Global temperature monitoring from space

Abstract

Global and regional temperature variations in the lower troposphere and lower stratosphere are examined for the period 1979–1992 from Microwave Sounder Unit (MSU) data obtained by the TIROS-N series of NOAA operational satellites. In the lower troposphere, globally-averaged temperature variations appear to be dominated by tropical El Nino (warm) and La Nina (cool) events and volcanic eruptions. The Pinatubo volcanic eruption in June 1991 appears to have initiated a cooling trend which persisted through the most recent data analyzed (July, 1992), and largely overwhelmed the warming from the 1991–1992 El Nino. The cooling has been stronger in the Northern Hemisphere than in the Southern Hemisphere. The temperature trend over the 13.5 year satellite record is small (+0.03°C) compared to the year-to-year variability (0.2°–0.4°C), making detection of any global warming signal fruitless to date. However, the future global warming trend, currently predicted to be around 0.3°C/decade, will be much easier to discern should it develop. The lower stratospheric temperature record is dominated by warm episodes from the Pinatubo eruption and the March 1982 eruption of El Chichon volcano.