The imprint of climate within Northern Hemisphere trees

Here we show how the seasonality and strength of climate signals recorded by tree-ring widths changes across the Northern Hemisphere, and outline major regional differences in the climate 'window' sensed by trees that both constrain and augment our ability to interpret these records as paleoclimatic proxies. After surveying nearly 2200 ring-width records, we find the spatial structure of tree-climate relations across the hemisphere matches behavior predicted several decades ago very closely, confirming the principles that guide dendroclimatology are robust despite the complexity of interactions between climate, ecology and tree biology. We also show that climate filtering conducted by individual trees creates major regional differences in information that may be recovered from the hemispheric network. This behavior can introduce geographic biases to dendroclimatic reconstructions, but it also may be useful to evaluate the success of reconstruction techniques that explicitly represent the physical processes linking climate to tree growth.