Climate change in Nova Scotia: temperature increases from 1961 to 2020

Abstract

An analysis of temperature in Nova Scotia, using climate normals for 1961-1990 and temperature records from 1961 to 2020, is presented for 16 sites across the province. These records show a slight warming trend in the first 40 years from 6.0 ± 0.5 °C (1961-1990), followed by a more significant increase in average temperature post-1990 of 1.0 °C to 6.7 ± 0.5 °C, and to 7.0 ± 0.5 in the post-1998 period. A jump in average temperature in 1998 is such that in only a few following years did the mean annual temperature fall below the average annual temperature for the previous period. A step change was coincident with La Niña events and increasing Atlantic Ocean temperatures associated with a shift of the Atlantic Multi-decadal Oscillation into a positive phase. The increase in mean monthly temperatures was more apparent in the Autumn when first frosts were later and there were fewer days with frost. This led to a significant increase in continuous frost-free days of 9.2 ± 7.9 days, with increases ranging from 0.4 to 30.6 days. Relative to other sites, Yarmouth had the smallest annual increase in mean temperature, of 0.5 °C, but this was associated with a major increase in continuous frost-free days, of 11.3. Because overall temperature change was based largely on a step change post-1998, rather than a continuous, gradual change (seen only in frost-free days), it is difficult to calculate a rate, or to predict future patterns of temperature increases. We suggest a significant influence of El Niño Southern Oscillation and Atlantic Multi-decadal Oscillation as potential contributors to the temperature increase. Increases in annual temperature and seasonality are discussed in terms of flowering phenology, including flowering in the Spring of 2021 when 31 species were blooming by the end of April.

Keywords: climate change, climate normal, flowering phenology, Nova Scotia, temperature, weather