I would
guess (albeit a guess based on decades of real life experience across several countries) that the instruments are still on the roof (it costs money to remove them) the data and instrument routines are being kept up by a DoD adjacent SIGINT team that look after a forest of antenna, instruments, rack mount IT gear etc, and the data is still going back home to the US.
The literal at embassy upkeep costs for these atmospheric instruments is zero given it's minor work piggybacking on required existing staffed infrastucture that's not going away.
What's probably been cut is the "making it public" part that has a third party contractor take pooled embassy data and put it up on a website for all the world to see.
That needn't be expensive .. but it's been cut all the same.
Of course the US still runs embassy instruments, esp. in 'hostile' locations - seismic to detect tunneling, air quality to detect gassing, radiometric for nuclear hazards, network sanity and canary services to trip digital intrusion, etc. None of that is going away.
> I think a dedicated, secure blah blah network for air quality sensor data is indeed over engineered.
I'm sorry, are you on HN but don't actually have any IT experience?
The dedicated secure high bandwidth network is for the embassy .. a literal US outpost in a foreign potentially hostile land.
It's for secure comms, SCIF to SCIF comms, diplomatic communications, backup for military | intelligence usage.
Air quality and other met data is a trivial low bandwidth data load that could transmit in full on a shitty low baud POTS phone .. there's no issue having an embassy SIGINT officer set and forget a pipe on the existing network infrastructure, their time is paid for, the equipment is there.