The imperative to reduce carbon emissions in astronomy
  For astronomers to make a significant contribution to the reduction of
climate change-inducing greenhouse gas emissions, we first must quantify our
sources of emissions and review the most effective approaches for reducing
them. Here we estimate that Australian astronomers' total greenhouse gas
emissions from their regular work activities are $\gtrsim$25 ktCO$_2$-e/yr
(equivalent kilotonnes of carbon dioxide per year). This can be broken into
$\sim$15 ktCO$_2$-e/yr from supercomputer usage, $\sim$4.2 ktCO$_2$-e/yr from
flights (where individuals' flight emissions correlate with seniority), $>$3.3
ktCO$_2$-e/yr from the operation of observatories, and 2.6$\pm$0.4
ktCO$_2$-e/yr from powering office buildings. Split across faculty scientists,
postdoctoral researchers, and PhD students, this averages to $\gtrsim$37
tCO$_2$-e/yr per astronomer, over 40% more than what the average Australian
non-dependant emits in total, equivalent to $\sim$5$\times$ the global average.
To combat these environmentally unsustainable practices, we suggest astronomers
should strongly preference use of supercomputers, observatories, and office
spaces that are predominantly powered by renewable energy sources. Where
facilities that we currently use do not meet this requirement, their funders
should be lobbied to invest in renewables, such as solar or wind farms. Air
travel should also be reduced wherever possible, replaced primarily by video
conferencing, which should also promote inclusivity.
