The Climate and Data Science behind the Department of Defense Climate Assessment Tool (DCAT)

In 2021, the Department of Defense (DoD) created its Climate Assessment Tool (DCAT), a screening-level geospatial tool for assessing the Department’s exposure to climate change. DCAT relies on authoritative data and model outputs that are downscaled and compiled into forms that support the production of actionable assessments of future climate exposure. Climate exposure is assessed at more than 2,000 DoD locations around the globe for eight climate hazards: coastal flooding, riverine flooding, extreme temperature, drought, energy demand, land degradation, wildfire, and historical extreme conditions. The tool aggregates exposure assessments across these eight hazards and, for all but Historical Extreme Conditions, provides information on how these hazards are projected to change over the 21st century. Assessments are averaged over three epochs: Base (1950–2005), 2050 (2035–2064), and 2085 (2070–2099). Hazards (except Historical Extreme Conditions) are further grouped into “Lower” and “Higher” scenarios, which reflect different trajectories of greenhouse gas emissions. The Higher scenario represents Representative Concentration Pathway (RCP) 8.5 within the Coupled Model Intercomparison Project Phase 5 (CMIP5) experiments, and the Lower scenario represents RCP4.5. (Note: DoD is exploring the use of CMIP6 data while maintaining robust data integrity of coastal and riverine hydrology parameters). More tailored hydroclimate refinements are applied to the Coastal and Riverine Flooding hazards to model the 1% Annual Exceedance Probability (AEP) and include the DoD’s Regional Sea-Level (DRSL) database. To provide consistent relative climate exposure scores, DCAT uses the Weighted Order Weighted Average (WOWA) methodology, which groups environmental indicators into eight hazard categories and produces composite index scores (or “WOWA scores”) for each of those hazard categories. The WOWA climate exposure index supports screening-level assessments of climate risk.

Building on work by the United States Army Corps of Engineers for their Civil Works Vulnerability Assessment Tool beginning in 2011, DCAT has evolved to incorporate key climate and data science updates fit for the purpose of DoD missions and capabilities. DCAT has incorporated several science updates in the past year alone. The DCAT team examined the sensitivity of the current WOWA exposure scoring approach, alternative scoring methods, and different data visualization techniques to understand if and how they might be adjusted or incorporated in future tool development. The team also recalculated and reproduced all 26 of the underlying global hazard indicator datasets using updated global climate model data and riverine flood mapping across DoD and allied-nation watersheds. Finally, the DCAT team updated its methodology to map projected coastal inundation at DoD sites and other allied-nation locations. Gaps in sea level datums and estimates of extreme sea levels at many sites globally were a challenge. To overcome this, the team combined existing interagency sea level change curves with extreme sea level estimates and global oceanic reanalysis data made available by Vousdoukas et al. (2018) as well as vertical EGM2008 datum estimates from Pavis et al. (2012) to generate depth and inundation mapping across selected overseas DCAT sites and for several allied nations.

In this presentation, we will provide a deeper dive into the climate and data science enhancements made to DCAT in the past year.