The Impacts of Climate Change on Wildfires

With the recent devastating infernos in California that have killed dozens and caused billions of dollars of damage, I thought now would be a suitable time to discuss what contemporary scientific research says about the impact of climate change on wildfires. Increases in fire activity have been documented in recent decades, particularly across the western United States [1]. Climate change is expected to increase the frequency, size, and severity of wildfires across the western USA. This is because warming temperatures and shifting precipitation patterns are altering landscapes, making them more susceptible to severe wildfires [1].

Typically, fire behavior is driven by topography, fuels, and weather. However, over the long-term, climate change is impacting plant productivity and moisture availability, which influences the quantity of fuel on the landscape. This is evident in the examples from the recent California wildfires. In the past two decades, California has experienced a Megadrought, a record-breaking drought with significant social, economic, and political repercussions [2]. Yet this period of drought was followed by one of the wettest winters on record in 2022-2023 [3]. The state also experienced significant snowpack thanks to a series of strong atmospheric river events [3]. While drought concerns were temporarily alleviated across much of the state, there is such a thing as too much of a good thing.

The copious amounts of rain that deluged California in the winter of 2022-2023 and parts of 2023 led to an explosion of growth the state’s forests and vegetation [4]. This growth of vegetation proved to be a significant fuel source in the subsequent wildfires we have seen [4]. All it took was a dry period spanning from May 2024 until January 2025, during which parts of Los Angeles did not receive a drop of rain, for this unusually lush vegetation to quickly turn into wildfire fuel.

With the future climate warming rapidly, dry areas are expected to become even drier and wet areas are likely to become even wetter [5]. Yet when rain does fall, it has the potential to be even more intense. This is because the saturation vapor pressure of water increases exponentially as temperature rises. This is known as the Clausius-Clapeyron relation, and it results in a more humid atmosphere, more rain, and, often, greater rainfall rates [6]. Even a 1°F rise in temperature results in a 4% greater water vapor capacity of the Earth's atmosphere (see Figure 1).

Figure 1: Schematic displaying the effect of a 1-degree Fahrenheit increase in temperature on the available water vapor content in the atmosphere. The relationship between water vapor and temperature is an exponential one, meaning that continued Earth warming will further accelerate the atmosphere’s ability to hold moisture. Image created by Diana Chao.

Thus, one can conclude that these sorts of "pendulum swings" in climate -- from a record dry period to an extremely wet one -- could become a more common facet of California’s and other states' future, increasing the risk of perilous fire behavior. Climate change is expected to continue to increase the frequency of extreme weather events [7]. If so, the need for effective forest management and climate mitigation/adaptation strategies is more critical than ever before.

Studies suggest that management actions can be effective in reducing the risk of high-severity fire [8, 9, 10]. Thinning overgrown forests, clearing deadwood and debris, and managing non-native invasive plant species are some of the ways that fire severity can be reduced. In addition, prescribed fires – controlled, intentional burns used to clear excess vegetation and reduce the amount of fuel for future fires – have been shown to be effective [11]. However, prescribed burning is sometimes difficult in western U.S. landscapes. Many areas experience prolonged drought and windy conditions, making it difficult to conduct these burns and keep them contained. Prescribed fires must also be ignited under tightly controlled weather and fuel conditions, and the relative lack of optimal conditions in the western U.S. means that the window for igniting these fires can be quite limited [11]. Nonetheless, prescribed fire remains an important tool for forest and ecosystem management and a way to reduce the risk of future fire severity.

What does the increase in extreme weather and perilous fire behavior mean for the residents and insurers affected? There is a well-documented increase in the number of U.S. billion-dollar disasters since 1980 as well as the cumulative costs of these disasters (Figure 2). Part of this is due to the rapid increase in population of people living in vulnerable areas, which has resulted in a corresponding increase in buildings, infrastructure, and residences. Damage estimates from this year’s Los Angeles County wildfires are as high as $100 billion to nearly $250 billion, which would be the costliest in history for the area [12, 13]. And as we’ve seen in other parts of the country, most notably hurricane-stricken Florida, these events pose serious threats to both the insurance industry and clients’ ability to maintain coverage in the face of these disasters. We’ll provide a more in-depth discussion of this topic in our next blog post, so stay tuned.