The nearly carbon‑neutral conference (NCNC) concept outlined by Ken Hiltner (2018) offers several clear advantages: outreach and inclusion, no need to ration attendance, and less carbon. I would suggest one modification to the arrangements Ken described: the Q&A might be best conducted using online chat rather than shuttle email and limited to say two days rather than extended over several days or weeks.
In which case, this community should consider establishing a private Mattermost server (MIT license server‑side and analogous to Slack) and a private Nextcloud server (AGPL‑3.0 license), the latter for persistent presentations, associated documents, and any online collaborative editing. Both services run client‑side using current web‑browsers (including Firefox) so the local admin overhead is zero. Mattermost also offers dedicated clients (Apache‑2.0 license) for those who prefer instead to run local apps on mobile devices and laptops (Linux included).
On air travel more generally, Marks (2019), despite the upbeat title of the article, makes very similar points to @bmcm in his November 2018 blog. The airline industry (through CORSIA) has finally opted for voluntary financial offsetting for post‑2020 emissions growth as its flagship response to our climate emergency. Such measures are totally inadequate under current carbon pricing and derelict in terms of burden sharing. Better also would be a moratorium on new public-financed climate damaging infrastructure like airports until comprehensive, realistic, and fair solutions can be determined and agreed.
Hiltner, Ken (2018). A nearly carbon-neutral conference model — White paper/practical guide. Ken Hiltner website. Santa Barbara, California, USA.
Marks, Paul (2 January 2019). Our addiction to flying is ruining the climate, but it doesn’t have to. New Scientist. London, United Kingdom. Print title: Green sky thinking. Paywalled.