Climate change and extreme heat waves

The ongoing heat wave across the western half of Canada and the northwestern United States has been historic. Many all-time record highs have not only been broken; they have been obliterated.

One question that is being asked today is whether or not climate change played a role?

I think it is clear that climate change most certainly played a role in how extreme this heat wave turned out to be.

Going back to the weather pattern, an unusually strong area of high pressure formed in the upper atmosphere over southern British Columbia late last week and lingered over the region through the early part of this week.

This area of high pressure acted as a block, forcing any storms up into Alaska and preventing any cool fronts from bringing any relief from the northwest and north.

As the high-pressure area strengthened in place through the weekend it allowed a tremendous amount of heat to build under it. Couple this with ongoing moderate drought in the region, a high sun angle and long periods of daylight the recipe was set for an extreme heat wave.

Places like Lytton, British Columbia, were like an outdoor fire pit, a low valley surrounded by mountains on almost all sides, which allowed the heat to build to extreme levels through the three-day period.

I have no specific as of yet data to back this up, but if the same heat wave with the same drought conditions occurred during the 1990s or 1980s, I still would have expected some all-time record highs in addition to the dozens of monthly and daily record highs. However, I believe the impacts of climate changed likely pushed it even farther and had a clear role in causing some of these all-time records to be surpassed by such a wide margin.

The Intergovernmental Panel on Climate Change (IPCC) has stated in their reports that heat waves are very likely to become more frequent and more intense as well as increase their duration by the end of this century due to climate change.

The report has also noted that a 1-in-20-year annual hottest day is likely to become a 1-in-2-year annual hottest day by the end of the century. So basically what they are saying is that extreme heat waves such as this current one are likely to become more common in the coming decades, increasing the risks to people, animals, forests and the water supply.

The core of this ongoing heat wave will shift eastward into the Prairies for the second half of this week with the potential for more record heat and little or no rainfall.

Back in BC and the Pacific Northwest, which experienced the worst of the heat, it will remain hot through the weekend, but not to the extreme of what we just saw. It will be more like a typical summer heat wave, which is not good.