Of course the effect of greenhouse gases and solar warming is quite important to look at, as the implications of an uncontrolled rise in Earth’s temperatures could result in drastic problems for the global ecosystem.  It’s very interesting to look back at earlier studies of greenhouse issues, such as during the 1980′s when the studies were just beginning.

Most searchers for a cooling in the lower stratosphere, where balloon-borne radiosondes can reach, have negative by strict statistical standards. The record is only about 25 years long, there is considerable natural variability of temperature, and coverage is far from complete. But even some statistically negative searches show a cooling in the lower stratosphere that is greater at higher latitudes, as predicted.

A few recent searches, however, have uncovered significant stratospheric coolings. Karen Labitzke of the Free University of Berlin and her colleagues took unusual care in developing monthly mean temperatures from an exceptionally large data base. For 10[deg.] latitude bands at mid-latitudes, means are based on about 3000 observations each. Averaged between 20[deg.]N and 70[deg.N, the lower stratosphere cooled at a rate of 0.34[deg.]C from 1966 to 1980. That cooling rate is significant, Labitzke and her colleagues believe, and they calculate that it is consistent with that expected from increasing carbon dioxide.

In the Southern Hemisphere, radiosonde coverage is much more sparse, but David Karoly of Monash University in Clayton, Australia, has found a significant cooling there in the lower stratosphere above selected stations. All but 2 of 19 stations have cooling trends from 1964 to 1985 ranging from 0.2 to 1.0[deg.] per decade. At only five of the stations is the trend statistically significant at the 95% level, but Karoly enhanced the greenhouse signal by contrasting the cooling in the lower stratosphere with the warming in the troposphere below. His index of this temperature differences showed a positive trend — the expected greenhouse signal — at all 19 stations, 13 of the trends being significant.

The 20-year stratospheric cooling trend that may be emerging from the climatic noise may also be marginally detectable during this decade, even though debris from the 1982 eruption of El Chichon absorbed solar radiation and temporarily warmed the lower stratosphere. Mark Schoeberl of the Goddard Space Flight Center in Greenbelt, Maryland, has coordinated a group of stratospheric specialists in a review of some temperature trend studies.

This group concludes that the global lower stratosphere cooled about 0.5[deg.] [plus-or-minus] 0.5[deg.] between 1979 and 1985. In the upper stratosphere, where the carbon dioxide effect should be accentuated, the cooling appears to have been 1.5[deg.] to 2[deg.]C, based on satellite and rocket observations.

Unfortunately for those looking for a greenhouse signal, other forces can cool the stratosphere. Decreasing solar activity since 1980 certainly has. And any decrease in ozone inducted by increasing concentrations of chlorofluorocarbons will itself induce a cooling, at least in the upper stratosphere. It could be as large as that due to carbon dioxide. The situation may be particularly complicated in the Southern Hemisphere where the springtime Antarctic ozone hole may have some influence.

Kerr, Richard A. “Is the greenhouse here?” Science 239.4840 (1988): 559+.