Radiative and Physiological Effects of Increased CO₂: How does this Interaction Affect Climate in the Mediterranean Region?

The radiative and physiological effects of doubled atmospheric carbon dioxide concentration (CO₂) on climate are described using climate simulations. When CO₂ was increased for vegetation only assuming no radiative effect, the response was a decrease in stomatal conductance followed by a temperature increase. This temperature increase was stronger when the vegetation physiological “down-regulation” was allowed in the model. The radiative forcing alone did not affect the global mean photosynthesis, however, some stimulation was observed in cold places. The interactions between the physiological and the radiative effects of doubled CO₂ are not linearly “additive” and when acting together they tend to reduce the warming in the Mediterranean region.