North America regularly sees wildfires – from Hawaii up to Maui, Canada. Across a typical summer there can be more than 1,000 active fires. Despite the geographical distances, the wildfires share some similarities. Here, there is a connection to climate shifts and the anthroprocene.
These are drawn out by Brian Lattimer, Director of Virginia Tech’s Extreme Environments and Materials Lab, who has explained the ramifications to Digital Journal.
Wildfires
Wildfires can be classified by cause of ignition, physical properties, combustible material present, and the effect of weather on the fire. Climatic cycles with wet periods that create substantial fuels, followed by drought and heat, often precede severe wildfires.
Wildfires impact atmospheric conditions through emissions of gases, particles, water, and heat. An important consideration is radiative forcing, which refers to the change in net (down minus up) irradiance (solar plus longwave) at the tropopause, the top of the troposphere where most weather takes place.
Climate changes
While studies show links between climate change and increased frequency or severity of fire weather — periods with a high fire risk due to a combination of high temperatures, low humidity, low rainfall and often high winds – there is a human-centric connection.
Rising global temperatures, more frequent heatwaves and associated droughts in some regions increase the likelihood of wildfires by stimulating hot and dry conditions, promoting fire weather, which can be used as an overall measure of the impact of climate change on the risk of fires occurring.
Common factors
According to Lattimer points of similarity include: “Very high winds and dry vegetation are two primary things that you typically will see with all such fires. High winds typically tilt the fire in such a way that it’s able to propagate quickly, advancing to vegetation that’s not ignited. Very high winds also tend to dry out vegetation even more, so you have this situation where things can ignite very quickly. Terrain is a factor as well. Where it’s sloped upward, fire will advance very quickly.”
Another factor is the presence of ‘firebrands’. Lattimer defines these as: “Firebrands are these small pieces of vegetation that break off from burning trees or grass, fly up in the air, land on stuff a mile or two away, and ignite things. (If it’s flying in the air, then that’s a firebrand, and once it lands, it’s an ember.) It appears that this kind of thing may have been happening in Hawaii and happens all the time — they ignite things a mile or two away from the main fire, where firefighters aren’t located. By the time they get there, there’s usually a lot of damage.”
Lattimer directs the Extreme Environments and Materials Lab, which focuses on safety in extreme environments primarily related to fire.
Remediation
While humans have created climatic conditions that have the potential to lead to more wildfires, humans can also exert a significant potential to control how this fire risk translates into fire activity, in particular through land management decisions and ignition sources.
