With NIME moving to a hybrid format, video conferencing and communication will be essential for the conference. Additionally, the spread of COVID-19 has meant that the already established practice of everyday video conference calls has increased manyfold. While the carbon footprint of video calls is often significantly lower than that of non-local in-person meetings, a number of parameters can be considered in choosing the least polluting technologies and practices. Additionally, there have been a few privacy concerns related to Zoom in the past .
What is the carbon footprint of a video call?
What parameters determine the footprint of video calls?
What are the different alternatives for video calls?
How does the footprint of video calls relate to that of travel?
The energy efficiency of the internet has been roughly doubling every two years .
Video calls use 250 MB - 1.3 GB of data per participant per hour, depending on the quality .
The most recent reputable peer- reviewed estimate of the energy intensity of the internet found an average of 0.06 kWh per GB for 2015. Assuming that it is still halving every 2 years, it would now be around 0.015 kWh/ GB .
The German grid carbon footprint is (2018) 0.4690 kgCO2e per kWh . Use link  to find the footprint of most countries.
One hour of video conferencing, then, is between 0.0018 and 0.0091 kgCO2e per hour of video conferencing.
Based on these numbers, a rough calculation of the relationship between virtual and physical attendance for one person from Berlin for NIME 2021 in Shanghai:
Estimated CO2 footprint
Videoconference 8hr a day for 4 days (8 * 4 * 0.0091)
0.292 kg of CO2e
Flight from Berlin to Shanghai
2.53 tonnes of CO2e
Self-hosting: By self-hosting the conference tools for NIME, we can choose a green provider rather than relying on servers beyond our control.
Jami: Recieves a high envorinmental score in  but seems to be in its infancy and may not be reliable enough for NIME. Another positive aspect of Savoir-faire Linux, (the company developing Jami) is a general Commitment toward a "sustainable economy based on cooperation and knowledge" .
Kopano Meet: Open source peer to peer video conferencing with paid options available (paid edition provides access to a hosted turn service). The company Kopano does not provide environmental statements, but Meet is mostly implemented in Golang which provides a small memory footprint.
Big Blue Button: Allows for selfhosting, and has features for limiting the need for screensharing (thus limiting bandwidth) by sharing the pdf slides to each participant's computer, rather than having to screen share.
Use optical fiber wifi rather than cellphone data: I haven't been able to find conclusive research, but  suggests that watching a video on the old 3G cellular network consumes 50 times more energy than on a wifi served by optical fiber cables.
Consider turning off your video when conferencing.
Lower the resolution of the video.