Ozone — best known for filtering out harmful UV light as a component of the Earth's stratosphere — could dramatically reduce plants' ability to act as a carbon sink and thus cause further accumulation of greenhouse gases in the atmosphere, according to a new study published in Nature. In addition to damaging human tissues (particularly those of the respiratory system), ground-level ozone has the ability to harm cells inside leaves, reducing photosynthesis rates and thus hindering plants' ability to absorb carbon dioxide from the atmosphere. This would both contribute to the intensification of global warming's effects and the reduction of global crop yields by slashing plant productivity.
The team of researchers, led by the Hadley Center for Climate Protection and Research's Stephen Sitch, calculated the effect of higher ozone levels in 2100 on carbon dioxide concentration and plant production — projecting these higher levels to cut plants' carbon storage accumulation by 143 - 263 petagrams (in other words, a reduction of 17 - 31% in the amount of carbon stored by the plants).
With many regions of the planet already experiencing ozone levels greater than 40 ppb (parts per billion) — more than enough to seriously harm plants — the researchers estimate levels will further rise over the next century and eventually top 70 ppb around most of the world. However, because levels of carbon dioxide are also expected to increase during the next century and beyond, they could help offset some of its damaging effects (high concentrations cause plants to close their stomata, reducing the amount of ozone entering the leaves).
Talk about a lose-lose situation...
Via ::Environmental Science & Technology: Ozone suppresses global carbon sink (news website), ::Nature: Indirect radiative forcing of climate change through ozone effects on the land-carbon sink (magazine)