Coincident temporal variation in the abundances of spatially separated populations, called spatial synchrony, has been detected in species of insects, fish, mammals, protists and many other taxa, spanning distances up to hundreds of kilometers. This ubiquitous phenomenon is a crucial component of population dynamics. It is also of primary importance to ecosystem functioning and services if the populations are pests, diseases, or harvested or threatened species. The components of dynamics that drive ecosystem services of species located in different locations are generally the synchronous ones. Non-synchronous components of dynamics disappear in the spatial average, by the central limit theorem. So the nature of synchrony will often be more important than local dynamics themselves. In spite of the importance of synchrony, changes in synchrony and potential impacts of climate change on synchrony are little studied. Climate change constitutes not just warming, but also changes in other statistical characteristics of environmental signals. Synchrony can also be transmitted through trophic interactions - e.g., synchronized predator populations can induce synchrony in prey. But the extent to which climate-induced changes in synchrony may cascade through complex species interaction networks via this mechanism is unknown. These gaps in knowledge probably result from historic difficulties in identifying specific climatic drivers of population synchrony, which in turn prevented research on possible impacts climate change could have on synchrony if it modifies these drivers. But recently a variety of novel statistical, experimental and modeling techniques have been developed, and researchers have begun exploring the causes of synchrony, secular trends and regime shift in synchrony, and the climatic and other reasons for such changes. Methods used are disparate, including matrix regression methods, wavelet statistics, laboratory experiments, spatial statistics, and linear and nonlinear models and fitting of models with data. Existing approaches examine different aspects of the overall characterization of synchrony. This symposium will help synthesize these methods as well as the ecological insights of a variety of researchers to produce an overall improvement in approaches to general questions such as 1) how is synchrony changing and why, and how might humans be responsible for this? 2) what is the detailed structure of synchrony, and what can we learn about population interactions from this structure? 3) how do changes in synchrony affect the larger ecosystem of which the focal species is a part, and human concerns that interact with that ecosystem?