allow us 

to measure how much of the carbon budget is controlled by 

carbon dioxide intake from ocean mixing, versus carbon dioxide fertilization, versus forest re-growth, etcetera. If we can 

determine that current land sinks are dominated by carbon 

dioxide fertilization, it would buy us more time to develop 

alternative energy and other mitigation measures.” 

Past attempts by researchers to measure terrestrial carbon dioxide were limited by an inability to account for the different 

ages of forests or how disturbances to the forests have affected 

their ability to absorb carbon dioxide. Similar attempts to 

measure carbon dioxide in human-managed ecosystems like 

cropland, pastures, golf courses and suburban landscapes are 

also difficult because such areas are so varied and numerous.

“We’re expecting the Orbiting Carbon Observatory to allow 

us to identify the precise geographic locations of these ‘missing’ carbon dioxide-absorbing areas as well as the make-up of 

the sinks and the rate at which they soak up carbon dioxide,” 

said Wofsy. “The efficiency of a sink and its location with 

respect to that of sources emitting carbon dioxide has critical 

implications for our ability to regulate carbon dioxide in 

global efforts to offset the well-documented global climate 

warming trend. We’re anticipating a big step forward on this 

front with the Orbiting Carbon Observatory’s help.” 

For more information on this topic, contact:

Steve Wofsy

Department of Earth and Planetary Science

Harvard University, Cambridge, Mass.

Phone: 617-495-4566 

Email: swofsy@deas.harvard.edu

Scott Denning

Department of Atmospheric Sciences

Colorado State University, Fort Collins, Colo.

Phone: 970-491-6936

Email: scott.denning@colostate.edu

Related Links:

NASA’s OCO Mission Web sites

http://oco.jpl.nasa.gov

http://www.nasa.gov/oco 

Forests Damaged by Hurricane Katrina Become Major Carbon Source

http://www.nasa.gov/mission_pages/hurricanes/archives/

2007/katrina_carbon.html

NASA Study Illustrates How Global Peak Oil Could 

Impact Climate

http://www.nasa.gov/centers/goddard/news/topstory/2008/

peakoil.html

NASA Study Finds World Warmth Edging Ancient Levels

http://www.nasa.gov/vision/earth/environment/world_warmth_

prt.htm 

Additional Web sites that might be of interest:

North American Carbon Program

http://www.nacarbon.org/nacp/

NASA Carbon Cycle and Ecosystems Focus Area

http://cce.nasa.gov/cce/index.htm
10

Orbiting Carbon Observatory SCIENCE WRITERS’ GUIDE

FEATURE STORIES

TOWARD A NEW GENERATION OF CLIMATE 

MODELS

Recent years have seen an increase in events related to climate 

change. For example, 2005 was the warmest year globally 

in more than a century, and in 2007, Arctic sea ice retreated 

more than any other time in recorded history. A new NASA 

mission is poised to help scientists better understand the most 

important human-produced greenhouse gas contributing to 

climate change—carbon dioxide. The knowledge gained may 

help us better predict how 

our climate may change in 

the future. 

Scientists rely on models 

to forecast future impacts 

of carbon dioxide on 

Earth’s climate. When the 

carbon dioxide concentrations used in, or predicted 

by, these models are not 

accurate, the resulting 

climate projections can 

have a large degree of 

uncertainty. To accurately predict atmospheric 

carbon dioxide concentrations in the future, we 

need to understand natural and human sources of 

carbon dioxide, as well as 

the natural “sinks” that 

remove this gas from our 

atmosphere. 

The rapid buildup of carbon dioxide from the burning of 

fossil fuels is a relatively well understood and predictable 

source. Other impacts, however, such as forestry and agricultural practices which can act as either sources or sinks, 

are far harder to predict with confidence. More importantly, 

measurements from a global network of greenhouse gas 

monitoring stations indicate that more than half of the 

carbon dioxide emitted by human activities is currently being 

absorbed by the ocean and by plants on land. But the current 

ground-based carbon dioxide monitoring network does not 

have the coverage or resolution needed to identify sufficiently 

the natural sinks responsible for absorbing this carbon dioxide. In addition, the amount of carbon dioxide absorbed by 

these natural sinks varies dramatically from year to year, for 

reasons that are largely unknown. Because the nature, location and processes controlling these natural sinks are not well 

understood, it is impossible to accurately predict how much 

carbon dioxide they might absorb in the future as the climate 

changes. NASA’s new Orbiting Carbon Observatory aims to 

help resolve these and other open carbon-cycle questions. 

“The Orbiting Carbon Observatory will provide the initial 

steps in the journey of measuring carbon dioxide from space, 

and the discoveries will be profound—we’ll gather basic 

information about the distribution of carbon that we wouldn’t 

have been able to do any other way,” says Graeme Stephens of 

Colorado State University, Fort Collins, and a co-investigator 

on the Orbiting Carbon Observatory science team.

Researchers have shown that warming, particularly from 

greenhouse gases including carbon dioxide, is driving Earth’s 

climate toward “tipping 

points.” Those are the 

points at which temperatures could set in motion 

processes that are very 

difficult to reverse. One 

potential example is the 

runaway disintegration 

of Arctic sea ice and of 

the West Antarctic ice 

sheet. In this scenario, 

warmer temperatures 

melt more ice and create 

more open water, which 

absorbs more heat. This, 

in turn, melts more ice, 

in a process that feeds 

upon itself. 

