海平面加速上升对低海拔岛屿、沿海地区及社会的影响和风险

doi:10.12006/j.issn.1673-1719.2019.225

摘要/Abstract

摘要：

IPCC《气候变化中的海洋和冰冻圈特别报告》评估了气候变化对全球、区域海平面变化和极端海面（极值水位）升高的贡献,以及海平面上升对低海拔（小鱼10 m）岛屿、沿海地区和社会的影响及相关的风险。评估表明,全球变暖背景下,全球平均海平面上升的证据是确凿的,且明显加速（高信度),极端海面高度升高,主要是由陆地冰川和冰盖融化以及海洋热膨胀引起,且前者的贡献已大于后者（很高信度);与此同时,海洋变暖速率倍增,强热带气旋、风暴潮增多,极值水位重现期缩短;至21世纪末,全球海平面还将上升约0.43 m（温室气体低排放情景,RCP2.6）和0.84 m（高排放情景,RCP8.5）（中等信度）,很多沿海地区当前较少发生的百年一遇的极值水位将变为一年一遇或更频繁,而对于许多沿海低洼地而言,类似事件甚至在21世纪中叶就可能发生（高信度)。评估还表明,持续上升的海平面、趋于频发的极值水位,以及人为地面沉降等因素,增加了沿海社会-生态系统的暴露度和脆弱性;并且,与海平面上升有关的危害（险）性事件,如海岸侵蚀、洪灾、盐碱化和生境退化等将显著增加（高信度)。报告指出,如未采取充分的适应海平面上升的措施,在RCP8.5情景下,沿海大城市、城市环礁群岛、热带农业三角洲地区和北极沿岸社区将处于高或很高的灾害风险中（高信度)。

关键词: 海平面上升, 低海拔, 沿海地区, 影响, 风险

Abstract:

The IPCC special report on the ocean and cryosphere in a changing climate (SROCC) presents an assessment of past and future contributions of climate change to global, regional and extreme sea level changes, the associated risk to low-lying islands, and response options and pathways to resilience as reported in the sea level chapter. The special report covers the field from observational changes, improved physical insights and projections to impacts and risk, and response options. The results indicate that, in the context of global warming, the global mean sea level (GMSL) is rising (virtually certain) and accelerating (high confidence), and the height of extreme sea level (ESL) is increasing significantly, attributed to the contribution of land glaciers and ice sheets that has exceeded the effect of the ocean thermal expansion since 2006. Meanwhile, the rate of ocean warming has more than doubled since 1993, strong tropical cyclones and storm surges have increased and the return period of ESL has greatly decreased. By 2100, GMSL will rise by about 0.43 m (low greenhouse gas emission scenario, RCP2.6) and 0.84 m (high emission scenario, RCP8.5) (medium confidence), and the currently rare ESL, e.g., today’s hundred-year event at many coastal locations, will become annually or more frequently, which will even happen by the mid-century for many low-lying coastal areas. The results also indicate that, rising GMSL, frequent ESL and anthropogenic drivers such as reclamation and subsidence, increase the exposure and vulnerability of coastal social-ecological systems. The sea level related hazards (such as submergence of land, enhanced coastal erosion, more frequent or intense flooding, salinization of soils, groundwater and surface waters, loss of and change of coastal ecosystems) will increase (high confidence). At the century scale and without adaptation, the vast majority of low-lying islands, coasts and communities, e.g., resources-rich coastal cities, urban atoll islands, tropical agriculture deltas, and Arctic communities, face substantial risk from these coastal hazards (high confidence).

Key words: Sea level rise, Low lying, Coasts, Impacts, Risk

蔡榕硕,谭红建. 海平面加速上升对低海拔岛屿、沿海地区及社会的影响和风险[J]. 气候变化研究进展, 2020, 16(2): 163-171.

CAI Rong-Shuo,TAN Hong-Jian. Impacts and risks of accelerating sea level rise on low lying islands, coasts and communities[J]. Climate Change Research, 2020, 16(2): 163-171.

图/表 3

图1 观测和模拟的全球海平面变化[1] 注：图中蓝色实、虚线为模拟值,其他颜色为验潮站观测值;黑色实线为卫星高度计观测值;图中阴影为不确定性范围。

Fig. 1 Comparison of observed and simulated global mean sea level change since 1901 (a) and since 1993 (b) [1]

图2 未来（2081—2100年）不同情景下（RCP2.6,RCP4.5和RCP8.5）全球12个验潮站的极值水位和重现期相对于1986—2005年的变化 [1] 注：观测的拟合值本质上是观测值,只是拟合后有一个不确定范围,如灰色宽度所示。

Fig. 2 The relation between expected extreme sea level events and return period at a set of characteristic tide gauge locations (see upper left for their locations), referenced to 1986-2005 mean sea level and 2081-2100 conditions for three different RCP (2.6, 4.5, 8.5) scenarios [1]

图3 21世纪末（2081—2100年）海平面上升对低海拔沿海地区影响风险[1] 注：左图为历史观测和未来RCP2.6、RCP8.5两种情景下全球平均海平面变化;右图为根据真实案例评估得到的海平面上升风险,分别选取了沿海大城市、城市环礁群岛、热带农业三角洲和北极沿岸社区等4种区域及未适应与充分适应两种情景。

Fig. 3 Additional risk related to sea level rise for low-lying coastal areas by the end of the 21st century[1] (left describes GMSL rise observations for the recent past (1986-2005) and projections under RCP2.6 and RCP8.5 by 2100 relative to the recent past (1986-2005). Right describes risk to local geographies, e.g., megacities, urban atoll islands, tropical agricultural deltas, and Arctic communities under two adaptation scenarios (“No-to-moderate adaptation” and “High adaptation”))

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