Alarmed by climate change, astronomers train their sights on Earth

On the morning of January 18, 2003, Penny Sackett, then director of the Australian National University's Mount Stromlo Observatory outside Canberra, received a concerning email from a student at the facility.

Bush fires that had been on the horizon the day before were now rapidly approaching. The astronomers on site were considering evacuating, the student wrote.

That afternoon, from her home some miles away, Sackett watched burning embers fall from a smoky sky and worried. Later, she learned that her colleagues had escaped just in time: As the fire raced up the mountain, they fled down the other side carrying discs full of research data.

All but one of Mount Stromlo's eight telescopes were destroyed that day, along with millions of dollars' worth of equipment that engineers had been building for observatories around the world. The fires also destroyed 500 homes across greater Canberra and killed four people.

The incident was an early warning for astronomy: Wildfires, exacerbated by climate change, were becoming a problem for their field. Since then, several other observatories have been damaged or threatened by fires and other extreme weather and changing atmospheric conditions have made ground-based astronomical research more challenging.

Such incidents have drawn attention to Earth's plight, and a growing number of astronomers are rallying to fight climate change. In 2019, professionals and students founded a global organisation called Astronomers for Planet Earth.

Astrobites, a journal run by graduate students in the field, held its third annual Earth Week in April. Also last month, a group of astronomers released Climate Change for Astronomers: Causes, Consequences and Communication, a collection of articles detailing the researchers' personal experiences with the climate crisis, its impact on their work and how they might use their scientific authority to make a difference.

Other astronomers are raising awareness in the classroom, incorporating Earth's climate into their research, or have left science and become full-time activists.

Sackett went on to serve as Australia's chief scientist from 2008 to 2011, and made climate change a major focus of her office.

"Between the 2003 fires and when I became chief scientist, it was clear that things were getting worse and it was going to impact every facet of society," she said. Today, Sackett has a consulting business and advises government agencies, companies and nonprofit groups on climate issues.

Travis Rector, an astronomer at the University of Alaska Anchorage, and a founder of Astronomers for Planet Earth who edited Climate Change for Astronomers, said that "people are often surprised to learn that astronomers are engaged in climate change work".

He added, "But there's a very strong overlap between the science of astrophysics and the science of climate change. We understand, more than anyone else, that Earth is our only home."

A cosmic perspective

The modern scientific understanding of greenhouse gases is built in part on studies of Venus, a planet choked with heat-trapping carbon dioxide gas. At more than 800 degrees Fahrenheit, Venus is hot enough to melt lead - as well as the few probes that have managed to land on its surface.

By comparing Earth's atmosphere with others, Raissa Estrela, an astrophysicist at NASA's Jet Propulsion Laboratory (JPL), has come to appreciate her own planet even more, she said. Estrela characterizes the atmospheres of exoplanets using techniques that she also uses to map plastics and other pollutants on Earth.

"We have this beautiful diversity of life that took us more than 2.5 billion years to reach," she said. Now, over just a few hundred years, humans have altered Earth's hard-won atmosphere and endangered its unique biodiversity.

"That's very selfish," she added. "I feel like I have the responsibility as an astronomer, and as an inhabitant of this planet, to take care of it." Estrela emphasised that she was expressing her own views and that they did not necessarily represent those of NASA or the Jet Propulsion Laboratory.

Other astronomers voiced a similar sense of responsibility. A forthcoming poll by the American Astronomical Society found that 98 per cent of respondents were concerned about climate change, according to Rector, who helped run the poll. Nearly as many respondents, he added, felt they needed to do something about it.

Anna Cabré, an independent oceanographer, moved away from her original career as a cosmologist in part because the work was too abstract. "There's not a lot of touching reality," Cabré said.

She has since used her expertise in mathematics and programming to study how global warming could affect marine animals and the ocean's circulation patterns, and to design an interactive map to assist with international climate negotiations.

"It's this theory of hope by doing," she said. "I'm doing my little part."

Peter Kalmus, a climate scientist at the Jet Propulsion Laboratory, began his career searching for gravitational waves in the universe.

"I started feeling a lot of anxiety that I wasn't committing my talents to doing something to stop global heating," said Kalmus, who stressed that he spoke for only himself, not his employer.