Research by James 

Hansen of NASA’s Goddard Institute for Space 

Studies in New York, and 

colleagues suggests that 

to avoid dangerous tipping points, Earth’s atmosphere should 

be limited to a carbon dioxide concentration of 450 parts 

per million at the most, and potentially much lower. Today, 

the level of carbon dioxide is about 384 parts per million, 

and over the last few decades that number has been rising by 

about two parts per million per year. But arriving at models 

that accurately predict how carbon dioxide levels will change 

in the future depends, in part, on whether researchers can 

collect enough data to untangle the mysteries of the carbon 

cycle. 

The Orbiting Carbon Observatory’s measurements throughout Earth’s atmosphere, from the surface to the top, will give 

researchers the means to indirectly track where carbon dioxide 

is emitted and absorbed. 

“As human-caused emissions change, what will happen to the 

carbon budget (the contribution of carbon dioxide’s various 

sources)?” Stephens asked. “There’s a gross lack of understanding as to where the re-absorbed carbon is going because it’s 

currently impossible to make global observations to see how 

carbon dioxide varies on both global and regional scales.” 

This image shows the past half-century of carbon dioxide trends, 

beginning in 1950 when global industrialization took off. A more 

complete understanding of Earth’s carbon cycle gained from the 

Orbiting Carbon Observatory will help researchers arrive at models that better predict future trends. Credit: NASA

300

320

340

360

380

1950 1960 1970

Date

1980 1990 2000

CO2
Orbiting Carbon Observatory SCIENCE WRITERS’ GUIDE

11

Currently, a sparse network of ground stations across the 

globe collects precise measurements of carbon dioxide, but 

is mostly limited to remote locations, far away from power 

plants, automobiles and other sources of carbon dioxide. The 

Atmospheric Infrared Sounder instrument on NASA’s Aqua 

satellite now provides some carbon dioxide measurements in 

the atmosphere, but they are limited to the atmosphere miles 

above where we live and where emissions occur. 

Measurements from ground stations and the Atmospheric 

Infrared Sounder have already shown that the level of carbon 

dioxide is more varied throughout the atmosphere than was 

previously believed. The levels fluctuate with weather and 

temperature and are influenced by land plants and the ocean. 

It’s the goal of carbon cycle models to explain and ultimately 

predict the response of this complex system. 

“It’s like a domino effect,” Stephens said. “The climate system 

is so interconnected, and the carbon dioxide system is an 

integral part of that system.”

A new generation of climate modelers already considers the 

interactions of carbon between land, ocean and atmosphere. 

These models predict that the growth rate of atmospheric carbon dioxide and of global warming will accelerate, as Earth’s 

land and ocean show a decreased capacity to absorb carbon 

dioxide. But with the current scant observations of the carbon 

system, the magnitude and timing of such model predictions 

are highly uncertain. The next generation of carbon-climate 

models will better represent these systems, thanks to more 

abundant global carbon dioxide data from the Orbiting 

Carbon Observatory and other future satellite missions. And 

while the data from these new satellites may not be as precise 

as data from ground stations, the models will nonetheless 

improve due to the tremendous volume of data from across 

the globe and throughout the atmosphere. 

Researchers expect the volume of carbon dioxide data to 

increase dramatically. “This is tremendous,” says Inez Fung of 

the University of California, Berkeley, and a co-investigator 

on the Orbiting Carbon Observatory science team. “There 

is much horizontal and vertical variation of carbon dioxide 

in the atmosphere due to sources and sinks and turbulent 

mixing processes that vary between day and night, from place 

to place, and from season to season. The Orbiting Carbon 

Observatory will give scientists a much more complete global 

picture of how the carbon cycle works.” 

The observatory will measure the percentage of carbon dioxide present within columns of the atmosphere that span less 

than 1.6 square miles (4.1 square kilometers) on the surface 

and extend all the way up to the satellite 438 miles (705 kilometers) above. “This is a major advance over the traditional 

surface observations, which are sparse and which sample only 

at fixed heights and mostly near the ground,” Fung said.

The Orbiting Carbon Observatory information will allow 

researchers to “see” for the first time carbon dioxide sources 

and sinks. The information will allow researchers to assess or 

“rank” the performance of carbon-climate models and will 

help to flag areas that need additional study. Researchers also 

expect the observatory to turn up surprises where little or 

no carbon dioxide data have been taken, such as over Africa, 

Eurasia and the open ocean. 

“I am extremely excited—I have been working on the carbon 

cycle for over 25 years and have been hampered by the data 

scarcity,” Fung said. “Christmas is coming.” 

For more information on this topic, contact:

Graeme Stephens

Department of Atmospheric Science

Colorado State University, Fort Collins

Phone: 970-491-8550

Email: stephens@atmos.colostate.edu

Inez Fung

Department of Earth & Planetary Science

Department of Environmental Science, Policy and Management

University of California, Berkeley

Phone: 510-643-9367

Email: ifung@berkeley.edu

Links:

NASA’s Orbiting Carbon Observatory Mission Web sites:

http://oco.jpl.nasa.gov

http://www.nasa.gov/oco

Research Finds That Earth’s Climate is Approaching ‘Dangerous’ Point

http://www.giss.nasa.gov/research/news/20070530/

Uncertainties in Understanding Low- and High-Latitude 

Climate Sensitivity Affect Ability to Predict Climate Change 

Impacts

http://www.giss.nasa.gov/research/briefs/rind_02/

NASA Study Illustrates How Global Peak Oil Could Impact 

Climate

http://www.giss.nasa.gov/research/news/20080910/
12

Orbiting Carbon Observatory SCIENCE WRITERS’ GUIDE

FEATURE STORIES

NASA MISSION MEETS THE CARBON DIOXIDE 

MEASUREMENT CHALLENGE

The challenge: very precisely measure carbon dioxide in Earth’s 

atmosphere all over the world, especially near Earth’s surface.

