Does proxy uncertainty affect the relations inferred between the Pacific Decadal Oscillation and wildfire activity in the western United States?

We examined a set of five proxy reconstructions of the Pacific Decadal Oscillation (PDO) to test whether the choice of reconstruction affected the association between the PDO and widespread forest fires in the western United States. Exact binomial tests suggest the PDO has little direct impact on wildfires, with a statistically-significant association between the phase of the PDO and regional fire activity observed with only one reconstruction. Region-wide fires were not consistently associated with specific phase combinations of ENSO and the PDO. Any conclusion that extensive wildfires are more or less common when the PDO is in one phase or the other depends entirely on the choice of PDO reconstruction. Without a better understanding of low-frequency behavior in the north Pacific prior to 1900, efforts using proxy data to determine whether or not the PDO affects wildfire activity in the western United States will produce ambiguous results.