The End of the Southeastern United States "Warming Hole"

The term “warming hole” has been applied to a region in the Southeastern United States where there are negative temperature trends over the historical record beginning in 1895. This area shows up as a negative anomaly in temperature trend maps used in historical climate studies such as the National Climate Assessment series, which cover the period from 1895 to the ending year of each study. However, much of this negative trend occurred in the period from roughly 1930 to 1970, when the annual average temperature of Southeastern observing stations was decreasing due to factors such as changing land cover and the presence of increased human-produced aerosols that reduced incoming sunlight. Since that time, the Southeast has warmed at a rate equal to or even greater than other areas of the continental U.S., so the term “warming hole” is no longer appropriate for this region. This presentation will explore whether the use of long time series to define regional climate is appropriate when there are significant changes to the factors that are driving climate variability over the period of record.