For Orbiting Carbon Observatory Principal Investigator 

David Crisp of NASA’s Jet Propulsion Laboratory, Pasadena, 

Calif., and his team, the logical solution was an Earth-orbiting 

spacecraft. But shopping for a science instrument that could 

accomplish these objectives was no easy task.

In this case, “shopping” meant finding the right technology to 

meet the mission’s demanding requirements. The observatory 

contains a custom-built instrument designed to make what 

Deputy Principal Investigator Charles Miller of the Jet Propulsion Laboratory calls “the most 

difficult atmospheric trace-gas 

measurement that’s ever been 

made from space.” To put that 

measurement challenge into 

perspective, consider that all of 

Earth’s trace gases combined, 

including carbon dioxide, make 

up less than one percent of 

Earth’s atmosphere. In addition, 

carbon dioxide levels vary by 

only about two percent from pole to pole. To substantially increase our understanding of how carbon dioxide sources (places 

where carbon dioxide is emitted) and sinks (places where it is 

absorbed, or stored) are geographically distributed on regional 

scales and study how their distribution changes over time, the 

new mission needed to be able to resolve differences in atmospheric carbon dioxide as small as 0.3 percent on regional scales 

every month. 

While one spaceborne instrument can already make carbon 

dioxide measurements from space—the Atmospheric Infrared 

Sounder on NASA’s Aqua satellite—it sees the gas high up in 

the atmosphere, not near the surface, where it is emitted and 

where some of it is absorbed into land systems and the ocean. 

A different technology was clearly needed. 

Enter NASA’s team of experts in atmospheric science, remote 

sensing instrumentation and the optical properties of the atmosphere’s components.

The principle behind the observatory’s measurement is relatively simple. Carbon dioxide, like all molecules, has an affinity 

for certain colors, or wavelengths, of light that have exactly the 

right energy to make the molecule vibrate or rotate at specific 

frequencies. A good analogy would be how a radio broadcasts 

sounds when it is tuned to a specific channel. So, if you could 

shine a light through Earth’s atmosphere and see how the different colors that are sensitive to carbon dioxide respond, you 

could use that information to calculate how much carbon dioxide is present. Do this precisely enough and often enough and 

it would be possible to see changes in carbon dioxide levels over 

time—the key to identifying carbon dioxide sources and sinks. 

The observatory uses the sun as its light source. To measure 

changes in sunlight as it passes through the atmosphere, its 

instrument incorporates a trio of high-resolution grating 

spectrometers, which divide light from the sun into a very fine 

rainbow of colors called a spectrum. They are known as grating 

spectrometers because they use a grate, or grid, to partition 

light into different wavelengths.

“You can see a good example of how a grating spectrometer 

works by looking at the back of a compact disc illuminated by a 

bright light,” said Crisp. “The narrow circular tracks that record 

the information on the disk are very effective at splitting light 

into different colors.”

As the Orbiting Carbon Observatory satellite circles the globe, 

the telescope on its instrument 

captures sunlight reflected by 

the surface below—light that 

has traveled from the sun, 

down through Earth’s atmosphere and back up again to 

space. It sends the light to the 

three spectrometers, each of which looks at a different range 

of colors and breaks that spectral range down even further 

into more than 1,000 discrete colors. Two of the three spectral 

ranges that the spectrometers target are sensitive to carbon 

dioxide, and one responds to molecular oxygen. 

The resulting spectra look something like bar codes, with dark 

lines showing where carbon dioxide or oxygen have absorbed 

specific colors. “By measuring the fraction of the light that has 

been absorbed in each of these dark lines, we can count the 

number of carbon dioxide or oxygen molecules in the atmosphere,” said Crisp. 

Three separate digital detectors, one for each spectrometer, record a spectrum three times each second as the observatory flies 

above Earth’s surface. Fast exposures are essential because the 

spacecraft moves at more than four miles per second along its 

orbit track. “We don’t want long exposures that could include 

clouds as well as clear sky within individual exposures,” says 

Crisp. “We also want to take the data fast and get more clear 

views to the surface.” 

While similar to the digital detectors in an ordinary camera, 

the observatory’s detectors take advantage of advances from the 

world of astronomy to achieve the greatest possible sensitivity. 

“These detectors were originally developed to measure objects 

that are faint, fuzzy and far-away,” said Crisp. “Here, we use 

them to measure very fine details in the spectrum of sunlight 

reflected from Earth.” 

The dark lines of the solar spectrum are produced as atoms 

and molecules in the sun’s atmosphere absorb specific colors of the spectrum. Molecules in Earth’s atmosphere also 

absorb specific colors, but these colors are primarily in the 

ultraviolet and infrared portions of the spectrum, beyond 

the left and right ends of this spectrum. Credit: The Institute 

for Astronomy, University of Hawaii
Orbiting Carbon Observatory SCIENCE WRITERS’ GUIDE

13

Grating

Detector

Telescope

Slit

The optical path of each spectrometer channel, showing 

the locations of the telescope, slit, grating and detector. 

