Hurricanes are also common occurrences. The Great Hurricanes of 1780s were some of the most devastating and consequential hurricanes in the recorded history of the Caribbean (Schwartz, 2015). Since then, at least 110 hurricanes have travelled within 120 miles of the USVI – a distance away from hurricanes’ eyes where winds often still have tropical storm strength (NOAA, 2018a; Schwartz, 2015). We find that, on average, the USVI has been within the zone of influence of approximately 2 hurricanes per year, and has experienced damaging hurricanes approximately every 6 years. Since 1950, the beginning of the modern era of naming and tracking hurricanes more precisely, the USVI has been in the zone of influence of 3 hurricanes per year, on average, and suffered from the impacts of nearly half of the hurricanes that were within 120 miles (Schwartz 2015; Paulson et al. 1991). Most of these storms were Category 3 or 4, until 2017.

Hurricanes Irma and Maria were the only two of the modern era that were classified as Category 5. However, it is too early to tell whether these events are the result of climate change. Indeed, the impacts of climate change on hurricanes genesis and pathways is still an active subject of research.

Saffir-Simpson Hurricane Wind Scale

Observed Global Temperature and Carbon Dioxide

Weather patterns are driven by differences in temperature of the Earth’s surface, leading to changes in pressure, wind, humidity and, ultimately rainfall patterns. Climate refers to the long-term regional or even global average of temperature, humidity and rainfall patterns over seasons, years or decades (NASA, 2018). The earth’s climate is affected by solar cycles, changes in ecosystems, or volcanic eruptions. But climate in different parts of the world has been changing in at least the past 100 years because of the global increase of temperatures. Indeed, for more than 100 years, humans have emitted vast amount of green-house gases in the atmosphere. These gases, which are common gases (e.g., carbon dioxide, methane, water vapor, etc.) and lesser known gases (e.g., fluorinated gases), usually trap heat in the atmosphere and help maintain livable temperatures on earth (EPA, 2018). However, excess emissions by humans, mostly carbon dioxide through the burning of fossil fuels, have caused more heat to be trapped, and global temperatures to slowly increase (Figure 1). The steady increase in global temperature, known as global warming, is leading to disturbances around the world that change weather patterns, and thus climate. As a result, many places in the world have experienced long-term changes in the frequency, intensity and duration of weather events: their climate has changed. These changes, and the impacts of these events, have been exacerbated by a global rise in sea-level, caused by the melting of glaciers – land-based reserves of water – due to increased global temperatures.

Temperatures in the USVI average around 88°F during the day, cooling to around 76°F at night. The warmer period starts in May and ends around November, with highs around 89°F; the cooler period starts in December and ends around April, with average highs around 83°F (Figure 2).

Temperatures vary with location and altitude by around 5°F. Figure 3 provide an estimate of such variation (Harmsen 2020; Goyal, González, and Chao de Báez 1998). Temperatures can sometimes reach above 95°F, but the heat is often tempered by the nearly constant sea breeze. Minimum temperatures can reach below 70°F, but such occurrences are rare.

Since 1901, average annual temperatures have modestly increased by approximately 4°F (Figure 4). This rate of increase has been consistent and similar for average, maximum and minimum temperatures. In addition, the number of days above 90°F seems to be increasing in the past 20 years, even though there is some variability. Similar observations were made in Puerto-Rico (Gould and Díaz 2018).