An international team of astronomers has determined the extent to which astronomical facilities – namely, the telescopes on Earth and in space that astronomers use to study the sky – contribute to climate change. Reporting in natural astronomythe team estimates that this footprint outperforms all other research-related activities, a finding that has significant implications for the future of the field.

The researchers felt motivated to conduct the study by current events: “Humanity is facing a climate emergency,” says team member Annie Hughes (Max Planck Institute for Astronomy, Germany). “The scientific evidence is unequivocal that human activity is responsible for modifying the climate. The scientific evidence is equally clear that we must change our activities in the next decade.”

Astronomers, like everyone else, have carbon traces. This used term can have subtly different definitions; In this case, Jürgen Knodelsder (University of Toulouse, France) and colleagues define it as the total greenhouse gas emissions of a facility over its life cycle. Emissions consist mostly of carbon dioxide and methane but include a number of other heat-trapping gases as well.

The general lack of data makes it difficult to determine how much astronomers contribute to greenhouse gas emissions. Previous studies focused on research-related activities such as traveling to conferences and using supercomputers. But the new study finds that the biggest source of astronomy’s carbon footprint is the construction and operation of increasingly larger telescopes.

Due to a lack of accurate data, often due to confidentiality issues, the team came to this conclusion using a technique called Economic Input and Output Analytics. Carbon emissions are determined primarily by cost and/or weight. Knödlseder compares the process to fueling a car: filling the tank fully instead of halfway will double its weight. Doubling the fuel would cost twice that and produce twice the emissions.

Using this input-output analysis, the team calculated that over their life cycles current astronomy facilities produce the equivalent of 20 million tons of carbon dioxide equivalent, with an annual emission of more than one million tons of carbon dioxide equivalent.

“To give you some perspective,” Knudelsder notes, “this is the annual carbon footprint of countries like Estonia, Croatia or Bulgaria.” Another piece of perspective: In 2019 the United States contributed more than 6.5 One billion tons of carbon dioxide.

It’s a start

Knodelsder says the cost/weight data has the benefit of being publicly available, although it can sometimes be difficult to find. This makes absolutely any type of calculation possible. But Andrew Ross Wilson (University of Strathclyde, UK), who wrote the accompanying perspective article for natural astronomysays the method is not commonly used in carbon accounting, especially for space activities.

“He found that the use of economic input-output methods . . . greatly overestimated the overall environmental impacts.” The reasons are numerous: First, the aerospace industry, which is often state-funded, is not a truly free market. Also, materials often cost Made-to-order used in space missions is more due to research and development rather than manufacture.

“As such, the European Space Agency (and others) have created a new process database to more accurately fill these gaps and do not recommend the application of economic input and output databases to space life-cycle assessments,” Wilson says.

Nodelsider’s team acknowledges these caveats, but argues that providing these initial estimates is a critical first step. The next step is for utilities to conduct their own, more detailed analyzes – and then take action.

Wilson agrees, saying, “I think Knodelsider’s assessment is a fairly appropriate approximation of the first order due to the lack of data that was available to him and his team.” “It’s definitely a good first step for more detailed assessments.”

But he warns, “I am not convinced that any practitioner in space life-cycle assessment would specifically use this finding to inform their own analyzes. The ESA would certainly not look twice at this estimate.”

slow flag

However, Knodelsider’s team argues that even approximate numbers are the basis of the work: “The solutions are in our hands, we just need to be able to accept them,” says team member Luigi Tibaldo (Institute for Research in Astrophysics and Planetary Science, France).

The first step is to convert existing facilities from fossil fuels to renewable energy sources, an effort already underway in many places. There are still difficulties for telescopes at remote locations, since they are not usually connected to the local power grid. The Atacama Large Millimeter / submillimeter range in Chile, for example, is powered by diesel generators. It may be easier to incorporate other facilities into ongoing methodological changes.

The team says these measures will not be enough. Astronomers must also slow the pace of building new facilities. The benefits extend beyond reducing emissions, because “slow science” would give us more time to make full use of the data we already have. Certainly, the entire PhD theses were searched using only the archived notes.

Jennifer Wiseman, chief scientist for the Hubble Space Telescope project, agrees on the value of the archival data. “We’ve made the Hubble data archive so powerful that at least as many scientific papers are published these days based on archival data as from new observations,” she says. “This means good, multiple uses of data that will be available for many years to come.”

But many astronomers object to the slowdown. In fact, some members encountered resistance from colleagues even before the paper was published.

“There’s nothing that says astronomy can’t or won’t transition to renewables along with the rest of the economy,” says John Mather (NASA’s Goddard Space Flight Center), James Webb Space Telescope project scientist. “The carbon footprints that are computed are not constants of nature, they are just estimates of a part of a system governed by feedback loops.”

Mather also raises a counter-argument for slowing the pace of science: “Some types of astronomy are already made difficult or impossible due to light pollution, radio interference, and satellite constellations,” he says. “It could be argued that we must increase our efforts to learn everything we can, as soon as possible, before we can.”

Nevertheless, the team remains firmly in its position: “Fighting climate change is a collective challenge, and everyone, every sector of activity and every country, must contribute to meeting this challenge,” Knudelsider says. “In the fight against climate change, there are no priority solutions; we have to activate all possible levers to reduce our emissions. Of course, some actions will be more efficient than others, but we need all of them in order to succeed.”

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