Credit: OCO Team

The three spectral ranges measured by the observatory’s spectrometers are in the near-infrared part of the electromagnetic 

spectrum, invisible to the human eye. Each provides a critical 

piece of information. One provides precise information about 

changes in the amount of carbon dioxide present in the atmosphere, while the others show just how much of the atmosphere 

is being measured. “We need all three of these measurements to 

do the job,” said Crisp. 

One spectral range absorbs carbon dioxide relatively weakly, but 

it measures carbon dioxide the most precisely, especially near 

Earth’s surface. 

The second spectral range absorbs carbon dioxide much more 

strongly, so much so that almost all of the light in this part of 

the spectrum is absorbed completely as it traverses the atmosphere. Adding more carbon dioxide produces little additional 

absorption, so this wavelength is less useful for showing changes 

in carbon dioxide amounts. However, it does provide needed 

information about the pathway the light has taken. It helps 

determine whether the observatory is looking at light coming 

up all the way from the surface, or if clouds or aerosols, such 

as particles of smog or smoke, have gotten in the way and 

reflected the light back to space before it can be absorbed by 

carbon dioxide. 

The third spectral range shows how much oxygen is present 

in the light’s pathway, another way to determine how much 

atmosphere the light has passed through. 

“Oxygen makes up about 21 percent of the atmosphere,” explained Crisp. “Because we know the concentration, we know 

how much sunlight it should absorb over any particular surface 

elevation. If the sunlight penetrates all the way to sea level 

before it is reflected back to the spacecraft, it will produce more 

absorption than if it penetrates only to the top of a mountain 

or to the top of a cloud before it is reflected to space. We can 

even use measurements of the oxygen absorption to infer the 

surface pressure differences associated with elevation changes 

as small as 100 feet (30 meters). We can also detect scattering 

by very thin clouds or hazes that reflect less than one percent of 

light back to space. These precise measurements of the atmospheric optical path are essential for accurate carbon dioxide 

measurements.” 

The high-resolution grating spectrometers and the digital 

detectors make it possible to make these measurements from a 

space-based instrument, according to Crisp. 

Another technological challenge for the mission was designing 

the instrument to meet the strict size and energy requirements 

of an Earth-orbiting spacecraft. 

“One of the most challenging aspects of the mission was not 

inventing components, but fitting a big instrument into a small 

spacecraft about the size of a phone booth and designing it 

to use very little power,” said the Jet Propulsion Laboratory’s 

Randy Pollock, the mission’s instrument systems engineer. The 

observatory’s instrument uses only about 100 watts of electricity, while the entire spacecraft uses only 400-500 watts, about 

half the amount used by most microwave ovens. 

Once received back on Earth, the observatory’s data will be 

analyzed to yield estimates of the carbon dioxide concentration 

over Earth’s sunlit hemisphere at spatial resolutions as small 

as one square mile using complex mathematical algorithms. 

Scientists will then analyze these carbon dioxide estimates using global transport models similar to those used for weather 

prediction to quantify carbon dioxide sources and sinks.

“Carbon dioxide is the primary human-produced greenhouse 

gas and, therefore, the primary human-caused driver of global 

warming,” said Crisp. “To estimate the rate of global warming, 

we have to understand the processes controlling the buildup 

of carbon dioxide in Earth’s atmosphere. Global, space-based 

monitoring systems like the Orbiting Carbon Observatory are 

essential tools for this task. The technology we validate on this 

mission will be used to develop future carbon dioxide monitoring missions.” 

For more information on this topic, contact:

David Crisp

Jet Propulsion Laboratory

Phone: 818-354-2224 

Email: David.Crisp@jpl.nasa.gov

Charles Miller

Jet Propulsion Laboratory

Phone: 818-393-6294

Email: Charles.E.Miller@jpl.nasa.gov

Randy Pollock

Jet Propulsion Laboratory

Phone: 818-354-0636

Email: Harold.R.Pollock@jpl.nasa.gov
14

Orbiting Carbon Observatory SCIENCE WRITERS’ GUIDE

FEATURE STORIES

ORBITING CARBON OBSERVATORY AIMS TO 

BOOST CARBON MANAGEMENT OPTIONS

As the concentration of heat-trapping carbon dioxide in Earth’s 

atmosphere continues to rise, so also does public awareness, as 

well as efforts to find solutions to this global problem. Increasing concentrations of this potent greenhouse gas threaten to 

alter Earth’s climate in ways that will have profound impacts on 

the welfare and productivity of society and Earth’s ecosystems. 

This year marks the 50th anniversary of Scripps Institution 

of Oceanography scientist Charles David Keeling’s Mauna 

Loa carbon dioxide record, the longest continuous record of 

atmospheric carbon dioxide measurements. Until now, precise 

ground-based measurements such as these have been the main 

tool for scientists monitoring the rise of atmospheric carbon 

dioxide concentrations.

