A review of 917 relative sea-level (RSL) data-points has resulted in the first quality-controlled database\ud constraining the Holocene sea-level histories of the western Mediterranean Sea (Spain, France, Italy, Slovenia,\ud Croatia, Malta and Tunisia). We reviewed and standardized the geological RSL data-points using a new multiproxy\ud methodology based on: (1) modern taxa assemblages in Mediterranean lagoons and marshes;\ud (2) beachrock characteristics (cement fabric and chemistry, sedimentary structures); and (3) the modern distribution\ud ofMediterranean fixed biological indicators. These RSL data-pointswere coupled with the large number of\ud archaeological RSL indicators available for the westernMediterranean. We assessed the spatial variability of RSL\ud histories for 22 regions and compared these with the ICE-5G (VM2) GIA model. In the western Mediterranean,\ud RSL rose continuously for the whole Holocene with a sudden slowdown at ~7.5 ka BP and a further deceleration\ud during the last ~4.0 ka BP, afterwhich time observed RSL changes are mainly related to variability in isostatic adjustment.\ud The sole exception is southern Tunisia, where data show evidence of a mid-Holocene high-stand compatible\ud with the isostatic impacts of the melting history of the remote Antarctic ice sheet.\ud Our results indicate that late-Holocene sea-level rise was significantly slower than the current one. First estimates\ud of GIA contribution indicate that, at least in the northwestern sector, it accounts at least for the 25–30% of the ongoing\ud sea-level rise recorded by Mediterranean tidal gauges. Such contribution is less constrained at lower latitudes\ud due to the lower quality of the late Holocene index points. Future applications of spatio-temporal\ud statistical techniques are required to better quantify the gradient of the isostatic contribution and to provide improved\ud context for the assessment of 20th century acceleration of Mediterranean sea-level rise

1The Last Interglacial (MIS 5e, is among the most studied past periods in Earth's history. The 2 climate at that time was warmer than today, primarily due to different orbital conditions, with smaller 3 ice sheets and higher sea-level. Field evidence for MIS 5e sea-level was reported from thousands of sites, 4 but often paleo shorelines were measured with low-accuracy techniques and, in some cases, there are 5 contrasting interpretations about paleo sea-level reconstructions. For this reason, large uncertainties still 6 surround both the maximum sea-level attained as well as the pattern of sea-level change throughout 7 MIS 5e. Such uncertainties are exacerbated by the lack of a uniform approach to measuring and 8interpreting the geological evidence of paleo sea-levels. In this review, we discuss the characteristicsof 9 MIS 5e field observations, and we set the basis for a standardized approach to MIS 5e paleo sea-level 10 reconstructions, that is already successfully applied in Holocene sea-level research. Application of the 11 standard definitions and methodologies described in this paper will enhance our ability to compare data 12 from different research groups and different areas, in order to gain deeper insights into MIS 5e sea-level 13 changes. Improving estimates of Last Interglacial sea-level is, in turn, a key to understand the behavior of 14 ice sheets in a warmer world. 15 12 Bruneau, N., Fortunato, A.B., Dodet, G., Freire, P., Oliveira, A., Bertin, X., 2011. Future evolution of a tidal 13 inlet due to changes in wave climate, Sea-level and lagoon morphology (Óbidos lagoon, Portugal). ., 2010. The last 21 interglacial sea-level high stand on the southern Cape coastline of South Africa. Quat. Res. 73, 351-22 363. 23Casella, E., Rovere, A., Pedroncini, A., Mucerino, L., Casella, M., Cusati, A.L., Vacchi, M., Ferrari, M., 24Firpo, M., 2014. Study of wave runup using numerical models and low-altitude aerial 25 photogrammetry : A tool for coastal management.

The evolution of past global ice sheets is highly uncertain. One example is the missing ice problem during the Last Glacial Maximum (LGM, 26 000-19 000 years before present) – an apparent 8-28 m discrepancy between far-field sea level indicators and modelled sea level from ice sheet reconstructions. In the absence of ice sheet reconstructions, researchers often use marine δ18O proxy records to infer ice volume prior to the LGM. We present a global ice sheet reconstruction for the past 80 000 years, called PaleoMIST 1.0, constructed independently of far-field sea level and δ18O proxy records. Our reconstruction is compatible with LGM far-field sea-level records without requiring extra ice volume, thus solving the missing ice problem. However, for Marine Isotope Stage 3 (57 000-29 000 years before present) - a pre-LGM period - our reconstruction does not match proxy-based sea level reconstructions, indicating the relationship between marine δ18O and sea level may be more complex than assumed.

Over the past 3.5 million years, there have been several intervals when climate conditions were warmer than during the preindustrial Holocene. Although past intervals of warming were forced differently than future anthropogenic change, such periods can provide insights into potential future climate impacts and ecosystem feedbacks, especially over centennial-to-millennial timescales that are often not covered by climate model simulations. Our observation-based synthesis of the understanding of past intervals with temperatures within the range of projected future warming suggests that there is a low risk of runaway greenhouse gas feedbacks for global warming of no more than 2 °C. However, substantial regional environmental impacts can occur. A global average warming of 1-2 °C with strong polar amplification has, in the past, been accompanied by significant shifts in climate zones and the spatial distribution of land and ocean ecosystems. Sustained warming at this level has also led to substantial reductions of the Greenland and Antarctic ice sheets, with sea-level increases of at least several metres on millennial timescales. Comparison of palaeo observations with climate model results suggests that, due to the lack of certain feedback processes, model-based climate projections may underestimate long-term warming in response to future radiative forcing by as much as a factor of two, and thus may also underestimate centennial-to-millennial-scale sea-level rise.