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Map of Earth showing regions of methane and carbon dioxide

The average amount of carbon dioxide in Earth’s global atmosphere is 400 parts per million (ppm).

The average amount of carbon dioxide in Earth’s global atmosphere is 400 parts per million (ppm), but according to Ken Davis, Atmospheric Carbon and Transport - America (ACT-America) principal investigator, areas near agriculture like cornfields can consistently run about 10 ppm lower in the summertime. That’s because terrestrial ecosystems like trees and corn suck about a quarter of our carbon dioxide emissions out of the atmosphere.

Thank you, trees and corn.

But wouldn’t you like to know exactly where this is happening, and by how much? Does the amount of carbon dioxide taken up by farms and forests change across seasons, across weather patterns? And even more important, will these ecosystems still be able to continue pulling our carbon pollution out of the atmosphere for us 50 years from now, especially if our climate changes unfavorably for these biological systems? Will dead trees start releasing carbon dioxide back into the atmosphere? It’s as if the forests and farms are “Get Out of Jail Free" cards and we’re not sure for how long the free pass will be good.

See, scientists have been measuring carbon dioxide and methane on a global basis. But we’d like to understand the mechanisms that are driving biological sinks and sources regionally. And we’d like to measure these greenhouse gases so that we can know if and when we’ve succeeded in reducing our emissions.

Davis explained that right now, most of our knowledge about regional sources of methane and carbon dioxide comes from a ground-based network of highly calibrated instruments on roughly 100 towers across North America. Yet being able to understand the regional sources and sinks of these two greenhouse gases is crucial to being able to predict and respond to the consequences of a changing climate.

“We don’t have all the data we need? That’s unbelievable,” I said, shocked. How is that even possible in 2016?” But Davis kept repeating: “No, we definitely don’t have enough data density.” Indeed, we take our data for granted, even as we continue burning fossil fuels.

The Atmospheric Carbon and Transport–America, or ACT-America, campaign will observe greenhouse gas transport with instruments on two NASA aircraft including the C-130H from NASA's Wallops Flight Facility in Wallops Island, Virginia.
The Atmospheric Carbon and Transport–America, or ACT-America, campaign will observe greenhouse gas transport with instruments on two NASA aircraft including the C-130H from NASA's Wallops Flight Facility in Wallops Island, Virginia.
That’s where NASA’s ACT-America comes in. ACT-America is an airborne Earth Venture Suborbital mission that will measure sources and sinks of carbon dioxide and methane over three swaths of the United States during all four seasons for five years from NASA’s modified C-130 and B-200 aircraft. The planes are fitted with remote sensing instruments, including a CO2 Lidar, cavity ring-down spectrometers to measure carbon dioxide and methane “in situ” on the aircraft and flasks to capture air samples around the plane.

The Atmospheric Carbon and Transport–America, or ACT-America, campaign will observe greenhouse gas transport with instruments on two NASA aircraft including the King Air B-200 from NASA's Langley Research Center in Hampton, Virginia.
The Atmospheric Carbon and Transport–America, or ACT-America, campaign will observe greenhouse gas transport with instruments on two NASA aircraft including the King Air B-200 from NASA's Langley Research Center in Hampton, Virginia.
“The accuracy standard we hold our instrument to is one tenth of a part per million,” Davis told me. “That’s hard. You can’t just go down to the store and get a carbon dioxide sensor that does that.”

Technician Jim Plant checks an instrument rack aboard the King Air B-200 at NASA's Langley Research Center in Hampton, Virginia, in preparation for the first ACT-America flights this month.
Technician Jim Plant checks an instrument rack aboard the King Air B-200 at NASA's Langley Research Center in Hampton, Virginia, in preparation for the first ACT-America flights this month.
We know a lot about the quantity of anthropogenic carbon dioxide emissions because it’s easy to count them at the pump and at the power plant. And scientists also take measurements of global carbon dioxide and other greenhouse gases from ground-based towers, mountaintops and satellites. But measuring methane, another important greenhouse gas, is more complicated. Methane that comes from biological systems like wetlands, rice paddies, cattle farms and landfills is not very well quantified. We don’t have monitors on rice paddies or landfills. There’s no reporting system. And methane from fossil fuel production and distribution typically comes from a leak.

