Climate Change Overview

Climate Scenarios

Climate scenarios in the SNC (2015) correspond to the Special Report Emission Scenarios 
(SRES). These projections of rainfall and temperature for Saint Vincent and the 
Grenadines through the end of the century are obtained, from a consensus of an
ensemble of 15 Global Circulation Model (GCMs), Regional Climate Model (RCM) and 
downscaling techniques. The models were run using the SRES that represent future 
change under three GHG emission scenarios: AIBI (medium emissions), A2 (high 
emissions) and B1 (lower emissions).


The mean temperature is expected to increase by 0.15° C per decade 
over the next century. Under the A2 scenario (high emissions), GCMs project maximum 
temperature changes of up to 4° C by the end of the century, with median annual 
increase of up to 1.0° C by the 2030s, 1.8 °C by the 2060s, and 2° C by the 2090s. Projection 
for seasonal changes also showed a similar warming trend throughout the century. By 
the end of the century, under the highest emission scenario, GCMs project the greatest 
seasonal warming will occur in December, January and February while the months of 
June to November showed the fastest average rates of decadal change. The frequency 
of hot days and nights is also expected to increase by 75 percent and 66 percent by the 
2060s, increasing up to 99 percent by the end of the century. Cold days and nights show 
marked decrease, almost reaching nonexistence by the 2060s.


Most models point to a drying throughout the year with negative median values 
range from 10 percent to 22 percent annually by 2090s. The maximum possible changes 
indicate up to 24 percent less annual rainfall by 2030s, 41 percent by 2060s and 58 
percent by 2090s. The results from the models also suggest drying in the wet season from 
June to November, with the greatest seasonal change seen in the summer months (7.1 
percent per decade). Decreased rainfall in the rainy season will significantly affect water 
availability for Saint Vincent and the Grenadines whose water source currently is from 
surface streams. The dry months early in the year are less severely affected in the median, 
but still show similar downward trends. Moreover, the proportion of total rainfall occurring 
in heavy events shows the greatest change in March, April and May, with a decrease of 
up to 30 percent under A2. Most scenarios, however, indicate a slight decrease in 
maximum 1-day rainfall, but up to 7 mm decrease in maximum 5-day rainfall by the end 
of the century.


According to predictions from the IPCC, the future hurricanes of the north 
tropical Atlantic will likely become more intense, with higher peak wind speeds and 
heavier near-storm precipitation. Similar to projections for hurricanes, the IPCC’s 
projections were relied on to estimate sea level rise. Changes in the Caribbean are 
expected to be near the global mean of 0.5 m to 0.6 m in the range of 2018 to 2100 when 
compared to 1986 to 2005 (under RCP 4.5 scenario). All models show continued ENSO 
inter-annual variability.

Sea level rise.

Ocean expansion (due to warming) and the inflow of water from melting 
glaciers have raised the global sea level over the last decade. Large deviations among 
the limited set of models addressing the issue, however, make future estimates of sea 
level change uncertain, including those for the Caribbean. Similar to projections for 
hurricanes, it is the IPCC‘s projections which are relied upon to estimate sea level rise. 
Whereas it is not presently possible to project sea level rise for Saint Vincent and the 
Grenadines, changes in the Caribbean are expected to be near the global mean. Under 
the A1B scenario, sea level rise within the Caribbean is expected to be between 0.17 m 
and 0.24 m by 2050 (IPCC 2007). For comparison, global sea level rise is expected to 
average 0.35 m (0.21 to 0.48 m) under the same scenario by the end of the century 
(relative to the period 1980-1999). It is important to note, however, that changes in ocean 
density and circulation will ensure that the distribution of sea level rise will not be uniform 
across the region.

Temperatures and ENSO.

All models show continued ENSO interannual variability in the 
future. However, there is no consistent indication of discernible changes in projected 
ENSO amplitude and frequency in the 21st century (IPCC 2007). According to the 
aforementioned projections, one can expect a drier, hotter Saint Vincent and the 
Grenadines with less natural coastal defense structures (mangroves, coral reefs, sand 
dunes) to buffer more intense and more frequent storm systems.