What is Fire Weather and why does it keep getting worse?

What is Fire Weather and why does it keep getting worse?

A new study in the western United States shows that climate change is increasing the number of hot, dry and windy days - the perfect condition for wildfires

© Ty O'Neil / SOPA Images / IPA California it is famous for its beach climate, but it is becoming more and more so for its "fire weather", a terminology used to indicate when high temperatures, strong winds and low humidity combine to promote the risk of fires. It is no coincidence that in recent years we have heard a lot about forest fires: as a recent analysis shows, due to climate change, the phenomenon of fire weather is on the rise.

“It's not just a matter of heat or dryness. The problem arises because all of these conditions occur simultaneously, "explains Kaitlyn Weber, data analyst at Climate Central, a non-profit organization that published the analysis. "The increase in days of fire weather is evident. It is a process that began in the early 1970s that has affected most of the western United States “.

Weber has analyzed data from 225 weather stations in 117 western states since 1973, looking at temperature, humidity and wind speed, the three main variables that fuel catastrophic fires. The high temperatures and low humidity suck the water from the vegetation creating dry fuels, so a simple spark can easily ignite a forest fire, which is then dragged across the territory by the winds with incredible speed. Camp Fire in 2018, for example, moved so quickly that it overwhelmed the city of Paradise, killing 86 people, many of them still locked in the cars they were trying to escape in.

Illustration: NOAA / NCEI'S LOCAL CLIMATOLOGICAL DATA In the maps above you can see the percentage change in the days of the year in which these three variables exceeded the threshold that Weber used for his analysis. (The bluer color means fewer days, the redder a higher number.) So for wind, for example, it means speeds over 15 miles per hour. While for the temperature, between 45 and 55 degrees Farenheit (7-12 ° C), depending on the season.

It can be seen that the Southwest, in particular, has become much warmer and drier - and perhaps this is not surprising. But at the same time, the region sees the number of windy days grow dramatically, those in which the slightest burning can turn into an intense and fast fire.

Illustration: NOAA / NCEI'S LOCAL CLIMATOLOGICAL DATA The map above displays when these three variables - temperature, humidity and wind - combined to produce days of fire weather, shown in their percentage change since 1973. All zones Colorado had at least 100 percent more days of fire weather. Texas is no better off, with the southern tip of the state posting a 284 percent increase. And identical problems are found in central California, where days of fire weather rose 269 percent. “The Southwest is really taking this sad record,” Weber says. "We even see parts of Oklahoma and Kansas, these are areas traditionally not considered to be at risk of fire."

But if you are wondering why you don't often hear about catastrophic fires in low-lying states like California, Oregon and Colorado, this is because the term fire weather only indicates that there are favorable conditions for a fire to develop, not that this must necessarily flare up. "We're not talking about starting fires," Weber explains. "We are talking about the number of days of the year in which the climatic elements have exposed the territory to the possibility of high-risk fires, which are actually more dangerous and more difficult to fight".

Atmospheric conditions are not the only variables that exacerbate the likelihood of forest fires. For example, land management by the administrations in California and Oregon also plays a role. These coastal regions are covered with forests that once burned regularly and in a harmless way: lightning could ignite a relatively small fire that ate some undergrowth, freeing up space for new growth, but leaving many mature trees alive. Historically, Native Americans also purposely lit fires to strategically reset ecosystems. The landscape burned a lot, but that also meant it burned less intensely, because the flammable weeds were not given a chance to expand their flames.

However, in the last century, those responsible for land management took the opposite approach: extinguishing fires, or the immediate elimination of anything that could invade residential areas. This allowed the accumulation of dry vegetation: more fuel. And with the growth of human communities living in areas where wild nature and urbanization are bordering, where forests meet cities, even people light accidental fires, with a cigarette butt thrown out of a window or due to a plant failure. electric .

This is partly why wildfires are more devastating in California than in Kansas or Oklahoma: there are far more forests with more fuel stored, and more people living close to danger. To adapt to this situation, land managers in western states would have to promote more controlled fires, which would fulfill the brushwood-clearing function that once did smaller and more frequent fires.

Climate change has also forced some seemingly contradictory seasonal changes. As a warmer atmosphere holds more water, rainfall may increase in the future, while the length of the wet season is shrinking. In California, the rains usually came in October and lasted until March. Now they come later. “The dry season will expand by taking up the space that usually belonged to the wet one,” says climatologist Ruby Leung, of the Pacific Northwest National Laboratory. "When we look at the climate models projected into the future, we see that the fire season is destined to lengthen".

The firefighters have already realized this. California once recorded its largest fires in the fall, just before the rainy season arrived, when the landscape was parched after a half year without water. This coincided with ferocious seasonal winds that fueled massive forest fires. Now, however, since the rainy season is so short and the landscape remains dry for most of the year, the fire season begins even earlier. "What we are seeing with increasing regularity and consistency is the fact that these fires are breaking out earlier than in the past and are getting bigger," Sanchez, communications battalion chief of the Department of Forestry and Fire told WIRED earlier this month. Protection of California. "So when August arrives, or late July, we see these dry conditions that are undoubtedly a consequence of climate change."

Even Oregon, recently, has seen an increase in catastrophic forest fires, triggered by the continuous increase in days of fire weather. And Weber is convinced that until we take action to slow global warming, things will only get worse. "If the climate continues to warm we can be sure that the days of fire weather will increase more and more," she says. “Whatever measures we take, there is no easy way out. We have to say things exactly as they are: there is no alternative way to reducing emissions, this is the game we are called to play ”.

Article originally published on Wired.com

Environment - 5 Oct

An assembly of ordinary people from all over the world will give their proposals to Cop26

Zalando starts repairing clothes

What are the “complex systems” that earned Giorgio Parisi the Nobel Prize in Physics 2021


Environment Climate globalData.fldTopic = "Environment , Climate "

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Powered by Blogger.