Temperature
At the end of the 21st century, the annual warming over the Antarctic continent is moderate but significant (Figure 11.21; Table 11.1; Chapman and Walsh, 2006). It is estimated to be 2.6°C by the median of the MMD-A1B models with a range from 1.4°C to 5.0°C across the models (Table 11.1). Larger (smaller) warming is found for the A2 (B1) scenario with mean value of 3.1°C (1.8°C). These warming magnitudes are similar to previous estimates (Covey et al., 2003). The annual mean MMD model projections show a relatively uniform warming over the entire continent (with a maximum in the Weddell Sea) (Figure 11.21; Carril et al., 2005; Chapman and Walsh, 2006). They do not show a local maximum warming over the Antarctic Peninsula. This is a robust feature among the individual models (Supplementary Material Figure S11.12). Thus, the pattern of observed temperature trends in the last half of the 20th century (warming over the Antarctic Peninsula, little change over the rest of the continent) is not projected to continue throughout the 21st century, despite a projected positive SAM trend (see Section 10.3). It has been argued that two distinct factors have contributed to the observed SAM trend: greenhouse gas forcing and the ozone hole formation (Stone et al., 2001; Shindell and Schmidt, 2004). Their relative importance for the peninsular warming is not readily understood (see Chapter 10).
The mean antarctic temperature change does not show a strong seasonal dependency; the MMD-A1B ensemble mean winter (summer) warming is 2.8°C (2.6°C) (Table 11.1; Supplementary Material Figure S11.29; Chapman and Walsh, 2006). This is also illustrated by how close the Tebaldi et al. (2004a) 5 to 95% confidence interval for the two seasons is: 0.1°C to 5.7°C in summer and 1.0°C to 4.8°C in winter (Supplementary Material Table S11.2). However, over the Southern Oceans, the temperature change is larger in winter/autumn than in summer/spring, which can primarily be attributed to the sea ice retreat (see Section 10.3).