Published online 25 February 2009 | Nature | doi:10.1038/news.2009.124
Corrected online: 26 February 2009
Corrected online: 1 March 2009
Updated online: 26 February 2009

News

Climate researchers in a spin after satellite loss

Orbiting Carbon Observatory crash sets back post-Kyoto emissions monitoring.

OCO launchSome hoped the Orbiting Carbon Observatory would smooth the way for future emissions agreements after Kyoto.NASA

The climate community is counting the costs of losing NASA's Orbiting Carbon Observatory (OCO), which plummeted into the ocean during launch on 24 February.

The satellite would have measured carbon dioxide concentrations in unprecedented detail, allowing scientists to track emission sources and identify 'carbon sinks' around the globe. Many also hoped that OCO would pioneer an approach for monitoring greenhouse gas emissions under a future Kyoto-style global warming treaty.

"I think it's a tragedy for carbon-cycle science," says Elisabeth Holland, a senior scientist who studies carbon and nitrogen cycles at the National Center for Atmospheric Research in Boulder, Colorado. "My experience is that every time we have a comprehensive new data set, we redefine the field," says Holland, who was not involved the project.

At present, samples are taken by hand every two weeks at roughly 100 ground stations situated unevenly around the world. In contrast, OCO would have made 8 million measurements every 16 days.

There are some older instruments aboard satellites capable of measuring carbon dioxide, and Japan's Greenhouse Gases Observing Satellite (GOSAT), launched in January this year, will measure carbon dioxide as well as methane and water vapour. But when it comes to carbon dioxide, none of these instruments have the precision that OCO was capable of providing.

"There is no equivalent to OCO," says Philippe Ciais, associate director of the Laboratory for Climate Sciences and the Environment in Saclay, France.

"Everyone is in shock," Inez Fung, an atmospheric scientist with the University of California, Berkeley who worked on the OCO project, said after a debriefing conference call on Tuesday afternoon. "It was like a grieving session. There were 13 buses at the launch. A lot of people contributed to this."

Emissions failure

Scientists say they need this kind of in-depth information to answer a particularly vexing question: roughly half of the CO2 now being emitted by humans stays in the atmosphere, where it acts as a greenhouse gas, but where does the other half go? Researchers know that oceans, forests and perhaps even deserts soak up carbon dioxide, but definitive descriptions of how much and where have proven elusive.

These questions could take on a whole new geopolitical dimension in the coming years if the international community implements carbon regulations that require each country to accurately assess its carbon emissions. OCO was billed as a demonstration of the kind of technology that could be more widely deployed to monitor these global agreements. Emissions from transport and industry are easily quantifiable, but those from other areas — notably land use and agriculture — are shrouded in uncertainty.

Data from the satellite could have helped to improve reporting, says Kevin Anderson, a researcher at the University of Manchester in the United Kingdom. Ultimately, he adds, satellites like OCO might smooth the passage of future climate agreements: "The absence of reliable emissions data is a problem at every level," he says. "Anything that gives us a clearer baseline will help policy."

"We could probably do with having a fleet of 20 of these satellites, because the issue is so important," says John Burrows, a co-investigator on the OCO project and science director at the Centre for Ecology and Hydrology in Wallingford, United Kingdom. "We start[ed] out with two this year, and now we've lost one."

Burrows is a lead investigator on SCIAMACHY, an instrument aboard the European Space Agency's Envisat that uses similar technology but has much lower resolution. In OCO's absence, he says, scientists will have to increase their use of ground monitoring as well as existing instruments such as SCIMACHY as they work to validate the data coming out of GOSAT. NASA can also perform some CO2 monitoring with the Atmospheric Infrared Sounder, AIRS, launched aboard the Aqua satellite in 2002.

Making do

The European Space Agency (ESA) is mulling whether to proceed on a more advanced version of the OCO mission. The proposed A-SCOPE (Advanced Space Carbon and Climate Observation of Planet Earth) would use a laser to actively probe the CO2 in the atmosphere. Unlike OCO, which was designed to use reflected sunlight, A-SCOPE would be able to perform measurements at night and in the presence of cloud cover. But existing lasers and sensors cannot measure CO2 accurately enough to provide meaningful results, according to François-Marie Bréon, a researcher who worked on an independent feasibility study of A-SCOPE for ESA at the Laboratory for Climate Sciences and the Environment in Saclay. Bréon believes that the ESA will not proceed with an A-SCOPE in the near term, but he believes that the loss of OCO may spur increased R&D investment in the concept.

For now, the climate community will have to settle for GOSAT. The Japanese satellite covers more ground but has less resolution, so it would have been a perfect match for OCO; the question moving forward will be how to validate observations from one satellite without the other.

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GOSAT project manager Takashi Hamazaki, who attended the launch, said his team has worked closely with OCO members on ways to integrate and validate the two data sets. He says his team can calibrate GOSAT using ground monitors, but the process would have been much faster and perhaps more accurate using OCO as well. Running the two satellites in parallel also might have produced insights into how both instruments work.

"We believe we can get the results, but the cooperation added value," he says. "That was lost."

Hamazaki says his team expects its first results as early as July and will continue working with OCO members in the US during the five-year life of the project. If NASA has the money, he hopes the agency will put another OCO up quickly while working on a next-generation satellite for launch in subsequent years.

The question facing NASA is whether to push forward with an OCO II as fast as possible or whether to take a step back and design a new instrument that will go significantly farther. "My reaction is that we can't wait," Berkeley's Fung says, citing the social and governmental implications of carbon dioxide. "I think we've got to get up what we can, as fast as we can." 

Updated:

Volker Liebig, ESA's Director for Earth Observation, has confirmed that A-SCOPE had not been selected for the next round of earth observing satellites. Liebig also says he doesn't believe the OCO incident will have a great impact on ESA’s funding strategy.

Corrected:

François-Marie Bréon did not work on the A-SCOPE proposal, but contributed to an independent feasibility study.

Corrected:

The OCO satellite would have made 8 million measurements every 16 days, not 1 million every two weeks as previously stated.
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