Humans making extreme weather worse: researchers
Francis Zwiers, director of UVic’s Pacific Climate Impacts Consortium, co-authored the first study linking global warming to extreme precipitation events across North America, Europe and Asian weather stations.
Published in the Feb. 17 edition of the journal Nature, Zwiers and lead-author Seung-Ki Min conclude that acts of nature – heavy rain and snow, floods and mudslides – are intensifying and are doing so at a rate faster than scientists were able to project.
“Climate scientists have made arguments that it’s caused as the atmosphere warms, (and is) able to hold more water vapours, not necessarily more days of heavy precipitation, but the events are more extreme,” Zwiers said.
Those events include the September mudslide in Bella Coola that cut off Cariboo communities and this winter’s flooding in the maritimes.
The worst annual storms were tracked from 1951 through 1999. The likelihood of a rainfall event being more extreme than the previous year’s highest precipitation increased slightly with each subsequent year.
“The average waiting time between major events is getting shorter,” added Zwiers, the former head of climate research at Environment Canada.
Zwiers, an expert in applying statistical methods to climate variability and change, said our understanding of climate change is limited by the speed and consistency of data.
There are fewer resources available in the Southern Hemisphere, making it more difficult to compile evidence on climate trends there.
Also, the impact of volcanic eruptions is another unknown factor, not fully understood by Zwiers and his colleagues.
In Greater Victoria, an extreme event might currently translate to 75-100 millimetres in precipitation at one time – numbers that suggest the need for more robust storm water handling infrastructure, from holding ponds to rain gardens, Zwiers said.
“One thing I think we can be sure of is that these events will be stronger over time,” he said.
How much humans will be able to reduce their impact on storms over the next 100 years through reducing their carbon footprint is up for debate.
“These are local actions, but they’re going to have to be taken everywhere.”