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�I P ari dl.. I m un p ac s o rii a'111 d,.. H abi n't ncreased concentrations of carbon dioxide and other greenhouse gases in the atmosphere generate complex dynamics that are reflect- ed in changes across the globe, but are likely to be regional in their impact. Atmospheric concentra- tions of greenhouse gases will influence temperature and precipitation patterns as well as hydrology, and feed into the complex dynamics regulating biologi- cal systems. In this chapter, we discuss some of the regional projections of temperature, precipitation, and sea level rise in the Southeast under climate change, and we highlight the available research on potential impacts to terrestrial and aquatic species. 2 ,u 1 �111� "�!�IUIIP'nC h1111n�I�es 11i"nI ithfir° Soi!,llrilheX111`rt As reported by the U.S. Global Change Research Program (Karl et al. 2009), the annual average temperature across the Southeast region has risen by approximately 2 °F since 1970, with the great- est increase during the winter months (Table 2 -1). Freeze days have declined by 4 -7 days per year for most of the region over this time period. Climate models project continued warming across the South- east, with an increasing rate of warming toward the end of the century. Rates of warming are expect- ed to be more than double those experienced in the Southeast since 1975. The greatest tempera- ture increases are projected to come during already hot summer months, and the number of very hot days is projected to rise at a greater rate than the average temperature. Different emissions scenarios lead to different projected temperature increases (Karl et al. 2009). Under a low emissions scenario, average tempera- tures in the region are projected to rise by about 4.5 °F by the 2080s, while a higher emissions scenar- G'1(,uixk' "ff}.4f f}P' fZ "k'(fit6' "ll %',6' "(4}4 (k'" to ,, / / //l' !r(9k //l` „` Falk "l'E'i "' 4ri/ r (� /6l / / % //c`'{ /6 /r,rn :1,, E "'ll'!! / , ") Ill,%/% %cr r,r lit /y ho/ to Table 2 -1. Observed temperature changes in the Southeast summarized for two different time peri- ods. Average temperature declined from 1901 to 1970 and then increased strongly from 1970 - 2008 (Source: Karl et al. 2009). io yields about 9 °F of average warming and a much higher heat index. For the same time period, the number of days per year with peak temperatures over 90 °F is expected to rise significantly, especially under a higher emissions scenario (Figure 2 -1). This increase in very hot days will have consequences for human health, drought, and wildfires. As tempera- tures rise, the number of days below freezing will also decrease (Figure 2 -2). A reduction in freezing days can improve survival for disease vectors and pests, alter growing seasons, and reduce the amount of water available from snow pack for spring thaw. Average Change in Temperature in the Southeast Temperature Change in T 1901 -2008 1970 -2008 Annual 0.3 1.6 Winter 0.2 2.7 Spring 0.4 1.2 Summer 0.4 1.6 Fall 0.2 1.1 io yields about 9 °F of average warming and a much higher heat index. For the same time period, the number of days per year with peak temperatures over 90 °F is expected to rise significantly, especially under a higher emissions scenario (Figure 2 -1). This increase in very hot days will have consequences for human health, drought, and wildfires. As tempera- tures rise, the number of days below freezing will also decrease (Figure 2 -2). A reduction in freezing days can improve survival for disease vectors and pests, alter growing seasons, and reduce the amount of water available from snow pack for spring thaw.