Comparisons of this data with carbon dioxide emission rates 

from fossil fuel combustion, biomass burning and other human activities tell us that only about half of the carbon dioxide 

released into the atmosphere during this period has remained 

there. The rest has apparently been absorbed by surface “sinks” 

in the land biosphere or oceans (see “The Orbiting Carbon Observatory and the Mystery of the Missing Sinks,” page 8). These 

measurements also show that, despite the steady long-term 

growth of carbon dioxide in the atmosphere, the buildup varies 

dramatically from year to year, even though emissions have 

increased smoothly. However, the ground-based carbon dioxide 

monitoring network is too sparse to identify the locations of 

these sinks or tell us what controls changes in their efficiency 

from year to year.

NASA’s new Orbiting Carbon Observatory is designed to help 

meet this need. It will measure the amount of carbon dioxide in 

the atmosphere over any spot on Earth’s surface and establish a 

record of how carbon dioxide concentrations change over time. 

Observations from the mission will improve our understanding of the carbon cycle—the movement of carbon among its 

“reservoirs” in the Earth system—and help us understand the 

influence of the carbon cycle on climate. 

The observatory’s ability to locate and monitor changes in carbon sources (places where carbon is generated) and sinks (places 

where carbon is absorbed or stored) will provide valuable 

information to support decision making by those responsible 

for managing carbon in the environment. It will assist them 

in developing effective strategies for managing global carbon 

dioxide and monitoring the effectiveness of those strategies. 

Phil DeCola, a senior policy analyst in the White House Office 

of Science and Technology Policy, and former Orbiting Carbon 

Observatory program scientist at NASA Headquarters in Washington, said solving the scientific mystery of the missing sinks 

and their curious variability is likely to have large policy and 

economic impacts. 

“If the nations of the world take serious action to limit the use 

of fossil fuels, the right to emit carbon dioxide will become 

scarcer, and emission rights would become an increasingly 

valuable traded commodity,” DeCola said. “Observations of 

the location, amount and rate of carbon dioxide emission into 

the air, as well as the stock and flow of all forms of carbon on 

land and in the ocean, will be needed to manage such a world 

market fairly and efficiently.”

Two commonly discussed strategies for reducing the amount 

of atmospheric carbon dioxide are a carbon tax and a “cap-andtrade” system. A carbon tax is a fee imposed on activities, such 

as burning of fossil fuels, which emit carbon compounds into 

the atmosphere. The carbon tax reduces carbon emissions by 

encouraging efficiencies of use, or by alternative, non-carbon 

emitting processes. 

Cap-and-trade systems establish limits on the carbon emissions 

that a company, industry or country is allowed to produce. 

Those who exceed their established limits must compensate by 

either purchasing emissions rights from those whose carbon 

dioxide emissions fall below their established limits, or by arranging, through contracts, for sequestration (i.e., storage) of their excess emissions in plants, soils or beneath Earth’s surface. Effective 

use of either strategy requires more accurate information on the 

existing sources, sinks and fluxes of carbon dioxide, information 

that the Orbiting Carbon Observatory can help provide. 

“The new mission will provide information to help develop 

and implement domestic policies and international collaborations to control the movement of carbon in the environment,” 

said Edwin Sheffner, deputy chief of Earth Science at NASA’s 

Ames Research Center, Moffett Field, Calif. “By identifying 

and monitoring carbon sources and sinks within a given region, 

the Orbiting Carbon Observatory will enable comparisons of 

net carbon dioxide emission sources among regions and coun2 3 4 5 6 7

1

2

3

4

5

6

7

8

9

Carbon Emissions/GtC

World Population/billions

Since 1900, increases in global carbon dioxide emissions have 

been strongly correlated with increases in global human population. Expected increases in world population, together with 

the desire for economic development, guarantee a growing 

demand for the products and services that energy enables. 

The extent to which fossil fuels and other energy sources continue to be used will determine future human influences on the 

global climate and whether the rapid increase in greenhouse 

gas concentrations will continue. Credit: NASA
Orbiting Carbon Observatory SCIENCE WRITERS’ GUIDE

15

ties, and will improve annual reporting of carbon budgets by 

industrial countries in northern latitudes, and by tropical states 

with large forests.”

“Future monitoring systems based on Orbiting Carbon Observatory technology could report on regional carbon sources and sinks 

to verify carbon reporting for many countries as well,” he added.

Use of Orbiting Carbon Observatory data in ecosystem models 

may reduce uncertainties about carbon uptake, a required 

part of any carbon management effort. The mission will help 

clarify the quantity of carbon dioxide being removed from 

the atmosphere in different geographic regions. For example, 

more carbon appears to be taken up by coastal and terrestrial 

ecosystems in North America than in many other parts of the 

world. Orbiting Carbon Observatory observations will help 

determine the specific roles that Alaska, Canada, the contiguous 

United States and Mexico play in this North American carbon 

sink. Understanding the relative roles of different regions will 

help policymakers develop the most efficient carbon dioxide 

sequestration and reduction policies.

The observatory’s measurements may also have direct applications for a variety of current efforts to reduce carbon dioxide in 

the atmosphere. While the mission will not be able to identify 

small, individual sources of carbon dioxide emissions, it will 

likely be able to detect high-emission events such as gas flares, 

where unwanted gas or other materials are burned in large 

quantities. This ability could allow it to verify adherence to 

policies aimed at reducing such flares.

