I'm seeing posts being shared fairly widely that the keynote issue at the first Earth Day was "global cooling".
This simply isn't true, not even a little.
The first Earth Day was prompted by a large oil spill, and the keynote topics were calls for federal oversight of clean air and water. A couple of years later, Nixon and Congress responded with the creation of the Environmental Protection Agency and the Clean Air Act.
The keynote speech delivered by the founder at the first Earth Day gathering was heavy on calls for clean air and water. Mentions of "global cooling" were entirely absent. The text of that speech can be read here:
https://doorcountypulse.com/sen-gaylord-nelsons-earth-day-speech/
While the media has always been spotty-at-best in science reporting, It's simply a myth, unsupported by data, that there was ever a serious concern about "global cooling" among the scientific community. A review of the journals of the day (in the 1970's) shows that there was no such widespread concern. Brian Dunning has a terrific examination of that claim here:
https://skeptoid.com/episodes/4487
There is plenty of room for debate in whether the EPA oversteps legal and Constitutional bounds and a whole host of other related environmental subjects.... but the idea that "Earth Day" was created out of concern of "global cooling" is utter nonsense.