Human-Caused Warming Is Shrinking the Caribbean's Early Rainy Season
World Weather Attribution reported on Aug. 28 that human-caused climate change has reduced early wet-season rainfall by about 6% in Jamaica and about 9% in Puerto Rico, based on its analysis of the drought that has gripped the islands since May.
The group, a research consortium that produces rapid analyses of extreme weather, studied May through July rainfall in Jamaica, Puerto Rico and the Lesser Antilles. Its results are stated as changes in likelihood rather than as a cause of the current drought: WWA says an event with effective precipitation as low as 2026's, meaning rainfall minus the water estimated to evaporate from soil and plants, is now about 40% more likely in Jamaica than in a climate 1.4 degrees Celsius cooler, and about 30% more likely in Puerto Rico than in a pre-industrial climate.
By WWA's reckoning, the low-rainfall event had a 50-year return period in Puerto Rico and a 30-year return period in Jamaica. Measured as effective precipitation, that same event had a 15-year return period in Puerto Rico and a 30-year return period in Jamaica.
Researchers from Jamaica, the Dominican Republic, Ireland, the United States, the Netherlands, Sweden and the United Kingdom combined observational datasets with climate models, using what WWA describes as established, peer-reviewed methods. The models show what the group calls a small but consistent drying. WWA reports a declining rainfall trend in Jamaica whose strength depends on which dataset is used, and it reports Puerto Rican weather stations showing decreases in some areas and not others. For the Lesser Antilles, where weather stations are sparse, WWA calls the results highly uncertain.
Modeled projections with a further 1.4 degrees Celsius of warming put the effective-precipitation event at three times more likely in Jamaica and 2.5 times more likely in Puerto Rico, WWA says.
Puerto Rico has introduced water rationing for some residents and recorded more than 300 brushfires in July, and Jamaica has restricted non-essential water use in several parishes as major reservoirs fall, according to WWA's account of conditions on the islands.
