Late Pleistocene glacial and lacustrine fluctuations preserved some of the best and most dramatic evidence of climate change on the continents. Unfortunately, paleoclimatic interpretation of those records has long been hampered by the mutual dependence of both hydrologic systems on temperature and precipitation, that is – glaciers and closed-basin lakes increase in size in response to decreased temperature as well as increased precipitation. Researchers have therefore typically relied on uncertain assumptions about one of these variables in order to infer changes in the other. In this study we show that reconciliation of glacial and lacustrine records by itself provides a means of constraining both temperature and precipitation. This is possible because each system has different relative sensitivity to those primary climatic variables. To convert the geologic record of changes in the glacial and lacustrine records to paleoclimatic constraints, we used physically-based models of the glacial and lacustrine systems to identify combinations of climatic conditions that could reproduce the changes preserved in the geologic record. The glacier model is a spatially distributed snow- and energy-balance model loosely coupled to a vertically integrated 2-D glacier flow model. It specifically addresses the need for a model that can reproduce not only the larger, easily estimated shapes of the last glacial maximum, but also the much more complex ice distributions of the latest Pleistocene. We used a Thornthwaite water balance model to estimate the sensitivity of the lacustrine system to climate change, as it is dominated by climatically induced changes in evapotranspiration and runoff. Applying this dual-system modeling approach to the glacial-pluvial record in the Owens Valley, we find that temperatures were ~6 degrees C colder during the last glacial maximum (LGM) but had warmed by about 4 degrees C, from that low, by about 13 thousand years ago, well before the onset of the Holocene. More significantly, we conclude that LGM precipitation was probably no more than 25 to 50 percent greater than today and that the increased precipitation continued, with intermittent dry periods, until the end of the Pleistocene.