Assessing Exposure to Climate Risk in U.S. Municipalities

May 22, 2018 – 427 REPORT. Cities and counties are bearing the costs of the sixteen billion-dollar disasters in the United States in 2017, raising concerns over the resilience of municipalities to the impacts of climate change and associated financial shocks. Credit rating agencies are increasingly integrating physical climate risk into their municipal rating criteria; however, they lack concrete metrics that compare and assess which municipalities are exposed to climate impacts. Four Twenty Seven’s new local climate risk scores provide comparable, forward-looking data to fill this gap. This report discusses our approach to measuring exposure to climate hazards and highlights cities and counties most exposed to the impacts of climate change.

Following Hurricane Harvey, Moody’s downgraded Port Arthur from A1 to A2 due to its “weak liquidity position that is exposed to additional financial obligations from the recent hurricane damage, that are above and beyond the city’s regular scope of operations.” (Moody’s). This follows the recent trend of rating agencies increasingly considering climate change and past extreme weather events in their evaluations of U.S. cities. While this consideration is an important step, their evaluations could be better informed by incorporating forward-looking comparable data on the climate risks that impact these municipalities.

Featuring Four Twenty Seven’s new local level exposure scores, our report Assessing Exposure to Climate Change in U.S. Munis, shares key findings from our scoring of all 3,143 U.S. counties and the 761 cities over 50,000 in population. The research results are based on Four Twenty Seven’s market-leading expertise in five major climate categories, including cyclones/hurricanes, sea level rise, extreme rainfall, heat stress, and water stress. “This new dataset provides a comprehensive suite of risk scores to better inform rating and pricing decisions,” says Emilie Mazzacurati, Founder & CEO. “We believe that our analytics will be very helpful for all market participants, including muni bond investors, local governments, and ratings agencies.”

This report highlights specific cities and counties most exposed to each climate hazard and also discusses regional trends and economic sensitivities that may exacerbate a muni’s vulnerability.  “Climate risk is increasingly a part of our credit analysis for municipal issuers across the country,” said Andrew Teras, senior analyst at Breckinridge Capital Advisors. “The climate risk scores developed by Four Twenty Seven provide a comparable way to evaluate climate exposure and will give us another factor for assessing our investment universe.”

Key Findings

  • Sea Level Rise: The mid-Atlantic, particularly New Jersey, Virginia, North Carolina and Florida, has the highest exposure to coastal flooding in the United States, with the Bay Area and Pacific Northwest also highly exposed in several of their coastal cities and counties.
  • Cyclones/Hurricanes: The majority of cyclone risk in the United States is concentrated in the Southeast, given its geographic proximity to the Gulf of Mexico and the tropical Atlantic Ocean. The coastal Mid-Atlantic and Northeast are also exposed to cyclones, but they tend to be less frequent than in the Southeast and somewhat weaker on average after interacting with land or cooler ocean waters.
  • Extreme Rainfall: The Midwest is particularly exposed to heightened flood risk due to changing rainfall patterns. Recent advancements in attribution science show extreme rainfall to be the main driver of recent floods rather than 20th century agricultural practices, as was largely believed to be the case until recently.
  • Heat Stress: The highest heat stress scores tend to be centered in the Southeast and Midwest, concentrated in Missouri and western Illinois and fanning out to the Great Plains, Mississippi River Basin, and Florida.
  • Water Stress: Key watersheds for agricultural production such as the Central Valley aquifer system in California and the Ogallala Aquifer in the Great Plains are highly exposed to water stress. The agriculturally-dominated areas of Bakersfield, Delano, and Visalia, CA along the Central Valley Aquifer are among the ten cities most exposed to water stress. Similarly, municipalities along the Ogallala Aquifer in the Great Plains also rely heavily on agriculture and are among the most exposed to water stress.

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