Depletion of Antarctic ozone has played a larger role in shifting the Southern Hemisphere jet stream in a southward direction, compared to increasing greenhouse gases. This is according to research appearing in the February 1st issue of the journal Science, which is the first to determine the extent to which each of these two forcings has contributed to the shift using observational data.
According to Sukyoung Lee, professor of meteorology, ‘Previous research suggests that this southward shift in the jet stream has contributed to changes in ocean circulation patterns and precipitation patterns in the Southern Hemisphere, both of which can have important impacts on people’s livelihoods,’ and environmental wellness. Professor Lee explained, ‘Understanding the differences between these two forcings is important in predicting what will happen as the ozone hole recovers. The jet stream is expected to shift back toward the north as ozone is replenished, yet the greenhouse-gas effect could negate this.’
With colleague Steven Feldstein, another professor of meteorology, Lee developed a new method to distinguish between the effects of the two forcings, using a cluster analysis to observe the effects on several wind patterns. Feldstein noted, ‘When most people look at ozone and greenhouse gases, they focus on one wind pattern, but my previous research suggests that, by looking at several different but similar patterns, you can learn more about what is really happening.’
He continued, ‘Climate models are usually run for many years; they don’t look at the day-to-day weather, but we learned that the four wind patterns fluctuate over about 10 days, so they change on a time scale that is similar to daily weather. This realization means that by taking into account fluctuations associated with the daily weather, it will be easier to test theories about the mechanism by which ozone and greenhouse gases influence the jet stream.’
Feldstein added that the research, which was funded by the National Science Foundation, is innovative in several ways. ‘Not only are the results of this paper important for better understanding climate change,’ he said. ‘But this paper is also important because it uses a new approach to try to better understand climate change; it uses observational data on a short time scale to try to look at cause and effect, which is something that is rarely done in climate research. Also, our results are consistent with climate models, so this paper provides support that climate models are performing well at simulating the atmospheric response to ozone and greenhouse gases.’