Science

On eve of climate summit, researchers sharpen emissions tracking

When world leaders gather on Sunday in Glasgow, U.K., for the start of their annual climate summit, discussions will focus on strengthening lagging efforts to hold global temperature increases to 1.5°C—a goal set in the 2015 Paris climate agreement.

To meet that target, the world needs to cut greenhouse gas emissions by 55% by 2030, but current national pledges only trim emissions by 7.5%, the United Nations Environment Programme warned this week. In a bid to achieve the Paris goal, some nations at the meeting, formally known as the 26th Conference of the Parties (COP26), are expected to commit to deeper emissions cuts, especially from the burning of fossil fuels.

While nations step up their pledges, some scientists and policymakers are focused on making sure they stick to them. They are nurturing rapidly emerging technologies—including satellites, sensors, and software—that promise a quick and accurate assessment of greenhouse gas emissions such as carbon dioxide (CO2) and methane. “It’s just a revolution in what’s possible,” says Steven Hamburg, a biogeochemist and chief scientist for the Environmental Defense Fund (EDF), which is leading an effort to launch a methane-tracking satellite into orbit next year.

Such systems would not only provide a clear and timely picture of emissions trends, but would also help hold governments accountable by independently verifying any pledges made in Glasgow. The first such accounting could come as soon as 2023, when the world is scheduled for its first “stocktake”—a provision in the Paris accords that calls for reviewing the state of global emissions every 5 years.

Currently, the Paris framework relies on countries to report their own emissions. But the numbers are not typically based on direct measurements of greenhouse gases. Instead, the accounting is drawn from other statistics, such as inventories of oil or natural gas and estimates of how much a nation burns.

Some governments and philanthropy-backed nonprofits are poised to take a different approach. They are preparing to launch at least a dozen satellites over the next 5 years that will monitor methane and CO2 emissions, and they are refining systems that track pollution with monitoring stations and sensors mounted on mobile units. Together, such systems could enable the public to get weekly readouts on emissions across the globe, for individual countries or cities, and even down to a single industrial facility.

Tracking methane

Recent work with methane illustrates the possibilities. The gas is far more potent at trapping heat than CO2, but shorter lived in the atmosphere. Over the past decade, a team of scientists led by EDF used methane sensors mounted on trucks, drones, and airplanes to check U.S. emissions estimates developed by the U.S. Environmental Protection Agency (EPA). EDF found that methane leaks from production fields, pipelines, and gas stations were far worse than what EPA estimated.

The EDF data nearly doubled the estimated impact that U.S. methane emissions are having on global warming. That helped prod EPA to update how it estimated methane releases. The effort also reportedly led the French government to block a company from buying natural gas from a part of Texas highlighted for methane leaks.

Now, EDF and its partners are expanding their gaze across the world. Next year, they plan to launch MethaneSAT, a satellite equipped with sensors that would detect methane plumes with a resolution of 400 square meters. In 2023, MethaneSAT could be joined by a $100 million pair of satellites launched by another private U.S. coalition, designed to zoom in even closer on gas refineries or storage tanks to pinpoint leaks. With the satellite systems, “I’m optimistic that by the middle of the decade we could have a global monitoring system for methane that’s pretty capable,” says Riley Duren, CEO of Carbon Mapper, the California-based nonprofit leading the project.

Getting a grip on CO2

Despite being less abundant than CO2, methane is easier to monitor from space. Human-induced methane emissions stand out because they are often much more concentrated than background natural levels. By contrast, CO2 rising from coal plants or tailpipes quickly blends with the vast and fluctuating releases from rotting vegetation, oceans, and other natural sources. Satellites now in orbit were built to watch the flow of CO2 through entire ecosystems, not smokestack plumes. For example, two U.S. carbon-tracking satellites, known as Orbiting Carbon Observatory-2 (OCO-2) and OCO-3 (which is mounted to the International Space Station) can only see carbon emissions with a resolution of approximately 2 square kilometers.

That picture could come into sharper focus after 2025, when the European Space Agency (ESA) aims to launch the first of three satellites built specifically to track fossil fuel emissions. The planned CO2 monitoring network could give a weekly view of fossil fuel emissions down to the level of individual power plants or large cities. “A fast system is really giving better transparency,” says Yasjka Meijer, the ESA mission scientist leading the satellite development.

Initial steps on display

At COP26, some researchers will show policymakers what satellite-based systems can do today. For example, the Committee on Earth Observation Satellites (CEOS), whose members represent the space agencies of 34 countries, will be showing off a recently completed estimate of how much carbon is released each year from natural systems, broken down to the national level. And Climate TRACE, a global alliance of researchers and environmental think tanks, will highlight what it calls the first independent, up-to-date, global inventory of greenhouse gases broken down by country and sources.

Climate TRACE aims to overcome the limitations of current carbon-tracking satellites by pairing other kinds of satellite imagery with computer programs trained to find relationships between emissions and images of things such as highway traffic or a steam plume from a power plant, says Gavin McCormick, executive director of WattTime, a group that helped found the project. The results, released last month, found that previous estimates of emissions from global oil and gas production might be understated by as much as 2 billion tons per year. That’s more than the annual climate pollution produced by Russia, which ranks fourth among countries.

Efforts like Climate TRACE suggest there will be “no hiding anymore” for nations not living up to their climate pledges, U.S. climate envoy John Kerry said at an April press conference. But David Crisp, an atmospheric physicist at NASA’s Jet Propulsion Laboratory and the lead scientist for the Orbiting Carbon Observatories, cautions that “the training wheels are still on” for the monitoring systems now in use. He is working with CEOS partners to collect and analyze satellite data robust enough to include in the first emissions stock take in 2023.

Arlyn Andrews, who heads greenhouse gas monitoring research for the U.S. National Oceanic and Atmospheric Administration’s Global Monitoring Laboratory, is cautiously optimistic that improved monitoring will soon be informing the global conversation about curbing climate change. Fielding better systems will take big investments in both measurement tools and computers, she said during a recent talk hosted by the U.S. National Academy of Sciences. “We’ve demonstrated that we can do it,” she said at the talk. “We just need to put it into a sustained operations system.”

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