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Abstract The Southwestern U.S. and Eastern Australia are two of the most fire-prone regions of the world. These two regions also have significant and opposite-signed hydroclimate teleconnections to sea-surface temperature (SST) anomalies in the tropical Pacific, such that an El-Niño-like west-to-east tropical Pacific SST gradient is associated with hot, dry conditions in Eastern Australia and cool, wet conditions in the Southwestern U.S. Additionally, the tropical Pacific has experienced a pronounced La-Niña-like cooling over recent decades. Here, we investigate the roles of the tropical Pacific and anthropogenic climate change (ACC) as drivers of observed trends in burned forest area and vapor pressure deficit (VPD) in the Southwestern U.S. and Eastern Australia, using observations and Coupled Model Intercomparison Project Phase 6 model data. We characterize the strength and spatial structure of relationships between fire-favorable climate variables in these regions and SST anomalies in the Pacific. We show that in both regions, VPD has increased with a large contribution from ACC. In the Southwestern U.S., the recent trend in the tropical Pacific west–east sea surface temperature gradient positively contributed to the VPD-induced increase in burned forest area since 1984. However, in Eastern Australia, the tropical Pacific SST gradient trend has likely offset the ACC-induced tendency to increase burned forest area.
Jacobson et al. (Fri,) studied this question.