AGAGE network marks 45 years of tracking and tracing potentially harmful atmospheric gases
By Mark Dwortzan | MIT Joint Program on the Science and Policy of Global Change (Photos by Kathy Thompson unless otherwise specified)
Emissions of CFC-11, a chlorofluorocarbon once frequently used in cooling and insulation systems to improve the quality of life, can also endanger life. Upon entry into the stratosphere where solar ultraviolet radiation is strong, CFC-11 decomposes, resulting in the release of chlorine, which degrades the ozone layer that shields life from harmful UV rays. In 2018, a team of scientists discovered an alarming upward spike in global CFC-11 emissions from 2013 to 2017. In 2019, a second team traced much of this spike to eastern China. Then in 2021, both teams found that global CFC-11 emissions had spiked downward from 2018 to 2019, and traced much of this downward spike to the same area—indicating that China had most likely curbed illegal manufacture of the ozone-depleting chemical. As a result, a major impediment to the ozone layer’s full recovery was now removed.
Key to the successful tracking and tracing of CFC-11 emissions from China was the Advanced Global Atmospheric Gases Experiment (AGAGE). Measuring the ozone-depleting and greenhouse gas composition of the Earth’s atmosphere continuously for the past 45 years through a global network of sophisticated monitoring stations, AGAGE has contributed significantly to the protection of life on Earth. In addition to monitoring and pinpointing sources of emissions of chemicals banned by international agreements such as the Montreal Protocol, which outlawed the use of chlorofluorocarbons (CFCs) such as CFC-11, the network has estimated the lifetimes of ozone-depleting and greenhouse gases in the atmosphere; determined concentrations of the atmosphere’s major “cleansing agent,” the hydroxyl radical (OH); and provided data to inform international policy discussions concerning atmospheric greenhouse gas emissions that drive climate change.
To celebrate these and other achievements, and to explore the network’s history and impact, recent results and next steps, more than 70 AGAGE scientists, collaborators and invited guests from research institutions around the world—many representing dozens more researchers at their home institutions—gathered on October 8-13 at the MIT Endicott House and online to attend a conference celebrating the 45th anniversary of AGAGE ((formerly known as the Global Atmospheric Gases Experiment (GAGE) and Atmospheric Lifetime Experiment (ALE)). (See 45th anniversary photo gallery.)
“AGAGE has long been a close collaboration between experiment and theory, each informing the other to achieve the siting, frequency, precision and accuracy of measurements needed to answer major scientific questions,” said MIT Department of Earth, Atmospheric and Planetary Sciences Professor Ronald Prinn, co-leader of AGAGE (and leader of ALE and GAGE), in his welcoming remarks. “For the past 45 years, we have been measuring ozone-depleting and greenhouse gases onsite at frequencies sufficient to identify both polluted and background air, and thus quantifying their emissions and sinks at regional to global scales. In that time, the number of ozone-depleting and greenhouse gases being measured has grown from 5 in 1978 to over 50 in 2023. Our network’s capabilities have proven invaluable for discovering and mitigating major threats to the global environment, and the need for them will become even more important in the future. Let us raise a toast to 45 years of excellence and hopefully many more to come!”
An expert in atmospheric chemistry who directs MIT’s Center for Global Change Science and Joint Program on the Science and Policy of Global Change, Prinn and his colleagues have, since 1978, provided the vision and direction that has enabled AGAGE to successfully merge theory with experimental procedures to measure atmospheric concentrations and thus emissions and lifetimes of target gases. During his 45 years at the helm, he has also led efforts to expand the network’s extent and support system, which now consists of 15 primary stations and more than 20 sponsors and participating institutions around the world.
That includes notably the U.S. National Aeronautics and Space Administration (NASA), which for the past 42 years has been the lead funder of AGAGE, including support for five of its stations, and the experimental infrastructure that enables international participation in the larger network—all as part of the broader NASA mission to advance Earth systems science through the integration of data obtained by satellite, airborne and surface observations.
“We’re not just advancing the science but making sure that it helps people live better and make better, environmentally informed decisions,” said Jack Kaye, Associate Director for Research at NASA’s Earth Science Division, and the conference’s keynote speaker. “AGAGE is living proof that research agencies can support environmental monitoring over the long term.”
Tracking and tracing ozone-depleting and climate-altering gases
Forty-five years ago, AGAGE pioneered the concept of a global network of continuous, in situ measurements of important trace gases involved in ozone depletion and climate change.
“AGAGE was conceived as a working partnership between the atmospheric measurement and modeling communities, and this enabled the network to estimate accurately the all-important atmospheric lifetimes of the trace gases (which in part determines their environmental impact) and to calculate their global and regional emissions,” says Paul Fraser, an atmospheric chemist who established the network’s first mid-latitude Southern Hemisphere measurements of CFCs in Tasmania in the late-1970s.
