An Observatory Spied on LA's Carbon Emissions—From Space

Cities.  Not corn fields or cow farts or flyover country.  Climate change is being caused by where fossil fuels are consumed; not where fossil fuels are produced.  Urban areas are the source of pollution causing climate change.  And addressing climate change will require drastically altering urban lifestyles.  Apparently there is a lot of resistance to NASA confirming what common sense should be telling us.

NASA's lackadaisical approach to the global crisis of climate change is rather amazing.  NASA can search for life on Venus, fly helicopters on Mars, search for exoplanets we won't be visiting, and explain liquid nitrogen convection shaping the surface of Pluto.  OCO-1 didn't make it into space.  OCO-2 apparently was flawed.  And now OCO-3 is busy-work for personnel on the International Space Station.

What is even more astounding is that NASA is not the only player in space.  Politics may be an exculpatory excuse for NASA's seeming disinterest in directly observing the anthropogenic influence on climate.  But that doesn't explain the absence of the European Space Agency.  Japan collected a sample from a distant asteroid.  Elon Musk can launch a Tesla and Jeff Bezos can fly tourists to space but no country on Earth can directly observe the polluting emissions responsible for the crisis of climate change?

The United Nations could fund Earth observation, led by the IPCC.  If scientists can be bought for a few shekels to shill for fossil fuels then buying scientists to observe Earth shouldn't be that difficult.   We'd know instead of being required to guess.  But if we know, we couldn't sweep it under the rug and argue about trees.

Perhaps we're not looking because we already know.  Cities.  Not corn fields or cow farts or flyover country.  The urban lifestyle is the cause of the existential crisis of climate change.  And the urban lifestyle is what must be changed to save the planet.

S E E D E D   C O N T E N T

While most people might be attracted by the perpetually sunny skies, nearby ocean, or mountains hugging the Los Angeles basin, environmental engineer Annmarie Eldering was drawn to the city's smog. "It's the best place to go," she says. "You've got tons of pollution!"

Urban areas release over 70 percent of human-made carbon dioxide emissions that wind up in the atmosphere, and LA is no exception. With over 13 million residents in its larger metropolitan area, a sophisticated network of freeways, and an international transportation hub, LA produces the fifth-most CO₂ of all the cities in the world. That makes it a sweet spot for studying the role humans play in climate change.

Eldering is the project scientist for NASA's Orbiting Carbon Observatory-3, or OCO-3, an instrument that measures atmospheric CO₂ levels from space to better understand the impact of human activity on the natural carbon cycle, the process by which plants, soil, oceans, and the atmosphere exchange carbon with each other. In a paper published this month, Eldering and her colleagues released a map showing the most detailed variations of CO₂ emissions over the LA basin ever seen from space. This research demonstrates that space-based monitors can be used to collect large swaths of data over pollution hot spots, information that could help inform policy to combat climate change.

"What's exciting about the OCO-3 result is that this is the first time we've gotten this kind of area map over a city like LA from space," says Joshua Laughner, a postdoctoral scholar at Caltech who works on a global ground-based monitoring system called the Total Carbon Column Observing Network. While useful for observing precisely how atmospheric carbon concentrations change over time, instruments like the TCCON are costly to run and require partnerships with skilled scientists, so their data collection is limited to specific areas. An orbiting observatory, by contrast, can scan parts of the planet that are hard to study from the ground, such as volcanoes or cities with high carbon footprints but few monitoring resources.

Launched in 2019, OCO-3 is now mounted on the International Space Station, where it sees nearly every city on Earth within an average span of three days, according to a NASA press release. It's an improvement over its still-active predecessor, OCO-2, which can collect only a 10-kilometer-wide swath of data and is locked in a sun-synchronous orbit that passes over LA at the same time every day, meaning it can only check the city's atmospheric CO₂ levels at 1:30 in the afternoon.

"With OCO-3, we have much better spatial coverage, and also temporal coverage, because it can now look at the city at different times," says Caltech postdoctoral scholar Dien Wu, who works closely with the team in analyzing urban emissions. OCO-3 can make multiple sweeps over a single location, mapping out a snapshot of about 80 square kilometers in as little as two minutes.

The color of each pixel on this map created by Eldering's team represents the atmospheric CO₂ concentrations in an area on the ground that's about 1.3 miles wide. Because carbon dioxide absorbs certain wavelengths of light, scientists can use this information to deduce how much is present in Earth's atmosphere. OCO-3 observed changes in the intensity of sunlight as it passed through a vertical column of air and created a reading for how much CO₂ was in that spot.

Then the OCO-3 team compared this satellite data to "clean air" readings already collected by a ground-based TCCON instrument at NASA's Armstrong Flight Research Center in the desert far north of LA, away from sources of local emissions. Using a baseline of about 410 parts per million (or 410 CO₂ molecules for every million molecules of dry air), OCO-3 was able to identify differences down to a half part per million. They saw peak excesses of CO₂ at over five parts per million over the LA basin. That may sound small, but it's equal to the amount that these emissions are rising on a global scale every couple of years.

One goal of the experiment was to check that readings from space matched measurements made on the ground—and they did. OCO-3's data agreed with recent results from a TCCON station in Pasadena, California, showing the instrument's promise for future use in locations where ground-based tracking is unavailable.

But space-based monitoring has its own complications. Measuring the CO₂ emitted at Earth's surface by looking down through columns of air is tricky because it's not always clear where that air is coming from. "The top part of the column will have CO₂ that could have come from halfway across the planet," says Northern Arizona University climate scientist Kevin Gurney, who was not involved in the study but whose previous work was cited in the paper. "The higher up in the atmosphere you go, the farther away that air actually came from."

Another shortcoming is that it's not currently possible to identify with much certainty the sources of excess carbon dioxide in the atmosphere: whether it came from human activity, vegetation, the ocean, or other natural carbon-emitting reservoirs. "CO₂ from a plant and CO₂ from fossil fuels look the same," Gurney says. (He has developed Vulcan, his own novel method of estimating human-made CO₂ emissions, by using statistics on local fuel consumption and city infrastructure.)

Eldering says scientists are developing techniques to eventually be able to discriminate between different CO₂ sources. She's already imagining an OCO-4, the next observatory they can launch into space. "The dream would be to have an instrument that can see a couple hundred kilometers across the globe with almost no gaps in between," she says.

Despite the current limitations of space-based monitoring, Gurney notes that the new OCO-3 maps are particularly powerful because they make the issue personal. "This is not any longer just about polar bears in the North Pole," he says. "Being able to see the emissions in your town makes the climate-change problem real."

He envisions that one day emissions tracking will be advanced enough for scientists to create an "information system" of local pollution predictions, the same way meteorologists forecast the local weather. "It should be on the evening news," Gurney says. "Here's the CO₂ today; here's what we think it's going to be tomorrow."

Better local data might even spur political action, says Laughner, identifying opportunities to reduce emissions or help government leaders evaluate how effective their climate policies are.

But to get to this point, Gurney says, scientists need to combine the strengths of space-based monitoring with other efforts. Eldering agrees, saying the goal isn't to replace other methods of carbon dioxide monitoring but rather to figure out how to use them together to inform climate-change policy across the globe. "We are one link in this grander chain of science," she says.