Astronomical research has as much impact on emissions as a country like Malta

We know today that space is not free from all pollution and that nearly 10,000 tons of space debris are wandering above our heads. A problem that space agencies are now looking into. But if they have their eyes turned to the sky, the climate emergency now also requires them to have their feet on the ground and to reduce the carbon footprint of astronomy research infrastructures to meet the commitments of the Paris Agreement on climate change.

And they are not the least since the overall production of greenhouse gases produced by the activity of around fifty space missions and around forty ground observatories since their creation has been estimated at around 20 million tons of carbon dioxide equivalent.

This is in any case the conclusion of a study carried out by Jürgen Knödlseder, astrophysicist within the Institute for Research in Astrophysics and Planetology of Toulouse and published in the magazine Nature Astronomy. It was while wanting to calculate the greenhouse gas emissions of his own laboratory that this scientist said to himself that he could not limit himself to the air travel of his members or the energy expenditure for heating buildings.

“But the weight of all the observation data that we use to do our research was missing”, explains this CNRS research director who has decided to widen his field of study to all the activities of the 30,000 astronomers and their instruments on earth or in space, the Hubble telescope, the Rosetta probe and the Very Large Telescope installed in Chile.

To arrive at an estimate of their carbon weight, he used the method of monetary ratios, which makes it possible to link carbon emissions to the cost of an activity. “It’s an official method for making the carbon footprint, it’s not very precise but it’s an estimate of the order of magnitude,” explains Jürgen Knödlseder. It was then necessary to find the cost of the observatories, which was not easy because if some are transparent, this is not the case for all.

Lack of data transparency

This is how he arrived at the figure of 20.3 million tonnes of emissions. “For one year, this represents 1.2 million tonnes emitted each year, which is roughly the emissions of Malta or Estonia. It is far from trivial. We divided it by the number of astronomers around the world, we arrive at 36.6 tons per astronomer and per year. When we know that the average per French person is around 10 tonnes and that in 2030 we must have halved and be at 5 tonnes, we see that there is a problem, ”insists the astrophysicist who hopes to take awareness of the scientific community.

Figures that raised questions, but also criticism from some of its members who felt that the method of monetary ratios had too high a margin of uncertainty since it is around 80%.

“It’s the only thing we can do today as a calculation method because we don’t have access to more detailed data. Each observatory should make more precise analyses, but also publish them. We want transparency for a real scientific debate. We have total responsibility for this carbon footprint and we are the only ones to have a lever on it to reduce it by doing things differently”, pleads Jürgen Knödlseder for whom we must aim for decarbonization.

Slow down the construction of telescopes?

This can involve supplying infrastructures with photovoltaic or wind power. There are precursors in this area, such as the ESO, the European Southern Observatory, which is reducing its footprint by using solar panels, electric vehicles or by reducing the movement of its members. He announces that he wants to reduce his emissions by 15%. “But ESO is building the Extremely Large Telescope which is the size of the Colosseum in Rome and they’ve done the carbon footprint of building it. When we add that of its operation, we realize that these additional emissions due to this new telescope will destroy all the reductions they have made on the other side. With one foot you brake, and with the other you accelerate”, laments the researcher involved in the Labs 1point5a collective of members of the academic world committed to understanding and reducing the impact of scientific research activities on the environment.

In the conclusion of his study, one thing is clear: certainly we must decarbonize as much as possible “but we must also slow down the construction of new telescopes”. A position that has struggled to pass at a time when many development projects are underway and technology is constantly evolving.

“There is a lot of data that exists, we can still do a lot of things with those that are in the archives. In a competitive system, we will not be able to solve the problem of global warming. There is no imperative that tells us to go at such speed, nothing tells us to do so and nature even tells us to slow down. We also need to change our narrative a little and put other values ​​at the center of our activities,” concludes Jürgen Knödlseder.


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