Climate change will likely mean warmer, rainier winters in B.C. as well as reduced summer stream flows, a forum in Vancouver heard Monday as new international findings were released.
Dr. Francis Zwiers, director of the Pacific Climate Impacts Consortium (PCIC) and vice-chair of the Intergovernmental Panel on Climate Change (IPCC) working group 1, said projections for B.C. point to further warming of 2.9 degrees in the winter and 2.4 degrees in the summer by 2100, under a moderate carbon emission scenario.
Winter warming on that scale could translate into 17 to 51 more days per year of frost-free conditions, he told the forum, in the wake of the already measured reduction of 24 annual frost days since 1900 and a 2.1-degree increase in the province’s winter temperatures.
While a longer growing season might be a boon to gardeners and farmers, Zwiers noted warming winters have also allowed unwanted species like the mountain pine beetle to flourish and wreak havoc on Interior forests.
“That’s an impact that has been linked to a changing climate,” Zwiers said.
“You can just imagine there would be many other organisms that would find B.C. to be a much more hospitable place to live, even in a slightly warmer climate than we have at the moment, or a slightly wetter climate than we have at the moment.”
PCIC researchers projected climate changes in B.C. over the rest of this century using the same models as the IPCC.
Winter warming would be greater in the northeast than other parts of the province, while summer warming projections are roughly uniform.
Zwiers said the modeling shows winter, spring and fall precipitation will increase in B.C., with a 10 per cent increase in precipitation in winters expected and summers potentially getting wetter in the north but drier in the south.
Wetter, warmer winters could affect the province’s supply of water for drinking, farming, power generation and salmon migration.
With less water being stored as snow over the winter, Zwiers said, B.C. can expect higher amounts of winter and spring runoff, leaving less behind in the upper elevations to deliver water in summer.
The new IPCC report reiterated that the planet is warming and people are the probable cause.
But some observers criticized it for downgrading projected temperature increases due to a 15-year “pause” in average surface temperature rise.
Zwiers maintained human influence is clear and action is urgently needed to both reduce emissions and adapt to expected “substantial” impacts.
The IPCC report predicts Canada will face more warming than the global average, along with more frequent and more intense extreme weather events.