Viticulture extension in response to global climate change drivers - lessons from the past and future projections

The potential areal extent of agricultural crops is sensitive to climate change and its underlying drivers. To distinguish between the drivers of past variations in the Mediterranean viticulture extension since Early Antiquity and improve projections for the future, we propose an original attribution method based on an emulation of offline coupled climate and ecosystem models. The emulator connects the potential productivity of grapevines to global direct and indirect climate drivers, notably orbital parameters, solar and volcanic activities, demography, and greenhouse gas concentrations. This approach is particularly useful to place the evolution of future agrosystems in the context of their past variations. We found that variations in potential area for viticulture during the last 3 millennia in the Mediterranean Basin were mainly due to volcanic activity, while the effects of solar activity and orbital changes were negligible. In the future, as expected, the dominating factor is the increase in greenhouse gases, causing significantly drier conditions and thus major difficulties for viticulture in Spain and North Africa. These constraints will concern significant areas of the southern Mediterranean Basin when global warming exceeds +2 degrees C above preindustrial conditions. Our experiments showed that even intense volcanic activity comparable to that of the Samalas - sometimes considered to be the starting point of the Little Ice Age in the mid-13th century - would not decrease aridity and so not slow down this decline in viticulture extension in the southern margin of the Mediterranean area. This result does not confirm the idea of geoengineering that solar radiation modification (SRM) is an efficient option to limit future global warming.