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Roger Smith

Toronto (city) reaches 180 year milestone

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The Toronto (downtown) weather observatory was founded near its current location in 1840 and began compiling data on March 1st, 1840. So we have recently passed the 180th year milestone of more or less continuous observations at this location (which is near the University of Toronto or the northwest margin of the central business district). While the setting is slightly parkland by mid-town standards, it is not as modified a location as New York's Central Park observatory might be. My data analysis includes ranking all months, before and after applying an urban heat island filter to reflect the growth of the city from a small town (with presumably no urban effects) in the first few decades, to a mid-sized city by turn of the 20th century, to a large metropolitan area by 1950. 

All of the data compiled can be seen at this link over on the UK equivalent of this forum, Net-weather. 


My plan is to transfer all of this information to a free-standing website just for the security aspects, but that may take a month or two. So for now this is the only place where the Toronto-180 project can be seen. You'll find a lot of information there including all daily records and notes on historical weather events. If you happen to have any information that didn't make my study, or feel any corrections are needed, please let me know,. This is a work in progress. 

My urban heat island factor was a rather conservative 1.1 C (2.0 F) adjustment to the recent data, and a scaled fraction of that from 1881 to 1980. It could be argued that the city has a larger heat island than 1.1 C, but a lot of weather patterns in the Great Lakes are UHI-unfriendly, for example, cold and wet spells, windy weather and cloudy conditions in general. The 1.1 C is really a blend of a few occasions of 3-5 C or more urban heating, and long intervals of smaller or zero increases. One needs to separate out the urban effect from the site's natural climatic tendency being close to the Lake Ontario shoreline (4-5 kms inland at various times in the 180 year history). Even with no city there, the location would see a natural warming tendency in southeast winds in winter, changing some mixed precipitation over to rain. The urban heat island probably adds somewhat to that geographical tendency. For whatever combination of reasons, winter snowfall is shown to have decreased by 30% in recent decades, and those had decreased by an even larger amount relative to the bonanza snowfall winters of about 1860 to 1875. 

There are some surprises in the adjusted temperatures even if my UHI estimate is too low. The warmest September becomes 1881, and the warmest July even before adjustments was 1921. The warmest January was 1932. It's not all about modern warming although there is plenty of that in evidence (in particular, record high minima are being set at a rapid pace in recent decades). 


Whatever your opinions on climate change, you'll find this an interesting data base. My objective was to produce something to rival the CET (and EWP) data bases for both longevity and data quality. I have spent a long time amassing these data, starting from a printed publication issued in 1968 covering the years 1840 to 1967. I've had that since a few days after it appeared in print and marked it up extensively. The rest of the data came from the on-line historical data section of the Environment Canada website. I also cross-checked my computer files built up over the past twenty years from the printed version and the on-line additions for accuracy. With this volume of data, it's perhaps inevitable that one or two typographical errors might remain but I did go through the ranking tables with a special program designed to verify that all years appeared once and only once, and in the correct location. I'm hoping hard work will prove to be an antidote to the virus but maybe living in the middle of nowhere might help also. :)


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Hey Roger,

Nice effort on your part.  Would you happen to have your data in Excel format to make it sortable/filterable?

Pity the station ceased operations in 2017.  At least we have record of those insane winters of the 19th century, whatever their explanation is. 

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I do have an excel file that I hope to make available after some cleaning up and quality control. The station has changed its operating procedures twice since 2003 and still exists at least in the format of daily temps, precip and snow depth. To maintain the record, I will need to estimate the snowfall from a combination of snow depth reports and closest actual measurements, plus any clues I can derive from reading reports here or on the Weather Network. I am hoping to make an appeal to the powers that be, to restore the level of observations in coming winters -- the other parts of the year do not suffer that much from the reduced format. I can't promise this excel file will be up within days, but will set end of April as a target date. It is fine for my own use because I know where everything is but it kind of grew out of a much different file that I was maintaining for my research and needs to be edited severely for anyone else to find their way around in it. Also, the core of the data is the original Fahrenheit temps and I have not logged daily precip, only noted the monthly totals and the daily records. Trying to decide how to proceed on all those fronts. However, there is no deadline, I can continue to improve the file going forward from any feedback that I get. 

So the short answer is yes, an excel file will be available within a relatively short period of time. 

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