Recent Climate Change in the High Elevations of the Southern Appalachians

Island species are often vulnerable to environmental change because the ecosystems are small and isolated. In a similar way, mountain peak ecosystems are isolated and may be referred to as “sky islands.” The southern Appalachian range provides an interesting case study with deciduous broadleaf tree species at elevations below 1500 meters above sea level, evergreen boreal species becoming common at elevations higher than 1500 meters above sea level, and other rare ecosystems known as grassy balds that include alpine tundra species. Past studies suggest that the southeastern United States, which includes the southern Appalachians, is one region on the planet that may have experienced cooling since the beginning of the twentieth century. However, because many weather stations are located in low-elevation sites, a closer look at high-elevation observations is valuable. Monthly summaries from the Global Historical Climatology Network spanning 1976-2014 indicate that statistically significant warming trends are present for minimum temperature, maximum temperature, mean temperature, extreme minimum temperature, and extreme maximum temperature at elevations above 1000 meters. Both daily and annual temperature ranges appear to be decreasing with the largest trend increases present in minimum and extreme minimum temperatures during winter months. For example, minimum temperatures for January warmed by 5.73 °C over the study period. Most significant warming trends are present for stations positioned 1000-1500 meters above sea level. Significant trends for stations located at 1500 meters or higher were less common. Increases in autumn and spring snowfall totals at those highest elevations may be a contributing factor.