In the Mediterranean Basin, recent accelerated changes in the environment (climate, land use, pollution, biodiversity loss) have caused loss of life and damages to infrastructure and ecosystems. The future presents unprecedented risks for human well-being, socioeconomic development, ecosystems and biodiversity. Policies for sustainable development need to aim for the mitigation of these risks but lack adequate information about the rates of environmental change and the combined risk they present to human society. For five interconnected impact domains (water, ecosystems, food, health and security), trends and scenarios point to significant risks during coming decades. More observations and better impact models exist for the Northern Mediterranean shores than for the South. This important bias is exacerbated by the large difference in financial resources available for adaptation and the development of resilience between north and south. A dedicated effort to synthesize existing scientific knowledge from all relevant disciplines is now underway to provide better understanding of the risks posed. In the Mediterranean Basin, human society and the natural environment have co-evolved over several millennia with significant climatic variations, laying the ground for diverse and culturally rich communities. The region lies in a transition zone between mid-latitude and subtropical circulation regimes. It is characterized by a complex morphology of mountain chains and strong land-sea contrasts, dense and growing human population and various environmental pressures. Observed rates of climate change in the Mediterranean Basin exceed global trends for most variables. Annual mean temperatures are now 1.4 °C above late nineteenth century levels (Figure 1), notably during the summer months. Heat waves occur more frequently, and the frequency and intensity of droughts have increased since 1950. 1,2,3 For each of the most recent decades, the surface of the Mediterranean Sea has warmed by around 0.4 °C. 4 During the period 1945-2000, sea-level has risen at a rate of 0.7±0.2 mm yr-1 , 5 accelerating to 1.1 mm yr-1 for the period 1970-2006. 6 During the last two decades, sea-level has been estimated to rise by about 3 cm decade-1 , 7 in part due to

Heat waves and drought are often considered the most damaging climatic stressors for wheat. In this study, we characterize and attribute the effects of these climate extremes on wheat yield anomalies (at global and national scales) from 1980 to 2010. Using a combination of up-to-date heat wave and drought indexes (the latter capturing both excessively dry and wet conditions), we have developed a composite indicator that is able to capture the spatio-temporal characteristics of the underlying physical processes in the different agro-climatic regions of the world. At the global level, our diagnostic explains a significant portion (more than 40%) of the inter-annual production variability. By quantifying the contribution of national yield anomalies to global fluctuations, we have found that just two concurrent yield anomalies affecting the larger producers of the world could be responsible for more than half of the global annual fluctuations. The relative importance of heat stress and drought in determining the yield anomalies depends on the region. Moreover, in contrast to common perception, water excess affects wheat production more than drought in several countries. We have also performed the same analysis at the subnational level for France, which is the largest wheat producer of the European Union, and home to a range of climatic zones. Large subnational variability of inter-annual wheat yield is mostly captured by the heat and water stress indicators, consistently with the country-level result.

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[1] A new data set of high-quality homogenized daily maximum and minimum summer air temperature series from 246 stations in the eastern Mediterranean region (including