Abstract Summer maximum temperatures () in the Sierra Nevada have risen rapidly since the turn of the 20th century, especially above 1,500 m where trends in the south exceed 3°C century −1 . To place this warming into context, we developed a 504‐year reconstruction of growing‐season (April–September) (1520–2023 CE) from blue‐intensity and maximum latewood‐density data at nine high‐elevation conifer sites. The model explains 60% of instrumental variance () and shows that the 20th–21st centuries were the warmest of the past five. The warmest year is 2021 (+2.38°C), while four of the five coldest years coincide with major volcanic eruptions. Since 1980, mean summer increased 1.14°C (; 0.026°C yr −1 ), concurrent with declining PDSI and a threefold rise in compound hot–dry‐fire years. Dynamic regression suggests a shift from snowpack‐buffered to temperature‐dominated soil‐moisture regimes after 1900. These results show that post‐1980 warming and unprecedented compound extremes mark a new era of temperature‐driven ecological vulnerability in the Sierra Nevada.
Harley et al. (Mon,) studied this question.