Orbiting Carbon Observatory data will also have implications 

for land management and agricultural practices. Plants take 

carbon dioxide out of the atmosphere as they grow—a natural 

type of carbon sequestration. By repeating its measurements 

over multiple seasons and over regions with different types of 

vegetation, such as cornfields or grasslands, the observatory 

will help identify how changes in land use affect the amount of 

carbon being sequestered. 

Agencies such as the U.S. Department of Agriculture may base 

policies for crop production and land conservation, in part, on 

information from Orbiting Carbon Observatory observations, 

according to Sheffner. Similar observations can be used by the 

Department of Energy to help evaluate the carbon-capture 

potential of various biofuels and to assess their impacts on the 

environment and the carbon cycle. “These findings will influence 

both near- and long-term policy decisions related to alternative 

energy,” Sheffner added. In regions with large-scale agricultural 

land cover, Orbiting Carbon Observatory-type observations over 

several growing seasons could help quantify the relative roles of 

different types of crops and assess the effectiveness of rangeland 

management strategies in statewide carbon budget management.

Orbiting Carbon Observatory data may also prove to be an 

important addition to the ongoing effort by the California Air 

Resources Board and NASA scientists to improve California’s 

database on fluctuations in greenhouse gas emissions. “These 

state figures, when used to enhance NASA ecosystem carbon 

models, can increase our precision and confidence in the allocation of industrial sources of carbon dioxide emissions as compared to emissions caused by terrestrial events such as wildfires 

or crop production,” Sheffner said. 

Evaluation of the ocean, which takes up about one third of the 

carbon humans put into the atmosphere, and its role in the 

global carbon cycle, will also benefit from the new mission’s 

observations. Orbiting Carbon Observatory data may help 

show how large-scale ocean events, such as El Niño or La Niña, 

affect carbon storage in the deep ocean and in coastal regions. 

They may also help verify the impacts of these events on carbon 

storage on the continents, such as reduced plant growth during 

an El Niño-influenced drought in the U.S. Southwest.

“As the ocean absorbs large amounts of carbon dioxide, seawater becomes more acidic, potentially threatening marine life. By 

monitoring changes in the ocean’s carbon uptake, the mission 

may shed new light on ocean acidification and the resulting 

changes in ocean ecosystems,” said Sheffner. Knowing more 

about how ocean carbon levels fluctuate will also help scientists 

evaluate the possibility of using biological or chemical processes 

in the ocean to sequester carbon and perhaps even mitigate 

ocean acidification. 

Sheffner explained that the Orbiting Carbon Observatory may 

also aid efforts to find effective ways to store excess carbon 

safely underground. Combining mission data with observations 

from airborne and ground-based instruments will create much 

more accurate maps of global carbon sources and sinks than 

were ever possible before. “Once we have a better understanding of the ‘background’ fluctuations in carbon dioxide near 

proposed underground carbon storage sites, the observatory’s 

data could be useful for monitoring underground carbon storage sites for leakage,” he explained.

“The Orbiting Carbon Observatory will provide information 

needed for evaluating policy options and monitoring the effectiveness of efforts to reduce carbon emissions and increase 

carbon sequestration locally, regionally and globally,” Sheffner 

said, in summing up.

Looking to the future, DeCola said the mission will serve as a 

prototype for the next generation of greenhouse gas space missions. “The Orbiting Carbon Observatory will be an important 

experiment because its results will be used to develop the future 

long-term, space-based missions needed to monitor carbon 

dioxide for science and decision support,” he said.

For more information on this topic, contact:

Ed Sheffner

NASA Ames Research Center, Moffett Field, Calif.

Phone: 650-604-5899

Email: Edwin.j.sheffner@nasa.gov 

Phil DeCola

White House Office of Science and Technology

Policy, Washington

Phone: 202-641-7178

Email: Pdecola@ostp.eop.gov 
16

Orbiting Carbon Observatory SCIENCE WRITERS’ GUIDE

OCO SPOKESPERSONS 

David Baker is a postdoctoral researcher at the Cooperative Institute 

for Research in the Atmosphere in Fort Collins, Colo. His research 

interests include the global carbon cycle, atmospheric data assimilation, atmospheric chemistry and climate change. He is developing a 

variational data assimilation system to estimate surface sources and 

sinks of carbon dioxide from retrieved Orbiting Carbon Observatory 

carbon dioxide measurements. Besides providing a “quick-look” for 

carbon scientists, this product will be used to help identify and remove 

biases in the carbon dioxide product.

David Crisp is an atmospheric physicist and a senior research 

scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. As 

principal investigator on the Orbiting Carbon Observatory mission, 

he led the development of the mission science objectives, implementation approach and operational concept. Crisp is responsible to 

NASA for the overall success of this mission. 

Scott Denning is a professor in the Department of Atmospheric 

Sciences at Colorado State University in Fort Collins, Colo., where 

he leads a research group interested in exploring the global carbon 

cycle and its relationship to terrestrial ecosystems. Underpinning 

Denning’s research is the drive to identify the “missing” carbon 

dioxide sinks. 

Scott Doney is a senior scientist at the Woods Hole Oceanographic 

Institution in Woods Hole, Mass. His specialties involve data assimilation, carbon cycle modeling and the ocean carbon cycle. During 

the Orbiting Carbon Observatory mission, Doney will investigate 

ocean carbon sources and sinks of carbon on seasonal and annual 

average time scales, as well as air-sea gas exchange rates. 