So on July 18th, Davis and his team will head out to the first of three study areas for a two-week stint. These three regional study areas were chosen to represent a combination of weather and greenhouse gas fluxes across the U.S. The Midwest has a lot of farms and therefore has an agricultural signal. It’s also the origin point of cyclones. The Northeast forests are different than the Southern coastal forests, which will give us both types of data. The Southern coastal weather, storms and flow off the Gulf of Mexico are unique, and there’s oil and gas development in both the Mid-Atlantic and Southern regions. This means that between these three study areas, the team will be able to observe a wide range of conditions.

In addition to measuring regional sources and sinks of carbon dioxide and methane, ACT-America is planning to fly on a path right underneath NASA’s OCO-2 satellite to measure air characteristics, provide calibration and validation and make OCO-2’s data more useful. The mission will also fly through a variety of weather systems to find out how they affect the transport of these greenhouse gases.

Davis told me he’s “excited to fly through cold and warm fronts and mid-latitude cyclones to find out how greenhouse gases get wrapped up in weather systems.”

Find out more about ACT-America here

Thank you for reading.


ACT-America? is part of NASA Earth Expeditions, a six-month field research campaign to study regions of critical change around the world.



Photograph of a landfill

We say we throw our trash away. But, where is 'away'?

Yesterday I was meeting with a few scientists down at the University of California, Irvine. Like any other campus, there were plenty of trash cans. Except they weren’t called trash cans. Some were labeled “recycling” and others were named “landfill.” It struck me how a simple shift in what we name something can make such a difference in how our mind sees it. Trash is a vague concept whereas landfill is a specific location with a concrete meaning and has an extremely different connotation from the word “trash.” If it’s trash, then we can say we’re “throwing it away.” Trash goes to that invisible place called “away.” If it’s landfill, then it goes in the, you know, landfill, the most unglamorous place of all.

Over the weekend a Mylar balloon landed in my yard. It reminded me of the idea of away. People like to release balloons into the sky as a celebration. The balloons are carried “away.” But the balloons don’t really go away. They don’t go anywhere; they stay here on Earth, sometimes in people’s yards, but most often balloons released into the sky end up in the ocean. This is why I’ve always hated balloons. To me, they represent society’s collective decision to not see how much we waste; to pay as little attention as possible to that place we’ve decided to label “away.”

Carbon pollution is one more of our “aways.”

We turn on the light to see, but all the wires that wind from the switch, through the wall, across town to the power plant that releases the colorless, odorless, heat-absorbing gas remain in the invisible realm of our “away.” We know it’s there because instruments such as NASA’s Atmospheric Infrared Sounder (AIRS) and Orbiting Carbon Observatory-2 (OCO-2) do see it. But carbon dioxide gas and the heat it traps aren’t going away, not any time soon, not until we start to change the way we see our world.

Because there is no such thing as “away.” The only thing that’s real is here.

Recycling and landfill bins.
Recycling and "landfill" bins on the campus of the University of California, Irvine.View larger image

I look forward to your comments.

Thank you,

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Dr. Sassan Saatchi speaking at the UN Climate Change conference

Riley Duren, chief systems engineer for the Earth Science and Technology Directorate at NASA's Jet Propulsion Laboratory, is reporting from the 2014 United Nations Climate Conference in Lima, Peru.

I mentioned previously that Peru is home to some of the most important forests in the world in terms of their vulnerability to future impacts from climate change and development pressure as well as their potential to mitigate climate change. This underscores the importance of certain elements of the UN Framework Convention on Climate Change. In particular, the Reduction of Emissions from Deforestation and forest Degradation (REDD+) program seeks to address the second-largest human contribution to climate change after fossil fuel use (see Friday's post).

Detailed definitions vary, but deforestation generally refers to conversion of forested lands to some other use -- particularly large-scale agriculture but also mining and expansion of infrastructure and cities. Degradation is distinct and refers to a diminished capacity of forests to store carbon, support ecosystems and other services. Forest degradation is caused by human activity such as commercial logging, fuel wood collection, charcoal production, and livestock grazing as well as natural forces like storms, insect damage and wildfires.

