[GS] [1.0.0.290] CO2 level reduced for no reason

[bbufa]

Turn 604, as below pictures: when I do anything (move units, send trade routes) or even do nothing, the World Climate panel changes immediately, CO2 level reduced from 7452 to 301. No one else reached future era civic to run CO2 recapture project, why the CO2 dropped dramatically in just 1 click?
I attached turn 603 and 604 auto-save files.