The model is based upon summer heat, which determines whether beetles mature in one year or two; fall cooling, which kills beetles if it occurs rapidly during a key timeframe; and extreme winter cold, which contributes to overwintering mortality, especially in the absence of insulating snowpack.  Using gridded daily historical data (Daymet) and outputs from four different global climate) models (GCMs), each run under plausible greenhouse gas futures (RCP 4.5 and 8.5).  Climatic protection levels are calibrated as “low,” “medium,” and “high,” where areas of high climate protection are unlikely to suffer outbreaks even if forest conditions are otherwise susceptible. Historically, most of the Interior of the state was highly protected from outbreaks, with moderate protection in the southcentral and southeastern regions of Alaska. By the end of the century, with warmer summers and loss of protective cold in fall and winter, even the most conservative model outputs show low protection in the southern parts of the state. Scenarios with higher warming suggest that large portions of western and central interior Alaska may also lose climatic protection from beetle outbreaks, with only regions near the Yukon border still in the “high” protection category.  This model does not directly predict beetle outbreaks, and some forested areas are likely to be protected by other ecological and biophysical factors.

Risk class values are encoded as follows in the data:

0: not modeled

1: High protection (low risk)

2: Medium protection (medium risk)

3: Low protection (high risk)

Files are named as follows:

risk_class_<summary period>_<GCM>_<emissions scenario>_<snowpack level>.tif

The climate model data used for this dataset were computed using the BCSD statistical downscaling method and can be found here: https://doi.org/10.5065/c3kn-2y77