U of T physicists predict climate change will lead to less ultraviolet radiation in northern areas

Friday, December 4, 2009 11:00:00 AM

Post Doctoral Fellow Michaela Hegglin, Professor Theodore Shepherd and colleagues in U of T's Department of Physics predict that changes in the Earth's ozone layer due to climate change will result in decreases in the amount of ultraviolet radiation in northern high latitudes and increases in the tropics and southern high latitudes. 

Climate models predict an accelerated stratospheric circulation, leading to changes in the spatial distribution of stratospheric ozone and an increased stratosphere-to-troposphere ozone flux.  In the study, published in the September 6 issue Nature Geoscience1, an atmospheric chemistry climate model was used to isolate the effects of climate change from those of ozone depletion and recovery on stratosphere-to-troposphere ozone flux and the clear-sky ultraviolet radiation index - a measure of potential human exposure to ultraviolet radiation.  They found that global stratosphere-to-troposphere ozone flux increases by 23% between 1965 and 2095 as a result of climate change.  During this time, the clear-sky ultraviolet radiation index decreases by 9% in northern high latitudes - a much larger effect than that of stratospheric ozone recovery - and increases by 4% in the tropics, and by up to 20% in southern high latitudes in late spring and early summer.  The latter increase in the ultraviolet index is equivalent to nearly half of that generated by the Antarctic 'ozone hole' that was created by anthropogenic halogens.  The results suggest that climate change will alter the tropospheric ozone budget and the ultraviolet index, which would have consequences for tropospheric radiative forcing, air quality and human and ecosystem health.

(This is an excerpt from the study available online at http://www.nature.com/ngeo/journal/v2/n10/full/ngeo604.html)

1 M.I. Hegglin and T.G. Shepherd. 2009. Large climate-induced changes in ultraviolet index and stratosphere-to-troposphere ozone flux. Nature Geoscience 2: 687-691.