Emergence of Climate Change Signals for Ecologically-Relevant Climate Variables

Species are expected to shift their distributions to higher latitudes, greater elevations, and deeper depths in response to climate change, reflecting an underlying hypothesis that species will move to cooler locations. However, species response to climate change is poorly understood and species range shifts may be related to climate change exposure. This project was designed to find when a new climate normal emerges beyond different thresholds of natural climate variability with the goal to help natural resource managers, other practitioners, and scientists concerned with emerging climate signals. Estimates are provided for the time (year) when a biologically-relevant temperature signal emerges (time of emergence - ToE) above natural variability considering an early industrial period climate and the strength of the signal (degrees C) at the ToE. The year-to-year “natural” variability is estimated as the noise in which the signal must persistently surpass for the emergence of a climate change signal. A time series of the signal to noise ratio is provided from which the ToE is estimated. The input data for the estimates include multiple observations as well as multiple large ensembles of Global Climate Models (GCMs). The GCMs include estimates of signal that may emerge in the future under a moderate emission scenario (RCP4.5/SSP2-45). The advantage of large ensembles of GCMs (many realizations of the future climate from a single GCM) is improved representation of the natural variability as well as ability to estimate the forced anthropogenic trend (e.g., warming).