(Los Angeles) Climate change has become the primary cause of wildfires continuing to wreak havoc in the western United States, according to a study released Monday at the start of the COP26 conference on climate in Scotland on Monday.
In Western American countries, the area destroyed by fire between 2001 and 2018 averaged 13,500 km2.2 Per year, more than twice as much as in 1984-2000.
“It happened much faster than we expected,” he said Los Angeles Times Rong Fu, a climate expert at UCLA University in California, led the study, which was published in the journal National Academy of Sciences (Pnas).
In an attempt to understand what contributed to this spectacular deterioration in such a short period of time, a team of American researchersMe Fu analyzed various factors that work in “Vapor Pressure Deficiency” (VPD), which reflects the dryness of the air.
VPD refers to the difference between the amount of water actually present in the atmosphere and the maximum that the latter can contain. As this deficiency is high, the ambient air absorbs water from the soil and plants, creating conditions that are highly flammable.
Scientists have established that the increase in wildfires in the western US is closely related to this shortage during the warm season. The study notes that between May and September, the number of days with high VPD during the period 2001-2018 increased by 94% compared to the previous period.
According to M calculationsMe Fu and his colleagues found that “natural” atmospheric variations only contributed to an average of 32% worsening of VPD. The remaining (68%) increase in water scarcity in the atmosphere over the past 20 years is due to global warming, which is largely caused by human activities.
“Before 2000, we could describe flammable weather using traditional weather models, but this is no longer the case,” Rong Fu told the LA Times.
According to some models, the study adds, anthropological warming, i.e. human origin, can explain up to 88% of the discrepancies found in VPD.
In August 2020, when the California region experienced the largest fire – the August Complex fire – it alone burned nearly 4,200 km, accounting for almost half of the anthropological warming deficit. Humidity is “exceptionally high”, the study concludes.
According to climate experts, the planet has already reached about 1.1 C since pre-industrial times, mainly through the consumption of man-made greenhouse gases, mainly fossil fuels. Much of this global warming has occurred over the past 50 years.