This is the first time that researchers have attempted to assess the quantity of greenhouse gases produced by the 30,000 astronomers and their working instruments, which are terrestrial radio telescopes, probes and rovers sent into space.

According to initial findings, published Monday in Nature Astronomy, the total activity of these instruments since their commissioning has produced at least 20.3 million tonnes of CO2, the equivalent of the annual carbon footprint of Estonia or from Croatia.

By astronomer, this would represent annual emissions of 1.2 million tons.

A quantity almost “five times higher” than that generated by the air flights of astronomers, when they travel for professional reasons, underlines the study.

"The community of astronomers is currently discussing the reduction of the carbon footprint linked to transport, as well as to the activity of supercomputers", explains to AFP Jürgen Knödlseder, CNRS research director and main author of the study.

"It's good, except that they don't see the elephant in the room: the question of infrastructure".

To assess the size of the "elephant", the researcher sifted through 50 space missions and 40 ground observation facilities: Hubble telescopes, Max Planck, Insight exploration missions (Mars), Rosetta probe (comet "Tchouri "), Very Large Telescope (VLT) in Chile...

"Ivory tower"

Ideally, construction materials, operating costs, electricity consumption should have been taken into account. But these data were often unavailable, sometimes due to a lack of transparency on the part of space agencies, explains Jürgen Knödlseder, who works at the Institute for Research in Astrophysics and Planetology in Toulouse.

To fill these gaps, his team used a method developed by the Ademe (Environment and Energy Management Agency) and the Carbon Balance Association (ABC): the so-called monetary ratios method, according to which the carbon emissions of an activity are proportional to its cost and mass.

Computer-generated image of the James Webb Telescope, transmitted by Astrium on October 20, 2009 ASTRIUM HO/ ASTRIUM/AFP/Archives

Thus, according to their calculations, the James Webb space telescope, worth 10 billion dollars, and the future giant radio telescope "Square Kilometer Array", in South Africa and Australia, would be alone responsible for the equivalent at least 300,000 tons of CO2.

“We have to think about reducing the greenhouse gases of our infrastructures,” says Jürgen Knödlseder.

And "everyone has to do their part, including astronomers who are not in an ivory tower," commented Annie Hughes of the Max Planck Institute, one of the study's authors, during a press conference.

"Slow down the machine"

"I know this may be shocking, but we have to slow down the machine if we want to reduce emissions by almost 50% by 2030," said his colleague astronomer Luigi Tibaldo.

"Like any activity, astronomy has a significant carbon footprint, our challenge is therefore to slow down the construction of infrastructures while continuing the search for excellence", estimated Éric Lagadec, president of the French Society of Astronomy and Science. astrophysics, which did not participate in the study.

General view of one of the SKA telescopes in South Africa, in Carnarvon, in July 2018 MUJAHID SAFODIEN AFP/Archives

But the methodology is much debated: the estimate by monetary ratios generates a high margin of uncertainty (up to 80%), which can "damage the credibility of the results", writes Andrew Ross Wilson in a commentary published in margin of the study.

"Failing to have the details of what an installation consumes, they calculated + at random +", is surprised for her part astrophysicist Françoise Combes, from the Paris-PSL Observatory.

Who also disputes the fact of having divided the overall cost by the number of astronomers: "When you build an observatory, it's for science, it benefits millions of people! It's as if you were dividing the cost of an opera only by those who go there", comments the scientist.

"The method is debatable, but the approach is a first step which has the merit of leading to reflection", concludes Éric Lagadec.

© 2022 AFP