DOI 10.1007/s10584-009-9593-3 EDITORIAL Rising seas and retreating coastlines

Any rise in the mean sea level will result in the retreat of unprotected coastlines (Bruun 1962). Fortunately, the still-stand (slow) conditions of global average sea level rise (SLR) during the last century has resulted in slow and mostly manageable coastline retreat (recession). Alarmingly, however, recent research indicates that the global average sea levels may rise at an unprecedented rate during the twenty-first century (Leuliette et al. 2004; Beckley et al. 2007). The latest IPCC projections (IPCC 2007) indicate an SLR range from 0.18 to 0.79 m by 2090–2099 relative to 1980– 1999, including an allowance of 0.2 m for uncertainty associated with ice sheet flow. Very recent research (Rahmstorf et al. 2007) also suggests that the measured SLR over the last decade was following the upper range SLR projections given in the IPCC Third Assessment Report (TAR) and the IPCC Fourth Assessment Report (AR4) (Note: The upper range TAR projections are very close to the upper range AR4 projections when the ice sheet contributions are considered). Furthermore, Rhamstorf (Rahmstorf 2007) suggests that higher SLR rates than those projected by IPCC TAR and AR4 may also be possible. In comparison, the global averag