A figure showing future annual carbon footprints for astronomical facilities in five illustrative scenarios. The first scenario is called Research as usual, and corresponds to the expected footprint in case that research practices remain unchanged. Research as usual will lead in the best case to no decline of the carbon footprint in the future, and in the worst case to a strong rise of the emissions. Other scenarios include a deep decarbonisation of the economy and/or a freeze in the number of operating facilities, which are measures that would lead to a reduction of the annual carbon footprint. Yet these reductions are far too slow and will not allow limiting global warming to below 1.5 – 2 degrees centigrade. Only a degrow in the number of operating facilities by 3% per year combined with a deep decarbonisation will make astronomical research sustainable.
Replies