Hot Days, Warm Nights, and Flooding: How Community Defined Critical Thresholds for Extreme Events can be used to Support Decisions and Build Climate Resilience

Many communities in the United States are already vulnerable to extreme events; many of these vulnerabilities are likely to increase with climate change. In order to promote the development of effective community responses to climate change, we tested a participatory process for developing usable climate science, in which our project team worked with decision­ makers to identify extreme event parameters and critical thresholds associated with policy development and adaptation actions.

Our hypothesis is that conveying climate science and data through user-defined parameters and thresholds will help develop capacity to use this information, streamline development strategies and actions, and motivate participation by a variety of preparedness planners. Our team collaborated with urban decision­ makers, in departments that included resilience, planning, public works, public health, emergency management, and others, in four cities in the semi­arid south­central plains and intermountain areas of Colorado, New Mexico, Oklahoma, and Texas. Through an iterative process, we homed in on both simple and hybrid indicators for which we could develop credible city­ specific projections that include changing climate conditions. Throughout the process, we communicated information about confidence and uncertainty, in order to develop a blend of historic and projected climate data, as appropriate, depending on levels of uncertainty. Our collaborations have resulted in (a) the identification of more than 50 unique indicators and thresholds across the four communities, (b) enhanced communication and collaboration between city departments, and (c) the implementation of actions, ranging from a climate leadership training program for city staff members, to a rainwater capture project to improve responses to expected increases in both stormwater runoff and water capture for drought episodes.