What is “fire weather” and why does it get worse?

The map above shows when these three variables (temperature, humidity, and wind) were combined to produce fire days, shown as a percentage change since 1973. The number of fire days experienced by all areas of Colorado has increased by at least 100%. The situation in Texas is also terrible, with the southern tip of the state growing by 284%. Central California is also in trouble, with the number of fire days increasing by 269%. “Southwest Airlines is indeed among the best,” Weber said. “We even saw places in Oklahoma and Kansas, some of which we didn’t traditionally think of fires.”

However, if you want to know why we don’t often hear about catastrophic fires in the Plains State, as we do in California, Oregon, and Colorado, it’s because “fire weather” just means the conditions are right for the fire—it doesn’t Yes does not mean that they will happen. “We are not talking about ignition Fires,” Weber said. “We are talking about how many days of the year are weather factors preparing for these high-risk fires, which are indeed more dangerous and harder to extinguish. “

Atmospheric conditions are not the only variable that exacerbates the likelihood of wildfires. For example, land management decisions in California and Oregon played a role. These coastal areas are covered by forests, which used to burn in a healthy way: lightning can cause relatively small fires, chewing through bushes, Clear the way for new growth, But left many mature trees alive. Historically, Native Americans also set fires on purpose to strategically reset the ecosystem.The scenery was burned down a lot of, But it also means that it burns less intensely, because flammable brushes have no chance to accumulate between burning.

But in the past century or so, land managers have adopted the opposite approach: put out the fire, or immediately put out anything that might encroach on the residential area.This allows to build Dry vegetation-More fuel.As more and more human communities live in the “wasteland city interface” where forests and towns meet, people are setting up more accidental fires, whether it is cigarette butts thrown from windows or Power infrastructure failure.

This is part of the reason why California fires are more catastrophic than Kansas or Oklahoma fires: more forests, more fuel accumulation, and more people living in danger. In order to adapt to this situation, land managers in the western states need to implement more controlled combustion, which will complete the cleanup work done by smaller wildfires that have occurred frequently in the past.

Climate change also forces some seemingly contradictory seasonal changes. Because the warm atmosphere can hold more water, quantity The amount of precipitation may actually increase in the future, while length The area in the rainy season is shrinking. In California, rain usually arrives in October and lasts until March. Now they will arrive later this year. “The dry season will extend to the normal rainy season,” said Ruby Leung, a climate scientist at the Pacific Northwest National Laboratory. “When we study climate models that predict the future, the fire season will become longer.”

Firefighters have seen this happen. California once had the biggest fire in the fall, just before the seasonal rains arrived, when there was no water for half a year and the landscape became even drier. This coincides with the strong seasonal winds that will trigger huge wildfires. But now because the rainy season is short and there is more time to dry up in the year, the fire season comes earlier. “We see the fact more consistently and more often that these fires are getting bigger and faster than they used to be in the past,” said Issac Sanchez, head of the communications camp at the California Forestry and Fire Department. Told Wired earlier this month“So when August comes, and late July comes, we see that these dry conditions are definitely the result of climate change.”