Climate modeling for the Caribbean region

Jonathan Stone, intern at UN ECLAC Caribbean in Port-of-Spain

Climate change is one of the greatest threats to human prosperity and security in relation to its negative social, economic and environmental impacts. In the Caribbean, climate change poses a significant challenge to the region’s small island states, which are increasingly vulnerable to the impacts of climate change. These vulnerabilities arise from the islands' small size and relatively low levels of development, which further limit their resilience and ability to respond to external pressures, whether environmental, such as sea level rise, tropical cyclone intensity and fluctuations in water availability, or socio-economic, including increased resource constraints and migrationary pressures.

Figure 1: Average annual precipitation response across the Caribbean by 2099. Source: Christensen et al., 2007.

Although instrumental records already indicate noticeable rises in average global temperatures, climate models are necessary to quantify future temperature trends and associated impacts. Computer modelling provides an opportunity to better understand the workings of the climate system and examine the relative contributions of climate change drivers to the observed trends. However, climate models are not without their problems. Generally problems arise as a result of constraints to the computing power and time available for modelling, as well as limitations in the level of scientific understanding and representation of certain climate processes involved. We can, nevertheless, have confidence in the model output due to the established physical laws upon which the models are based and more importantly, their ability to reproduce past and recent climate change trends as observed and reconstructed from the instrumental and proxy records.

For the Caribbean, climate model output has been documented for both Global Climate Models (GCMs) and regional climate models. However, GCMs are often solved at too low a grid-scale resolution to include representation of many of the small islands in the Caribbean (See Explanation Box). To cover more accurately the effects on the islands and regional processes involved, the model has to be downscaled so that the GMC output is inputted in the regional model at a higher resolution. All models, including those for the Caribbean region, are unanimous in predicting the global trends of increased average temperatures and fluctuations in precipitation and water availability over the 21st century. Although the Caribbean region may experience slightly lower than average warming and sea level rise, decreases in average precipitation across the region are likely and these changes will still have a significant impact on human livelihoods within the region.

While there is a level of uncertainty involved in the model outputs for the Caribbean region, as with any other region, there is a need to raise awareness of the likely impacts of the predictions. Less developed islands are particularly vulnerable to climate impacts as they have more limited socio-economic adaptive capacity. While an average rise in temperature of a few degrees may seem insignificant to the lay-person, such temperature changes are likely to worsen existing risks and developmental challenges to the region. There is a need for quantification of changes in extremes rather than averages, as well as the social and economic implications of the changes. As current model outputs may underestimate the level of changes to be expected, one should invoke the precautionary principle, and adequate mitigation and adaptation strategies should be urgently developed. ■


References

S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and
H.L. Miller (eds.) Climate Change 2007: The Physical Science Basis. IPCC, 2007.
Available online at ipcc.ch.