The Earth System Models (ESMs) used to make climate projections are continually becoming more sophisticated, and now incorporate a wide range of terrestrial processes. However, some potentially important processes are still omitted because they are either poorly understood or not quantified well enough to warrant inclusion. One such process is the decrease in sensitivity of photosynthesis and respiration to temperature that occurs after plants are given time to adjust, or acclimate, to a temperature change. This process, termed temperature acclimation, could critically influence projections of atmospheric CO2 increase by altering the amount of CO2 taken up by plants in a future, warmer world. This project will support a series of field measurements designed to quantify the potential of a variety of plant species (grasses, trees, crops) from a variety of biomes (tropical, temperate, and boreal) to acclimate to different temperatures. Species will be measured at pairs of sites that lie at different latitudes and, thus, have different growing season temperatures. Measurements at the different sites will be compared to assess the ability of each species to acclimate to the different temperatures. These field measurements will supplement a larger dissertation project designed to improve climate projections through the creation of temperature acclimation formulations suitable for ESMs.