This topic has been discussed in numerous posts. This report is worth a look: Forest fires in Sierra Nevada driven by past land use. It will not come as a surprise to people who have traced the Indian use of fire in the Sierras and more recent actions/policies.
“We were expecting to find climatic drivers,” said lead co-author Valerie Trouet, a UA associate professor of dendrochronology. “We didn’t find them.”
Instead, the team found the fire regimes corresponded to different types of human occupation and use of the land: the pre-settlement period to the Spanish colonial period; the colonial period to the California Gold Rush; the Gold Rush to the Smokey Bear/ fire suppression period; and the Smokey Bear/fire suppression era to present.
That said, drought is certainly a factor in the current and expanding die-off of pines in the Sierras, but that may not be a climatic change.