A multi-hazard approach in an era of global boiling
By Claire Phillips Wed, Dec 18, 2024
Let’s start with a hypothetical. Your community faces three main climate threats: heat waves, heavy rains, and wildfires.
A local official plans for heat with subsidies for air conditioning, and retrofitting trusted community spaces to serve as cooling centers. For flooding, the same official works with engineers and landscape designers to explore bioretention basins with tree plantings, to both manage flood waters and reduce urban heat island. The official invests in wildfire risk management too, as fires can be more likely after heat waves and can intensify the potential for severe flooding. This planner, like many climate leaders, recognizes that climate hazards are interconnected, and leads with a holistic, multi-hazard approach.
Why is this holistic approach vital, particularly in this “era of global boiling”? Individual climate hazards pose serious threats to our health, our environment, and our infrastructure. But these risks can be exponentially larger than they may seem at first glance, because multiple hazards can compound.
Cascading impacts and the climate crisis
Some climate hazards, including heat, can have cascading impacts that affect or amplify other hazards.
What might this look like? Let’s consider heat, precipitation, and wildfires.
Prolonged heat, especially when combined with low rainfall, can dry out soil and ground vegetation. Come wildfire season, dry vegetation is prime tinder. As one study on recent California megafires explains, “High temperatures, low relative humidity, and daytime southerly winds were all highly correlated with extreme rates of modeled [fire] spread.”
Heat’s influence on the landscape does not stop at the fire. After the flames subside, a burn scar left by a fire may increase flash flood and debris flow risks for years. If heavy rain comes only weeks after a wildfire, still-dry soil may be unable to absorb as much water, resulting in more water in surface floods, landslides, and mudslides.
And these landscape impacts aren’t just geographic. They have immense personal, financial and social costs.
What are cascading impacts?
Some climate hazards can create conditions that directly influence how other hazards play out. This is one form of “cascading impacts” where hazards affect each other, or other things.
To learn more about cascading impacts and other climate science, check out the 2023 Synthesis Report by the Intergovernmental Panel on Climate Change (IPCC). The report comes with a glossary of key terms, including cascading impacts.
Unrelated climate hazards and ripple effects
Even when hazards are unrelated, fallout from one hazard can still make the impacts of another
more dangerous. While rainstorms and heat waves may seem to offset one another, for example, they could instead exacerbate each other’s impacts.
How might this happen? First, a severe rainstorm hits. It creates flood waters, damaging homes and necessitating evacuations in some places. In pockets, heavy rain saturates the ground, triggering landslides and debris flow (incidents of this phenomenon occur around the world – from Italy to China to India). In some areas, strong winds coupled with the rain break branches and uproot trees, resulting in power outages.
Each person may face a different set of personal and financial setbacks. They may need to invest time and money to repair damages from flood waters, fallen debris, or landslides; buy groceries to replace food that spoiled when they or loved ones lost power; or cut back on planned expenses if they couldn’t safely get to work and lost wages as a result.
When summer heat arrives months later, the lingering effects of the storm continue to ripple, and climate equity issues become ever more stark. Subsidized air conditioning units might be unaffordable for a family that lives paycheck to paycheck, or had to spend their emergency funds on storm recovery. Or a household might have an air conditioning unit but keep it off for the same reason: the costly electric bill.
Just like that, people who could have kept cool during heat waves may be at risk of heat exhaustion or heat stroke. It is nearly always those with less disposable income, who have historically experienced marginalization or disinvestment in their communities, who face impacts first and worst.
Multiple hazards, one sobering climate crisis
Two recent storms in the United States threw into sharp relief the severity of heat risks in our multi-hazard reality.
In 2021, Hurricane Ida struck the southeast United States. It caused an estimated $65 billion in damages and claimed 38 lives in Louisiana alone. Panoramic images of wrecked buildings made headlines. But, critically, after skies cleared, a heat wave hit the state, and high humidity pushed heat index levels over 100 degrees Fahrenheit. With widespread power outages from Ida, many residents were left without adequate air conditioning or accessible, safe cooling spaces. In New Orleans, fourteen people died because of Ida. Of those fourteen, at least ten people were killed due to heat-related causes, making heat ultimately the “greatest killer” from the storm.
Similarly, in February 2024, an atmospheric river storm in California led to evacuations and heavy debris flows. Hundreds of thousands of people lost power, and nine residents died. Just months later, in July, California recorded its hottest month ever and wildfires including the Park Fire swept through Northern California. Then, in August, California communities that had faced the Park Fire were placed on alert, as heavy rains threatened to create flash floods in its burn scars.
Notably, in both of these events, the impacts could have been much worse if not for the hard work of many people—both leaders in the public and private sectors and dedicated community members.
As climate disasters continue to drive increasing mortality, infrastructure damage, and public health challenges, straining our fundamental systems and support networks, the role of these leaders has become increasingly critical.
What we can do?
There is no one-size-fits-all solution to multi-hazard climate resilience. Different climates, geographies, sociopolitical contexts, and resources make tailored solutions necessary. Climate leaders must actively seek to understand how the climate hazards in their region might affect each other and aim to address them holistically.
Fortunately, there are many multi-hazard approaches to learn from around the world. Some of these examples come from members of the Extreme Heat Resilience Alliance. Miami-Dade County and its Chief Heat Officer Jane Gilbert and global nonprofit Build Change are two of the members working to build resilience across hazards.
In Miami-Dade County, hurricane season often overlaps with extreme heat events. That’s why the County and Gilbert streamlined hazard training sessions, combining heat and hurricane preparedness. Similarly, Build Change, a nonprofit working to make homes disaster-resilient, employs a multi-hazard approach in housing retrofits. They consider the greatest regional climate risks – including heat, fire, flooding, and earthquakes – to support community members effectively.
This multi-hazard perspective can also apply to other resilience measures, such as nature-based solutions, innovative financing strategies for resilience projects, or community engagement sessions to prepare for climate and other risks. Indeed, some of the most effective resilience strategies offer co-benefits and can address multiple hazards simultaneously.
When the weather gets cooler, heat resilience can feel less urgent. Especially if the region is facing winter storms or monsoons. But it is worth it to make the time to holistically plan for heat alongside other hazards. Because it doesn’t just help during heat waves. Heat resilience can quietly protect communities from other hazards, too, long after temperatures drop.
