Sea-level rise projections and knowledge of their uncertainties are vital to make informed mitigation and adaptation decisions. To elicit projections from members of the scientific community regarding future global mean sea-level (GMSL) rise, we repeated a survey originally conducted five years ago. Under Representative Concentration Pathway (RCP) 2.6, 106 experts projected a likely (central 66% probability) GMSL rise of 0.30–0.65 m by 2100, and 0.54–2.15 m by 2300, relative to 1986–2005. Under RCP 8.5, the same experts projected a likely GMSL rise of 0.63–1.32 m by 2100, and 1.67–5.61 m by 2300. Expert projections for 2100 are similar to those from the original survey, although the projection for 2300 has extended tails and is higher than the original survey. Experts give a likelihood of 42% (original survey) and 45% (current survey) that under the high-emissions scenario GMSL rise will exceed the upper bound (0.98 m) of the likely range estimated by the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, which is considered to have an exceedance likelihood of 17%. Responses to open-ended questions suggest that the increases in upper-end estimates and uncertainties arose from recent influential studies about the impact of marine ice cliff instability on the meltwater contribution to GMSL rise from the Antarctic Ice Sheet.

海平面上升预测及其不确定性的了解对于做出明智的减灾和适应决策至关重要。为了引起科学界成员对未来全球平均海平面（GMSL）上升的预测，我们重复了五年前进行的一项调查。在代表浓度路径（RCP）2.6下，相对于1986-2005年，106位专家预测GMSL到2100年可能增加0.30-0.65 m，到2300年则增加0.54-2.15 m（概率为66％）。在RCP 8.5下，同一位专家预计到2100年GMSL可能上升0.63–1.32 m，到2300年可能达到1.67–5.61 m。2100的专家预测与原始调查的相似，尽管2300的预测具有延伸的尾部和高于原始调查。专家估计，在高排放情景下，GMSL的上升将超过政府间小组第五次评估报告估计的可能范围的上限（0.98 m），分别为42％（原始调查）和45％（当前调查）。关于气候变化的报告，其超标可能性为17％。对开放式问题的回答表明，南极冰盖引起的有关海洋冰崖不稳定性对融化水对GMSL贡献的影响的最新影响研究增加了高端估计和不确定性。