Inez Fung is a professor of atmospheric science at the University of 

California, Berkeley. She specializes in studying the carbon cycle and 

climate change. As a member of the Orbiting Carbon Observatory 

science team, Fung will work to infer carbon dioxide sources and 

sinks and quantify uncertainty.

Daniel Jacob is a professor of atmospheric chemistry and environmental engineering at Harvard University in Cambridge, Mass. 

Jacob’s focus is using modeling of atmospheric chemistry and climate 

to better understand the chemical composition of the atmosphere. 

Tom Livermore of NASA’s Jet Propulsion Laboratory, Pasadena, 

Calif., is the Orbiting Carbon Observatory project manager and can 

address questions on mission implementation.

Charles Miller of NASA’s Jet Propulsion Laboratory in Pasadena, 

Calif., is the Orbiting Carbon Observatory mission’s deputy principal investigator and science team lead, representing the team in project activities and decisions. He is interested in finding out how well a 

trace gas can be measured from space. Pushing the accuracy of such 

measurements in the laboratory and in atmospheric remote sensing 

data is what drives most of the work by Miller and his colleagues. 

Denis O’Brien is a senior research scientist in the Department of 

Atmospheric Sciences at Colorado State University in Fort Collins, 

Colo. His focus with the Orbiting Carbon Observatory mission is in 

retrieving carbon dioxide information from spectra. 

Jim Randerson is an associate professor of Earth system science at 

the University of California, Irvine, and contributed early in the 

mission to its design. Randerson’s specialty is the global carbon cycle, 

and he looks forward to using Orbiting Carbon Observatory data in 

modeling and analysis to better understand changes in tropical forest 

ecosystems, including rates of carbon loss associated with deforestation and fires.

Peter Rayner is a senior researcher at the Laboratory for the Sciences of Climate and the Environment, Saclay, France. His general 

research interest is the global carbon cycle, with a particular focus on 

determining the distribution of carbon sources and sinks using atmospheric data. He was the first to point out the potential utility of an 

Orbiting Carbon Observatory-like instrument for this task. He will 

be part of a group estimating carbon dioxide sources and sinks with 

Orbiting Carbon Observatory data and validating these estimates 

with direct measurements.

Ross Salawitch is a professor at the University of Maryland in College Park. His focus is on the uptake of carbon by the world’s ocean 

and terrestrial biosphere and interactions between the global carbon 

cycle and climate change. As the Orbiting Carbon Observatory 

mission’s validation lead and a science team member, Salawitch is 

focused on assuring the measurements are of high quality for addressing the science questions that drive the mission.

Graeme Stephens is a professor in the Department of Atmospheric 

Sciences at Colorado State University in Fort Collins. His activities 

include research into applying remote sensing to better understand 

climate change. The Orbiting Carbon Observatory mission instrument that will measure carbon dioxide is based on an approach that 

Stephens, the principal investigator for NASA’s CloudSat mission, 

had first planned for CloudSat. 

Pieter Tans is a senior scientist at the National Oceanic and 

Atmospheric Administration Earth System Research Laboratory 

in Boulder, Colo. Tans discovered, with Fung and Takahashi, the 

existence of a very large “sink” of carbon dioxide by terrestrial ecosystems at mid-latitudes in the northern hemisphere, partially offsetting 

the emissions caused by the burning of coal, oil and natural gas. In 

2007, his group launched CarbonTracker, a data assimilation system 

that turns global observations of atmospheric carbon dioxide concentrations into time-varying maps of surface sources and sinks of 

carbon dioxide that are optimally consistent with the observations. 

As a member of the Orbiting Carbon Observatory science team, 

Tans plans to perform ongoing comparison of Orbiting Carbon Observatory retrievals with direct measurements from CarbonTracker, 

and explore ways to combine the information from satellite retrievals 

with the directly measured data.

Paul Wennberg is a professor at the California Institute of Technology in Pasadena, Calif. Through the construction of the groundbased Total Carbon Column Observing Network, Wennberg’s team 

has built the validation system for the Orbiting Carbon Observatory. They will analyze Orbiting Carbon Observatory observations 

together with those from the network to assure that the final carbon 

dioxide products from the Orbiting Carbon Observatory are as 

precise and accurate as possible. 

Steven Wofsy is a professor of atmospheric and environmental 

chemistry in the School of Engineering and Applied Science and the 

Department of Earth and Planetary Science at Harvard University in 

Cambridge, Mass. His interest is atmospheric composition and the 

carbon cycle. As part of the Orbiting Carbon Observatory mission, 

he intends to help refine the calibration of the Orbiting Carbon Observatory sensor and to use the Orbiting Carbon Observatory data to 

infer sources and sinks of carbon dioxide.
Orbiting Carbon Observatory SCIENCE WRITERS’ GUIDE

17

OCO SCIENCE TEAM MEMBERS

Breon, Francois-Marie, Laboratoire des Sciences du Climat et l’Environnement, France

Brown, Linda, NASA Jet Propulsion Laboratory, Pasadena, Calif., U.S.

Burrows, John, University of Bremen, 

Institute of Environmental Physics, Bremen, 

Germany

Ciais, Philippe, Laboratoire des Sciences du 

Climat et l’Environnement, France

Connor, Brian, National Institute of Water 

& Atmospheric Research, Lauder, New 

Zealand

Crisp, Dave, NASA Jet Propulsion Laboratory, Pasadena, Calif., U.S.

