One of the most significant consequences of climate warming is the likely change in streamflow as a result of warming air temperatures. Hydrologists have responded to the challenge of understanding these effects. Many recent studies quantify historical trends in streamflow and usually attribute these trends to climate warming, via altered evapotranspiration and snowpack (Figure 1.a). However, without questioning the fundamental reality of a warming climate, hydrologists should also consider biotic and social processes whose omission may produce misleading interpretations about climate change effects on hydrology. The aim of this commentary is to raise awareness of ecological and social processes that may confound the interpretation of climate effects on hydrology, to review how the geographic context of streamflow records affects interpretation of the climate signal, and to suggest a 'checklist' of working hypotheses that can be used to structure studies of streamflow responses to climate change. A wide variety of trends in streamflow have been detected and attributed to climate change and variability, but a few themes dominate the literature. The most common studies report earlier snowmelt, a shift to earlier streamflow timing, altered spring maximum flows, and/or intensified summer drought (Adam et al.