Future Caribbean Climates in a World of Rising Temperatures: The 1.5 vs 2.0 Dilemma

A 10-member ensemble from phase 5 of the Coupled Model Intercomparison Project (CMIP5) is used to analyze the Caribbean's future climate when mean global surface air temperatures are 1.5 degrees, 2.0 degrees, and 2.5 degrees C above preindustrial (1861-1900) values. The global warming targets are attained by the 2030s, 2050s, and 2070s respectively for RCP4.5. The Caribbean on average exhibits smaller mean surface air temperature increases than the globe, although there are parts of the region that are always warmer than the global warming targets. In comparison to the present (using a 1971-2000 baseline), the Caribbean domain is 0.5 degrees to 1.5 degrees C warmer at the 1.58 degrees C target, 5%-10% wetter except for the northeast and southeast Caribbean, which are drier, and experiences increases in annual warm spells of more than 100 days. At the 2.0 degrees C target, there is additional warming by 0.28-1.0 degrees C, a further extension of warm spells by up to 70 days, a shift to a predominantly drier region (5%-15% less than present day), and a greater occurrence of droughts. The climate patterns at 2.5 degrees C indicate an intensification of the changes seen at 2.0 degrees C. The shift in the rainfall pattern between 1.5 degrees C (wet) and 2.0 degrees C (dry) for parts of the domain has implications for regional adaptation pursuits. The results provide some justification for the lobby by the Caribbean Community and Small Island Developing States to limit global warming to 1.5 degrees C above preindustrial levels, as embodied in the slogan 1.5 to Stay Alive.''