Atmospheric concentrations of CO2 began a marked increase that coincides with the Industrial Revolution of the late 1800s. CO2 levels rose by more than 20% in the 50-year period 1958–2008. CO2 Program of the Scripps Institute of Oceanography, scrippsco2.ucsd.edu. A 2014 assessment of the magnitude and direction of ongoing climate changes in Yellowstone National Park showed that recent climatic conditions are already shifting beyond the historical range of variability. Ongoing and future climate change will likely affect all aspects of park management, including natural and cultural resource protection as well as park operations and visitor experience. In order to deal with the predicted impacts, effective planning and management must be grounded in concrete information about past dynamics, present conditions, and projected future change. Some effects are already measurable. Warmer temperatures are accelerating the melting of mountain glaciers, reducing snowpack, and changing the timing, temperature, and amount of streamflow. These changes are expected to result in the loss or relocation of native species, altered vegetation patterns, and reduced water availability in some regions. Wildfire seasons have expanded, and fires have increased in severity, frequency, and size. More acres burned in the fire season of 2016 than in any year in the last century, except for 1988. Conditions that favor outbreaks of pests, pathogens, disease, and nonnative species invasion occur more frequently than in the recent past. In Alaska, melting sea ice threatens marine mammals as well as coastal communities, while thawing permafrost disrupts the structural basis of large regions, jeopardizing the physical stability of natural systems as well as buildings, roads, and facilities. Rising sea levels, ocean warming, and acidification affect wildlife habitat, cultural and historic features, coastal archeological sites, and park infrastructure, resulting in damage to and the loss of some coastal resources. Some studies suggest that extreme weather events such as thunderstorms, hurricanes, and windstorms that damage park infrastructure and habitat are increasing in frequency and intensity. Climate change will manifest itself not only as changes in average conditions, creating a “new normal,” but also as changes in particular climate events (e.g., more intense storms, floods, or drought). These extreme climate events may cause widespread and fundamental shifts in conditions of park resources.
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