Climate Change and the Central American Mid-summer Drought - The Importance of Changing Precipitation Patterns for Food and Water Security

In addition to periodic long-term drought, much of Central America experiences a rainy season with two peaks separated by a dry period of weeks to over a month in duration, termed the mid-summer drought (MSD). Food and water security for smallholder farmers in the region hinge on accommodating this phenomenon, anticipating its arrival and estimating its duration. Model output from 1980 through the late 21st century projects changes in precipitation amount, variability, and timing, with potential to affect regional food production. Using surveys of farmer experiences in conjunction with gridded daily precipitation for a historic period on multiple scales, and with projections through the 21st century, we characterize the MSD across much of Central America using four measures: onset date, duration, intensity, and minimum, and test for significant changes. Our findings indicate that the most significant changes are for the duration, which, by the end of the century, is projected to increase by an average of over a week, and the MSD minimum precipitation, which is projected to decline by an average of over 26%, with statistically significant changes for most of Nicaragua, Honduras, El Salvador, and Guatemala (assuming a higher emissions pathway through the 21st century). These changes toward a longer and drier MSD have important implications for food and water security for vulnerable communities through the region. We find that for the four metrics the changes in interannual variability are small compared to historical variability, and are generally statistically insignificant. New farmer survey results are compared to findings from our climate analysis for the historic period, are used to interpret what MSD characteristics are of greatest interest locally, and are used for the development of adaptation strategies.