In the South, lower income African-Americans and Hispanics are employed as wage laborers either directly or indirectly in the agricultural industry, which is particularly sensitive to weather and climate variability, especially drought.To these factors I would add - at least in some places - a lack of trust in the government and governmental sources of information about health and emergency preparedness. In one study I read looking at indicators by which you can measure a country's ability to recover after a natural disaster (The determinants of vulnerability and adaptive capacity at the national level and the implications for adaptation- Brooks, Adger, Kelly, 2005), a top indicator was the effectiveness of a government. While that study was international in scope, the idea is relevant to communities within the U.S. If your community has a history of being deprived the full protection of the law, and/or your community doesn't believe the government is taking its interests to heart, it is less likely to respond to a call to retreat from an oncoming storm, or take shelter from a heat wave in government-sponsored cooling centers, or to follow instructions about how to create a household emergency kit.
This study and others I've read like it all point to the need to discuss vulnerability at a sub-national level, trying to identify communities with special exposure to climate impacts, just as Dr. Shepherd has done.
The next, step, of course, is to put this research to work improving the emergency preparedness and health care access for African-American communities in the U.S.-- a good thing to do in any case, but particularly in the face of climate change.