Figure 5. Anomalies in global average annual temperature from the 1958-77 mean derived from radiosonde data for the period 1958-92 and shown here for (top) the lower stratosphere (16-20 km) and (bottom) the tropopause region (9-16 km) [Source: J.K. Angell, NOAA]. The recent upward temperature spike for the lower stratosphere was a result of the Mt. Pinatubo eruption.