British Columbia

Shifting climate baselines in B.C: Get ready for the new normal

As climate change progresses, our perception of weather normals varies from generation to generation

vancouver weather

A sunny May long weekend with lots of snow still up on the mountains meant some kids got to play in both sand and snow. A changing climate means our perceptions of what is normal also changes from generations to generation. (Deborah Goble/CBC)

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For those of you hoping for more summer days in the forecast, you should be getting your wish by 2050. But climate change has already considerably shifted what we consider normal here in British Columbia, and that has come with a cost.

When meteorologists share a forecast for a particular location, they often compare the predicted temperature to "normal" temperatures for that time of the year.

It helps give context to the public. Is tomorrow going to be warmer or colder than what we are used to for this time of the year?

But did you know that even though most weather stations have data dating back to the turn of the century, the "normals" forecasters use to describe the average climatic conditions of a particular location are based only on data from 1981 to 2000?

That's because these so-called normals are changing.

Historical and projected annual average temperatures in B.C., 1990-2080.

Historical and projected annual average temperatures in B.C., 1990-2080. (Pacific Climate Impacts Consortium)

British Columbia already 'not normal'

Simon Donner, associate professor of climatology at the University of British Columbia, says that most of us are used to something warmer than normal already.

"I think people do get used to a new normal, but there's a lot of evidence that most of our experiences are based on what we had when we were young. And so, our definition of normal is something from when you were a child," he explained.

This is the concept behind shifting baselines: the change in perception of our climate varies from generation to generation.

1916 record vancouer snow

Main and Pender after a record snowfall for the City of Vancouver back in 1916. But winters have been getting less snow in recent decades. ((B.C.). Engineering Services)

When Metro Vancouver saw records amounts of snow this winter — that was only unusual based on the past couple decades of our climate history. In fact, there were far snowier winters back in the 50s and 60s. 

Take typical June weather for example. An afternoon forecast high of 17 degrees for Vancouver would be slightly below our normal for this time of the year.

But if you were to look at the normals for the same weather station from 1961 to 1990 when 16 degrees was what people were used to, then it would feel like a warmer-than-normal day. In fact, nearly all the stations across B.C. are a lot warmer today than even 30 years ago. 

Today's extremes will be tomorrow's normals

As far as figuring out our new future normals, it's not quite as simple as looking at a region's climate closer to the equator — like southern California — and assuming we will get exactly their weather in 30 years.

Donner says that it may be more accurate to look at our current extreme seasons as examples of what's to come.

"I would say the one thing El Niño events, especially in the recent past, have given us is a little bit of a window as to what the future could be like. We've had a few winters in the past few years where there's almost no snow on the North Shore mountains. It was warm and mild and interrupted by the occasional big pineapple express storm," he said.

Trevor Murdock is the lead on regional climate impacts at the Pacific Climate Impacts Consortium. He takes global climate change data and figures out what it will mean for our province. He says that by 2050 it's possible that today's extremes will become their normal.

"If we have three degrees of warming, what you're talking about is a future where the new normal is like the extreme warm years of the past. And the warm years [even with climate variability like El Niño years] it's warmer again, and breaking into new territories in terms of warm temperatures."

bc-090727-heat-wave-vancouver

Temperature data shows B.C. has been getting warmer over the past few decades, and the climate models show temperatures will continue to climb. (CBC)

Murdock says that if we continue down the greenhouse gas emissions path we are currently on — the City of Vancouver could be looking at nearly triple the number of days above 25 C than we currently get. In a more middle-of-the-road future scenario, we could still see our number of days above 25 C double. 

Warmer, but at what cost? 

Murdock acknowledges that to some people, warmer days in our future might sound great. But the temperature increase will come with a continued increase in severe weather too.

"More heatwaves, more need to have shelters for elderly people to avoid mortality. It also means more cooling demand. So something we don't really have a lot of need for in the Lower Mainland for now ..."

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