What are record temperatures now will become the norm by middle of century

A new report predicts the number of days with temperatures above 25C will triple to 36 days a year.

The hottest summers on the record will be the new norm within 20 years, and by 2050 virtually every summer will be hotter than ever experienced before. Those are some of the findings of an academic study, whose co-authors include scientists from the University of Victoria (UVic).

Co-author Francis Zwiers, president of the Pacific Climate Impacts Consortium at the University of Victoria (UVic), says the report adds to the already large body of evidence that humans are responsible for climate change, and represents a call to arms to reduce emissions responsible for climate change and adopt measures that mitigate the effects of climate change.

The study argues that anthropogenic (human-made) climate change “has very substantially increased the likelihood” of extreme high summer wet bulb globe (WBGT) temperatures. WBGT is a measure of apparent temperature that captures both temperature and humidity in the management of physical human workloads in direct sunlight as endured by athletes, outside workers and military personnel.

The frequency of extreme WBT temperatures will increase over time. Specifically, the study finds that summer WBGTs exceeding the record between 1973-2012 is already 70 times more likely, and that records recorded within this period will be norm within 20 years. By 2030s, at least every second summers will have mean WBGT higher than the observed historical record value in all parts of the world, with the frequency of occurrence increasing to 95 per cent by mid-century.

In other words, it is likely that every summer starting in 2050 will be an extreme summer in northern hemispheric regions.

This development will have practical consequences. It means more occasions during which humans will have to protect themselves against the effects of extreme heat, said Zwiers.The threshold at which heat poses an threat varies region by region, and the Greater Victoria region is fortunate thanks to its moderate climate with dry summers that are not that warm, said Zwiers.

This said, the region will have to prepare for the changes that lie ahead to ensure the health and safety, he said.

Consider hospitals. They require a lot of energy, and also generate a lot of heat themselves thanks to all of their equipment, he said. Officials need to make sure that patients will be comfortable, as summers get hotter, he said.

The study by Pacific Climate Impacts Consortium offers a big picture perspective that nonetheless matches the findings of more regional studies, like a Capital Regional District report released earlier this year.

“While temperature can be expected to increase year round, the greatest increases will occur in the summer months,” it read. Specifically, it predicts that the summer days of 25°C to triple, from an average of 12 to 36 days per year. Rising temperatures will not only to lead to hotter summer days and nights, but also milder winters with the near loss of frost days and snowpack in all but the highest elevation locations in the region.

Predicted consequences of these temperature changes include significant water shortages and “a very different lived experience.”

Projected warming will have implications for human health. Periods of heat can worsen respiratory illnesses that particulates and compounds cause, the report noted. “Impacts have the potential to be more significant in urban centres due to urban heat island effect, unless adaptive measures are taken, including air conditioning, cooling stations, and an increase in the urban tree cover,” it read.

Higher year-round temperatures can also raise the potential for vector-borne diseases.