Table 4: The average number of tropical storms across the globe during the August–November period as characterized by the Saffir-Simpson scale simulated by fvCAM2.2 as shown in Figure 10. Percent change is shown in the 4th column relative to the 1990–1999 ensemble average. Student’s test statistic, calculated with 14 degrees of freedom is shown in the 5th column. The last column shows the level of confidence for the rejection of the null hypothesis of no change in the number of tropical storms. The “present” ensemble is forced with 1990–1999 sea surface conditions. The “future” ensemble is forced with sea surface conditions representative of the SRES A1B scenario at the end of the 21st century.

Present no. of tropical stormsFuture no. of tropical stormsPercent changeStudent’s test statisticStatistical significance of change

All named storms62.787.740%11.5 99.9%
Tropical storm25.840.959%6.7 99.9%
Category 120.124.321%3.04 99.5%
Category 28.39.515%1.09 90%
Category 37.910.329%2.24 97.5%
Category 40.52.6387%3.76 99.9%