Global mean surface temperatures during 1993 were virtually unchanged from their 1992 levels as they remained about 0.2 degrees C above the 1951- 80 average. The sulfate aerosols injected into the stratosphere from the 1991 Mt. Pinatubo volcanic eruption had settled out of the atmosphere by the end of 1993. For 1994 this means that the direct surface cooling effects from Mt. Pinatubo should be small. Temperatures during the later part of 1993 were at record low levels. Extremely cold stratospheric temperatures aid in ozone destruction.
Stratospheric temperatures are now very low throughout much of the globe.
Past records suggest that 1994 is also likely to also have record low temperatures, barring another major volcanic eruption. This caused a decrease in the diurnal temperature range . The increase in temperature during the first half of the year has been enhanced by a decrease in spring snow cover over North America and Asia. Precipitation over the U.S.A. was of record proportions in the Mississippi River Drainage Basin , but the Southeast U.S.A. ended 1993 with the second driest summer of the Century. The frequency of tornadoes continues to be near or above record levels for the fourth consecutive year.