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LOS ANGELES — There’s a dangerous but basic equation behind the killer Yarnell Hill wildfire and other blazes raging across the West this summer: More heat, more drought, more fuel, and more people in the way are adding up to increasingly ferocious fires.
Scientists say a hotter planet will only increase the risk.
More than two dozen wildland fires are burning from Alaska to New Mexico, fueled by triple-digit temperatures and arid conditions. In the Arizona mountain town of Yarnell, a blaze apparently sparked by lightning killed 19 members of a specialized firefighting squad who had deployed their emergency shelters Sunday when erratic monsoon winds sent flames racing in their direction.
While no single wildfire can be pinned solely on climate change, researchers say there are signs that fires are becoming bigger and more common in an increasingly hot and bone-dry West.
‘‘Twenty years ago, I would have said this was a highly unusual, fast-moving, dangerous fire,’’ said fire history expert Don Falk at the University of Arizona at Tucson, referring to the Yarnell Hill fire. ‘‘Now unfortunately, it’s not unusual at all.’’