Background
The authors write that "current global yield losses have been estimated to be in the range of 3-16% for four major food crops due to exposure to surface O3 concentrations, with additional reductions under possible higher O3 concentrations in the future, posing a serious threat to food security (Van Dingenen et al., 2009)." However, they note that "the negative effects of O3 on vegetation are more closely related to the uptake of O3 through the stomata than to the concentration in the ambient air," citing the work of Emberson et al. (2000), Pleijel et al. (2004), Uddling et al. (2004) and Karlsson et al. (2007)," and they say that "factors influencing the stomatal uptake of O3 therefore have to be considered in risk assessment," which is what they proceed to do.

What was done
Klingberg et al. accomplished their goal by investigating the influence of climate change on simulated stomatal uptake of O3 by a generic crop and a generic deciduous tree at ten European sites, using the LRTAP Convention (2004) stomatal flux model, where O3 concentrations are calculated by a chemistry transport model for three 30-year time-windows (1961-1990, 2021-2050 and 2071-2100), with constant precursor emissions and meteorology that they derived from a regional climate model (Robertson et al., 1999).

What was learned
In the words of the five researchers, "despite substantially increased modeled future O3 concentrations in central and southern Europe, the flux-based risk for O3 damage to vegetation is predicted to remain unchanged or decrease at most sites, mainly as a result of projected reductions in stomatal conductance under rising CO2 concentrations," about which much more can be learned by perusing the many journal reviews we have archived under the heading of Ozone (Effects on Plants) in our Subject Index.

What it means
Were it not for the stomatal-aperture-constricting effect of atmospheric CO2 enrichment, both Europe and the world of the future would be in for a world of hurt, due to the debilitating effect of the increased concentrations of atmospheric ozone that are expected to continue to occur as time progresses.

References
Emberson, L.D., Ashmore, M.R., Cambridge, H.M., Simpson, D. and Tuovinen, J.P. 2000. Modeling stomatal ozone flux across Europe. Environmental Pollution 109: 403.

LRTAP Convention. 2004. Manual on Methodologies and Criteria for Modeling and Mapping Critical Loads & Levels and Air Pollution Effects, Risks and Trends. Available and continuously updated at www.icpmapping.org.

Pleijel, H., Danielsson, H., Ojanpera, K., Temmerman, L.D., Hogy, P., Badiani, M. and Karlsson, P. E. 2004. Relationships between ozone exposure and yield loss in European wheat and potato -- a comparison of concentration- and flux-based exposure indices. Atmospheric Environment 38: 2259-2269.

Robertson, L., Langner, J. and Engardt, M. 1999. An Eulerian limited-area atmospheric transport model. Journal of Applied Meteorology 38: 190-210.

Uddling, J., Teclaw, R.M., Pregitzer, K.S. and Ellsworth, D.S. 2009. Leaf and canopy conductance in aspen and aspen-birch forests under free-air enrichment of carbon dioxide and ozone. Tree Physiology 29: 1367-1380.

Van Dingensen, R., Dentener, F.J., Raes, F., Krol, M.C., Emberson, L. and Cofala, J. 2009. The global impact of ozone on agricultural crop yields under current and future air quality legislation. Atmospheric Environment 43: 604-618.