Observed Long-Term Trends for Agroclimatic Conditions in Canada

Abstract

A set of agroclimatic indices representing Canadian climatic conditions for field crop production are analyzed for long-term trends during 1895–2007. The indices are categorized for three crop types: cool season, warm season, and overwintering. Results indicate a significant lengthening of the growing season due to a significantly earlier start and a significantly later end of the growing season. Significant positive trends are also observed for effective growing degree-days and crop heat units at most locations across the country. The occurrence of extremely low temperatures has become less frequent during the nongrowing season, implying a more favorable climate for overwinter survival. In addition, the total numbers of cool days, frost days, and killing-frost days within a growing season have a decreasing trend. This means that crops may also be less vulnerable to cold stress and injury during the growing season. Extreme daily precipitation amounts and 10-day precipitation totals during the growing season have been increasing. Significant trends associated with increased availability of water during the growing season are identified by the standardized precipitation index and seasonal water deficits. The benefit of the increased precipitation may have been offset by an upward trend in evaporative demand; however, this would depend on the amount of growth and productivity resulting from increased actual evapotranspiration.

Recent climatic, cryospheric, and hydrological changes over the interior of western Canada: a review and synthesis

“…This led to widespread forest fires, low water levels in streams, lakes, and reservoirs and low soil moisture levels, and it was unusual in that it stretched over a vast area from Mexico to Alaska. Since the beginning of the 20th century there has been decadal-scale variability in drought occurrence as indicated by various precipitation and soil moisture indices, but there has been no consistent long-term trend in drought frequency or magnitude (Millett et al, 2009;Qian et al, 2010;Bonsal et al, 2013). This variability has tended to coincide primarily with precipitation variations modulated by largescale modes of oceanic-atmospheric circulation Shabbar and Skinner, 2004;Bonsal and Shabbar, 2008).…”

Arthropods of Canadian grasslands: a retrospective of a 40-year project of the Biological Survey of Canada

“…For example, mean maximum and mean minimum temperatures during spring on the prairies from 1950 to 1989 have increased by 3.8°C and 2.8°C, respectively (Skinner and Gullett 1993). In combination with killing frosts occurring later in the fall, this has resulted in a general trend towards a longer growing season (Qian et al 2010) with endemic species experiencing milder winters. Climate change directly and indirectly affects arthropod populations, but studies of direct effects in the Canadian Prairies Ecozone have been largely limited to exotic species that are pests of crops (Olfert and Weiss 2006;Olfert et al 2011Olfert et al , 2016.…”

Effects of climate change on killing frost in the Canadian prairies

“…A baseline (1961−1990) and 3 projected future climate change scenarios in the 2050s (2040−2069) for each station were generated using the stochastic weather generator AAFC-WG by perturbing weather generator parameters (Qian et al 2005(Qian et al , 2010a(Qian et al , 2010b) based on climate change simulations conducted by the third generation Canadian global climate model (CGCM3) (Kim et al 2002(Kim et al , 2003. The latter simulations were generated using 3 greenhouse gas (GHG) emissions forcing scenarios -IPCC Special Report on Emissions Scenarios (SRES) scenarios A2, A1B and B1-which represent the range of emissions trajectories projected to the end of this century (IPCC 2000).…”