Reversals in Temperature‐Precipitation Correlations in the Northern Hemisphere Extratropics During the Holocene

Future precipitation levels remain uncertain because climate models have struggled to reproduce observed variations in temperature‐precipitation correlations. Our analyses of Holocene proxy‐based temperature‐precipitation correlations and hydrological sensitivities from 2,237 Northern Hemisphere extratropical pollen records reveal a significant latitudinal dependence and temporal variations among the early, middle, and late Holocene. These proxy‐based variations are largely consistent with patterns obtained from transient climate simulations (TraCE21k). While high latitudes and subtropical monsoon areas show mainly stable positive correlations throughout the Holocene, the mid‐latitude pattern is temporally and spatially more variable. In particular, we identified a reversal from positive to negative temperature‐precipitation correlations in the eastern North American and European mid‐latitudes from the early to mid‐Holocene that mainly related to slowed down westerlies and a switch to moisture‐limited convection under a warm climate. Our palaeoevidence of past temperature‐precipitation correlation shifts identifies those regions where simulating past and future precipitation levels might be particularly challenging. Plain Language Summary Predicting future precipitation levels reliably is more challenging than predicting temperature change. Accordingly, we need to understand the relationship between temperature and precipitation and its changes in space and time. We used climate proxy‐data derived from 2,237 pollen records from lake sediments and peats from the Northern Hemisphere extratropics for the early, middle, and late Holocene (i.e., 12,000–8,000, 8,000–4,000, 4,000–0 years before present, respectively). Our results reveal a significant latitudinal dependence and temporal variation of the temperature‐precipitation relationship. These proxy‐based variations are largely consistent with patterns obtained from simulations using climate models. While high latitudes and subtropical monsoon areas show mainly stable positive correlations throughout the Holocene (i.e., warm conditions co‐occur with wet conditions), the mid‐latitude pattern is temporally and spatially more variable. In particular, we identified a reversal to negative temperature‐precipitation correlations in the eastern North American and European mid‐latitudes from the early to middle Holocene. We hypothesize that weak westerly circulation, warm climate, and climate‐soil feedbacks limited ev