Doney, Scott, Woods Hole Oceanographic 

Institution, Woods Hole, Mass., U.S.

Fung, Inez, University of California, Berkeley, U.S.

Jacob, Daniel, Harvard University, Cambridge, Mass., U.S.

Miller, Charles, NASA Jet Propulsion Laboratory, Pasadena, Calif., U.S.

O’Brien, Denis, Colorado State University, 

Fort Collins, U.S.

Pawson, Steven, Global Modeling and 

Assimilation Office/NASA Goddard Space 

Flight Center, Greenbelt, Md., U.S.

Randerson, Jim, University of California, 

Irvine, U.S.

Rayner, Peter, Laboratoire des Sciences du 

Climat et l’Environnement, France

Salawitch, Ross, University of Maryland, 

College Park, U.S.

Sander, Stan, NASA Jet Propulsion Laboratory, Pasadena, Calif., U.S.

Stephens, Graeme, Colorado State University, Fort Collins, U.S.

Tans, Pieter, National Oceanic and Atmospheric Administration, Boulder, Colo., U.S.

Wennberg, Paul, California Institute of 

Technology, Pasadena, U.S.

Wofsy, Steven, Harvard University, Cambridge, Mass., U.S.

Yung, Yuk, California Institute of Technology, Pasadena, U.S.

OCO SCIENCE TEAM ASSOCIATES

Baker, David, Colorado State University, 

Fort Collins, U.S.

Boesch, Hartmut, University of Leicester, 

Leicester, U.K.

Bruegge, Carol, NASA Jet Propulsion 

Laboratory, Pasadena, Calif., U.S.

Chevallier, Frederic, Laboratoire des Sciences du Climat et l’Environnement, France

Christi, Mick, Colorado State University, 

Fort Collins, U.S.

Day, Jason, Colorado State University, Fort 

Collins, U.S.

Denning, Scott, Colorado State University, 

Fort Collins, U.S.

Deutscher, Nick, University of Wollongong, 

New South Wales, Australia

Engelen, Richard, European Center for 

Medium Range Weather Forecasts, Reading, 

U.K.

Griffith, Dave, University of Wollongong, 

New South Wales, Australia

Martin-Torres, Javier, NASA Jet Propulsion 

Laboratory, Pasadena, Calif., U.S.

McDuffie, James, NASA Jet Propulsion 

Laboratory, Pasadena, Calif., U.S.

Michalak, Anna, University of Michigan, 

Ann Arbor, U.S.

Natraj, Vijay, California Institute of Technology, Pasadena, U.S.

O’Dell, Christopher, Colorado State University, Fort Collins, U.S.

Palmer, Paul, Leeds University, U.K. /The 

University of Edinburgh, U.K.

Pollock, Randy, NASA Jet Propulsion 

Laboratory, Pasadena, Calif., U.S.

Polonsky, Igor, Colorado State University, 

Fort Collins, U.S.

Rider, David, NASA Jet Propulsion Laboratory, Pasadena, Calif., U.S.

Rogers, Matt, Colorado State University, 

Fort Collins, U.S.

Wunch, Debra, California Institute of 

Technology, Pasadena, U.S.

OCO COLLABORATORS

Aben, Ilse, Netherlands Institute for Space 

Research, Utrecht, Netherlands

Bennartz, Ralf, University of WisconsinMadison, U.S.

Buchwitz, Michael, University of Bremen, 

Bremen, Germany

Chance, Kelly, Smithsonian Astrophysical 

Observatory, Harvard University, Cambridge, Mass., U.S.

Cressie, Noel, Ohio State University, Columbus, U.S.

Fischer, Marc, Lawrence Berkeley National 

Laboratory, Berkeley, Calif., U.S.

Jones, Dylan, University of Toronto, Ontario, Canada

Kawa, Randy, NASA Goddard Space Flight 

Center, Greenbelt, Md., U.S.

Kopacz, Monika, Harvard University, Cambridge, Mass., U.S.

Mount, George, Washington State University, Pullman, U.S.

Nair, Hari, The Johns Hopkins University 

Applied Physics Laboratory, Laurel, Md., 

U.S.

Spurr, Rob, RT Solutions, Cambridge, 

Mass., U.S.

Suntharalingam, Parvadha, Harvard University, Cambridge, Mass., U.S.

Swartz, Bill, The Johns Hopkins University 

Applied Physics Laboratory, Laurel, Md., 

U.S.

Tangborn, Andy, NASA Goddard Space 

Flight Center, Greenbelt, Md., U.S.

Torn, Margaret, Lawrence Berkeley 

National Laboratory, Berkeley, Calif., U.S.

Vay, Stephanie, NASA Langley Research 

Center, Hampton, Va., U.S.

Washenfelder, Rebecca, National Oceanic 

and Atmospheric Administration, Boulder, 

Colo., U.S.

Yang, Zhonghua, California Institute of 

Technology, Pasadena, U.S.

Yee, Sam (Jeng-Hwa), The Johns Hopkins 

University Applied Physics Laboratory, 

Laurel, Md., U.S.
National Aeronautics and Space Administration

Jet Propulsion Laboratory

California Institute of Technology

4800 Oak Grove Drive

Pasadena, Calif. 91109-8099

http://www.jpl.nasa.gov

http://oco.jpl.nasa.gov

www.nasa.gov

NP-2008-12-062-GSFC