A. V. Karmalkar

A review of observed and projected changes in climate for the islands in the Caribbean

Resumen Los cambios climaticos observados y proyectados tienen implicaciones socioeconomicas importantes para las islas del Caribe. El objetivo de este articulo es presentar informacion esencial sobre el cambio climatico —basada en estudios previos, observaciones disponibles y simulaciones de modelos climaticos— a escalas espaciales relevantes para las islas caribenas. Se utilizan datos del modelo general de circulacion (GCM) incluidos en el Proyecto de Comparacion de Modelos Acoplados fase 3 (CMIP3), asi como del modelo climatico regional (RCM) del Centro Hadley del Reino Unido, para aportar tanto informacion actual como informacion basada en proyecciones sobre precipitaciones y temperatura en estados insulares especifcos. Se utilizan observaciones reticuladas de estaciones y datos satelitales para estudiar el clima del siglo XX y evaluar el desempeno de los modelos climaticos. Con un enfoque centrado en la precipitacion, tambien se analizan factores como la temperatura superficial del mar, la presion al nivel del mar y los vientos que influyen en las variaciones estacionales de la precipitacion. La media del ensamble del CMIP3 y el RCM captan satisfactoriamente las peculiaridades de la circulacion atmosferica de gran escala en la region, pero no asi el ciclo estacional bimodal caracteristico de la precipitacion. La aridez en epocas de lluvias prevista en escenarios de cambio climatico en la region se ha abordado en estudios previos, pero la magnitud de la variacion es muy incierta en las simulaciones tanto del GCM como del RCM. La disminucion proyectada es mayor al inicio de la temporada de lluvias y suprime la sequia del medio verano en el Caribe occidental. Las simulaciones del RCM muestran avances respecto del GCM, sobre todo por sus mejores representaciones de la extension territorial, pero su desempeno depende en gran medida de la conduccion del GCM. El presente estudio destaca la necesidad de contar con observaciones de alta resolucion y comparar simulaciones de modelos climaticos para entender a fondo el cambio climatico y su impacto en las pequenas islas del Caribe.

Consequences of Global Warming of 1.5 °C and 2 °C for Regional Temperature and Precipitation Changes in the Contiguous United States

The differential warming of land and ocean leads to many continental regions in the Northern Hemisphere warming at rates higher than the global mean temperature. Adaptation and conservation efforts will, therefore, benefit from understanding regional consequences of limiting the global mean temperature increase to well below 2°C above pre-industrial levels, a limit agreed upon at the United Nations Climate Summit in Paris in December 2015. Here, we analyze climate model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to determine the timing and magnitude of regional temperature and precipitation changes across the contiguous United States (US) for global warming of 1.5 and 2°C and highlight consensus and uncertainties in model projections and their implications for making decisions. The regional warming rates differ considerably across the contiguous US, but all regions are projected to reach 2°C about 10-20 years before the global mean temperature. Although there is uncertainty in the timing of exactly when the 1.5 and 2°C thresholds will be crossed regionally, over 80% of the models project at least 2°C warming by 2050 for all regions for the high emissions scenario. This threshold-based approach also highlights regional variations in the rate of warming across the US. The fastest warming region in the contiguous US is the Northeast, which is projected to warm by 3°C when global warming reaches 2°C. The signal-to-noise ratio calculations indicate that the regional warming estimates remain outside the envelope of uncertainty throughout the twenty-first century, making them potentially useful to planners. The regional precipitation projections for global warming of 1.5°C and 2°C are uncertain, but the eastern US is projected to experience wetter winters and the Great Plains and the Northwest US are projected to experience drier summers in the future. The impact of different scenarios on regional precipitation projections is negligible throughout the twenty-first century compared to uncertainties associated with internal variability and model diversity.

Interpreting results from the NARCCAP and NA-CORDEX ensembles in the context of uncertainty in regional climate change projections

Capsule SummaryEnsembles of dynamically downscaled simulations provide valuable information on regional climate change projections, but their interpretation remains challenging due to complexities in the experimental design.