How to reduce the carbon footprint of Earth and Space Science? Potential strategies based on a comprehensive greenhouse gas budget for five French labs

To maintain global warming below 1.5°C the last IPCC report indicates global greenhouse gas (GHG) emissions should be reduced by 45% and 80% before 2030 and 2050, respectively, reaching an average of 2tCO2e.pers^-1.yr^-1 on Earth. Recent estimates of the carbon footprint of universities and research centers accounting for indirect emissions often exceed 10tCO2e.pers^-1.yr^-1.

Here we find similar or higher values (10-30tCO2e.pers^-1.yr^-1) for the year 2019 for five research labs encompassing the solid Earth and the environment, the superficial biosphere, oceanography and glaciology, atmospheric physics and chemistry, and astronomy and astrophysics. These values are derived through a common procedure (see Mariette et al., 2022) in which any activity data quantifying the usage of a given resource (e.g., in kWh or km) is multiplied by an appropriate emission factor quantifying the unitary carbon footprint of the resource (e.g., electricity production or air travel). Our budget quantifies the share of emissions from local facilities (about 1tCO2e.pers^-1.yr^-1), lunch meals and commuting (about 1tCO2e.pers^-1.yr^-1), professional trips (2-6tCO2e.pers^-1.yr^-1), services and equipment (3-5tCO2e.pers^-1.yr^-1), and the use of observational data from research infrastructures, in particular scientific satellites (up to 10tCO2e.pers^-1.yr^-1; derived similarly to Knödlseder et al., 2022).

These numbers imply radical changes to make scientific activity sustainable and have strong implications on potential strategies to reduce GHG emissions. For example, a predominant discussion in the literature in the past years focused on avoiding air travel. However, in our case, shifting all national travels to train or halving the number of plane trips would reduce the total emissions by a fraction only. Similarly, any strategy targeting local building efficiency or individual habits will little influence the budget. In contrast, reducing or changing practice for services and equipment may have stronger impact but requires collective thinking, especially for research infrastructures that are planned and managed at national and international levels.

The sheer magnitude of our GHG emissions questions the degree of reduction that can be achieved without redirection of scientific activity. We present and discuss examples of changes such as shifting to interdisciplinary research including social sciences, focusing on archived data, relocating field work, or engaging more with students and society.