Increases in vapor pressure deficit (VPD) have been hypothesized as the primary driver of future fire changes. The Coupled Model Intercomparison Project Phase 5 (CMIP5) models agree that western U.S. surface temperatures and associated dryness of air as defined by the VPD will increase in the 21st century for Representative Concentration Pathways (RCPs) 4.5 and 8.5. However, we find that averaged over seasonal and regional scales, other environmental variables demonstrated to be relevant to flammability, moisture abundances, and aridity—such as precipitation, evaporation, relative humidity, root zone soil moisture, and wind speed—can be used to explain observed variance in wildfire burn area as well or better than VPD. However, the magnitude and sign of the change of these variables in the 21st century are less certain than the predicted changes in VPD. Our work demonstrates that when objectively selecting environmental variables to maximize predictive skill of linear regressions (minimize square error on unseen data) VPD is not always selected and when it is not, the magnitude of future increases in burn area becomes less certain. Hence, this work shows that future burn area predictions are sensitive to what environmental predictors are chosen to drive burn area.

中文翻译：

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驱动美国西部夏季野火燃烧区域的环境条件的过去变化和未来预测


蒸气压不足（VPD）的增加被假设为未来火灾变化的主要驱动因素。耦合模型比对项目第 5 阶段 (CMIP5) 模型一致认为，对于代表性浓度路径 (RCP) 4.5 和 8.5，VPD 定义的美国西部地表温度和相关空气干燥度将在 21 世纪增加。然而，我们发现，在季节和区域尺度上平均，其他环境变量被证明与可燃性、水分丰度和干旱相关，例如降水、蒸发、相对湿度、根区土壤湿度和风速，可用于与 VPD 一样或更好地解释观察到的野火烧伤面积的变化。然而，这些变量在 21 世纪变化的幅度和符号不如 VPD 的预测变化那么确定。我们的工作表明，当客观地选择环境变量以最大化线性回归的预测能力（最小化未见数据的平方误差）时，并不总是选择 VPD，如果不选择，烧伤面积未来增加的幅度就变得不太确定。因此，这项工作表明，未来的烧伤面积预测对选择什么环境预测因子来驱动烧伤面积很敏感。