Forests play a critical role in Earth's carbon budget because healthy, growing trees and other forest elements remove and store carbon from the atmosphere -- converting it to "biomass" in trees, shrubs and soil. This makes forests one of the most effective countermeasures for fossil fuel CO2 emissions (see graph, below).

A cloud forest on the flank of Hualalai volcano on the Big Island of Hawaii

The Earth's evolving carbon budget from the start of the Industrial Revolution through present day. Carbon dioxide (CO2) flux is shown in units of Giga (billion) tons of carbon per year (GtC/year). Fluxes of carbon emitted to the atmosphere are indicated by "+". Fluxes of carbon removed from the atmosphere are indicated by "-". The plot shows the dramatic growth in fossil fuel CO2 emissions since the mid-20th century and slight decline in emissions from deforestation and other land use change. The graph also shows the corresponding growth in the three major carbon sinks: the atmosphere, land (forests) and oceans. The variability or "jumpiness" in the land sink from year to year is likely due to changes in precipitation associated with climate variability like El Nino. The future ability of the land and oceans to remove CO2 from the atmosphere remains an area of great uncertainty. Image source: Global Carbon Project

However, when forests are degraded or destroyed, the storage potential of the forest is reduced or eliminated. Additionally, if the downed trees are burned and/or decay and forest soils are disturbed, they release their stored carbon (sometimes centuries worth) into the atmosphere. So there's an incentive to both keep forests growing to store carbon and to avoid disturbing the carbon already stored in them.

Programs like REDD+ are intended to incentivize governments and landowners to preserve and restore their forests. For example, in carbon-trading programs, governments and business can "offset" their fossil fuel CO2 emissions by purchasing credits from forest owners who can prove they're storing an equivalent amount of emissions by implementing certain protocols, including independent measurement and verification. These efforts are particularly important in the tropics, which are home to most of the world's forest carbon, as well as the countries experiencing the most rapid growth and development pressures, very similar to the period of growth the US underwent in the 1800s.

Over the weekend, I attended the Global Landscape Forum to interact with policy makers, conservation groups and scientists on the subject of forest carbon monitoring. One of the panel sessions featured JPL's Dr. Sassan Saatchi and other experts who described the current capabilities and limitations of remote-sensing tools to assess the status and health of forests, including their carbon stocks and "fluxes" (removals from and emissions to the atmosphere).

The remote-sensing methods discussed included imaging systems like the US Landsat satellites that are being used to track forest-cover change as well as future systems that will improve understanding of forest degradation such as NASA's ICESAT-2 mission, the NASA-India Synthetic Aperture Radar (NI-SAR) and the European Space Agency's BIOMASS mission. The role of flying radar and lidar (laser radar) instruments on aircraft over high priority areas was also discussed.

Of course decisions about forest management involve dimensions other than climate change mitigation -- typically involving a balance between economic growth and the value of existing ecosystem services offered by forests. Biodiversity in particular is gaining prominence in decision-making given the societal and economic value it represents. Biodiversity, which refers to the number of species in a given area, is often highest in forest ecosystems (particularly in the tropics) given they provide a combination of food, shelter and water resources. The information required to evaluate biodiversity is related to, but distinct from, the data used to assess forest carbon. (I'll try to describe the role of remote-sensing in assessing biodiversity in a future post.)

Meanwhile, closing with some personal experience, I'm posting a couple of photos I took while working on my own forest conservation and biodiversity project in Hawaii.