After a few years of research in astrophysics, he pivoted to studying the physics of clouds and, later, to using climate models to examine the risks of extreme heat.

(Kalmus has also become an outspoken climate activist who has been arrested for his protest tactics.)

"I'm still kind of angry that, because of policymakers not doing enough to stop global heating, I felt compelled to leave astrophysics and become the climate scientist," he said.

Rising risks

Telescopes must be built in places that are high, dry and removed from light pollution, and they have often ended up in fire-prone places like mountaintops.

So it came as no surprise, in 2013, when a fire reached Australia's Siding Spring Observatory, a sister facility to Mount Stromlo located in a national park in New South Wales.

By then, astronomers had learned some lessons. Employees had maintained the grounds at Siding Spring to keep vegetation away from telescope domes. Flames destroyed some infrastructure, but most of the observatory was spared.

"Bushfires are a normal part of Australia's life," said Céline d'Orgeville, director of the Advanced Instrumentation and Technology Center, a state-of-the-art facility that opened at Mount Stromlo three years after the 2003 disaster. "But in recent years, it's been clear that the frequency and the severity of the fires has increased significantly."

In 2022, a wildfire destroyed several buildings at Kitt Peak Observatory in Arizona. And fires aren't the only danger: In 2020, the giant Arecibo telescope in Puerto Rico collapsed, in part because of repeated stress from hurricanes, according to a 2022 forensic investigation commissioned by the National Science Foundation.

"People have become acutely aware that they actually have to account for climate change when they're going to choose new sites," d'Orgeville said.

Global warming has also had subtler effects on astronomy. Telescopes aim to collect as much light as possible for detailed views of the night sky. But this sensitive work is easily disrupted by atmospheric turbulence, the irregular movement of air, which increases as temperatures rise.

In 2020, a team of scientists analyzed long-term weather data at Paranal Observatory in Chile's Atacama Desert and found that climate-related research complications were increasing.

"It was the first time we did such a thing, and at first, my colleagues were not super happy about it," said Faustine Cantalloube, an exoplanet researcher at National Center for Scientific Research in France who led that study.

Some astrophysicists, she said, worried that the results would suggest Paranal was not a good site for astronomical observations.

She added that more news coverage and public awareness of climate change in recent years has made it easier to discuss climate-related issues. "It's really changed," Cantalloube said. "And I think it's the whole society, actually, that changed."

Taking action

To help preserve their ability to study the stars, astronomers are working to reduce their field's carbon footprint.

A study in 2022 estimated that the observatories, satellites and the other physical infrastructure that astronomy relies on release 1.2 million metric tons of carbon-equivalent greenhouse gases annually, roughly what would be released by the electricity use of 230,000 American homes in a year.

The National Science Foundation's National Optical-Infrared Astronomy Research Laboratory, or NOIRLab, which runs Kitt Peak and other observatories across the Americas, estimated that its facilities and activities emit 12,500 tons of carbon-equivalent emissions each year, or about as much as 2,500 American homes.

In Australia, the power cost of supercomputing, which astronomers use to run simulations and crunch data, is the largest contributor to the field's emissions.

And a study published in April found that the total amount of air travel by researchers to astronomy conferences in 2019 was more than the distance between Earth and the sun.

In 2022, the American Astronomical Society announced a new task force charged with reducing the field's carbon footprint by 50% over the next decade.

Its efforts include improving options for attending conferences virtually and observing through telescopes remotely, changes that began to happen organically during the coronavirus pandemic.

Employees at NOIRLab have also crafted a plan to cut their travel in half by 2027. The money saved from those reductions would be used to invest in more efficient infrastructure, like double-paned windows.

In Chile, NOIRLab plans to install a system of solar batteries that would charge up during the day and power the entirety of the Gemini South telescope, and about 60 per cent of the Rubin Observatory, at night.

A decade ago, Bernadette Rodgers, former head of science operations at NOIRLab's Gemini South, made a significant change of her own: She stepped down from her post and moved to Oregon, where she directs a youth climate activism group called SustainUS.

Rodgers conceded that some scientists consider it irresponsible to involve themselves in political matters, but she argued "the physical world doesn't listen to politicians. It follows its own laws".

That human-caused emissions are disrupting Earth's carbon cycle "is established science," Rodgers added. "There's no risk to scientific credibility to state that emphatically."