Warm, wet weather could be a sign of things to come
Torrential rain events are expected when temperatures rise, experts say
The Pineapple Express that brought record-breaking warm temperatures and torrential rain to the B.C. coast Wednesday is the latest in a string of extreme weather events that characterized 2017.
As temperatures in many places pushed past 15 degrees, records fell along with the rain Wednesday afternoon. The rain triggered at least two mudslides, closing Highway 1 near Hope early Thursday.
The “atmospheric river” that caused the warm, wet weather isn’t unusual for B.C., with several such events occurring each year, said UBC research associate Dr. Greg West.
However, the “magnitude” of the storm was out of the ordinary, as temperature records toppled in at least 16 B.C. communities.
While West, an atmospheric scientist, was reluctant to attribute a single weather event to climate change, he said storms will become more common as global temperatures increase.
Warm air has a greater capacity to hold water, which in turn “energizes the whole atmosphere” through the formation of clouds and the release of heat.
“It essentially intensifies weather systems,” West said.
A recent Metro Vancouver climate change study found that regional temperatures will likely rise three degrees by 2050. While annual precipitation will only increase five per cent, most of that rain will fall on the wettest days of the year, making major rain events more extreme.
Climate change may also explain some of B.C’s other major weather events of 2017. The year began with snow and a cold snap that lingered for several weeks. The chilly winter gave way to a decidedly soggy spring, with crops delayed and flooding in some parts of the province.
A hot, dry summer followed. July and August combined to make the driest summer ever recorded at the Vancouver airport, with just seven millimetres of rain over two months.
A heat waved scorched the south coast on the Labour Day weekend when 35 B.C. temperature records fell, some dating back to 1939.
Philip Austin, chairman of UBC’s atmospheric science program, said the jet stream has been making “larger meanders” in recent years. That means, at some times, warm air is pushing further north — and lingering longer — than in the past, while at other times, cold air is moving further south. One theory is that the “meandering ” is linked to the melting of sea ice at the North Pole. Austin said he used to tell his students that skiing at Whistler and Grouse could someday be impossible due to climate change. But with a meandering jet stream possibly bringing more persistent cold weather, it seems certain that the weather will become more uncertain in the future.
“We predict that there will be surprises,” he said.
It is also the beginning of a La Nina winter, which could mean colder and wetter temperatures that have nothing to do with climate change, he added.