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Isabella Velicogna on Measuring the Gravity of Climate Change—Using Gravity

headshot of AAAS Fellow Isabella Velicogna
AAAS Fellow Isabella Velicogna, Ph.D.

After completing her Ph.D. in applied physics in Italy in 1999, Isabella Velicogna came to the U.S. in the hopes of landing a post doctoral position. With little initial luck, she decided to try and increase her chances by traveling across the country and presenting talks. Her efforts proved fruitful and she landed a dream job – working at the University of Colorado in Boulder on the National Aeronautics and Space Administration’s (NASA) Gravity Recovery and Climate Experiment (GRACE) project. The mission involved using satellite data to assess the Earth's water systems, including changes in its ice sheets, and the results have been invaluable for understanding the impacts of climate change.

It was very exciting working for a new NASA mission,” recalls Velicogna, noting that existing methods for measuring ice sheet mass at the time were lacking or would typically involve difficult logistics, like flying planes over Greenland. “GRACE was really a game changer.”

The mission involved two twin satellites that could determine the distance between themselves with micro-meter precision – essentially the width of a human hair – despite flying about 137 miles apart from each other. Differences in the gravity field measurements from the two satellites could then be used to infer changes associated with ice and water masses on the Earth’s surface, and even groundwater under the surface.

In the early 2000s, Velicogna pioneered the method for using this technology to track the mass balance of ice sheets in Antarctica and Greenland, as well as changes in groundwater systems, which proved particularly useful for tracking changes associated with human activities. The technique requires careful analysis and accounting for a myriad of other factors, such as the weight of the atmosphere, the rebound of the Earth’s crust, and components of the gravity field that are not so well measured with GRACE. Fortunately for Velicogna, she enjoys a challenge and putting her critical thinking skills to the test.

The GRACE satellites were launched in 2002, and after just a few years, the data yielded ground-breaking results. By 2006, Velicogna and her colleagues published a report in Science Magazine showing that the immense ice sheet covering Antarctica was losing mass.

Velicogna notes that these data were particularly surprising given that scientists had predicted that the Antarctica ice sheet would grow due to increases in precipitation. The unexpected results – showing mass ice sheet shrinkage instead – held significant implications for the impact of climate change in polar regions, especially Antarctica, and also for sea level rise.

Since that initial report, as Velicogna has continued her work on the GRACE project with NASA, she has seen its importance grow – more than she could have ever expected as a young scientist.

“This work has an impact on society, and it has an impact on enabling and motivating government to change policy, which is really what’s going to make the difference in being able to fight climate change, and mitigate and adapt to what is happening,” says Velicogna, who became a AAAS Fellow in 2021 as a result of her exemplary impact in climate science.

But, finding a solution will be a group effort among scientists, policymakers, and the public. In this sense, Velicogna’s job extends beyond mathematics and physics to include communication. “Scientists can discover how the ice sheets work, but we need to convey it to others in a way that is practical,” she says.

As a result, Velicogna has also been reflecting and exploring ways of communicating the GRACE project’s data. She emphasizes the need for scientists to stay positive, especially when communicating with the public about climate change. “We want to make sure to let people know that they can make a difference,” she adds. Including people with diverse perspectives and backgrounds in the search for climate change solutions is crucial as well.  “It’s two wins, because it’s the right thing to do and we’re going to get better science,” says Velicogna.

In line with her belief of a multidisciplinary approach, Velicogna has been working with social scientists, economists, and other experts to advance climate change communications and the search for solutions. “I am confident that we are moving in the right direction and honestly, this is the only way to go. We have to work together on this,” she says. “I am in this with all my heart.” 

While working to bring more diverse perspective into science, Velicogna has not stopped her research. After the conclusion of the initial GRACE project in 2017, she began working on the GRACE Follow-On (FO) mission in 2018, which continues the time series of measurements made by GRACE and extends it with even better precision data. She also has her sights set on NASA’s Mass Change study, which will be launched after GRACE-FO is completed.


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