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Climate change: Hotter, drier summers are our future
This July was the driest ever in Revelstoke. Over the course of 31 days, it rained a mere 6.2 mm. The dry weather sent the wildfire danger into the extremes for more than a week and forced logging companies into shutdown. The Southeast Fire Centre had to bring in crews from the rest of the province to help fight all the fires burning in the area – most of which were caused by lightning.
It’s a sign of things to come if climate change forecasts bear out. According to the Pacific Climate Impacts Consortium, the average summer temperature in Revelstoke can be expected to rise by 2.4–3.2 C by the 2041–2070 period, compared to the 1961–1990 average. A three-degree change in temperature may not seem like a lot, but it currently means the difference between very cold and very hot years.
A climate change report released by the Columbia Basin Trust last year outlines what this will mean for basin residents.
For one, there will be four times as many warm days – that is, days when the temperatue are above the 90th percentile for that day. Record highs will also occur more frequently and the hottest days could be almost 5 C hotter than they are now.
Summers will also be drier, with precipitation throughout the basin expected to decreases by as much as 14 per cent compared to 1961–1990 levels. Extreme weather events, in the form of severe thunderstorms, are expected to two- to three-times more common.
What do these numbers mean in real-world terms?
The combination of hot and dry weather with increasingly severe storms is expected to lead to a big spike in wildfire activity. Last week there were 115 lightning-caused wildfires in the Southeast Fire Centre, which covers most of the Columbia Basin.
The climate change report predicts the situation to get much worse over the years, with the fire season lasting one to two weeks longer, and the wildfire danger rating becoming higher. Fire starts are predicted to increase by anywhere from 21 per cent to almost triple by 2100.
“The hazard conditions start earlier and they go later and they get more extreme,” said consultant Cindy Pearce, who helped work on the CBT report. “In Australia they created a new category of extreme conditions.”
The category is called catastrophic and is triggered when conditions have reached extreme for several weeks. That could be necessary here, said Pearce. “After a while the extreme conditions get beyond what anyone would have thought.”
Logging companies could see a significant impact from this. Already, they have to shut down operations when conditions reach extreme for an extended period. Shutdowns could become lengthier, and more costly, should wildfire danger ratings become more extreme in the future.
The potential for fires will be taken into account when planning logging operations, said Mike Copperthwaite, the general manager of the Revelstoke Community Forest Corporation.
“We’re looking at planning our operations around that a little bit by potentially doing more south-facing operations in the spring and fall,” he said. “We’ll try to concentrate in summer on north facing slopes.”
Climate change will have a big impact on water flows. The peak spring melt is expected to happen earlier, and flows will be lower in late summer and early fall. Some of this will be compensated by increased glacial melt, but that is also expected to decrease over time.
The low water flows are expected to put pressure on community water systems. Water shortages in the summer, when demand is highest, will become more common, and larger reservoirs will be needed to store more water in the spring to make up for the drier conditions.
“Cities are building new water storage dams so they store more water in the spring, they catch more of the runoff,” said Pearce. “They’re also doing water conservation really aggressively and seriously.”
The city’s draft Greeley Creek Watershed Source Protection Plan looks at the impact of climate change. Notably, it forecasts a 13-per cent increase in annual precipitation by the 1950s, but a decreases in summer rain.
“This potential change could have an effect on the quantity of water and the timing of streamflow, and there could be associated affects to water quality,” the plan states.
There is a positive side to this – notably an increase in growing-degree days, or days that it is possible to grow crops. The CBT report says the growing season could increase by 18–35 days by the 2050s.
“Because it gets hotter, we have more heat days so we can grow different crops,” said Pearce. “I don’t think that that’s been a huge adjustment here in Revelstoke yet but I know there are gardeners who are always experimenting with things.”
Another positive is that local lakes could end being warmer, which would mean a boon for boaters and swimmers. Don’t get too excited – Lake Revelstoke is a glacier-fed reservoir who’s water is constantly being replenished, so it probably won’t warm up too much.