Climate Impacts Have Multiple Causes

Trees are down from a wind storm in Vancouver

Why did the late August windstorm in British Columbia’s lower mainland cause record power outages for BC Hydro? There are some clues in this story:

“Windstorm shakes the foundation of BC Hydro’s weather prediction system” by Jeff Lee, Vancouver Sun, September 1

The storm came at the end of a severe 3 month drought. Trees were stressed, and branches were weak. Soils were softened by heavy rains after a summer of limited root growth. Deciduous trees were also in full leaf, unlike during winter months when leaves have fallen off. Wind speed was high, and the wind resistance of tree branches was high, while their strength was lower.

This is a good reminder of the kind of climate impacts we are likely to see in future. It’s not just a single extreme event, but a combination of effects caused by climate and other factors. It will be very difficult to predict the specific impacts likely to result, as it was difficult for BC Hydro to predict the damage this event would cause. If we try to predict future impacts and then plan to avoid them, we are likely to be surprised by unexpected combination events such as this one. Another reason why resilience is a better strategy than adaptation.

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