Canadian agroclimatic scenarios projected by a global climate model

Localized daily climate scenarios, including maximum and minimum temperatures and precipitation for a future time period, 2040-2069, were generated by a stochastic weather generator (AAFC-WG) for Canadian agricultural regions on a 0.5º×0.5º grid. Four scenarios were developed, based on results of the climate change simulations conducted by the CGCM3 global climate model with four forcing scenarios: IPCC SRES A1B, A2, B1 and the so-called “committed” scenario in which greenhouse gas concentrations and aerosol loadings were held fixed at year 2000 levels. A suite of agroclimatic indices were calculated from these four localized daily climate scenarios. The agroclimatic indices were used to measure growing season start, end and length, as well as heat accumulations and moisture conditions during the growing season for three types of field crops – cool season, warm season and over-wintering crops. Growing season start and end were estimated based on crop cardinal temperatures, and heat accumulations and moisture conditions were further calculated for the estimated growing season. Compared to the baseline period 1961-1990, growing seasons will start earlier, end later and become longer in all four scenarios, although the magnitude of change is largest in the A2 scenario, and smallest in the “committed” scenario. Two indices measuring heat accumulations during the growing season, effective growing degree days (EGDD) for over-wintering crops and crop heat units (CHU) for warm season crops, both indicated a notable increase in heat accumulation. The A2 scenario also showed a larger change than other scenarios and the “committed” scenario showed the smallest. However, moisture conditions appear not to be substantially affected in any of the scenarios based on precipitation deficit (P-PE) accumulated over the growing season. The projected results suggest that moisture stress is likely to be a limiting factor for crop production in a future climate in areas currently affected by it, although an increase in heat accumulation may increase the potential for warm season field crop production.