Yes, but not in the way you're portraying it. The big shift downwards comes in a major shift in strategy in dealing with forest fires in the early to mid 1900s; it doesn't tell you much about the climate at the time. https://foresthistory.org/research-explore/us-forest-service...
> In 1935, the Forest Service established the so-called 10 a.m. policy, which decreed that every fire should be suppressed by 10 a.m. the day following its initial report. Other federal land management agencies quickly followed suit and joined the campaign to eliminate fire from the landscape.