Turks and Caicos Islands

3. CLIMATE MODELLING
3.1. Introduction to Climate Modelling Results
This summary of climate change information for The Turks and Caicos is derived from a combination of
recently observed climate data sources, and climate model projections of future scenarios using both a
General Circulation Model (GCM) ensemble of 15 models and the Regional Climate Model (RCM), PRECIS.
General Circulation Models (GCMs) provide global simulations of future climate under prescribed
greenhouse gas scenarios. These models are proficient in simulating the large scale circulation patterns
and seasonal cycles of the world’s climate, but operate at coarse spatial resolution (grid boxes are typically
around 2.5 degrees latitude and longitude). This limited resolution hinders the ability for the model to
represent the finer scale characteristics of a region’s topography, and many of the key climatic processes
which determine its weather and climate characteristics. Over the Caribbean, this presents significant
problems as most of the small islands are too small to feature as a land mass at GCM resolution.
Regional Climate Models (RCMS) are often nested in GCMs to simulate the climate at a finer spatial scale
over a small region of the world, acting to ‘downscale’ the GCM projections and provide a better physical
representation of the local climate of that region. RCMs enable the investigation of climate changes at a
sub-GCM-grid scale, as such changes in the dynamic climate processes at a community scale or tourist
destination can be projected.
For each of a number of climate variables (average temperature, average rainfall, average wind speed,
relative humidity, sea-surface temperature, sunshine hours, extreme temperatures, and extreme rainfalls)
the results of GCM multi-model projections under three emissions scenarios at the country scale, and RCM
simulations from a single model driven by two different GCMs for a single emissions scenario at the
destination scale, are examined. Where available, observational data sources are drawn upon to identify
changes that are already occurring in the climates at both the country and destination scale.
In this study, RCM simulations from PRECIS, driven by two different GCMs (ECHAM4 and HadCM3) are used
to look at projected climate for each country and at the community level. Combining the results of GCM
and RCM experiments allows the use of high-resolution RCM projections in the context of the uncertainty
margins that the 15-model GCM ensemble provides.
The following projections are based on the IPCC standard ‘marker’ scenarios – A2 (a ‘high’ emissions
scenario), A1B (a medium high scenario, where emissions increase rapidly in the earlier part of the century
but then plateau in the second half) and B1 (a ‘low’ emissions scenario). Climate projections are examined
under all three scenarios from the multi-model GCM ensemble, but at present, results from the regional
models are only available for scenario A2. Table 3.1.1 outlines the time line on which various temperature
thresholds are projected to be reached under the various scenarios according to the IPCC.
14