See how hot Canadian cities are becoming

A researcher has created a new way to chart Earth's warming temperatures, one that he believes paints a clearer picture of a changing climate.

'Bar code charts' created by British scientist illustrate worldwide warming

The sun sets over the Baltic Sea in Heidekate, Germany on July 31. A heat wave has gripped large stretches of Europe this summer. To demonstrate historical changes in temperatures, a British professor has created "bar code charts" that show the changes as colours. (Frank Molter/dpa via Associated Press)

A researcher has found a new way to chart Earth's warming temperatures, one that he believes paints a clearer picture of a changing climate.

Ed Hawkins, a climate professor at the University of Reading in the U.K., created "bar code charts" that show rising temperatures as colours. The result is a snapshot of how much warmer, on average, the world has been getting, particularly in the last decade.

He made this one showing average global temperatures since 1850.

Each line in this chart of global average temperatures represents a year from 1850 to 2017. The difference between the darkest blue and deepest red is 1.35 C. (Ed Hawkins)

Inspired by this, CBC News made similar charts  for several Canadian cities using data from Environment and Climate Change Canada. Each stripe represents the average temperature for a year. The deeper the blue, the colder is was that year. Reds indicate warmer temperatures. 

Usually when scientists communicate rising temperatures due to climate change, they use a line graph. But Hawkins says these charts usually don't show the changes in a clear and intuitive way.

Here's how the standard line chart would look for Winnipeg:

Compare that to the bar code chart:

"This style of visualization removes all the distractions of standard graphs and allows the viewer to clearly see the long-term trends and variations in temperature without needing to interpret anything else," Hawkins said. 

Change in local temperatures, which can be difficult for an individual to perceive over time, "are made obvious," he said.

In general, the farther north, the bigger the changes. For example, the annual temperature increase for Hay River, a town on the shore of Great Slave Lake in the Northwest Territories, rose from -5.5 C in 1900 to -1 C in 2015. This increase of 4.5 degrees was one of the biggest changes in the country.

Fort McMurray, in northern Alberta, experienced a jump from -2.2 C in 1917 to 2.2 last year, a change of 4.4 degrees. By comparison, southerly Halifax went from 6 C in 1885 to 7.7 C in 2016, a difference of only 1.7 degrees.

What are the implications of rising annual temperatures? It depends on where you live, said Nigel Roulet, a professor of geography at McGill University in Montreal, and former director of McGill's School of Environment.

Many different causes

"In the north, the issue may be melting permafrost or sea ice, while in Montreal it might be extreme heat and storms in the summer, and more or less snow in the winter," he said.

Even though cities may show different patterns, greenhouse gas concentrations are fairly uniform around the globe, according to Environment and Climate Change Canada.

"This means that emissions anywhere in the world affect the atmospheric concentration everywhere, including Canada," said spokesperson Jenn Gearey. "These changes in atmospheric greenhouse gas concentrations affect surface temperatures throughout the world."

Large white gaps in some charts represent years with missing data.

Hawkins hopes that these charts help people understand that climate change is not a distant, abstract threat, but an urgent matter.

"I hope that these graphics ensure that the public are aware of the changes currently happening to the climate where they live," he said.

Still too abstract?

Not everyone agrees on the effectiveness of these charts. Roulet thinks changes in average annual temperatures are too abstract for people to relate to.

"The charts show climate data, which are longer-term averages. People relate to weather more: it's hot, it's raining, it has not snowed in two weeks and I want to ski," Roulet said.

Using the same colours for different cities, each with its own climate, gives the impression that changes are comparable.

"They make one think initially the magnitude of change is about the same everywhere, which is clearly not the case," he said.


Roberto Rocha


Roberto Rocha is a data journalist with CBC/Radio-Canada.