Since its inception, the AGAGE network has expanded from 4 to 15 primary stations, while vastly improving its ability to model the atmosphere at finer and finer scales. Whereas the original ALE network measured 5 gases 4 times per day with sources and sinks inferred using very low-resolution 2D models on desktop computers, today’s AGAGE instruments measure well over 50 gases 20-40 times per day, with sources and sinks inferred using very high-resolution 3D models and supercomputers.
“This major expansion of the measurement network, coupled with advances in high-performance computing, has enabled a greater focus on resolving emissions from individual countries,” says Anita Ganesan, an associate professor at the University of Bristol in the United Kingdom, who has contributed to the development of new AGAGE network measurements and data emissions estimation methods.
As its capabilities have advanced, the network has made great strides not only in monitoring emissions of potentially harmful ozone-depleting and climate-altering gases into the atmosphere, but also in informing and strengthening adherence to policies aimed at reducing those emissions.
The network’s ongoing tracking, tracing and analysis of global and regional emissions of ozone-depleting substances (ODS) has played a major role in the development of emissions-reduction policies under the Montreal Protocol. AGAGE has also enabled the world to verify international adherence to Protocol restrictions on the manufacture and sale of CFCs and other ODS. For example, by engaging with South Korean and Japanese scientists to set up stations to measure for the first time the outflow of ODS from eastern China, AGAGE provided the basis for strengthening China’s ODS mitigation policies.
“Identification of emissions sources and quantities through atmospheric observations has played a critical role in preventing potential environmental impacts that might have arisen from unreported or illegal production,” says Professor Sunyoung Park of Kyungpook National University, who runs the South Korean Gosan AGAGE station that detected the recent CFC-11 emissions spikes in eastern China.
Over the past 45 years, the AGAGE network has also made significant contributions to the world’s understanding and mitigation of global and regional greenhouse gas emissions associated with climate change.
For example, the high-altitude Jungfraujoch AGAGE station in the Swiss Alps has been measuring halogen-containing greenhouse gases for more than 15 years to help improve our understanding of global trends and regional emissions patterns over large parts of Europe, says Martin Vollmer, a senior scientist at Empa - Swiss Federal Laboratories for Materials Science and Technology. This station has also been instrumental in identifying newly-emerging synthetic compounds in the atmosphere—potent greenhouse gases that also deplete stratospheric ozone—and thus informing decision-makers about the hazards of these compounds before they become mass-produced.
Greenhouse gas measurements taken at the Zeppelin AGAGE station, located in the Arctic on Zeppelin Mountain far from the influence of pollution sources, have served as an early warning system for climate change trends that tend to be amplified at the Earth’s poles, notes Chris Lunder, a senior scientist at the climate and environmental research institute NILU. The Kennaook/Cape Grim (KCG) station, located in the clean mid-latitudes of the Southern Hemisphere, also provides early warning of both climate-altering and ozone-depleting emissions.
“If we see changes here then we know something major has changed with emissions somewhere globally, most likely the northern hemisphere,” says KCG runner Paul Krummel, Atmospheric Composition and Chemistry Research Group Leader at CSIRO Environment in Australia.
On the national level, KCG has helped the Australian government to meet its reporting requirements under the United Nations Framework Convention on Climate Change (UNFCCC). “We provide them with our estimates of emissions of synthetic greenhouse gases (most of which are replacements for the ozone depleting substances), which they report alongside their inventory estimates,” notes Krummel. “Australia is one of only a few countries worldwide that provide estimates based on atmospheric measurements in addition to inventory methods.”
Envisioning the future
In the coming years, the AGAGE network aims to add more monitoring stations and achieve even finer-scale emissions tracking and tracing, in order to provide the global community with more comprehensive and precise atmospheric observations and estimates of global, regional and nation-level emissions of ODS and greenhouse gases.
“This information will be key to verifying national and global inventory-based emissions estimates of ozone-depleting gases used by the Montreal Protocol process to define progress in emissions-mitigation policies,” says Fraser. “It will also be critical in verifying the progress of policies targeting zero-emissions of greenhouse gases in 2050 in alignment with the Paris Agreement, and interim emissions targets for 2035, which are about to be reassessed.”
The societal importance of measuring human-caused emissions into the atmosphere will only increase with time, says Ray Weiss, a professor emeritus at Scripps Institution of Oceanography, University of California San Diego, and co-leader of AGAGE since the early 1990s. “AGAGE is a model of international collaboration to measure what ozone-depleting and greenhouse gases are actually emitted,” he says. “The future will require a transition to new people to carry these efforts forward, and the prospects for this are strong.”
For additional information on the history of the AGAGE network and its capabilities, see our 40th anniversary news story.
Photo: AGAGE scientists, collaborators and invited guests from research institutions around the world—many representing dozens more researchers at their home institutions—at the ALE/GAGE/AGAGE network’s 45th anniversary conference on October 8-13 at the MIT Endicott House