Data are mean annual homogenized surface air temperatures from Vincent et al. (2020), available from Environment and Climate Change Canada (see file Monthly mean of daily mean temperature). Trend line based on least squares regression (note that trend is not a projection of future change). Code available at github.com/patrickbarks/canada-clim.
Data reference: Vincent, L. A., Hartwell, M. M., and Wang, X. L. (2020) A third generation of homogenized temperature for trend analysis and monitoring changes in Canada’s climate. Atmosphere-Ocean, 58, 173-191. doi.org/10.1080/07055900.2020.1765728