Caribbean climate change vulnerability: Lessons from an aggregate index approach

The study examines the potential influence of sub-regional variations in climate, and specifically heavy rain events, in determining relative vulnerabilities of locations in twelve Caribbean countries. An aggregate vulnerability index, referred to as the Caribbean Vulnerability Score (CVS), is created using historical demographic and socioeconomic data and climate data representing extreme rain events. Four scenarios are explored. Firstly, comparative vulnerabilities are determined when heavy rainfall is incorporated in CVS versus when it is excluded. The impact of climate change is also investigated using future climate data derived from statistical downscaling but holding demographic and socioeconomic sub-indices constant. The analysis is repeated with projections of future demographic structure from the Shared Socioeconomic Pathway data (SSP3), future climate projections and constant socioeconomic. Finally, the sensitivity of the results is examined with respect to applying different weights i.e. versus using equal weights for the climate and non-climatic components of CVS as is done for the first three scenarios. Results suggest that the inclusion of historical susceptibility to rainfall extremes influences relative vulnerabilities within the Caribbean when compared to the rankings of vulnerability derived using only socioeconomic and demographic inputs. In some cases significant increases in relative rankings are noted. Projected changes in the intensity of rain events across the Caribbean region in the 2030s and 2050s, do not significantly alter the top and lowest ranked vulnerable locations when demographic and socioeconomic indices are held constant. Changes may however occur in the order of the top ranked locations dependent on scenario and time slice. In general, future shifts in relative vulnerabilities were found to be dependent on (i) changes in both future climate and demographic scenarios, (ii) the time horizons being considered, and (iii) the weighting assigned to climate in the future.

本研究探讨了气候次区域差异（尤其是强降雨事件）对12个加勒比国家各地区相对脆弱性的潜在影响。研究构建了综合脆弱性指数——加勒比脆弱性得分（Caribbean Vulnerability Score, CVS），该指数基于历史人口统计与社会经济数据、以及表征极端降雨事件的气候数据生成。本研究共设置四种分析情景：其一，对比纳入强降雨因子与不纳入强降雨因子时的各地区相对脆弱性差异；其二，采用统计降尺度得到的未来气候数据，且固定人口统计与社会经济子指数，以探讨气候变化的影响；其三，采用共享社会经济路径（Shared Socioeconomic Pathways, SSP3）数据中的未来人口结构预测结果、未来气候预测数据，并固定社会经济子指数，重复开展前述分析；其四，针对加勒比脆弱性得分中气候组分与非气候组分设置不同权重（前三种情景均采用等权重分配），检验研究结果的敏感性。研究结果显示，相较于仅基于社会经济与人口统计数据得到的脆弱性排名，纳入历史极端降雨暴露度指标会显著改变加勒比地区各地区的相对脆弱性，部分地区的相对脆弱性排名出现显著提升。当固定人口统计与社会经济指数时，加勒比地区2030年代与2050年代的降雨强度预测变化，不会显著改变脆弱性排名最高与最低的地区，但在不同情景与时间切片下，高脆弱性地区的排名顺序可能发生变化。总体而言，相对脆弱性的未来变化主要取决于三个因素：(i) 未来气候与人口情景的双重变化，(ii) 所选取的时间跨度，以及(iii) 未来研究中赋予气候组分的权重。