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

Abstract. There is growing concern that flooding is becoming more frequent and severe in Europe. A better understanding of flood regime changes and their drivers is therefore needed. The paper reviews the current knowledge on flood regime changes in European rivers that has traditionally been obtained through two alternative research approaches. The first approach is the data-based detection of changes in observed flood events. Current methods are reviewed together with their challenges and opportunities. For example, observation biases, the merging of different data sources and accounting for nonlinear drivers and responses. The second approach consists of modelled scenarios of future floods. Challenges and opportunities associated with flood change scenarios are discussed such as fully accounting for uncertainties in the modelling cascade and feedbacks. To make progress in flood change research, we suggest that a synthesis of these two approaches is needed. This can be achieved by focusing on long duration records and flood-rich and flood-poor periods rather than on short duration flood trends only, by formally attributing causes of observed flood changes, by validating scenarios against observed flood regime dynamics, and by developing low-dimensional models of flood changes and feedbacks. The paper finishes with a call for a joint European flood change research network.

International audienc

The observed trend towards warmer and drier conditions in southern Europe is projected to continue in the next decades, possibly leading to increased risk of large fires. However, an assessment of climate change impacts on fires at and above the 1.5 °C Paris target is still missing. Here, we estimate future summer burned area in Mediterranean Europe under 1.5, 2, and 3 °C global warming scenarios, accounting for possible modifications of climate-fire relationships under changed climatic conditions owing to productivity alterations. We found that such modifications could be beneficial, roughly halving the fire-intensifying signals. In any case, the burned area is robustly projected to increase. The higher the warming level is, the larger is the increase of burned area, ranging from ~40% to ~100% across the scenarios. Our results indicate that significant benefits would be obtained if warming were limited to well below 2 °C.

Summer fires frequently rage across Mediterranean Europe, often intensified by high temperatures and droughts. According to the state-of-the-art regional fire risk projections, in forthcoming decades climate effects are expected to become stronger and possibly overcome fire prevention efforts. However, significant uncertainties exist and the direct effect of climate change in regulating fuel moisture (e.g. warmer conditions increasing fuel dryness) could be counterbalanced by the indirect effects on fuel structure (e.g. warmer conditions limiting fuel amount), affecting the transition between climate-driven and fuel-limited fire regimes as temperatures increase. Here we analyse and model the impact of coincident drought and antecedent wet conditions (proxy for the climatic factor influencing total fuel and fine fuel structure) on the summer Burned Area (BA) across all eco-regions in Mediterranean Europe. This approach allows BA to be linked to the key drivers of fire in the region. We show a statistically significant relationship between fire and same-summer droughts in most regions, while antecedent climate conditions play a relatively minor role, except in few specific eco-regions. The presented models for individual eco-regions provide insights on the impacts of climate variability on BA, and appear to be promising for developing a seasonal forecast system supporting fire management strategies.

A system of rainfall events classification on the basis of their hydrometeorological characteristics is proposed. The objective is the characterization of the different event classes and their application in modelling intensity-duration-frequency curves and design hyetographs. A parameter related to the greater or lesser convective character of the precipitation, designated as i*, is defined, while its distribution throughout the entire series of the sample is studied. In addition, the main features of the different classes obtained and their relationship to floods and rainfall damage events have been analysed. The intensity series of the Jardí pluviograph (Barcelona, Spain) between 1927 and 1981 is used as a sample series.

Abstract. There is growing concern that flooding is becoming more frequent and severe in Europe. A better understanding of flood regime changes and their drivers is therefore needed. The paper reviews the current knowledge on flood regime changes in European rivers that has been obtained through two approaches. The first approach is the detection of change based on observed flood events. Current methods are reviewed together with their challenges and opportunities. For example, observation biases, the merging of different data sources and accounting for non-linear drivers and responses. The second approach consists of modelled scenarios of future floods. Challenges and opportunities are discussed again such as fully accounting for uncertainties in the modelling cascade and feedbacks. To make progress in flood change research, we suggest that a synthesis of these two approaches is needed. This can be achieved by focusing on flood-rich and flood-poor periods rather than on flood trends only, by formally attributing causes of observed flood changes, by validating scenarios against observed flood regime dynamics, and by developing low-dimensional models of flood changes and feedbacks. The paper finishes with a call for a joint European flood change research network.

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