The Constitution of the State of Montana, ratified in 1972, affirms Montanans’ inalienable “right to a clean and healthful environment” (State of Montana 1972). Since the signing of the constitution, that declaration has galvanized Montanans to protect the state’s air and water, and to work toward keeping the state free from toxic pollutants. Today, that declaration also means living safely, successfully, and with foresight in a world undergoing climate change. The right to a clean and healthful environment, including issues around climate change, requires that Montanans have access to the best and most relevant scientific information, updated at regular intervals, and consider new discoveries as they become available. The information behind the Montana Climate Assessment reflects decades of peer-reviewed research from Montana’s universities and agencies, new analyses by chapter authors, as well as the insights and observations of resource managers, farmers, tribal community members, and other citizens from across the state. It also builds on research undertaken across the country and around the world. At the end of the day, it is important to understand what climate change means for Montanans now, and how current information will help us make wise decisions for future generations.

The Montana Climate Assessment (MCA) is an effort to synthesize, evaluate, and share credible and relevant scientific information about climate change in Montana with the citizens of the State. The motivation for the MCA arose from citizens and organizations in Montana who have expressed interest in receiving timely and pertinent information about climate change, including information about historical variability, past trends, and projections of future impacts as they relate to topics of economic concern.This first assessment reports on climate trends and their consequences for three of Montana’s vital sectors: water, forests, and agriculture. We consider the MCA to be a sustained effort. We plan to regularly incorporate new scientific information, cover other topics important to the people of Montana, and address the needs of the state.