Impact of Climate Change on the Extremes of Observed Daily Temperature Data in the Greater Toronto Area

By Tanzina Mohsin and William A. Gough.

Published by The International Journal of Climate Change: Impacts and Responses

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Article: Print $US10.00
Article: Electronic $US5.00

Indices of extreme of daily observed temperature during the 1971-2000 period using several meteorological stations in the Greater Toronto Area (GTA) are examined. The indices that are based on daily minimum temperature exhibit statistically significant decreasing trends at all stations in the GTA. The trend analysis of the extremes based on daily maximum temperature shows increasing trends at urban and suburban stations. The temporal and spatial distributions of cold extreme indices are more coherent throughout the region compared to the warm extreme indices. The trend analysis of seasonal extreme temperatures for warm days, warm nights, cold days, and cold nights show statistically significant trends leading to more days with extreme high temperature in winter and spring, but no indication of any significant trend of extreme high temperature in summer. The percentage of cold nights shows decreasing trends in the winter, spring, and summer, while the percentage of warm nights shows increasing trends for the same seasons. The significant decreasing trend in diurnal temperature range, mainly in the urban and suburban areas, is, therefore, due to the nighttime warming of these stations, which could be a positive feedback effect from urban warming. The regional analysis of the seasonal extremes reveals that there is a shift towards warmer climate in the GTA region with an increase in extreme high temperature and a reduction in extreme low temperatures during the study period, which are more apparent in winter and spring compared to summer and autumn. There are also fewer nights with extreme low nighttime temperatures, which are observed in summer, but more nights with extreme high nighttime temperatures are found in all seasons. The impact of climate warming in addition to the urban warming could lead to an increase in the intensity and frequency of heat-related extreme events in the GTA.

Keywords: Scientific Evidence, Climate Extremes, Temperature Indices, Trend Analysis, Urban Warming, Toronto

International Journal of Climate Change: Impacts and Responses, Volume 5, Issue 1, pp.11-33. Article: Print (Spiral Bound). Article: Electronic (PDF File; 984.933KB).

Dr Tanzina Mohsin

Lecturer, Department of Physical and Environmental Sciences, University of Toronto, Toronto, Ontario, Canada

Dr. Tanzina Mohsin is a climatologist specialized in urban climatology. She received her Master’s degree from University of Newcastle, Australia, and her Doctorate degree from University of Toronto, Canada. Currently she is working as a lecturer at the University of Toronto at Scarborough and is also affiliated with the Climate Lab, where she earned post-doctoral experience working on statistical downscaling techniques. Her research interests include time series analysis of climate data using sophisticated statistical techniques, climate change in cities, estimation and quantification of urban heat island effect and statistical downscaling of climate data using the output from global circulation models. Dr. Mohsin was one of the lead scientists for the study of ‘Climate Change at Toronto’ led by Environment Canada.

William A. Gough

Associate Professor, Physical and Environmental Sciences, University of Toronto at Scarborough, Toronto, Ontario, Canada

Dr. Gough is an associate professor of physical and environmental sciences at the University of Toronto at Scarborough (UTSC), Canada. He is a world-renowned climatologist who teaches physical geography through his environmental science courses at UTSC and geography at the graduate level at the St. George campus. His research focuses on sea ice and permafrost in the Arctic. His most recent teaching award is from the Canadian Association of Geographers (CAG) in 2010. Dr. Gough is the Vice-Dean, Graduate Education and Program Development at the University of Toronto in Scarborough.

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