A cloud forest on the flank of Hualalai volcano on the Big Island of Hawaii

A cloud forest on the flank of Hualalai volcano on the Big Island of Hawaii. The giant, ancient trees and native understory plants thrive in the high-altitude, moist environment provided by the persistent presence of clouds -- providing carbon storage as well as a habitat for threatened plant and bird species. The benefits of the unique Kona weather pattern are offset by the introduction of invasive weeds and destructive feral animals like pigs and sheep.Image credit: Riley Duren

A cloud forest on the flank of Hualalai volcano on the Big Island of Hawaii

A threatened I'iwi honeycreeper, endemic to the Hawaiian Islands, sips nectar from an Ohia tree blossom. Historically, this species ranged across the Hawaiian Islands but today only survive in a few high-elevation forests given the combined pressure of deforestation and avian malaria at lower elevations from non-native mosquitoes. The I'iwi, like many other Hawaiian bird and plant species, lacks the natural defenses to withstand the combined pressure from development and climate change. Management efforts focus on conserving, restoring and building resiliency in threatened forest habitats. Image credit: Riley Duren


  • Riley Duren

Screengrab from a time-lapse video of Los Angeles

Illustration of the ground-based instruments and aircraft tracking CO2 in Los Angeles

Riley Duren, chief systems engineer for the Earth Science and Technology Directorate at NASA's Jet Propulsion Laboratory, is reporting from the 2014 United Nations Climate Conference in Lima, Peru.

We arrived in Lima, Peru, late last night and made our way to the United Nations climate conference venue this morning -- an impressive complex known locally as the Pentagonito or “Little Pentagon.” As host country and city, Peru and Lima are representative of several key fronts in the international effort to confront climate change. Peru is home to some of the most significant tropical forests on Earth that are the focus of programs to preserve their vital role in storing carbon and critically endangered ecosystems (more about that tomorrow). With a population approaching 10 million people, Lima itself is a rapidly growing megacity -- one of many in the developing world.

The latter topic is the focus of this post and the event I’m participating in later today at the US Center: “Understanding the Carbon Emissions of Cities.” I’ll be joining colleagues from the US National Institute of Standards and Technology, Arizona State University, Laboratoire Des Sciences du Climat et de l'Environnement (France), and Universidade de São Paulo (Brazil) in presenting the motivation for and recent scientific advances in monitoring urban carbon pollution. There won’t be a live stream but the event will be recorded - keep an eye on the US State Department’s YouTube page where it should be posted this weekend.

So what is “carbon pollution” and why should we care about it? Most of us are familiar with the general topic of air pollution; just ask anybody who has asthma or knows a friend or family member with respiratory problems. Cities are notorious sources of air pollutants or smog -- including visible particles (aerosols) and invisible but caustic ozone. One can find many examples of success stories where air quality has improved in response to clean-air standards as well as horror stories in cities lacking such standards. However, this familiar topic of air quality is mostly limited to short-lived pollutants -- compounds that only persist in the atmosphere for hours or days. Those pollutants are important because of human health impacts but they’re not primary drivers of climate change. Carbon dioxide (CO2) and methane (another carbon-based molecule) on the other hand, are long-lived gases that trap heat in the atmosphere for many years. Once CO2 and methane are in the atmosphere, they remain there for a long time -- centuries, in the case of CO2. Most people are unaware of the presence of CO2 and methane because they’re invisible and odorless and don’t have an immediate impact on health, but those gases are THE big drivers of climate change.

There are many sources of CO2 on Earth, including natural emissions that, prior to the industrial revolution, were balanced by removals from natural carbon scrubbers like forests and oceans. However human activity is rapidly changing the balance of CO2 in the atmosphere, leading to an unprecedented growth rate. Most of these human CO2 emissions come from burning fossil fuels like coal and oil. These fossil emissions are responsible for about 85 percent of humanity’s CO2 footprint today and, globally, they’re continuing to accelerate. So any successful effort to avoid dangerous climate change must have fossil CO2 mitigation at its core. Managing methane is also important given its greater heat trapping potential than CO2.

Why focus on carbon from cities? It turns out that urbanization – the increasing migration of people from rural areas to urban centers – has concentrated over half the world’s population, over 70 percent of fossil CO2 emissions and a significant amount of methane emissions into less than 3 percent of the Earth’s land area! So cities and their power plants represent the largest cause of human carbon emissions. In 2010, the 50 largest cities alone were collectively the third largest fossil CO2 emitter after China and the US – and there are thousands of cities. At the same time, in many cases, emissions from cities are undergoing rapid growth because of urbanization.

But there’s also a silver lining here.

