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This policy brief presents the application of ensembles of agricultural models in assessing emissions and mitigation practices The MACSUR SciPol knowledge forum is a pilot exercise initiated by the Joint Programming Initiative for Agriculture, Food Security and Climate Change (FACCE-JPI) to bring science and policy actors together for the strategic design of climate change adaptation and mitigation solutions in the agri-food sector in Europe. This policy brief contributes to this mission by providing evidence-based information to policy for achieving carbon neutrality by 2050, adapting to climate change and understanding synergies and trade-offs in achieving these targets. This policy brief presents the application of ensembles of agricultural models in assessing emissions and mitigation practices

International audience; Reconstructing the occurrence of diluvial storms over centennial to millennial time-scales allows forplacing the emergence of modern damaging hydrological events in a longer perspective to facilitate abetter understanding of their rate of return in the absence of significant anthropogenic climaticforcing. These extremes have implications for the risk offlooding in sub-regional river basins duringboth colder and warmer climate states. Here, we present thefirst homogeneous millennium-long(800–2018 CE)time-series of diluvial storms for the Po River Basin, northern Italy, which is also thelongest such time-series of monthly data for the entire Europe. The monthly reconstruction ofdamaging hydrological events derives from several types of historical documentary sources and reveals387 such events, allowing the construction of storm severity indices by transforming the informationinto a monthly, quantitative, record. A period of reduced diluvial storms occurred in the ninth andtenth centuries, followed by a stormier period culminating in the eleventh and thirteenth centuries.More complex patterns emerge in the fourteenth to sixteenth centuries, with generally wetter andstormier conditions than during other centuries. From the seventeenth century onwards the numberof damaging hydrological events decreases, with a return in recent decades to conditions similar tothose prior to the thirteenth century Theflood frequency tended to increase for all seasons duringperiods of low solar irradiance, suggesting the presence of solar-induced circulation changesresembling the negative phases of the Atlantic Multidecadal Variability as a controlling atmosphericmechanism.

The occurrence of hydrological extremes in the Amazon region and the associated sediment loss during rainfall events are key features in the global climate system. Climate extremes alter the sediment and carbon balance but the ecological consequences of such changes are poorly understood in this region. With the aim of examining the interactions between precipitation and landscape-scale controls of sediment export from the Amazon basin, we developed a parsimonious hydro-climatological model on a multi-year series (1997&ndash, 2014) of sediment discharge data taken at the outlet of &Oacute, bidos (Brazil) watershed (the narrowest and swiftest part of the Amazon River). The calibrated model (correlation coefficient equal to 0.84) captured the sediment load variability of an independent dataset from a different watershed (the Magdalena River basin), and performed better than three alternative approaches. Our model captured the interdecadal variability and the long-term patterns of sediment export. In our reconstruction of yearly sediment discharge over 1859&ndash, 2014, we observed that landscape erosion changes are mostly induced by single storm events, and result from coupled effects of droughts and storms over long time scales. By quantifying temporal variations in the sediment produced by weathering, this analysis enables a new understanding of the linkage between climate forcing and river response, which drives sediment dynamics in the Amazon basin.

Collected rainfall records by gauges lead to key forcings in most hydrological studies. Depending on sensor type and recording systems, such data are characterized by different time-resolutions (or temporal aggregations), ta. We present an historical analysis of the time-evolution of ta based on a large database of rain gauge networks operative in many study areas. Globally, ta data were collected for 25,423 rain gauge stations across 32 geographic areas, with larger contributions from Australia, USA, Italy and Spain. For very old networks early recordings were manual with coarse time-resolution, typically daily or sometimes monthly. With a few exceptions, mechanical recordings on paper rolls began in the first half of the 20th century, typically with ta of 1 h or 30 min. Digital registrations started only during the last three decades of the 20th century. This short period limits investigations that require long time-series of sub-daily rainfall data, e.g, analyses of the effects of climate change on short-duration (sub-hourly) heavy rainfall. In addition, in the areas with rainfall data characterized for many years by coarse time-resolutions, annual maximum rainfall depths of short duration can be potentially underestimated and their use would produce errors in the results of successive applications. Currently, only 50% of the stations provide useful data at any time-resolution, that practically means ta = 1 min. However, a significant reduction of these issues can be obtained through the information content of the present database. Finally, we suggest an integration of the database by including additional rain gauge networks to enhance its usefulness particularly in a comparative analysis of the effects of climate change on extreme rainfalls of short duration available in different locations.