Climate warming due to human activity responsible for wildfires in western United States – Belgium

In the western United States, wildfires destroyed an average of 13,500 square kilometers of surface area annually between 2001 and 2018, twice as much as in 1984-2000. “It happened faster than we expected,” Rong Fu, a climate scientist at UCLA told the Times. A climate scientist is leading the study, which was published yesterday in the scientific journal PNAS (Proceedings of the National Academy of Sciences, USA). To understand the reason for this rapid deterioration, Fu’s team analyzed the various factors at work in the “vapor pressure deficit,” which represents dry air. VPD stands for the difference between the amount of water present in the atmosphere and the maximum amount that this atmosphere can hold. The greater the deficit, the more water is absorbed by the air from the soil and plants. This leads to conditions that lead to fires. Scientists have found that the increase in wildfires in the western United States is proportional to the increase in VPD in the warm season. The study finds that the number of days when VPD is high nearly doubled in 2011-2018, compared to the previous period. Fu and colleagues calculated that “natural” changes in the atmosphere account for only one-third of the causes of VPD deterioration, on average. The rest, more than two-thirds, has been due to climate change over the past 20 years, largely as a result of human activities. “Before 2000, classical meteorological models allowed us to explain the meteorology that fueled wildfires,” Rong Fu told the Los Angeles Times. But this is no longer the case. In fact, according to some of the models in the study, human-caused climate change could account for nearly 90 percent of VPD anomalies. The study concluded that in August 2020, when California was hit by the region’s largest fire ever, human-induced climate change was responsible for nearly half of the “exceptionally high” vapor pressure deficit. About 4,200 square kilometers were set ablaze in this forest fire. (Belgium)

In the western United States, wildfires destroyed an average of 13,500 square kilometers of surface area annually between 2001 and 2018, twice as much as in 1984-2000. “It happened faster than we expected,” Rong Fu, a climate scientist at UCLA told the Times. A climate scientist is leading the study, which was published yesterday in the scientific journal PNAS (Proceedings of the National Academy of Sciences, USA). To understand the reason for this rapid deterioration, Fu’s team analyzed the various factors at work in the “vapor pressure deficit,” which represents dry air. VPD stands for the difference between the amount of water present in the atmosphere and the maximum amount that this atmosphere can hold. The greater the deficit, the more water is absorbed by the air from the soil and plants. This leads to conditions that lead to fires. Scientists have found that the increase in wildfires in the western United States is proportional to the increase in VPD in the warm season. The study finds that the number of days when VPD is high nearly doubled in 2011-2018, compared to the previous period. Fu and colleagues calculated that “natural” changes in the atmosphere account for only one-third of the causes of VPD deterioration, on average. The rest, more than two-thirds, has been due to climate change over the past 20 years, largely as a result of human activities. “Before 2000, classical meteorological models allowed us to explain the meteorology that fueled wildfires,” Rong Fu told the Los Angeles Times. But this is no longer the case. In fact, according to some of the models in the study, human-caused climate change could account for nearly 90 percent of VPD anomalies. The study concluded that in August 2020, when California was hit by the region’s largest fire ever, human-induced climate change was responsible for nearly half of the “exceptionally high” vapor pressure deficit. About 4,200 square kilometers were set ablaze in this forest fire. (Belgium)