|Harry van Loon|
Harry and Labitzke used the flux in the 10.7-centimeter radio waveband, an objectively observed quantity highly correlated with the 11-year cycle. They compared these radio data with FUB's daily analyses of the stratosphere. The results show a strong correlation between the solar cycle and the 10- to 12-year oscillation of two quantities in the lower stratosphere: mean temperatures (particularly during each hemisphere's summer) and constant pressure heights above sea level.
The new findings, say Harry, "increase our confidence that the solar-stratospheric relationship is more than a statistical coincidence." For many years scientists have tried to find an earthly link to the sun's 11-year cycle. Previous attempts have turned up humorous correspondences to the number of Republicans in the House of Representatives and the length of women's skirts. Until Harry and Labitzke's work, even serious scientific stabs at the problem eventually proved false. A solid link takes on added significance now as scientists search for a clear sun-earth connection for computer models used to predict climate change.
"The role of the sun in climate change is still an unsolved problem," says Harry. "Any relationship between changes in solar output and what happens here on earth is important for understanding long-term climate." The sun's output has varied about 0.1% over one solar cycle during the past several decades. Over centuries, however, larger variations may occur.
To represent more accurately the physical processes of the entire surface of the sun, the NCAR team is taking a detailed look at how individual features, like sunspots, change the amounts of radiation in several different wavelengths. The team uses observations from the precision solar photometric telescope (PSPT), combined with computer modeling that incorporates prior observations and solar physics theory. The PSPT is operated by HAO at its Mauna Loa Solar Observatory in Hawaii as part of NSF's Radiative Input from the Sun to the Earth (SunRISE) program.
"Tree rings and ice cores tell us a little about variations in the sun over centuries. But we have only the 11-year sunspot record for the last 300 years to link directly to today's sun, and we don't have direct measurements of the radiation before the 1970s," Peter explains. The new information will