Memory has a way of distorting our perceptions of climate change. We remember snow drifts as high as our heads when we were kids, but forget that we were only three feet tall. We remember experiencing weeks on end of ‘windchill 2000’ weather in February, but forget that that way of measuring wind chill hasn’t been used for decades. We remember snow at Halloween and having to layer our costumes overtop our winter parkas, but forget how easily our six-year-old bodies got cold. Climate change is a generally slow process and is therefore difficult to measure using memories alone. Fortunately, climate data doesn’t suffer from memory distortion.
Take a look at this graph, which shows the change in mean annual temperature for Manitoba from the year 1950. The upward trend is hard to miss. What’s particularly striking is the magnitude of the change: 2.2 °C over just 65 years. To put that into perspective, the globe as a whole has warmed about 1 °C over since 1900 and many climatologists warn of serious and irreversible climate change impacts if the globe is allowed to reach 2 °C.
The warming is not spread evenly across all months. In fact, December and January have been warming the fastest. This map illustrates January mean temperature change. The bright red colours indicate warming of more than 12 °C per century (or a little over a tenth of a degree per year). Incredibly, this means that Januarys in the 1950s were indeed noticeably colder than they are today.
January mean temperature trend (1950-2013). Values are shown as degrees Celsius change per century.
Farmers, who are more keenly aware of changes in the weather and climate, have noticed that the growing season is now much longer than it used to be. The following table shows the change in the average length of the frost-free period (the period of time where the temperature remains above freezing) for select communities across Alberta, Saskatchewan and Manitoba. In some places, the frost-free period has been increasing at a rate of approximately half a day per year. This may not sound like much, but that adds up to a change of well over one month when stretched over the whole of the 20th century.
Length of the frost-free period (days)
We sometimes need a little reminding that climate change is real and something to worry about. Living in the Prairies, we are used to wild extremes in weather and so many of us think of climate change as extension of something we’ve had to deal with for decades. The reality is that the real worrisome changes are still to come. Climate model projections indicate that the ‘double the global average’ trend for Manitoba will continue throughout the next century. This means that if the globe is allowed to reach 2 °C, Manitoba will have warmed more than 4 °C. All of the changes we’ve witnessed to date—across Manitoba and the rest of the world—have been a result of just 1 °C of global warming. What’s worse, if we do little to nothing to slow or stop future climate change from happening, the global temperature may easily climb to 4+ °C (8+ °C for Manitoba). At this point, the benefits of a longer growing season will likely be outweighed by the large increase in temperature extremes and severe weather.
The data used to create the above figures and tables comes from Natural Resources Canada
Full citation: Hopkinson, et al. (2011). Impact of Aligning Climatological Day on Gridding Daily Maximum-Minimum Temperature and Precipitation over Canada. American Meteorological Society, vol. 50.