Climate Space Shifts for each Wildlife Refuge
We calculated the ranges, from minimum to maximum value, of the two climate variables to define the two-dimensional current-climate space for each refuge using conditions from 1981-2010. We used the annual average of minimum temperature because it is expected to warm faster than maximum temperature at most locations (Hartmann et al. 2013).
We identified where the current-climate space of each refuge will be found among all the refuges for three future periods, 2010-2039, 2040-2069, and 2070-2099. For future-climate scenarios, we used four projections that bracket a range of possible future-conditions predicted by 12 Global Climate Models (GCMs) (Thorne et al., 2016; Thorne et al., 2017). The four futures are derived from two GCMs that respectively are hotter and drier (MIROC ESM), and warmer and wetter (CNRM-CM5) than current conditions; and two Representative Concentration Pathways (RCPs), which were defined by their total radiative forcing pathway and level by 2100 (IPCC 2014). We used the RCP8.5 emissions scenario, IPCC’s highest rate of anthropogenic greenhouse gas emissions, already surpassed by current emissions (Hayhoe et al. 2017); and the RCP4.5 emissions scenario, representing an attempt to limit global warming to 2°C (Thomson et al. 2011). Each emission scenario was used with each GCM.