Environment Canada’s 30-year data shows average temperatures on rise

This article was written by Patty Winsa and was published in the Toronto Star on November 13, 2023.

When it comes to the weather, what does “normal” mean anymore?

It’s a question that Environment and Climate Change Canada answered recently, releasing the latest round of “normals” — data that includes averages of temperature and precipitation over a 30-year period, in this case from 1991 to 2020, for a number of weather stations across Canada.

What the new data shows is that, in many cities and towns, average monthly temperatures have increased, in some cases by more than three degrees Celsius.

In Toronto, the most recent normals show that average temperatures are half a degree to one degree higher most months compared to what was considered normal for the period between 1961 to 1990.

In northern cities such as Whitehorse, the changes are more pronounced.

The latest average (“normal”) for the city in January is -15 C, 3.7 degrees Celsius warmer than it was in the normals released 30 years ago. In December, it’s 3.1 degrees Celsius higher.

Experts say those degrees matter. “Every degree of temperature change can have exponential impacts on climate conditions,” said Dan Henstra, a political science professor and co-lead of the Climate Risk Research Group at the University of Waterloo. “Warmer air carries more moisture, meaning more potential for more extreme rainfall and even extreme snowfall. Average temperatures, even one degree warmer, can exacerbate heat waves in the summer months, which are already unbearable for many residents in cities like Toronto and other dense urban areas who don’t have access to air conditioning.”

Residents in cities can be especially vulnerable because concrete and other materials absorb the warmth and re-emit it, leading to heat islands — areas that are hotter than those with more natural vegetation.

In northern areas of the country, the warmer temperatures can lead to permafrost thaw, which can cause roads to heave in the freeze and thaw cycle.

The new normals have been released at the same time Environment Canada modelling is predicting the entire country can expect a fall and winter that is warmer than even the new 30-year normals.

Part of that warmth could come from El Niño, a warmer weather pattern in the Pacific, which the National Oceanic and Atmospheric Administration confirmed began in June and could be moderate to strong by late fall or early winter.

The World Meteorological Organization (WMO) predicts a high probability that one of the next five years will be the hottest on record due to El Niño, which could result in a rise in the annual mean global temperature of between 1.1 to 1.8 C in the next five years.

The weather pattern is expected to lead to an increase in temperatures over Alaska, Yukon, B.C. and, to some extent, the Prairies, as well as an increase in precipitation on the U.S. West Coast.

It’s less certain if it will bring more precipitation to Canada’s West Coast, because El Niño doesn’t typically have the same impact as it does further south, said Greg Flato, director of the Climate Research Division of Environment and Climate Change Canada (ECCC).

Modelling by ECCC didn’t show a high probability the next six months would be wetter, or dryer, than normals for most of Canada.

Currently, the global average temperature is 1.1 C above the pre-industrial average. The global average is used because warming won’t occur everywhere at the same rate.

Under the Paris Agreement, countries have pledged to try to keep the global long-term average temperature from increasing much more than 1.5 C, and ideally well belo 2 C relative to pre-industrial temperatures, said Flato.

The new normals from ECCC show some Canadian cities have warmed close to a degree or more compared to normals 30 years ago.

“From that point of view, one degree is big because that’s kind of the same target that we’re trying to not let the global average temperature get too much above,” said Flato.

The normals released by ECCC are calculated once a decade using data from the preceding 30 years, a time period defined by the WMO as a kind of standard that averages out “the day-to-day, year-to-year variability that is the weather we experience,” said Flato.

It “gives you an indication of the average conditions over that 30year time frame,” he said. “And we refer to those as climate normals.”

Unlike weather predictions, which provide an actual value for temperature or precipitation, the normals are used for comparison to indicate whether temperature or precipitation will be above or below normal.

There is data going back to 1850, but more recent data is used for the normals because “nobody alive today has any recollection of what the 1850 to 1900 average was like,” said Flato. “So it’s not so compelling.”

However, when it comes to climate change, it’s the historical data that is used as the marker to measure the increase in the average global temperature because it predates the emission of greenhouse gases from human and industrial activities, according to the WMO.

And Canada has been warming more quickly than the global average because the country’s land mass is large and warms more quickly than ocean areas.

And, in the higher latitudes of the country, particularly in the Arctic, warming is happening more quickly because of the loss of snow and sea ice, creating larger areas of open ocean, a darker surface that absorbs more solar radiation.

Flato said data already shows the snow cover season is getting shorter over most places in Canada, aside from a few areas in the mountainous parts of the Rockies. “The snow doesn’t stay on the ground until later in the fall and it melts away earlier in the spring,” he said.

In northern areas of the country, the warmer temperatures can lead to permafrost thaw, which can cause roads to heave in the freeze and thaw cycle