Wildfires: the smoking gun of Western climate change?

As cooler temperatures and precipitation finally bring relief to smoke-weary Montanans, the unusual nature of summer 2017 is coming into focus and the influence of climate change is impossible to ignore.

Extreme weather has no doubt been the dominant story throughout the country this past summer as hurricanes and tropical storms have ravaged the Southeastern United States and wildfires have wreaked havoc in the West. A simple Google search will yield hundreds of stories about the impacts of these events, but very few mention climate change as a contributing factor. And that’s unfortunate.

Collectively, we have over 65 years of experience studying Western climate and forest systems, and we are among the authors of the Montana Climate Assessment, a report that focuses on climate trends and their consequences for three of Montana’s vital sectors: water, forests, and agriculture. The assessment sheds some light on common questions about climate change and its effects on things like drought and wildfires.

Was this fire season remarkable?

2017 is already a record-breaking wildfire season in some regions of Montana, and the fingerprints of climate are easy to spot. In many ways, what we’ve seen this year is exactly what we’ve come to expect, but in other ways, it’s even more worrisome.

There has been an increase in large fires in the last three decades, and this year will be one of the worst, especially in Montana where wildfires have burned over 1 million acres (www.nifc.gov). The persistence of some of these fires has been unusual, choking western Montana valleys with health-threatening smoke for weeks on end.

What role did climate change play?

Climate has played a big role. While it’s impossible to tie any one weather event or wildfire directly to climate change, what we can say with certainty is this: increases in temperature in the last decades have set the stage for drier conditions and more fires. In a given year, warmer weather and less precipitation dries out fuel loads and creates conditions for rapid fire spread. Fire records dating back decades to millennia show a clear link between warmer temperatures, lower precipitation and an increase in the number of fires and acres burned. This situation is precisely what we expect to see from climate change.

Montana has been on a steady warming trend for decades, up over 3°F since 1950, and all projections are that it will continue. This summer was the second warmest on record since 1950 at 4°F above average, and the persistent high temperatures coupled with the record lowest rainfall in July and August shifted the relatively wet conditions of spring into extreme drought by mid summer. The speed of the transition from wet to dry was so rapid that the term “flash drought” has been coined.

What can we expect in the future?

These extreme weather events weren’t unforeseen and they are not without a systemic cause. As the buildup of greenhouse gases in our atmosphere intensifies, our overall climate and weather patterns will continue to change.

The Montana Climate Assessment goes into great detail about our climate future, and with respect to wildfire, we can expect additional warming with less precipitation in the summer months. Over the next century, extreme heat days (above 90°F) are projected to increase by an additional 5-35 days across the state. And as a result of greater drought, forest fires will likely increase in size, frequency, and possibly severity.

Factors contributing to wildfire are complicated, but we know that they involve both forest management and climate conditions. From 2006-2015, 95 percent of wildfires were suppressed at a cost of $13 billion (See Schoennagel et al., www.pnas.org/cgi/doi/10.1073/pnas.1617464114). This level of expenditure is not sustainable and the burden on state and local resources is enormous. New adaptive approaches are needed to manage forest fuel loads and reduce wildfire risk and costs (e.g., fuel treatments, especially on private land, and fire-adapted planning and land use) while also recognizing that fire is part of healthy forests. In addition we must also consider policies that will curb greenhouse gas emissions, which are the main driver in climate change.

Together, working from the best available science, we can and must develop plans to increase resilience, mitigate expected impacts and address the known causes of climate change.

The Montana Climate Assessment is a product of the Montana University System’s Montana Institute on Ecosystems, in collaboration with the Montana Climate Office, Montana Water Center and MSU Extension. It provides a thorough look at how Montana’s climate has changed and what we can expect in the coming years. This information is intended to help families and communities plan for and adapt to changing conditions. We invite everyone to consult the report, which is available at www.montanaclimate.org. Please also join us in local discussions around the state in the coming year.

Cathy Whitlock is professor of earth sciences at Montana State University. Kelsey Jencso is associate professor of watershed hydrology and director of the Montana Climate Office at the University of Montana. Nick Silverman is a research scientist in the Montana Climate Office at the University of Montana.