Many cities are beginning to serve as “first responders” to climate change. While national governments continue to negotiate over country-level commitments, mayors of some of the largest cities are already taking action to reduce their cities’ carbon footprints, and they’re working together through voluntary agreements. Additionally, the concentrated nature of urban carbon emissions makes measuring those emissions easier than measuring entire countries.

Measuring the carbon emissions of cities is important (you can’t manage what you can’t measure) and challenging given the number of sources and key sectors and uncertainty about how much each contributes to the total carbon footprint. For example, in a typical city, CO2 is emitted from the transportation sector (cars, trucks, airports, seaports), energy sector (power plants), commercial and industrial sectors (businesses, factories) and residential sector (heating and cooking in homes). Likewise, urban methane sources include landfills, wastewater treatment plants, and leaks in natural gas pipelines. Mayors, regional councils, businesses and citizens have a number of options to reduce their carbon emissions. Measuring the effect of those efforts and understanding where and why they’re not having the intended impact can prove critical to successful mitigation. It also has economic implications -- toward identifying the most cost-effective actions and supporting emissions trading (carbon markets) between cities and other sub-national entities.

How can we measure the carbon emissions of cities? That’s the focus of the Megacities Carbon Project and the topic of our event in Lima today. Briefly, this involves combining data from satellites and surface-monitoring stations that track concentrations of CO2, methane and other gases in the atmosphere over and around cities with other, local data sets that contain information about key sectors. Pilot efforts in Los Angeles, Paris, Sao Paulo and other cities are beginning to demonstrate the utility of these methodologies. Satellites like NASA’s Orbiting Carbon Observatory-2 and other future missions, when combined with a global network of urban carbon monitoring stations, could ultimately play an important role in enabling more effective mitigation action by the world’s largest carbon emitters: cities.


  • Riley Duren

Artist concept of Orbiting Carbon Observatory.

Imagine if you could scoop exactly one million molecules out of the air in front of you (while being careful not to grab any water vapor). Now, start sorting these molecules into different piles. Start with the two most common molecules and you've sorted 99 percent of your sample -- the nitrogen pile will have about 780,000 molecules, and oxygen pile will have about 210,000 molecules. Working on the third most common molecule, argon, gets you a new pile with about 9,000 molecules. Congratulations, you've sorted 99.9 percent of the molecules into just three piles. The remaining 1,000 molecules are called "trace gases." The most famous and the most common trace gas is carbon dioxide, or CO2. Out of the million you had at the beginning, you'll count about 385 CO2 molecules.

Now, imagine repeating this experiment 12 times per second while flying over Earth at more than 16,000 miles per hour. Each of those counts needs to be accurate enough to note the addition or subtraction of one molecule of CO2 per one million of air. This is the experiment that a group of scientists and engineers at NASA's Jet Propulsion Laboratory conceived almost 10 years ago. We call it the Orbiting Carbon Observatory, and it is now at the launch pad waiting for its ride into space.

The heart of the mission is a very accurate instrument -- called a "spectrometer" -- tuned to sense the presence of CO2. A spectrometer is a type of camera that splits incoming light into hundreds of different colors and then measures the amount of light in each of these colors. In the case of this mission, the spectrometer measures sunlight that has passed through the atmosphere twice: once on the way down to the surface, and then again on the way up to the orbiting spacecraft. When the light passes through air containing CO2, certain colors are absorbed. The spectrometer creates an image with dark bands where the sunlight is partially or completely missing. This image looks similar to a barcode. Encoded in that barcode is the information to infer how many CO2 molecules the sunlight encountered on its way to the spacecraft.

I joined the project in early 2001 as the lead engineer for the spectrometer. In the eight years that have followed, we've gone from an idea to a fully built and tested system sitting on top of a rocket, ready for launch. Along the way, a group of talented people has put in countless hours designing, building, and testing the system. When doing something for the first time, there are always issues that come up -- some of which look insurmountable at the time. It's been a challenge, but the hard work and creativity of our team saw us through all of them.

Now we are waiting for the payoff -- the first data from space. We've done everything we can to be ready. Now, launch awaits ...